WO1992022777A2

WO1992022777A2 - A full-range, high-efficiency liquid chiller

Info

Publication number: WO1992022777A2
Application number: PCT/CA1992/000238
Authority: WO
Inventors: Marc A. Paradis
Original assignee: Paradis Marc A
Priority date: 1991-06-18
Filing date: 1992-06-11
Publication date: 1992-12-23
Also published as: US5435155A; ATE163751T1; WO1992022777A3; EP0603182B1; CA2044825C; DE69224646D1; ES2116337T3; JPH06508912A; EP0603182A1; AU1777192A; DE69224646T2; CA2044825A1; BR9206165A

Abstract

A method of generating very cold liquid flows, comprising sending said liquid to a heat pump circuit; said circuit including a hot-side heat exchanger (HSHE) and a cold-side heat exchanger (CSHE); said CSHE being provided with conduit means through which said liquid flows; said conduit means being in contact with and being cooled externally by cold medium. The improvement in the method comprising the installation of proper thermal barriers between said cold medium and said liquid in all areas where the velocity of said liquid is much lower than the average velocity found inside said conduit means; said improvement also comprising proper design of the entrance of said conduit means to prevent flow detachment; said design preventing any freeze-up of said liquid as well as improving efficiency and durability. An alternative to the above said improvement is simply the elimination of all areas where the velocity of sais liquid is much lower than the average velocity found inside said conduit means. Other alternatives are proposed. Apparatus is disclosed for practicing the described method. The improvement in the method also comprises the capability to generate and manipulate supercooled liquids in a way that prevents liquid line and cooler freeze-ups. The improvement in the method also comprises new vapor compression cycles as well as new absorption cycle arrangements for better practicing the described method. Applications in very diversified fields are described. The technology is given the name 'SUPERPAC', which stands for 'SUPER Pompe A Chaleur', or super heat pump.

Description

A FULL-RANGE, HIGH-EFFICIENCY LIQUID CHILLER

BACKGROUND OF THE INVENTION

This invention relates to methods of, and apparatus for, cooling any liquid, said cooling being performed for any purpose, including the extraction of energy from said iiquid for heating purposes. More particularly, this invention is concerned with a simple and efficient method of obtaining and handling very cold liquids, down to and below their solid-liquid equilibrium temperature.

A cooler is a component of a liquid-chilling system in which a liquid, usually an aqueous liquid (e.g. water or brine), is cooled by a refrigerant, in a conventional system, the coo¬ ling effect comes from the evaporation of said refrigerant. The most common cooler types are: direct expansion and flooded (1990 ASHRAE Handbook: Refrigeration Systems and Applications).

In a typical direct expansion shell-and-tube cooler, the refrigerant evaporates inside tubes, while the fluid to be cooled is channeled throughout the shell by a series of baffles. In a typical flooded shell-and-tube cooler, the fluid, flowing through the tubes, gives its heat to the boiling liquid refrigerant on the shell side. These coolers are usually mounted horizontally. They are normally found in larger systems using screw or centrifugal compressors. In very large diameter shells, the heat transfer at the bottom can be adversely affected by the head of the refrigerant. This problem can be solved by spraying the liquid refrigerant all over the tubes instead of flooding them.

Freezing of the fluid can cause considerable damage to coolers therefore some freeze protection must be provided. Two methods are used. Suction pressure can be held above the one corresponding to the freezing point of the fluid; or the system can be shut down when the fluid temperature gets too close to the freezing point. For pure water, an evaporator-outlet temperature of 5°C is often considered as a safe lower limit.

UBSTITUTE SHEET Limitations of present systems

a^ The freeze-up problem

If one tries to obtain low fluid temperatures, say 1°C, from a conventional cooler, a freeze-up will occur: the freezing process will start at a location where the wall tem¬ perature is well below phase-equilibrium temperature and where the fluid velocity is low. In a flooded type cooler, the flow of water in the tubes does not exhibit any low velocity region; except maybe at the inlet where the flow might be detached for a certain distance inside: a low velocity bubble is then created where freezing might start. The real problem is in the cooler heads, where low-velocity water is exposed to the cold tubesheets. The freezing process will start there if the tubesheet is at a temperature below freezing. In a direct-expansion cooler, several low water velocity regions exist in the shell, which is crossed by cold tubes containing the evaporating refrigerant.

b) The small AT limitation

In a conventional chiller used in air conditioning, the cooler outlet on the fluid side will usually be kept at 7°C. Since the inlet is at about 13°C, a ΔT (temperature differential) of only 6°C is thus available for energy absorption. This is an important limitation. If the ΔT could be doubled (e.g. by using a cooler capable of generating 1°C fluid outlet tempe¬ ratures), the system capacity could be doubled without even having to increase the size of the distribution system (pumps, piping and heat exchangers).

c) The constant-temperature phase-chanαe problem

If a high system COP (Coefficient Of Performance) is to be obtained, it is important to have a cycle with the minimum source-sink ΔT: this is possible only with an efficient heat transfer in the hot-side heat exchanger (HSHE) and in the cold-side heat exchanger (CSHE), which supposes a large heat transfer area and small ΔTs in both heat exchangers (HX). The latter condition is quite difficult to obtain in conventional systems. Indeed, if the fluid had to be cooled from 13°C to 1°C in a conventional cooler, the refrigerant would have to evaporate at about -4°C. The ΔT between the entering fluid and the refrigerant would then be about 17°C: this large value of the ΔT increases the irrever- sibility of the heat transfer and causes a significant decrease in the COP of the chilling system. d) The COP / capacity dilemma

As explained by Didion and Bivens ("The Role of Refrigerant Mixtures as Alternatives". Didion, D.A. and Bivens, D.B. Proceedings, A.S.H.R.A.E. 1989 C.F.C. Conference, Washington, Sept. 1989), when using the usual one-component refrigerants, we have to choose between a large volumetric capacity and a large COP. With non-azeotropic mix¬ tures, on the other hand, we could theoretically get the best of both worlds.

SUMMARY OF THE INVENTION

The above-described drawbacks can all be eliminated. Indeed, with the invention, com¬ plete control over the cooling and freezing processes of liquids is actually obtained.

In one of its aspects, the invention provides a method of cooling liquids inside a liquid cooler, said cooler being connected to a liquid supply circuit including one or more conduit means through which said liquid flows; said conduit means passing through and being in contact with a cold medium in said cooler, said cooler and or said conduit means being straight or smoothly curved; said cooler being characterized by the fact that it is capable of cooling liquids down to very low temperatures, including the phase-equilibrium tempe¬ rature as well as supercooling temperatures, without inducing freezing of said liquid in said conduit means; said capability being obtained by one, two or all of the following three ways; the first of said ways being preventing the contact of the said liquid with a cold surface in locations where said liquid is stagnant or has a low velocity as compared to the average liquid velocity inside said conduit means passing through said cooler; the second of the said ways being the elimination of all said stagnant regions or said low velocity regions near said cold surfaces; the third of said ways being the elimination of the cold surfaces themselves. Several evaporator designs incorporating these characteristics will be described later.

In another aspect, the invention also provides a method of handling supercooled liquids generated by a cooler in which outlet ends of individual supercooled-iiquid conduit-means of said cooler are provided with extensions, said extensions being capable of transferring said supercooled liquid to a remote location, said extensions being made out of any conve¬ nient material, e.g. metal, plastic, etc., said extensions being connected to said outlet ends, said connections being of any type, including the simple press-fit type.

In another aspect, the invention also provides a method of handling supercooled liquids

SUBSTITUTE SHEET generated by a cooler in which outlet ends of individual liquid conduit means of said coo¬ ler or extensions of said individual outlet ends of said liquid conduit means of said cooler, or outlet ends of main liquid conduit means, from which said supercooled liquid flows, are equipped in such a way as to prevent the formation of ice crystals at said outlet ends; said formation provoking a rapid blockage of said extensions or said main conduit means by inducing a phase change of part of said supercooled water, said phase change pro¬ ducing ice crystals, formation of said ice crystals being caused by said outlet ends being colder than ambiance; said ambiance being any liquid, including water, or any humid atmosphere; said atmosphere containing any gas or mixture of gas, including air, humi¬ dity in said humid atmosphere condensing on said outlet ends and eventually changing to ice crystals. Said supercooled liquid being stored in a reservoir for later use; or said supercooled liquid being used for any purpose, including, in the case of water, the cooling of meat, fruits and vegetables.

In another aspect, the invention also provides an extremely efficient method for heating liquids initially at or near their solid-liquid equilibrium temperature; said heating being performed using very little outside energy; said heating being performed using thermal energy still present in rejected liquid; said rejected liquid being still warm; most of said heating being performed in a passive way using a liquid-liquid HX; said heating also being partly performed by the HSHE of a heat pump; said heat pump also having a CSHE, said CSHE being capable, when necessary, to supercool said rejected liquid.

In one of its other aspects, the invention also provides a method of cooling liquids com¬ prising a cooler, said cooler being the CSHE of a heat pump, said heat pump being used for heating or cooling purposes, or for any other purposes; said heat pump being of the vapor-compression (VCHP) type, the refrigerant circulating in said heat-pump circuit being of the non-azeotropic mixture type, said heat pump being characterized by the presence in the cycle of a reformer LPR; said reformer being a reservoir capable of containing said refrigerant in liquid and vapor phases; said vapor from the top of said reformer being entrained, compressed, condensed, and expanded within the hot-side por¬ tion of said circuit; said liquid from the bottom part of said reformer being entrained, circulated and evaporated within the cold-side portion of said heat-pump circuit; said cir¬ culation in said cold-side portion being produced by a refrigerant pump P; said pump being capable of producing an overfeeding of said cooler EV; said cycle being an improvement over conventional cycles in that the composition of said refrigerant vapor circulating in said hot side is rich in the more volatile (and higher density) component(s) of said mixture while the composition of said refrigerant liquid, circulating in said cold side is rich in the less volatile (and higher latent heat) component(s) of said mixture; said modified cycle thus providing at the same time higher system efficiency and larger sys¬ tem capacity.

In another aspect, the invention also provides methods of making artificial snow. In one of said methods, a continuous flow of supercooled liquid water is changed to a flow of su¬ percooled droplets using any method, each of said supercooled droplets then rapidly changing into droplets containing a mixture of dendritic ice and water at 0°C, said dro¬ plets then being sent into cold ambiant air where they evolve to become snowflakes; or said droplets are used as seeders for larger droplets which will then grow into larger snowflakes.

In still another aspect, the invention provides a method of generating ice with a liquid cooler, said cooler possibly being the CSHE of a liquid chiller, said chiller being capable of cooling any liquid; said liquid being cooled by said cooler to supercooling temperatures; said exiting supercooled iiquid being made to partially change phase; said phase change providing a mixture of solid and cold liquid at the phase-equilibrium temperature; said change of phase being provoked by any convenient method; said mixture, and/or said solid, and or said cold liquid being used for any purpose. Of the numerous possible uses for such mixtures, one is the manufacture of snow from a solid-liquid water mixture, said solid part being separated from said mixture; said resulting solid part being high- quality snow, said snow thus being manufactured independently of atmospheric conditions.

In still another one of its aspects, the invention provides a method of removing a slurry from within a reservoir and bringing said slurry, via conduit means, towards another location where it is needed; said method using a Coanda-effect wall-jet ejector, said ejector being characterized by the fact that said wall jet, having a relatively high speed, is capable, because of the Coanda effect, of following bellmouth-shaped entrance to said conduit means, its turbulent eddies thus being capable of breaking agglomerations of solid particles near said entrance, said wall jet being also capable of entraining said slurry into said conduit means, thus helping liquid pump in moving said slurry to said other loca¬ tion.

In a further aspect, the invention also provides a method of breaking up crystal agglo¬ merations inside a reservoir containing a liquid and said crystals; said breaking up being performed for any reason, including improving entrainment of said crystals into an outlet towards slurry conduit means; said method being characterized by the installation, in said outlet, of a "self-propelled" rotor, said rotor being made in such a way that it can be partly located inside conduit means and partly inside reservoir; the part of said rotor

SUBSTITUTE SHEET located inside said conduit means acting as a turbine capable of driving any device, said device being the part of said rotor protruding inside said reservoir; the purpose of said device being mainly the breaking-up of ice-crystal agglomerations and also the entrain¬ ment of crystals towards said outlet; said turbine being designed approximately like one of the well known types of hydraulic turbines (e.g. axial type; or mixed flow type); said device being made approximately like a propeller or an axial flow pump or any component that can at the same time break-up said agglomerations and entrain said crystals; said method using relatively little external energy.

In still another one of its aspects, the invention provides another method of breaking up crystal agglomerations inside a reservoir for the purpose of improving entrainment of said crystals into an outlet, said breakup being performed by the action of several liquid jets, said jets preferably generating a vortex inside said reservoir, axis of rotation of said vortex passing through (or close to) said outlet; said vortex being generated because axes of said jets are not parallel to one another and do not meet at a point, the path of every individual jet crossing said axis of said vortex at approximately identical angles much smaller than 90°, preferably of the order of 30°; said crossings being made at a small and preferably identical distance from said axis of said vortex; said crossings all being approximately in the same plane; said plane being approximately perpendicular to said axis of said vortex; said jets creating entrainment of said agglomerations towards said outlet; said jets also creating rotation of said agglomerations; said jets then acting as so many jet saws capable of cutting through said agglomerations and moving broken-up pieces towards said outlet.

In one other aspect, the invention also provides still another method of breaking up crystal agglomerations inside a reservoir, said breakup being performed by the action of a giant "egg-beater" type of device, said device being preferably installed close to the re¬ servoir outlet in such a way as to direct resulting slurry towards said outlet.

in still another of its aspects, the invention provides a method of generating artificial snow independently of weather conditions, in which a continuous flow of supercooled li¬ quid water at about -0,8°C is changed into a mixture of ice crystals and water by any convenient method, said ice crystals being separated from mixture and accumulated by any convenient method, said crystals having the look and feel of natural snow.

In a further important aspect, the invention provides a method of conditioning water in fish hatcheries and other similar applications in which heating (or cooling, in summer) is mostly performed passively in a heat exchanger HX and also partly by the HSHE (or CSHE, in summer) of a heat pump, said heat pump being of any type, including the VCHP type; in winter, cold fresh water at 0°C (or more) being circulated into said heat ex¬ changer HX where it picks up energy, said warmed water then going through HSHE of said heat pump where it picks up more energy and from which it exits at the proper temperature and enters fish reservoir; overflowing warm gray water then flowing out of fish reservoir, being circulated through said HX where it loses most of its energy to incoming fresh water; colder gray water out of said HX then going through CSHE of said heat pump; coming out of said CSHE and then being disposed of; said gray water then being at about the same temperature (0°C or more) as when it first came in as fresh water; with system in normal operating conditions in winter, said CSHE thus having to cool water down to the "freezing point" of water; with system in start-up conditions, said CSHE then having to supercool water, said CSHE thus being designed according to in¬ vention; positions of said CSHE and HSHE in water circuit being inversed during summer, in order to be capable of cooling warm fresh water before its entrance into said reser¬ voir.

In one of its other aspects, the invention provides a method of solid/liquid separation whereby slightly supercooled liquid inside a reservoir is forced through a porous mem¬ brane of any type, ice then starting to build up all over said membrane, said membrane then acting as a crystallizer.

In still another one of its aspects, the invention provides a method of joining flows of supercooled liquid from two or more conduit means in order to create a larger flow of supercooled liquid inside a larger conduit means, by making sure that said flows of su¬ percooled liquid; between said small and said larger conduit means, do not endure any im¬ portant mechanical or thermal perturbation, including large changes in velocity (i.e. speed and direction).

In a further important aspect, the invention provides a method of cooling liquids down to or below their phase equilibrium temperature using a hybrid multiple-cascade heat- pumping system comprising preferably 3 absorption heat pumps (AHP-j to AHP3), said AHPs using any working pair, including LiBr-H2θ; said system also preferably using 2 vapor-compression heat pumps (VCHP2 and VCHP3); said AHPs being normally unable to attain the very low temperatures necessary for providing desired final state, said AHPs being helped here by VCHPs in cascade; warm liquid coming from load first being cooled by AHP-) ; then chilled liquid out of AHP-) entering VCHP2 where it is cooled a few more degrees, cold-liquid circuit of said VCHP2 being installed in series with cold-liquid circuit of said AHP-j ; said liquid out of VCHP2 finally entering VCHP3, cold-liquid circuit of said VCHP3 being installed in series with cold-liquid circuit of said VCHP2; fully cooled li¬ quid, out of VCHP3, then going back to said load; AHP2, installed in cascade with VCHP2, being used as a source of cooling water for the condenser of VCHP2; AHP3, installed in cascade with VCHP3, also being used as a source of cooling water for the condenser of VCHP3. This method of generating very cold or supercooled liquids is characterized by the fact that the system, while remaining essentially an absorption system (most of its driving power still coming in as heat energy), permits the use, as main components, of conventional AHPs which would normally be unable by themselves of deeply cooling liquids. This method is further characterized by the fact that, despite the low working temperatures, the resulting COP is almost as good as the one obtained normally with AHPs working at much higher temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be described and schematic drawings presented. Unless otherwise noted, it will be assumed here, for the sake of simplicity, that the type of heat pump cycle used is of the VCHP type. Figures 1 and 2 show schematic diagrams of one-pass and two-pass flooded shell-and-tube coolers based on the present invention. Figures 3, , 5 and 6 show several alternative designs also ba¬ sed on the present invention. Figures 7 and 9 show schematic diagrams of improved refrigeration cycles permitting an efficient generation of very cold liquid flows. Figures 8 and 10 show true counterflow coolers based on the present invention and capable of using, to the fullest, the non-azeotropic refrigerant mixtures. Figure 11 shows a sim¬ plified atomizer for supercooled liquids, the probable main application being the genera¬ tion of "artificial" snow. Figure 12 shows a heat-pump arrangement permitting a very efficient conditioning of water, one application being in fish aquaculture installations.

DESCRIPTION OF THE INVENTION

The invention provides simple methods of yielding very cold liquid flows, down to tem¬ peratures heretofore impossible to attain with any machine. It also proposes improved thermodyπamic cycles permitting attaining these low temperatures in a very efficient manner. a) A low temperature cooler

The freeze-up problem described above can be solved by first modifying the liquid coolers to make them practically freeze-proof. The concept applies to most types of coolers. We will first take as an example the case of the flooded shell-and-tube cooler featuring con¬ ventional circular cross-section fluid tubes. Other types of coolers will be discussed la¬ ter. Figure 1 shows a modified flooded cooler (9) designed according to the present in¬ vention. It features double tubesheets (7a, 7b and 7'a, 7'b), the spaces (13, 13') between the latter being filled with insulation, e.g. polyurethane foam, air, etc. The width of that space (13, 13') should be sufficient to provide a good heat barrier, e.g. about 10 to 20 tube diameters (O.D.), or more in special cases. Said spaces (13, 13') can also be partly or fully open to atmosphere. The improvement here is that the low-velocity liquid in the cooler heads (4), (14), is nowhere in contact with a cold surface (7b, 7'b). Alternate de¬ signs will be shown later where the low iiquid velocity regions (4a, 14b) and/or the cold surfaces themselves are simply eliminated.

Preventing the cold medium (e.g. refrigerant R) from getting into the spaces (13, 13') between the tubesheets (7a, 7b and 7'a, 7'b) is easy; for example by expanding the tube (10) diameter into said tubesheets by means of an expander. Many expansion methods are available (see "Heat Exchangers; Selection, Design and construction", a book by E.A.D. Saunders; John Wiley and Sons, New York).

Another minor modification that will improve considerably on the cooler's reliability, is a smooth entrance (3a) at the inlet end of the fluid tubes (10), as shown in figure 1. This: -will decrease the pressure drop on the fluid side -will prevent gradual erosion of the tubes at the inlet end (3a) -will further reduce the chances of freezing inside the tubes (10). The last statement can be explained by the fact that a detached flow at the abrupt en¬ trance to a conduit means (10) creates a "bubble" of reduced velocity where fluid free¬ zing could possibly start. Preventing erosion is also important because said erosion can cause surface pitting, thus creating minute pockets of stagnant iiquid which might start the freeze-up process.

Figure 2 shows another cooler (9) designed according to the present invention. It features two tubeside passes (that is, the fluid goes twice through the shell, e.g. once from left to right, in the lower part of the shell, and back from right to left in the higher part), which reduce the length of said cooler (9) for a given fluid temperature difference between inlet (5) and outlet (6). It also features the above described double tubesheets and smooth fluid-tube inlets (3a). An optional baffle (1) is also added for separating the outlet (2) and inlet (3) flows, said baffle extending far enough inside the cooler right-hand head (14) to effectively prevent one fluid flow (2) from disrupting the other (3). A baffle length equivalent to about 10 tube diameters should be sufficient.

One could obviously think of many other ways of creating a thermal barrier between the cold medium and the liquid to be cooled. Instead of installing a second tubesheet (7b), one could, for example, install a piece of rigid or semi-rigid insulating material (16) between the cold medium (R) and the tubesheet (7a) (fig. 3). Expansion of the tubes (10) into the insulator (16) and the installation of O-rings (15) between the insulator (16) and the shell (9) would prevent the cold medium (R) from leaking to the tubesheets (7a).

The insulating material (16) could also be installed on the liquid side of the tubesheets, i.e. between the liquid to be cooled and the tubesheet (7a), thus eliminating the cold sur¬ face itself. One could also add extensions (20) to the conduit means (10) and even elimi¬ nate the cooler head (14) at the exit end (fig. 4a), or even at both ends, if desired (fig. 4b), thus eliminating all the low fluid velocity regions close to the tubesheets (7a,7'a): in this case the inner tubesheets (7b, 7b') would become superfluous.

Instead of being passively warmed up by means of insulation (16 or 13), tubesheet (7a) could also be actively heated in some way. Although this active heating normally would not be done, it is possible to imagine instances in which it could become desirable, ther- modynamicaliy speaking. For example, in a VCHP system, subcooling of the iiquid refrige¬ rant from condenser, before its entrance into the expansion device, provides improved cycle efficiency. Said subcooling could be performed by sending said liquid refrigerant into the space (13) between tubesheets (7a, 7b). Care should be taken as the final tempe¬ rature of said subcooled liquid refrigerant should not fall below entering-liquid (5) temperature. This might necessitate the presence of some thermal insulation on the sur¬ face of tubesheet (7b), preferably within space (13). Said subcooling within space (13) would save the cost of a refrigerant-to-refrigerant HX. Of course, said subcooling could be performed just as well within space 13'. Many other methods of actively protecting the stagnant liquid inside cooler head (4a) from freezing could be imagined.

When fed with a liquid at 3°C, a cooler (9) like the one in figure 4a, having the proper length and the proper coolant-to-liquid ΔT, will give an outlet temperature of 0°C. When fed with a liquid at 0°C instead, other things being equal, the same cooler (9) would have the capability of providing an outlet temperature of about -3°C. If the liquid were pure water, that outlet temperature would correspond to a supercooled state. A liquid is said to be supercooled if it is at a temperature well below the phase-equilibrium temperature while still in the liquid phase. The supercooled state is a metastable state. In such a state, a substance has a certain phase stability; but if disturbed, it will try to acquire a greater stability, i.e. it will try to go up in temperature (up to the phase equilibrium temperature, e.g. 0°C for pure water) by partially changing phase. For a metastable flow to continue to exist, sources of perturbations (mechanical, thermal, etc.) must be eliminated or at least significantly reduced.

Looking at figures 4a and 4b, it is seen that such designs are capable of generating su¬ percooled liquids; indeed, the liquid (23) at the outlets is not subjected to any perturba¬ tion (abrupt changes in direction, etc.) and no stagnant or low velocity regions exist near to a cold surface (7'a). In figure 4a, the liquid will not have a tendency to freeze near the inlet because the tubesheet (7a) is not cold, being protected by a thermal barrier (13). In figure 4b, the liquid will not have a tendency to freeze near the inlet either because the iiquid flow (5) does not exhibit any stagnant region near a cold surface (7a). Supercooled iiquid (23) out of extensions (20) can be discharged directly into some reservoir or large body of water. Extensions (20) of conduit means (10) can be of any length.

When fitted with longer conduit extensions (21), cooler (9) will also be capable of deli¬ vering said supercooled liquids to a nearby (or remote) reservoir (26) (fig. 4c). Said ex¬ tensions (21) can be of any length and made out of any convenient material, including plastic. Connection (51) between said extension (21) and said extended fluid tube (20) can be of any type, including using soft-plastic unions, e.g. press-fitted in place.

Note that the liquid (5) entering individual tubes in figure 4b will normally come from a distribution chamber located at some distance upstream, said chamber being in any con¬ venient position (e.g. above) relative to shell (9). Said chamber thus replaces the inlet head (4) of cooler (9), being in effect a cooler head (4) separated from shell (9) by a large space (13), said space being completely open to atmosphere.

Note also that the reservoir (26) does not have to be open to atmosphere: the system will work just as well, for example, with reservoir (26) under high inert gas pressure. It should be stressed also that supercooled liquids can be stored in a reservoir (26) almost as easily as any conventional liquid, the only condition being a careful handling (minimum of perturbations). That can be done, for example, by guiding jet(s) of super¬ cooled liquids so that it hits container walls at an angle much smaller than 90° (preferably 30° or less). It is also possible to deliver supercooled liquids to a reservoir through an inlet located below liquid surface. Instead of being stored, supercooled liquids

SUBSTITUTE S EET can also be delivered to locations far from the cooler (9), provided said liquids are handled according to the principles given in the present invention.

It should be noted that, contrary to what was previously thought by the inventor, flows of supercooled liquids inside conduit means can tolerate a certain degree of large scale turbulence; indeed, tests with flows of water inside a tube have shown that increasing abruptly said tube diameter by a factor of 3 (and decreasing it as abruptly a few cm fur¬ ther downstream) did not normally provoke a freeze-up in the line. The problem is that it sometimes didl Small changes in diameter never were a problem, however; neither were connections made using different materials. For example, connecting a plastic tube exten¬ sion onto a metal tube, downstream of the cooler, never provoked a freeze-up, at least not under normal operating conditions.

It should be noted also that very high rates of heat transfer can be used in a supercooling CSHE. For example, rates as high as 45 kW per square meter of (internal) heat exchange area have been used successfully with (internally and externally) smooth tubes. Tube- wall temperatures below -7°C were obtained in these cases. Using tubes that are finned on the refrigerant side, higher values of said rate might even be possible. These heat rate values are higher than what is normally used in the refrigeration industry. This permits the use, when necessary, of very short fluid tubes (10) (i.e. having low values of Ld).

The design shown in figures 1 is not capable of generating supercooled liquids in a reliable manner: the liquid (2) flowing in the outlet head (14) is subjected to too many perturba¬ tions (abrupt changes in directions, in speed, in flow cross-sections, etc.). It has been found, however, that increasing the length of the head (i.e. effectively increasing the distance between outlet (6") and tubesheet 7'a) improved the situation somewhat. With the design shown in figure 2, it is possible to obtain limited supercooling at the exit, again with limited reliability.

The designs of figures 1 and 2 can easily be modified for reliable supercooling operation, however. For example, figure 5a shows one of several possible designs for a one-tube- side-pass cooler capable of generating supercooled liquids: connectors (31) are used to connect the tube extensions (20), inside the cooler head (14), to the main conduit means (33). Depending on the material used for making said connectors (e.g. metal or plastic) said connectors (31) can be joined in different ways. For example, they can be glued or soldered to one another, side by side, and press fitted inside an extension (32) of the head (14). Said head (14) could be made in 2 parts one of which could be removed for inspec¬ tion. Of course, one can think of an infinite number of variations of the same theme, the fundamental idea being simply to eliminate low velocity regions near cold surfaces (e.g. internal tubesheets) and to provide smooth flow inside the cooler (9), between said cooler (9) and main conduit means (33), and also inside said main conduit means (33), large scale turbulence being reduced to a minimum. Figure 5b shows a 3-tubeside-pass cooler designed according to the present invention, perfectly smooth flow being maintained bet¬ ween inlet (5') and outlet (32) of said cooler (9). It should stressed that the 180° elbows (34) in figure 5b could be located inside the shell (9), if desired, instead of inside the heads (4, 14): this, however, would prevent easy cleaning of the inside of conduit means (10). It should also be mentioned that said 180° elbows (34) can exhibit relatively sharp turning radiuses. For example, mean radiuses as small as 0,7 times the tube outside dia¬ meter have been used successfully.

One might also want a chiller capable of cooling a liquid down to (or close to) its phase equilibrium temperature, using a one-pass or a multi-pass cooler, while still keeping its options open as to the possibility of generating supercooled liquids at a later date. For example, figure 5c shows a liquid cooler that can easily be transformed into a liquid "supercooler" of the type shown in figure 5a, said transformation being obtained by the addition of extensions (connectors) (31) to individual liquid conduit-means (20), said ex¬ tensions (31) then permitting the creation of a large flow in a large conduit means (33). It is also possible to transform the cooler of figure 5c into the "supercooler" of figure 4 c by the addition of individual extensions (21) and by the removal of the head (14).

Once generated and sent through a line (33) of some sort, a supercooled liquid must still be handled with special care. Major perturbations must be eliminated from said line; particularly the presence of ice crystals at any point in the flow. Even solid particles that might resemble ice crystals should ideally be eliminated from the flow, for example by filtering the liquid at a location upstream of the cooler (9). The presence of ice crys¬ tals must be prevented especially at the final outlet ends (22', 22, 36), where the flow leaves the conduit means (20 or 21 or 33) and enters the ambiance (said ambiance being any space having a characteristic dimension sensibly larger than that of said conduit means, said space containing any liquid, vapor or gaz). Said outlet ends or tips (22', 22, 36) are sometimes in a very humid atmosphere, for example in the space above the liquid level inside a reservoir (26). Said outlet ends or tips (22', 22, 36) also tend to be very cold, at about the same temperature as the supercooled liquid. Humidity will thus con¬ dense on said cold tips. Being at a temperature below phase equilibrium temperature, the condensed humidity will eventually freeze and ice crystals will touch the flow of super¬ cooled water (23). Ice will then rapidly accumulate on said tips, thus preventing the liquid from flowing. This in turn will provoke freezing inside the conduit means (10).

SUBSTITUTE SHEET The problem can be solved by preventing the freezing of said condensation on said tips (22', 22, 36), or by preventing said condensation itself. There are many ways of doing this. For example, constructing said tips using certain materials like urethanes helps a lot. Depositing on said tips an anti-fogging material can also prevent condensation. Another method is simply the local heating of the surfaces of said tips. Said heating can be done by any of the known heating means, using conduction and/or convection and/or ra¬ diation as the basic heat-transfer methods. Local surface heating using resistive paper or conductive paints as a heating element is a possibility. Using chemical (exothermic) paints is another. Circulation of a warm liquid in a small conduit means (36') at or near the tip (36) of the main conduit means (33) is another possibility (fig. 5a). Simply heating said tips with a flow of warm room air using a small fan was also found to be effective in the case when the reservoir is open to atmosphere. Many other methods could be imagined.

Very little heating is needed in practice, since the area involved is small and since the ΔT is also small. Indeed, for preventing said condensation from freezing, the local surface temperature has only to be kept above the phase change temperature of the liquid. For preventing said condensation from occurring at all, the surface temperature would have to be kept above the local dew point; this would imply more intense heating than in the previous case.

Any iiquid droplet splashed onto or near the cold tip (22', 22, 36) of the conduit means (20, 21, 33) will have the same disastrous effect on the flow of supercooled liquid: said droplets will freeze on said tips, eventually provoking blockage of said conduit means. The problem can be solved in the same way as above (e.g. with localized heating).

Local freezing and blockage at the tips (22', 22, 36) can also occur if said tips are loca¬ ted below liquid level of a reservoir (26) or large body of water. Being at a temperature below phase equilibrium temperature, said tips will tend to induce the formation of ice at the very tips of the outlet ends. Localized heating can be used here also, but in this case, more power will be needed. Warm liquid circulation at said tips, inside a small-diameter conduit means (36') is a valuable option (fig. 5a). It has also been found that making said tips out of an insulating material (e.g. plastic) and/or keeping ambiant liquid moving rela¬ tive to said tips (convection) helped in preventing freeze-up. Outlet designs favoring am¬ biant liquid entrainment (convection) will also work well.

The modifications described here were applied to flooded shell-and-tube coolers (9). As mentioned earlier, the invention applies also to most other types of coolers. For example, figures 6, 8 and 10 show some of the numerous possibilities. Figure 6a shows a coil-in-

BSTITUTE SHEET shell type cooler where the cold medium (R) is inside the shell (9) and the liquid (5) being cooled circulates in the coiled conduit means (10), the top of said shell (9) acting as the tubesheet (7) for said coiled conduit means (10). Figure 6b shows an element (60) of a plate type cooler featuring internal channels (61). Both types (fig. 6a, 6b) can be desi¬ gned to cool liquids down to and below the freezing point if the fundamental concepts ex¬ plained above are applied. In both cases, regions of low velocities near cold surfaces have simply been eliminated. In the latter case, the plates (e.g. roll-bonded aluminium) could be stacked-up, the space (62) between plates (60) being used for the circulation of the cold medium, the individual flows (2) of cold liquid merging in a manifold designed according to the present invention. By properly directing the fluid and the cold medium flows (in a fashion similar to what is done in the case of shell-and-tube coolers), it is possible to design plate-type coolers capable of countercurrent heat exchange. Other de¬ signs of plate-type HX capable of supercooling liquid are possible.

In a previous Canadian patent (#1 253 353), the applicant described an apparatus for generating ice slurries based on the supercooling phenomenon. It was then mentioned that in order to be capable of generating supercooled water, the cooler had to comprise water tubes having a certain geometry, the length-to-diameter ratio being a controlling para¬ meter. Since then, and to the applicant's surprise however, it has been found that length- to-diameter ratios of liquid conduit means are not an important parameter; neither is absolute value of diameter (for example, diameters of 22 mm have been tested suc¬ cessfully), neither is pressure, type of flow (laminar or turbulent), exact value of ve¬ locity, shape of said conduit means (circular, oval, etc), Reynolds number, smoothness of the inside of the conduit means, rate of heat transfer, etc. During the supercooling pro¬ cess, the same heat transfer rules apply as in any standard CSHE.

b) A laroe AT chilling system

One of the above-mentioned limitations of the present systems, namely the freeze-up problem, can thus be solved, as we have just seen. Let us now explain how the other 3 limitations can also be eliminated. To simplify the explanations, let us first continue using the simple case of the VCHP chiller. It has been shown above that with a conventional one- component refrigerant, the constant-temperature phase change eliminates the possibility of getting a large fluid-side ΔT (e.g. from 13 °C to 0 °C) inside a single shell (9) while keeping a high system COP. There are at least three solutions to this problem. Two will make use of multiple subsystems in series; the other ones will use another type of re¬ frigerant, the non-azeotropic mixture, and will feature improved thermodynamic cycles.

SUBSTITUTE SHEET —Multiple cooler systems

An example of such a system would be composed of 4 subsystems of equal capacities installed in series, each one being capable of cooling the liquid by about 3°C, this small fluid ΔT across each cooler helping in maintaining good efficiency. The fluid would enter the lead subsystem at about 12°C, go through each subsystem, one after the other, and leave the lag unit at about 0°C. The condenser water would enter the lag unit at, say, 26°C, in turn go through each condenser, and leave the lead unit at 38°C. Since the ΔT between the fluid and the refrigerant would be uniformly small, in the CSHE as well as in the HSHE, the overall heat-transfer efficiency would be good and the system COP would be nearer its theoretical maximum. The arrangement would also have the advantage that in case of a decrease in the load, one or more of the subsystems could be shut down.

The same type of arrangement could theoretically be used with other types of heat pumps, for example the absorption heat pump (AHP) or the chemical heat pump (CHP). The problem here, however, is that large AHPs or CHPs capable of providing low tempe¬ rature liquids (e.g. 0°C water, or ice slurries) are not available on the market and will probably not be for many years to come. The large machines that are normally available use the pair H2θ-LiBr and can only provide water at a minimum of approximately 6°C.

Since there is a need for such low-temperature systems in the 0,1 to 30 MW capacity range, especially in space-cooling applications, the following arrangement is suggested. Figure 7a shows an example of what we could call a hybrid multiple-cascade system, ca¬ pable of generating very cold liquids (e.g. 0°C water) or supercooled liquids efficiently if large quantities of cheap, low-grade heat are available. An infinity of arrangements is possible. The important feature here is the fact that one (or more) AHP be arranged in series fashion (along the liquid circuit) with one (or more) VCHP, in order to bring, in two or more steps, the liquid temperature down to its desired low final value. In such a system, as shown in figures 7a to 7d, one (or more) AHP (or CHP) is also coupled in cascade fashion with one (or more) VCHP heat pump.

Let us take an example: here is how a hypothetical hybrid water-chilling system for space cooling might work. AHP-j, with a capacity of 4 MW (about 1100 tons) is capable of bringing the 12°C water (80), coming from load, down to 6°C (81). The cascade sub¬ system AHP2 VCHP2 (2 MW capacity) is installed in series (in the liquid circuit) with AHP1 in order to bring water (81) from 6 °C to 3 °C (82). By itself, AHP₂ would not be capable of bringing the water (81) temperature down from 6°C to 3°C. It is merely used here as a source of cooling water (CW ) at about 6°C for the condenser of VCHP2. In a similar fashion, VCHP₃ (2 MW), is capable, with the help of AHP₃ (about 2,2 MW) as a source of cooling water (CW3), of bringing the water (82) to its final temperature of 0°C

(83).

The advantage of this arrangement is the fact that most of the power (about 96%) for cooling the load still comes from low grade heat sources (Q-| , Q2. 03)- Some mechanical power (W2, W3) is necessary to drive the compressors of the VCHPs. But the quantities involved are very small (about 3% of total incoming energy). The other 1% is used to drive the pumps of the AHPs. Indeed, in this case, said VCHPs have a very high COP since they are optimized to work between fixed (or almost fixed) source and sink tempera¬ tures, said temperatures being very close to one another (about 6 °C apart, here). Said COPs are calculated to be around 12, if all the components, as well as the refrigerant, are well chosen. In this example, the overall system capacity is 8 MW. The sources of power could be: about 12 MW of low grade heat, and about 0,5 MW of mechanical power, assuming a typical COP of 0,75 for the AHPs. Of course.this mechanical power does not have to be provided by an electric motor; a diesel engine (or any convenient driver) could be used, the fuel being oil, natural gas or any other convenient fuel.

Several strategies could be imagined for operating the system at part load conditions, the large number of subsystems in this arrangement offering all the flexibility needed. For example, one could choose to operate the VCHPs at full load all the time, the variations in load being taken over completely by AH Pi ; this would save the cost of a variable speed drive on the motors and improve on the overall COP.

Of course, many variations of the above arrangement are possible. For example, (fig. 7b) the evaporator of AHP could be used directly as the condenser of VCHP2: the re¬ frigerant in the VCHP2 circuit would then condense, in indirect contact with the refrige¬ rant evaporating in AHP2. Same thing for AHP3 and VCHP3. Two HX would thus be saved and the COP of the system would be even greater than in the above described case.

One could even go a few steps further and keep only one AHP and one VCHP (fig. 7c), the chilled water out of the larger AHP providing all the water needed by the smaller VCHP: the condenser cooling water (entering at 6°C and leaving at 12°C) as well as the cooler water (entering at 6°C and leaving at 0°C). Warm water from load (at 12°C) and con¬ denser cooling water (also at 12°C) would join and both go back to the inlet of the AHP to be chilled again. Such an arrangement still features the original idea of a VCHP in cascade with a AHP, but has a much smaller number of components. It would thus be cheaper but would also be somewhat less versatile than the previous versions, considering the redu-

SUB ced number of possible part-load control strategies.

The above-described cascade arrangements are of course capable of supercooling water and generating either solid ice, snow or ice slurries. For example, the system shown in figure 7c is capable of delivering supercooled water at -2°C directly. In the case of building-cooling systems with ice storage, ice could be made during off-peak hours, for later daytime use. A night-operation scheme could then look like the one shown in figure 7d; in such a case, the AHP would operate at part load, generating cooling water both for the condenser of said VCHP and for the nighttime (reduced) building load., said building then being cooled using 6°C water

The above described cascade arrangements are also capable of cooling almost any liquid down to temperatures below their so-called freezing point. Moreover, it should be stressed that the working pair in the AHPs is not limited to UBr-H2θ.

—Non-azeotropic refrigerant mixtures

The multiple-subsystem arrangements described above are rather expensive. Using non- azeotropic refrigerant mixtures (NARM) inside a single chiller will help decrease costs and further improve on the operating efficiency. Indeed, with this type of refrigerant, phase changes are not constant temperature processes; it is thus possible to keep a small and constant ΔT between the fluid and the refrigerant. Depending on the composition of said NARM, the evaporation in the CSHE can induce a 10, 20 or even 30°C temperature increase (or glide). A corresponding decrease in temperature will happen in the HSHE, during condensation.

There are two main criteria for an efficient machine of this type. The first is that the temperature glide of the refrigerant during phase change be the same as the temperature glide of the fluid, in the evaporator as well as in the condenser. The other criterion is that both the evaporator and the condenser be counter-flow heat exchangers. The conven¬ tional flooded shell-and-tube HX (cooler) is thus inappropriate for such an application. In very small systems, the best type of HX for real counterflow heat exchange is the basic double-pipe or tube-in-tube element. For large systems, however, other arrangements have to be found. A real counterflow HX suitable both for secondary refrigerants and for non-azeotropic phase-change fluids, and designed according to the present invention, is shown in figure 8: it is what we might call a one-tubeside-pass "shell-and-multi-double- tube" cooler featuring three tubesheets (7a, 7b, 7c) at each end. It provides full coun¬ terflow without presenting any limit to the maximum capacity. It can be built with any convenient number of passes, both on the fluid side and on the refrigerant side. If modi¬ fied according to the general principles explained above, it can also be used to generate supercooled liquids.

A simplified counter-current cooler will be described later. As already mentioned, it is also possible to build counter-current plate-type coolers designed according to the pre¬ sent invention.

It has also been mentioned that for maximum system efficiency, the fluid-side tempera¬ ture glide must match exactly the one on the refrigerant side. In practice, the perfect refrigerant mixture, with a perfectly linear temperature glide, might never be found. Fluid-side and/or refrigerant-side parameters will thus have to be adjusted accordingly to try and keep the refrigerant-to-fluid ΔT as uniform as possible from cooler inlet to exit, and also from condenser inlet to exit.

—Improved cycles

Figure 9a shows an improved VCHP cycle featuring a low-pressure receiver, LPR, acting as a reformer (i.e. a partial distiller), capable of partially separating the components of the NARM: the liquid at the bottom, rich in high-boiling-temperature ( less volatile, more dense) component(s) (70) leaves, going towards the pump P and the evaporator EV, while the vapor (71), being rich in the low-boiling-temperature component(s) (more volatile) leaves, going towards the compressor C. A fresh flow of partially evaporated refrigerant mixture (72) comes from an overfed evaporator EV, appearing here as a two-shell HX (EV-j , EV2). Said fresh flow (72) provides the reservoir LPR with vapor (71) for the compressor (C) as well as with new liquid (70) for the evaporator, said liquid and vapor having roughly the needed composition. Liquid refrigerant also comes at a smaller rate through valve FL from condenser CR (appearing here as a two-part HX, CR-| and CR2) and high-pressure accumulator HPA. The liquid (5) to be chilled flows counter-current to the flow of refrigerant in evaporator EV and leaves at (6). Condenser cooling water also flows counter-current to the refrigerant in condenser CR.

The particular choice of refrigerant mixture is partly dependant on the temperature dif¬ ferential needed in the evaporator, on the fluid side. An almost infinite number of NARM can be used. A possible choice, for example, is the pair R13B1/R152a: the high density of the first component provides a high system capacity while the high latent heat of the second provides superior efficiency. Another possibility is the pair R22/R114. Many other binary or ternary mixtures are possible. It should be noted that if the overfeed rate

SUBSTITUTE SHEET is large, the refrigerant (R) will behave in the cooler (9) almost like a (non-evaporating) highly subcooled fluid. The design of the coolers- (9) can then be simplified, as will be seen below. The pump P is capable of providing us with that large flow. In a way, the cycle is thus similar to the well known liquid-overfeed system, which has many well known advantages: smaller sized components, high system efficiency and well reduced operating costs (ASHRAE Handbook: op. cit.).

This basic cycle can be modified and/or improved upon in different ways; what is impor¬ tant is the presence here of a reformer LPR which permits sending mixtures of different composition to the hot side and the cold side of the heat pump circuit. How different these compositions will be, depends in a large part upon the overfeed rate through the eva¬ porator. It also depends upon the NARM chosen. To give an idea, the denser component can represent more than 75% of the total mass flow in compressor C, but less than 50% in evaporator EV; i.e. the concentration of the dense component can thus go from 1 :1 in the evaporator to 3:1 in the compressor (C). The higher the density of the vapor going to the compressor (C), the greater the capacity of the system.

The capacity of such a system can also be modulated by using methods similar to the ones used in more "conventional" systems. For example, the extraction system shown in figure 9b can change the average level of pressure and density in the system, permitting a modulation of the capacity (dayly, weekly or seasonal modulation). This is done by re¬ moving from circulation (extracting and temporarily storing) some refrigerant extrac¬ ted from either one of two points: at or near the condenser exit, for example at the top (73) of the high-pressure receiver HPA; or along the condenser itself, immediately after the point where the desuperheating is complete (about one fourth to one third of the way along the condenser), using separator reservoir SR-j .

Vapor at the top of HPA is rich in the low-boiler, volatile, higher-density component(s): removing this vapor from the circuit (via valve V3), by condensing it and storing it in the extraction receiver ER, will give a decrease in system capacity. Extracting the liquid (rich in the high-boiler, non-volatile components) from the bottom of SR-₎ (via valve V ) will have the opposite effect. The valves V-jto V3, which control the extraction process, can be made to respond automatically to a change in demand.

At part load conditions there will be changes in temperature glide of the fluid along the cooler. The refrigerant temperature glide in the evaporator EV should thus be changed to keep a good match. This in turn will change the glide in the condenser CR: a change in condenser fluid flow (74) will keep a good temperature-glide match there. This change in the refrigerant temperature glide along the cooler EV can be accomplished in different ways; for example, by varying the refrigerant mass-flow rate through said cooler: a variable-speed drive on the pump P can achieve this.

Other methods can be used which will at the same time improve on the cycle perfor¬ mance. For example, a subcooler S can be installed: the liquid (75) from condenser CR and/or high pressure accumulator HPA is subcooled by giving up heat to the cold liquid (76) coming from pump P. Said subcooling of said liquid refrigerant (75) can also be ob¬ tained by putting it in indirect contact (75) with cool liquid about to enter (5) the cooler EV (fig. 9c).

Removing the already vaporized refrigerant at the exit of EV-j (77) (fig. 9c) and sending it (78) directly to reformer LPR will also ensure a still larger concentration of non-vo¬ latile components in cooler EV and more of the dense vapor at the top of reformer LPR, thus improving cycle capacity and efficiency. In a similar fashion, extracting some iiquid from the bottom of SR2 and sending it to the reformer LPR (via valve V5 and expansion device CP) will ensure that the mixture entering CR2 is rich in volatile component(s), thus improving on the heat-transfer properties on the refrigerant side in CR .

Another interesting modification to the cycle is the overfeeding of the condenser, the idea being to send into the condenser CR more vapor than it is capable of condensing in one pass. This will have at least three positive effects. First, said overfeeding will permit sending a denser mixture to the compressor C; this, as we have seen, is very desirable. It will also improve on the heat-transfer coefficient (HTC) on the refrigerant side, said HTC being known to be quite low for all condensing NARMs. A large value of said HTC will reduce the size and cost of said condenser CR. It will also decrease the ΔT between re¬ frigerant and coolant in said CR, thus improving system COP. Different circuits could be imagined for doing said overfeeding; what is new here is the condenser overfeeding itself, and the fact that it is used in a circuit with NARM.

For example, figure 9d shows a cycle featuring a low-pressure reformer LPR, an over¬ fed evaporator EV within a low-pressure circuit L-j , an overfed condenser CR within a high-pressure circuit L3, and, in between, a compression circuit L2. Said high-pressure circuit L3 also comprises a high-pressure reformer HPR for partially separating the re¬ frigerant mixture (79) into its components. L| and L2 are thus connected via LPR; L2 and L3 are connected via HPR. Said mixture (79) out of the condenser CR is not completely condensed: its liquid part, poor in dense component(s), will accumulate at the bottom of HPR, from where it will go towards LPR, via expansion device FL; the vapor part in (79),

SUBSTITUTE SHEET rich in dense compoπent(s), will be re-routed to the condenser CR by the blower B. Said blower B is capable of overfeeding said condenser CR, the overfeed rate having any va¬ lue, including 1. Said blower B and said pump P will thus have very similar functions.

The cycle in figure 9d can also be used with advantage with pure refrigerants or with azeotropic mixtures of refrigerants. In this case, HPR and LPR will simply become li¬ quid-vapor separators. Said overfeeding in CR and/or EV will still be very useful because of its potential for improving system COP and decreasing costs. Said condenser overfee¬ ding can be used independently of said evaporator overfeeding. For example, a condenser overfeeding system would be perfect in an application like the one shown in figure 7b, where calculations show that AHP2's evaporator will normally be unable to completely condense the refrigerant circulated in circuit VCHP2; the same thing being said for AHP3.

More than one of the above-described cycle modifications (fig. 9b to 9d) could be im¬ plemented at the same time, if desired.

Figure 10 schematically shows a countercurrent cooler designed according to the inven¬ tion and having one shell-side pass and one tube-side pass. The number of liquid conduit means (10) in the shell (9) can be as large as needed. When used with one of the systems shown in figure 9, such a cooler is capable of providing whatever fluid ΔT is needed, assuming the shell (9) is long enough. With a large refrigerant flow rate (high overfeed rate), the relative volume-flow rate of vapor generated will be small and the cooler will behave almost like a true countercurrent liquid-to-liquid HX, the closeness of the fluid tubes providing the guiding walls needed by the refrigerant for an orderly coun¬ tercurrent flow: the tube-in-tube arrangement of figure 8 is thus unnecessary here. Still more orderly flow could be obtained with conduit means (10) featuring longitudinal fins. Figure 10 shows quite clearly how the mere presence of 2 longitudinal fins per conduit means (10) could provide very good flow guidance as well as improved heat transfer. Of course, many other fin arrangements could be used.

The cooler (9) of figure 10 could be further improved upon with the installation of a tu¬ besheet (37) made out of a porous material or out of any material providing a small pressure drop, for the purpose of improving the crosswise evenness of the refrigerant flow in the cooler. A second porous tubesheet (37') could also be installed in a similar fa¬ shion at the other end of the cooler. Such a cooler (9) will give the same good results as the one shown in figure 8, being particularly useful with liquid-overfeed systems and/or with non-azeotropic refrigerants, but with reduced size, complexity and cost. In the case of more conventional cycles (without a reformer LPR), the said porous tubesheet (37) could also perform part of the "expansion" of the liquid refrigerant exiting from the hot side of the heat pump.

Liquid "expansion" from high to low pressure inside the cooler (9) itself could be per¬ formed in many other ways. For example, one of the fluid conduit means (10) inside said cooler (9) could be replaced by a capillary tube extending between tubesheet 7'b and tu¬ besheet 7b; the iiquid refrigerant under pressure would, for example, enter space 13', where it would be partly subcooled, go through said capillary tube while being cooled (countercurrent) by neighbouring evaporating refrigerant mixture R. After going through cooler EV, said liquid refrigerant would have a reduced pressure and would be sent di¬ rectly to reservoir LPR (valve FL then being superfluous).

For a fluid ΔT of 13°C, the single shell of cooler (9) in figure 10 would have to be quite long, its length could be cut in half by installing two shorter shells in series. Building each one of said shorter shells with two shell-side passes and two tube-side passes would further reduce the length of said shorter shells for a given fluid ΔT. Many such combina¬ tions could be imagined. Of course, the counterflow cooler (9) of figure 10 and all of its possible adaptations can be made to handle supercooled liquids by applying the general principles explained above.

APPLICATIONS OF THE FULL-RANGE CHILLER

The full-range chiller has obvious applications in the field of space cooling. It also has many other applications in very diversified fields. Following are more details on some of these applications.

—Space cooling

The liquid chillers described above can be used in a large number of cooling applications, especially space cooling. For example, in retrofit applications, the (SUPERPAC) full-range chiller can be installed in series with a conventional chiller to obtain water at any tempe¬ rature between 6°C and 0°C (using one SUPERPAC unit or, preferably, two SUPERPAC units in series, for better efficiency). A final temperature of 0°C would give an increase in system capacity of more than 100% without any change in the size of the main chilled- water line.

If a further increase in capacity is ever needed, another cooler capable of generating su¬ percooled water can be installed in series: when sent to a reservoir, this supercooled

Ϊi^'- U i fc water can be made to partially change phase: the ice crystals are accumulated while the liquid is recirculated to obtain more ice. The floating ice crystals can be used for short or long term energy storage. The water at the bottom of the reservoir can be circulated in the building and used as the energy transport fluid. The slurry itself can also be used as the energy transport fluid.

Another possible arrangement for obtaining an ice slurry for energy storage purposes would be the following: during off-peak hours, the lag unit (used normally for generating very cold water, e.g. at 0°C), could be used to obtain supercooled water and ice crystals. During day time, this ice could be used to shave the peak load, while said lag unit would come back to its normal use, e.g. the cooling of water from 3°C to 0°C.

It should be noted that with CSHE inlet temperatures of 6°C (or more), it is also possible to obtain oulet temperatures of, say, -2°C directly, within the same cooler, at the ex¬ pense of efficiency, however.

The crystallization of supercooled liquids (e.g. inside the reservoir) can be obtained by a mechanical or thermal perturbation; for example, an abrupt change in direction, a vibra¬ tion of any frequency (e.g. from a sonic or ultrasonic generator); by a cooling element (e.g. of the thermo-electric type) touching the liquid (e.g. partly under and partly above liquid level), etc.; or by seeding the supercooled liquid with ice crystal or a piece of ice obtained elsewhere.

When one tries to accumulate a large quantity of large crystals in a reservoir, a diffi¬ culty often arises: the cristals tend to accumulate and pile up at one spot. This can create problems. A simple solution is to have a multitude of small jets uniformly distributed all over the surface of the reservoir, rather than having one or two large jets: this will create a multitude of small heaps rather than a large one. This is easily done when the system is built like the one in figure 4c: tube extensions are then supported in such a way that said resulting jets are uniformly distributed. This problem, however, is less likely to happen when the crystals are generated at lower supercooling temperatures (say, below 1,6°C for pure water): the crystals are then very fine and the resulting "slush" tends to flow like a thick fluid and does not pile up to any great extent.

The ice slurry accumulating in the reservoir is probably the ideal energy transport fluid, in new installations as well as in retrofit situations: at the proper solids concentration (e.g. 20%), it will circulate in pipes, pumps and heat exchangers. Its energy absorption capability being more than 4 times that of iiquid water at 6°C, mass flows in main lines will be 4 times less, pumping power will be about 5 times less, line diameters about 50% smaller, etc. Different storage strategies can be- utilized depending on the application, the main advantage always being that pure water can be used instead of solutions containing glycol or other environmentally sensitive freezing-point depressants. If desired, ho¬ wever, additives can be added to the slurry to further improve its characteristics: anti¬ friction and anti-corrosion additives, dispersants that will prevent the agglomeration of the crystals, etc.

Indeed, if the ice slurry (24') (i.e. a mixture of ice crystals (24) and cold liquid (25)) is to circulate well between reservoir (26) and the location where it is needed, one can add dispersants into said reservoir (26). Said dispersants will prevent crystal agglomeration and ensuing blockage of outlet (42) with ice crystals (24). Said dispersants will also im¬ prove slurry flow inside conduit means (28), said flow being provided by slurry pump (SP). A special design of the reservoir outlet (42) can also help ice crystals (24) to en¬ ter the ice-slurry conduit means (28). Figure 4c shows one possible design, based on the ejector principle, with the added feature of a "Coanda" inlet. The pump (29) removes li¬ quid (25) from reservoir (26) and sends it (43) to distribution chamber (44) from where it is pushed through thin slot (45); because of the "Coanda effect" (and of the pump SP, here), the resulting wall jet (46) (having, in this example, a circular symmetry) "sticks" to the wall of bellmouth-shaped outlet (27) (see any good book on fluid mechanics for an explanation) and enters into conduit (28). Liquid (25) and ice crystals (24) from reser¬ voir are entrained very efficiently by said wall-jet (46) into conduit (28), agglomera¬ tions close to outlet (27) being easily broken-up by turbulent wall jet (46). Many varia¬ tions of the same theme are possible; for example, two co-axial jets could be used, one helping the other. What is new here is the efficient combination ejector/wall jet(s)/"Coanda effect".

The ice crystals (24) would move more easily towards said outlet (42) if large ice- crystal agglomerations were broken down into smaller agglomerations by one or more jets (49) of liquid, said liquid (47) flowing through pipe (48) having been pumped from the bottom of reservoir (26) by a pump similar to pump (29). Several jets (49) could also be arranged in such a way as to produce a vortex having its axis going through outlet (42), all axes of said jets (49) being at an approximately identical angle (e.g. 30°) with said axis of said vortex, said axes of said jets (49) all passing at a small and approxima¬ tely identical distance frorø said axis of said vortex. Said large ice agglomerations would then be broken down by said multiple jets (49), said jets acting like so many water-jet saws. Outlets of pipes (48) should preferably be located above liquid level. Entrainment of small agglomerations towards said outlet (42) would also be very efficient. Other phy- sical arrangements are possible. What is new here is the combination of sawing action and entrainment action, resulting in moving and cutting said large agglomerations at the same time.

A simpler way of destroying ice-crystal agglomerations, using relatively little external energy, is the installation, inside said reservoir outlet (42), of a "self-propelled" rotor, said rotor being made in such a way that it can be partly located inside conduit means (28) and partly inside reservoir (26), the part of said rotor located at least partly inside said conduit means (28) acting as a turbine capable of driving any device, said device being the part of said rotor protruding inside said reservoir (26), the purpose of said device being mainly the breakup of ice-crystal agglomerations and also the entrainment of crystals towards said outlet (42); said turbine being designed approximately like one of the well known types (e.g. axial (Kaplan) type; or mixed flow type); said device being made approximately like a propeller, an axial flow pump or any component that can at the same time break up said agglomerations and entrain said crystals.

Another way of destroying ice-crystal agglomerations very efficiently, without using much external energy, is the installation, inside said reservoir (26), of slowly-rotating giant "egg beaters". Preliminary tests have shown that such a device, when properly lo¬ cated (e.g. in front of the outlet (42)), induces a well-behaved slurry flow into inlet (42) and conduit means (28).

—Heat pumps

The coolers constructed according to the present invention can also be used as CSHE for liquid-source heat pumps, using conventional cycles as well as the new improved cycles described above. Indeed, with a CSHE design such as the one in fig. 1 , for example, water cooled to about 2°C or 3°C can be used as a source of heat, for space heating as well as for many other uses. In the case of saline water, the temperature of the source can be as low as 0°C. This cannot be done with other types of CSHE now on the market. With CSHE designs such as the ones shown in fig. 4, 5, etc., liquids at the freezing point (e.g. from a lake, during the winter period) can be used as a heat source. The supercooled water coming out of the machine is simply returned to the large body of water where it will tend, being lighter than water at 4 °C (and at 0 °C), to rise to the surface and mix with the ambiant water; if ice is generated by this mixing process, it will tend to float on the surface.

Such heat pumps can be used for space heating. They can also be used in many special si- tuations, e.g. snow-melting plants, mine heating systems, etc.

— Snow-meltino plants

in some northern cities, disposing of the polluted snow, removed from city streets, can be a problem. With the invention, energy from a partly frozen lake or the sea can be transferred to the hot side of the heat pump and to the snow to be melted. A possible ar¬ rangement could be the following: a large pit similar to a very large swimming pool is dug in the ground. Its walls are then covered with a large number of pipe loops in which the warm fluid (e.g. a brine heated with the energy from the heat-pump HSHE) will circulate. Said loops are then covered with several cm of earth. When trucks dump their load of snow into the pit, the bottom and the sidewalls of the pit being warm, the snow will melt and drain down into the soil. If needed, the melted snow can also be sent to a water treatment plant; in this case, an impermeable sheet (e.g. a plastic sheet) would have to be layed down over the bottom and side-walls of the pit (e.g. after covering said pipe loops with earth). Many improvements to such an installation could be imagined.

—Mine heating

During the cold season, in northern climates, the ventilation air in mines has to be pre¬ heated. This prevents the freezing of the water which is always dripping down the walls of the different parts of the mine: this is due to the fact that mine shafts are always well below the local water table. This water tends to accumulate at the bottom of the shafts; it has to be continuously pumped out of mine shafts. At present, oil, natural gaz, propane gaz or electricity is being used as a source of energy to heat said ventilation air. In such a situation, a SUPERPAC heat pump would save large amounts of energy and save money.

The arrangement could be the following. The quantity of water which has to be pumped out is specific to each site, but is normally quite large, say of the order of 5 LVs and more. This water is normally at a temperature of about 7°C all year long. It is thus a good source of energy for a heat pump intended for heating ventilation air. The problem is that air mass flows are enormous compared to water flows. It is thus important to remove as much energy as possible from said mine water. It means that said water should exit the CSHE of the said heat pump at 0°C or less, which is only possible when using the invention. But even so, the quantity of water available is still too small for the amount of heating involved. One solution to this problem is the following. Let us say that a circulation of 25 IJs in said CSHE were needed to perform said air heating with the HSHE of said heat pump. Said 25 s of water could be removed from the mine shaft, pumped

SUBSTITUTE SHEET up and circulated through said CSHE of said heat pump, the latter being located, for example, in a building at ground level. At the outlet of said CSHE, water would be at 0°C or less; part of it (5 IJs, here) would be discarded, say in a river or a lake, the rest being reinjected into an adjacent mine shaft, thus reestablishing hydraulic equilibrium inside the mine.

— Deep mines cooling

Very deep mines must be cooled because the earth gets warmer as one digs deeper: at 4000 m, it is at an approximate temperature of 60°C. Obviously, the ambiant air down below must be cooled. Since the above described full-range chiller is capable of genera¬ ting very cold water down to about -2°C, it becomes possible to send cold or supercoo¬ led water into the mine from ground level (or any underground level), being sure that it will arrive at the bottom still very cold. This could even be a more economical proposition than the circulation of ice slurries being studied for certain very deep mines. If desired, such ice slurries can also be generated by the above described invention and circulated inside the mine.

—Snow-making machines

Most ski slopes are now equipped with one type or another of snow-making machines. The machine-made snow, however, is often of poor quality: depending on the ambiant condi¬ tions, it will sometimes have the look and feel of hard ice pebbles, sometimes of wet slush, rarely that of real snow. The difference in quality comes from the fact that real snow is made from deeply supercooled water droplets (i.e. the clouds).

Contrary to what happens in conventional snow-making machines, it is possible, with the invention, to directly obtain all the supercooled water needed, without the help of the cold ambiant air. When a jet of said supercooled water from a conduit means is changed into a flow of droplets (e.g. because of the action of turbulent viscous forces between a jet of air and said supercooled water jet), the resulting supercooled droplets, being in a metas¬ table state, will rapidly start freezing in a dendritic fashion, said droplets becoming mixtures of dendritic ice and water which, in a cold ambiance (e.g. ambiant air), will grow to full-size snow flakes, because of the heat and mass transfers (convection and evaporation between droplets and ambiance) involved.

There is no limitation as to the method used for delivering said supercooled liquid into droplet form, the basic parameter being the fact that the snow is made here from liquid previously cooled or supercooled by a machine. For example, if a flow of supercooled water exits from a nozzle at high velocity, said water is thrown at great distances. The turbulence generated by the friction between air and said water is capable of changing the stream of supercooled water into a multitude of supercooled droplets: said changing of the type of stream is a disturbance capable of initiating the phase-change process of the metastable droplets. As the droplets travel through cold air at high speed, they lose heat (by convection and evaporation) and thus continue to grow into full size snowflakes. Such a snow-making process does not need compressed air and is therefore very energy effi¬ cient.

The atomizer shown in figure 11 is also capable of generating very small droplets: su¬ percooled liquid (90) flows out of a conduit (91) as a thin, wide film (93); compressed air (94) going through tube (95) and through a nozzle (96) provides a high-speed jet of air. Depending on the type of nozzle, said jet can be subsonic, sonic or supersonic. A well de¬ signed nozzle will produce an almost isentropic expansion; the result will be a very cold, high-speed air jet requiring relatively small upstream pressures, thus saving some energy. Said air jet is then blown through said thin liquid film (93) of supercooled liquid, changing the film flow into a small droplet flow (97). As mentioned earlier, tip (92) of said tube (91) must be modified (e.g. said tip being heated) for reliable operation. When the partly frozen droplets generated by an atomizer are very small in size, like the ones generated by an atomizer similar to that of figure 11 , they can also be used as seeders for larger droplets of cold liquid generated by more conventional methods: when the small dendritic crystal touches a larger drop of liquid which has been pre-cooled, e.g. by am¬ biant air, it provokes, in said larger drop, the beginning of the phase-change process.

Many variations of the same theme are possible. For example, the air and water jets do not have to be at right angle to one another; they can be at any angle, including parallel. They can be side by side or concentric, the jet at the center being either the air jet or the supercooled-water jet. Both jets can be of any shape, e.g. circular, annular, etc. In such a system, the air jet is used mainly for changing the liquid stream into droplets (due to the action of turbulence) but also for accelerating the cooling process, and thus the speed of the phase change.

The supercooled water necessary for generating snow can sometimes be obtained (weather permitting) simply by circulating cold water in a properly designed air-to-wa¬ ter HX (v.g. a pipe loop or a plate HX located above ground in cold ambiant air). Such a system would be more difficult to control but would save energy. The HX would have to be designed according to the invention.

TITUTE SHEET Water being used for generating snow normally arrives at the snow-making machine at a temperature approaching 1°C. But in certain weather conditions and/or at certain times of the year, approaching water can be at a temperature as high as 5°C or more. In order to be able to manufacture high quality snow, it is then preferable to precool said approa¬ ching water down to 1°C or below with a full-range chiller, i.e. with the invention, even when using conventional snow-making machines down the line.

Instead of using ambiant air for providing further cooling of water droplets and/or for completing the phase change process, a flow of colder air could be used, said colder air having been cooled by some type of HX, e.g. the CSHE of a refrigerating system, or some other device. It would then be possible to generate snow in difficult weather conditions, e.g. when the wet-bulb temperature of the ambiant air is at or slightly above 0°C.

An even better way of manufacturing snow independently of the atmospheric conditions is the following. As already mentioned, when sent to a reservoir, a flow of supercooled water can be made to partially change phase: 1 ,25% of the mass flow, per degree of su¬ percooling, becomes solid. The ice crystals can be made to accumulate in said reservoir while the liquid part is recirculated to obtain more ice. It is possible to obtain different types of crystals, depending on the operating conditions. For example, if tap water is supercooled down to about -0,8°C (±0,1 °C, approximately) and sent to said reservoir, and if crystallization is provoked, the resulting crystals will be very similar to snow. More (or less) supercooling can be used (e.g. using temperatures of -0,6°C), but the re¬ sulting "snow" will look and feel less natural, higher temperatures producing larger and dryer crystals, lower temperatures giving the inverse result. One way of "harvesting" this snow is simply to keep operating the machine until there is practically no liquid left in said reservoir: we then end up with a reservoir full of high-quality snow.

Many other methods of harvesting the snow are possible. For example, the supercooled water jets can be made to crystallize on a plate, a piece of screen or any other type of support located above the liquid surface of the reservoir; after the desired thickness of crystals has accumulated on said support (say, 50 cm or 1 m), said support and crystals are removed from underneath said jets of supercooled water and liquid water remaining between crystals is left to drain for a few minutes. The result again is high quality snow. If said support were a slowly-moving conveyor belt, the handling of said snow would be easier, especially when large quantities of snow are needed. The quality of this snow can be further improved by removing the small amount of humidity still remaining between crystals. Different methods exist to perform this removal. Centrifugal action is one. A high-capacity machine fitted with a large reservoir would be capable of generating enough snow to cover a ski slope. Skiing during summertime thus becomes possible. The snow on the ground will last longer if insulation (preferably porous) was installed below the snow cover. Or said ground could be kept cold artificially with an underground refri¬ gerating system. This type of high-quality snow can also be used for many other pur¬ poses.

—Freeze concentration

Freeze concentration (FC) applications are divided into two categories. In the first one, the desired product is the solvent and the degree of concentration is low because the concentrate is easily disposed of. Water desalination is an example: the concentrate (e.g. 50% or more of the original solution) is discharged back into the sea. In the second cate¬ gory, the desired product is the concentrate. A relatively high concentration is needed; what is disposed of is the solvent. Examples are the concentration of acids, alkali, milk, salts, coffee extract, etc. Being formed without any physical constraint, the ice crystals formed from a supercooled aqueous liquid flow are absolutely pure solid water. Supercooling can thus become the basic process in a new freeze concentration method. An example is that of obtaining potable water from polluted water. When separated from the original solution, washed clean and melted, the crystals become pure water.

The separation process can be very simple: indeed, crystallization and separation can be made in a single operation. For example, sending a jet of supercooled water (from a re¬ servoir or directly from a cooler) onto a conveyor belt (made of any convenient mate¬ rial, including thin perforated sheet metal) creates a mechanical shock which will initiate the crystalization process, the crystals remaining on the belt while the liquid is drained back into the reservoir. The accumulated crystals can then be moved elsewhere (v.g. into a wash column) by the belt. Other crystallization methods are possible, including vibra¬ tions from a sonic or an ultrasonic generator. Other separation methods are possible, in¬ cluding centrifugation.

The cleaning of crystals can be done in wash columns. This is a relatively mature techno¬ logy and two types of systems are used: the gravity column and the pressurized column. The former is very tall, the height thus being sufficient to squeeze the ice bed, helping in the final cleaning process, which is done by introducing wash liquid at the top of the co¬ lumn. Said wash liquid is obtained from melted pure crystals. In pressurized columns, hydraulic pressure forces the wash liquid to flow down.

EET An important advantage of the invention in FC applications is the fact that by modifying the operating conditions, the crystal size can easily be changed. "Deeply" supercooled li¬ quids (e.g. -1,5°C water) will produce soft and fragile dendritic ice, while slightly su¬ percooled liquids (e.g. -0,5°C water) will give hard ice: blocks of pure ice having a mass of several kg have even been obtained during experiments with supercooled water at -0,5°C. Such blocks are obviously very easy to clean, without the expense of wash columns. Different installations can be imagined permitting the fabrication of much larger blocks of pure ice. For example, one can imagine that a large flow of supercooled water at -0,5°C has been generated; directing one or more jets of such water along a large plate will permit hard ice to build up to unlimited thicknesses on the plate.

In such an installation, it would be better (but not necessary) for the plate to be slightly cooled by some type of cooling system for two reasons. First, it would be easier to in¬ duce crystallization at the beginning of the process (crystallization of 0,5 °C water is relatively difficult to induce; but once started, it is self propagating); second, it would prevent the ice from slipping away from the plate, which would preferably be slanted a few degrees from a horizontal position to facilitate the draining of the liquid. Temporarily stopping the plate-cooling process would permit the block of ice to slip and be transported to a nearby reservoir where it could be melted. The entire process could easily be automated, it is important to realize here that the slight cooling of the said plate is not performed for freezing the supercooled water but to help in the handling pro¬ cess.

From what has been said above, it can be concluded that the temperature of the supercoo- led-liquid flow is the dominant factor controlling the type of ice generated. But there are other significant parameters, like the jet velocity (speed and direction), the diameter of said jet, the number of jets arriving at one point, etc.; it has been found that these other parameters have an important effect on the form of the ice crystals. For example, by va¬ rying the velocity of a jet of -0,5°C water, it is possible to go from a crude stalagmite shape to a lovely flower having regularly shaped petals)

The invention also provides another interesting solid/liquid separation process. It works like this. As said earlier, supercooled liquids can be stored in reservoirs. Moreover, if supercooling is to be obtained at the cooler (9) exit (5), crystals (24) should be preven¬ ted from entering the liquid cooler (9), e.g. by using a filter (52) (fig. 4c), as said in a previous patent, (op. cit.). Simple cotton filters (pieces of old bed sheets covering a perforated 40 cm length of 5 cm diameter pipingl) have been used successfully for this purpose. When crystallization is not provoked (26), the bulk of the liquid (25) slowly be- comes supercooled inside said reservoir (26); ice then starts to build up all over said filter (52), said filter (52) acting as a crystallizer. Said ice is relatively porous, so that liquid (5) keeps flowing towards pump P: ice thicknesses of up to 3 cm have been obtained over said filter. Also, said ice is relatively hard and quite easy to remove by hand from around said filter (52). Said ice being easy to wash clean, this phenomenon can be used as the basis for a simple freeze concentration method. Several variations of the same theme could be imagined. For example, the "filter" does not have to be installed as in figure 4c; and it can have any shape; be made of any material; it could be the whole bottom of said reservoir (26); or it could be its side walls; or a large perforated plate located anywhere inside the reservoir (26), the liquid (25) being sucked from both sides of said plate. The harvesting of the resulting ice can easily be automated.

Melting of ice crystals can be done with the energy from any source, including that from the HSHE of the machine; or with the energy from a building to be air conditioned: one then has a dual-purpose system capable of purifying polluted water (or desalinating sea water, or treating waste water, e.g. industrial) and cooling a building. Other dual-purpose systems could be imagined.

—Water conditioning in aquaculture applications.

Fish hatcheries, and aquaculture installations in general, have huge energy needs for con¬ ditioning the water in which the different types of fish will grow. In northern climates, when the water is available only from, say, a small river, the range of temperatures of said water will often go from 0°C to 20°C. Both temperature extremes are unfit for hatcheries, which, ideally, need temperatures between 12°C and 14°C. This implies hea¬ ting said water in winter and cooling it in summer. Since the flow rates needed are often huge, it is vital to use the most efficient heating method. This implies recuperating the greatest amount of energy from the gray water overflowing from the fish tank. This maximum recuperation, in winter, means bringing the gray water from say 14°C back to 0°C or less, the recuperated energy being used for heating the fresh water from 0°C to 14°C.

This can be done with very little external energy using a modified version of the inven¬ tion. The system is shown in figure 12a: the heat pump circuit will usually be of the VCHP type, and the type of evaporator used will be any of those described above. In this system, however, most of said heating is performed in a passive way by using a liquid- liquid HX, the remainder of the heating being performed by the HSHE of the heat pump, said heat pump also having a CSHE, said CSHE being capable, when necessary, to super- cool said rejected liquid.

The system works this way. Fresh water (101) is drawn say from a river (100) at 0°C and sent (102) by a pump P1 through HX, where heat is absorbed. Said fresh water thus comes out (103) of HX at, say, 12 °C and goes through the HSHE where its temperature is again increased to about 14,5°C. Said fresh water (104) then enters the fish tank (105). Some evaporation exists over said tank (105) and the gray water coming out (106) of said tank (105) is at a temperature of about 14°C. Another pump P2 sends said gray water (107) through HX, where it gives its heat to incoming fresh water (102). Said grey water then goes (108) through said CSHE, where it loses the remainder of its energy: said gray water comes out (109) of said CSHE at a temperature of about 0°C and is sent back into the river (100).

The above-described system of figure 12a needs a CSHE capable of supercooling water. Indeed, when said system is started up in wintertime, circulating pumps P1 and P2 are first switched on: the temperatures are then uniform at 0°C. When the heat-pump circuit is started, the water then entering (108) the CSHE is at 0°C and will remain so for a considerable length of time. The water coming out (109) of the CSHE will thus be su¬ percooled to about -2°C. As the temperature in said tank (105) slowly increases to 14°C, the temperature at point 108 will slowly increase to 2°C and the temperature at point 109 will slowly increase to 0°C.

Assuming normal operating conditions and further assuming an electrical input power of 1 kW_e into compressor C, one can presume that the thermal output of said HSHE will be about 5 Wth- From the indicated temperatures in the water circulation system (fig.

12a), one can deduce that the contribution of HX to the heating process will then be about 24 kW_tn, for a total heating power of 29 kW_tn. Considering the assumed compressor C input power, the overall COP of the installation will thus be 29.

As the river temperature increases in springtime, operating conditions will change. The machine thus needs controls in order to insure continuous optimum efficiency. During summertime, the river water temperature will often be above the tank design tempera¬ ture of, say, 14°C. Some fresh-water cooling will thus have to be performed. The water circuit would be altered and the system would appear as the one shown schematically in figure 12b, where it is seen that most of the cooling is obtained with HX. Of course, temperature values indicated in figures 12a and 12b are approximate and will depend on many factors, including the design of the HX, the capacity of the heat pumping circuit, the ambiant conditions around the fish tank, etc. Moreover, many modifications can be incor-

EET porated into the heat-pumping circuit in order to further improve its efficiency, e.g. the use of a refrigerant subcooling heat exchanger, installed, for example, along the gray water line (108) between HX and CSHE.

In a situation when water at about 7°C is available from a ground source all year round, the same component arrangement as the one in figure 12a can be used. In such a case, however, the CSHE will never have to supercool water, which simplifies CSHE construc¬ tion. The high-efficiency system described here is rendered possible because the water temperature at the tank outlet is almost the same as the one at the inlet. Whenever this is the case, similar efficient systems could be installed.

— Miscellaneous applications

Cold or supercooled water from a full-range chiller can be used in the fishing industry. In fishing boats, it will keep the fish fresh, these being sprayed directly with said cold or supercooled water. In the case of a supercooled water spray, some ice crystals will normally form on and around the fish. In the fish plant, said water can be used for wa¬ shing the fish. Said water can also be sprayed onto the fish before or after it is prepared by the workers to make sure that it stays cold and fresh.

A full-range chiller can also be used in agriculture, the cold or supercooled water being sprayed onto fruits or vegetable before or after they have been picked up: this cleans them and increases their shelf life appreciably. An ice slurry can also be generated with the invention, said slurry being injected, for example, into the boxes containing fruit and/or vegetables, said boxes being normally used for transport purposes.

A full-range chiller can also be used in slaughter houses, where jets of very cold or su¬ percooled water, or mists of very cold water can be used to shower carcasses of ani¬ mals (beef, pork, etc.): this prevents weight loss by evaporation and precools the meat before its entrance into the cold room.

Said cold or supercooled water can also be used in the computer industry. Indeed, main¬ frame computers have to be cooled. Using said cold or supercooled water will permit the use of much smaller conduit means and HX, which will save space and money. Circulating an ice slurry is another possible solution.

Said cold or supercooled water (or the ice slurry formed with the latter) can also be used for the mixing of concrete. Indeed, problems arise during the construction of dams, bridges, etc. because of the heat generated during the hardening of the thick concrete. A solution is the mixing of the concrete using very cold water, supercooled water or an ice slurry, all of which can be obtained with the above-described technology.

Finally, an important application can be found in the kitchens of hotels, hospitals, etc. Indeed, the trend now is to prepare meals days in advance and vacuum pack them in plas¬ tic bags. Said plastic bags should then be cooled very rapidly so as to keep the meat in good condition. The problem is in the cooling process: if it is cooled by a cold air stream, the meat will freeze on the surface and prevent further cooling deep underneath: dange¬ rous bacteria will then develop, especially in the case of poultry. The best method is to quickly dip said plastic bags either into water at 0°C or into an ice slurry (also at 0°C). Both can be easily obtained with the invention. Putting the bags under a shower of 0°C water is another possible method.

The new cooler designs presented above have often been described as parts of VCHP sys¬ tems. Absorption and chemical heat pump systems were also briefly mentioned. It is worth mentioning that the new cooler designs can be used, if desired, within any of the known (and future) heat pumping cycles; even as part of far-fetched cooling "cycles" like the sound-wave cooling method. Two or more very different cycles can even be used in a cascade arrangement. There is no limitation as to the phase of the cold medium used in the cooler (e.g. liquid, gas). There is no limitation as to the method of circulation of the re¬ frigerant in the cooler (e.g spray type, overfeed type, etc.). There is no limitation as to the type of liquid refrigerant used in the system: primary (halocarbons, etc.) or secon¬ dary (e.g. brine, etc). There is no limitation as to the number of components in the liquid refrigerant: single component refrigerants or multi-component mixtures of refrigerants can be used. There is no limitation as to the type of liquid chilled or supercooled: acids, alkalis, coffee extracts, water, etc. When the term ice crystal is mentioned, it can ac¬ tually be a crystal made out of any liquid, e.g. pivalic acid crystalizing from a methanol solution. When water is mentioned in the above text, there is no limitation as to the purity of said water.

As we have seen, the basic ideas relating to cooler design presented above can also be applied to practically any cooler type, even to the very unusual: plate type, coil in shell, flooded shell-and-tube, shell-and-multi-double-tube, etc. All of these can be designed according to the general principles outlined above. There is no limitation as to the position of the cooler, e.g. horizontal or vertical. The counter-flow HXs described in this inven¬ tion are not only for using with non-azeotropic refrigerants. When the term "tubesheet" is mentioned in the text, there is no limitation as to the number and type of "tubes" going through said tubesheets. There is no limitation as to the material used for making the conduit means and/or the shell and/or parts thereof: metals, plastics, etc. There is no limitation either as to the shape of the conduit-means cross-section: circular, oval, flattened, etc. Said conduit means can be provided with internal and/or external fins. There is no limitation as to the exact fin size, shape, number and arrangement, except that in the case of supercooled liquid flows, the internal fins should respect the general principles stated in the invention, e.g. smooth flow, etc. There is no limitation either as to the fluid velocity and pressure inside said conduit means: velocities and pressures compatible with common HX design practice are acceptable. There is no limitation either as to the method of construction and assembly of the CSHE: all welded, expanded conduit means, etc. When double or triple tubesheets are used, there is no limitation as to the distance between said tubesheets. The space between said tubesheets can be partially or completely open to atmosphere. There is no limitation as to the nature of the insulation used for filling the said space: urethane foam, air, etc. Said insulation, in thin sheet form, could also be fixed to one or both tubesheets, on the cold or on the warmer side, depending on the application. There is no limitation as to the temperature of the fluid at the outlet of the CSHE: liquids can be cooled above, at, or below their phase equilibrium temperature (i.e. supercooled).

When supercooled, the exiting fluid can be partly changed to ice; there is no limitation as to the method of crystallization: any mechanical or thermal perturbation can be used, in¬ cluding vibrations, etc. Seeding with a crystal or a block of ice is another method. There is no limitation as to the type of solid-liquid separation method: conveyor belts, gravity draining, centrifugal drives, etc. There is no limitation as to the type of ice ge¬ nerated: depending on operating conditions, soft and fragile dendritic ice as well as hard ice can be obtained. There is no limitation as to the method of preventing ice from for¬ ming at the outlet of supercooled liquid conduits; if local heating is used, above or below liquid level, there is no limitation as to the heat transfer method used for heating: con¬ duction, convection or radiation.

Coolers built according to the present invention do not have to be used within any parti¬ cular heat-pumping cycle. Actually, said coolers can be used to obtain very cold or su¬ percooled liquids or an ice slurry without using any thermodynamic cycle; for example, said cooler can be simply an air-to-liquid HX, said air being ambiant air. Other arrange¬ ments could be imagined.

As is common practice in the refrigeration and air-conditioning industries, cold parts of a "supercooler" must be thermally insulated, care being taken to prevent condensation on

SUBSTITUTE SHEET the cooler and on all other cold parts.

This new technology is given the name SUPERPAC, which stands for "SUPER Pompe A Chaleur. The chiller capable of generating supercooled liquids will be called a SUPERCHILLER and its evaporator will be called a SUPERCOOLER. Supercooled water ge¬ nerated with said invention will be called SUPER WATER. Ice obtained from a supercooled aqueous liquid will be called SUPER ICE. Snow obtained from the invention will be called SUPER SNOW. The thermodynamic cycles of figure 9 will be called SUPER CYCLES, even when said cycles are not being used to produce supercooled liquids.

SUBSTITUTE SHEET

Claims

1- A liquid cooling method in which the liquid (5) to be cooled flows inside a liquid cooler (9), said cooler being connected to a liquid supply circuit including one or more conduit means (10) through which said iiquid (5) flows, said conduit means passing through and being in contact with a cold medium (R) in said cooler (9), said cooler (9) containing any number of said conduit means, including one, said cooler and/or said conduit means (10) being straight or smoothly curved, said cooler (9) also comprising tubesheet(s) (7 or 7a and 7'a) being characterized by the fact that it is capable of cooling said iiquid (5) down to very low temperatures, including its phase-equilibrium temperature without inducing freezing of said iiquid (5) in said conduit means (10) said capability being obtained by one, two or all of the following three ways, the first of the said ways being preventing the contact of the said liquid (5) with a cold surface in regions (4a, 14b) where the said liquid is stagnant or has a low velocity as compared to the average liquid velocity inside the said conduit means (10) passing through said cooler (9); the second of the said ways being the elimination of all the said stagnant regions or the said low velocity regions near said cold surfaces; the third of the said ways being the elimination of the cold surfaces themselves.

2- A method according to claim 1 in which said cooler (9) comprises a cooler head (4) at the inlet end, said head (4) acting as flow distributor (4a) for said liquid (5), contact of the said liquid (5) with a cold surface, within said cooler head (4) being prevented by the presence of a double tubesheet (7a, 7b), said tubesheets being far enough from one another to form a thermal barrier between the said liquid (5) and the said cold medium (R), the space (13) between said tubesheets being filled with any type of insulating ma¬ terial, including air, said space (13) being closed, partially open or fully open to atmos¬ phere.

3- A method according to claim 1 in which said cooler (9) comprises a cooler head (14) at the oulet end, said head acting as flow receiver (14b) for said liquid (5), contact of the said liquid with a cold surface in said cooler head (14) being prevented by the presence of a double tubesheet (7'a, 7'b), said tubesheets being far enough from one another to form a thermal barrier between the said liquid (5) and the said cold medium (R), the space (13') between said tubesheets being filled with any type of insulating material, including air, said space (13') also being closed, partially closed or fully open to atmos¬ phere. 4- A method according to claim 2 or 3 in which said cold surfaces (7a, 7'a) separating cold medium R from liquid (5) in head (4) are actively heated by any convenient means, instead of being passively warmed up by a thermal barrier (13, 13').

5- A method according to claim 4 in which said cold surfaces (7a, 7'a) are actively hea¬ ted by a warm fluid circulating within space (13 and or 13'), said warm fluid being any convenient fluid, including hot refrigerant from HSHE, said hot refrigerant thus being subcooled by said circulation.

6- A method according to claim 1 or 2 or 3 in which said cooler (9) is converted to a shell-and- multi-double-tube cooler featuring true counterflow heat exchange between a liquid cooling medium (R) and said fluid (5), said cooler (9) comprising a set of inner tubesheets (7c, 7'c) and also featuring around each conduit means (10) a larger conduit means (30), the space between said inner and outer conduit means becoming the conduit means through which said cold medium (R) flows and receives heat from fluid (5) being cooled, the space (41) between new tubesheets (7c) and neighbouring tubesheet (7b) ac¬ ting as a distributor for said liquid cooling medium (R) after its entrance (8) into said cooler (9), the space (41') between new inner tubesheet (7'c) and neighbouring tubesheet (7'b) acting as a receiver for said cooling medium (R), before its departure (11) from said cooler (9).

7- A method according to claim 6 in which the outer conduit means (30) are eliminated as well as the inner tubesheets (7c, 7'c), the guiding effect provided by said outer conduit means (30) being simply obtained by the closeness of the fluid tubes (10), the cross¬ wise evenness of the refrigerant flow in said cooler being obtained by the presence of an optional modified tubesheet (37'), said modified tubesheet being made of any convenient material, including a porous material, capable of offering a small pressure drop to the said refrigerant flow, said cooler then acting as a true counter-current heat exchanger, said pressure drop offered by said modified tubesheet possibly being part of total pres¬ sure drop between hot side and cold side of a heat pump when said cooler (9) is part of a heat pumping circuit, said part representing any percentage of said total pressure drop.

8- A method according to claim 1 in which freezing of the said liquid in said conduit means (10) is further prevented by ensuring that no region of large scale turbulence or detached flow is present at or near the inlet of said conduit means and all along the said conduit means (10), elimination of said turbulence and detached flow regions being obtai¬ ned by any method including the presence of a faired and smooth entrance (3a) to said conduit means (10).

UBSTITUTE SHEET 9- A method according to claim 1 in which the individual fluid conduit means (10) at the inlet end of said cooler (9) are extended past tubesheet (7a), length and material used for making said conduit means extensions (35) being chosen according to application, said extensions being capable of eliminating low liquid velocity regions near cold surfaces.

10- A method according to claim 6 in which the individual fluid conduit means (10) at the inlet end of said cooler (9) are extended past tubesheet (7a), length and material used for making said conduit means extensions (35) being chosen according to application, said extensions being capable of eliminating low liquid velocity regions near cold surfaces.

11- A method according to claim 7 in which the individual fluid conduit means (10) at the inlet end of said cooler (9) are extended past tubesheet (7a), length and material used for making said conduit means extensions (35) being chosen according to application, said extensions being capable of eliminating low liquid velocity regions near cold surfaces.

12- A method according to claim 9, 10, or 11 in which said fluid (5) about to be cooled is being fed individually to each of the inlet fluid conduit means extensions (35) by a distri¬ butor located at some distance upstream of said cooler (9).

13- A method according to claim 1 in which individual fluid conduit means (10) are ex¬ tended (20) past an exterior tubesheet (7'a) at the outlet end of said cooler, in such a way that the cooled fluid (23) can, if desired, be fed directly to a location where it is needed (e.g. a reservoir (26) or a large body of water) by each conduit means extension (20) individually, said cooler (9) then being capable of generating and handling a flow of very cold liquid, down to and below the phase-equilibrium temperature, said cooler (9) then being characterized by the basic fact that the flow of liquid between inlet and outlet is everywhere smooth and never subjected to any major perturbation.

14- A method according to claim 6 in which individual fluid conduit means (10) are ex¬ tended (20) past an exterior tubesheet (7'a) at the outlet end of said cooler, in such a way that the cooled fluid (23) can, if desired, be fed directly to a reservoir (26) or a large body of water by each conduit means extension (20) individually, said cooler (9) then being capable of generating and handling a flow of very cold liquid, down to and be¬ low the phase-equilibrium temperature, said cooler (9) then being characterized by the basic fact that the flow of liquid between inlet and outlet is everywhere smooth and never subjected to any perturbation.

15- A method according to claim 7 in which individual fluid conduit means (10) are ex-

SUBSTITUTE SHEET tended (20) past an exterior tubesheet (7'a) at the outlet end of said cooler, in such a way that the cooled fluid (23) can, if desired,- be fed directly to a reservoir (26) or a large body of water (or anywhere it is needed) by each conduit means extension (20) in¬ dividually, said cooler (9) then being capable of generating and handling a flow of very cold liquid, down to and below the phase-equilibrium temperature, said cooler (9) then being characterized by the basic fact that the flow of liquid between inlet and outlet (5 to 23) is everywhere smooth and never subjected to any major perturbation.

16- A method according to claim 13, 14, or 15 in which individual fluid conduit means extensions (20) are further extended (21) in such a way that the cooled fluid (23) can, if desired, be fed directly to a reservoir (26) or a large body of water (or anywhere it is needed) by each conduit means extension (21) individually, said extension (21) being as long as necessary, said extension (21) being made out of any convenient material, in¬ cluding plastic; Connection (51) between said extension (21) and said extended fluid tube (20) being of any type, e.g. made using soft-plastic unions, possibly press-fitted in place; said cooler (9) then being capable of generating, handling and delivering to any distance, a flow of very cold liquid, down to and below the phase-equilibrium temperature.

17- A method according to any of the claims 9 to 11 and/or 13 to 15 in which the tu¬ besheets) (7b, 7'b) at the cooler inlet and/or outlet ends is (are) eliminated, having be¬ come superfluous because of the presence of the extensions (35, 20) and/or the absence of low fluid velocity region(s) near a cold surface.

18- A method according to any of the claims 9 to 11 and 13 to 15 in which only one half of the conduit means extensions (35) at the inlet end are fed individually with fluid (5), outlet end of said half of said conduit means extensions (20) also being individually joined to the other half at the same cooler end by smoothly curved portions of conduit means (34), said portions (U-bends) being made of any material, including plastic or metal; dis¬ tance between two conduit-means extensions (20) having any value, including very small ones, thus giving the possibility of very sharp turning radiuses of the U-bends; the fluid (5) being cooled thus being capable of going twice through said cooler (9), said cooler thus becoming a double-tubeside-pass cooler capable of generating and handling a flow of very cold liquid, down to and below the phase-equilibrium temperature

19- A method according to claim 18 in which the individual connections (U-bends) (34) between conduit means extensions (20, 35) are arranged in such way that the cooler be¬ comes a multi-tubeside-pass cooler, the number of times the fluid goes through the cooler (9) being any number. 20- A method according to claim 19 in which the flow of cold medium (R) in said cooler (9) and the flow of liquid (5) being cooled are arranged in such a way that said cooler be¬ comes a multi-shellside-pass and multi-tubeside-pass cooler.

21- A method according to any of the claims 9 to 11 and 13 to 15 in which a special head is installed between the outer tubesheet (7'a) at the outlet end of said cooler (9) and a main conduit means (33), said head acting as a manifold, said manifold being characteri¬ zed by the fact that a smooth path is offered to the flow of cooled iiquid coming out from each individual conduit means (10), said smooth path being obtained in any convenient way, thus forming a special outlet manifold capable of handling supercooled liquids, said convenient way including the installation of straight or smoothly curved conduit means extensions (31), said extensions being made of any material including metal, the outlet end of said conduit means extensions (31 ) being brought close together and introduced into a larger conduit means (32), thus being capable of smoothly discharging said cooled liquid into said main conduit means (33).

22- A method of handling supercooled liquids generated by a cooler in which outlet ends (22) of individual conduit means extensions (20, 21) or outlet ends (36) of said main conduit means (33), from which the supercooled liquid (23) flows, are equipped in such a way as to prevent the formation of ice crystals at said outlet ends (22, 36), said for¬ mation provoking a rapid blockage of said extensions (20, 21) or said main (33) by in¬ ducing a phase change of part of said supercooled water (23), formation of said ice crys¬ tals caused by said outlet ends (22, 36) being colder than ambiance, said ambiance being any liquid, including water, or any humid atmosphere, said atmosphere being filled with any gas or mixture of gas, including air.

23- A method according to claim 22 in which said blockage of said outlet ends (22, 36) of said cooler extensions (20, 21) or of said main conduit means (33) from which super¬ cooled fluid (23) flows, are heated in such a way as to prevent the formation of ice crys¬ tals at said outlet ends (22, 36), said heating of the said outlet ends being done with heat coming from any source, and transfered to said outlet ends using any of the basic heat transfer methods, namely conduction, convection or radiation or any combination of said methods thereof.

24- A method according to claim 23 in which said heating of said outlet ends (22, 36) of said conduit means (33) transporting supercooled liquid (23) is carried out by a flow of warm liquid (e.g. water warmed up by HSHE of heat pump), said liquid circulating inside small conduit means (36') installed at the tip of said outlet end (22, 36), said heating

SUB preventing the formation of ice crystals on said tip and eventual blockage of said conduit means (33).

25- A method according to claim 1, 2, 3 or 7 in which said cooler (9) has heads (4, 14 ) and double or triple tubesheets (7a, 7b, 7c) at each end, said heads being modified in such a way that the cooler becomes a double-tubeside-pass cooler (9), said head (4) having two openings, one being the fluid inlet (5') and the other, the fluid outlet (6'), said head (4) also being divided in two parts (4a, 4b), one acting as a fluid flow distributor (4a), the other part (4b) acting as a fluid flow receiver, other head (14) of said cooler (9) also acting as a flow receiver (14b) and a flow distributor (14a), said other head (14) ha¬ ving no opening and acting as a 180° elbow, said cooler (9) then being capable of cooling said iiquid (5) down to its phase equilibrium temperature.

26- A method according to claim 6 in which said cooler (9) has heads (4, 14 ) and double or triple tubesheets (7a, 7b, 7c) at each end, said heads being modified in such a way that the cooler becomes a double-tubeside-pass cooler (9), said head (4) having two openings, one being the fluid inlet (5') and the other, the fluid outlet (6'), said head (4) also being divided in two parts (4a, 4b), one acting as a fluid flow distributor (4a), the other part (4b) acting as a fluid flow receiver, other head (14) of said cooler (9) also acting as a flow receiver (14b) and a flow distributor (14a), said other head (14) having no opening and acting as a 180° elbow, said cooler (9) then being capable of cooling said liquid (5) down to its phase equilibrium temperature.

27- A method according to claim 25 in which said head (14) of said cooler (9) also com¬ prises a baffle (1) acting as a flow separator in such a way that incoming flow (2) coming from fluid conduit means outlets (2a) does not disturb the flow (3) into the fluid conduit means inlets (3a), said baffle being of a length sufficient to prevent such flow distur¬ bances, said cooler then being capable of cooling said liquid (5) down to its phase equili¬ brium temperature.

28- A method according to claim 26 in which said head (14) of said cooler (9) also com¬ prises a baffle (1) acting as a flow separator in such a way that incoming flow (2) coming from fluid conduit means outlets (2a) does not disturb the flow (3) into the fluid conduit means inlets (3a), said baffle being of a length sufficient to prevent such flow distur¬ bances, said cooler then being capable of cooling said liquid (5) down to its phase equili¬ brium temperature. 29- A method according to claim 25 in which said cooler heads (4), (14) of said cooler (9) are modified in such a way that said cooler (9) has several tubeside passes, the number of times the fluid (5) passes through the cooler (9) being any desired number.

30- A method according to claim 26 in which said cooler heads (4), (14) of said cooler (9) are modified in such a way that said cooler (9) has several tubeside passes, the number of times the fluid (5) passes through the cooler (9) being any desired number.

31- A method according to claim 1 , 2, 3 or 7 in which the thermal barrier is instead provided by the presence at one or both ends of the said cooler (9) of a rigid or semi¬ rigid piece (16) of insulating material, said piece being sufficiently thick to provide said thermal barrier between the said cold medium R and the said iiquid, said pieces being ins¬ talled on the cold medium side or the fluid side of the tubesheets, or both sides, said pieces of insulation also being installed with enough care to prevent any leakage of cold medium (R), or liquid (5), towards the tubesheets (7a, 7'a).

32- A method according to claim 6 in which the thermal barrier is instead provided by the presence at one or both ends of the said cooler (9) of a rigid or semi-rigid piece (16) of insulating material, said piece being sufficiently thick to provide said thermal barrier between the said cold medium R and the said liquid, said pieces being installed on the cold medium side or the fluid side of the tubesheets, or both sides, said pieces of insulation also being installed with enough care to prevent any leakage of cold medium (R), or liquid (5), towards the tubesheets (7a, 7'a).

33- A method according to claim 1 in which said cooler (9) is the CSHE of a heat pump, said CSHE being capable of extracting energy from a flow of iiquid (5) at any tempera¬ ture, including the so-called "freezing point", said liquid (5) being of any type, including pure, saline or polluted water, said liquid coming from any source including a mine shaft or a large body of water like a lake or the ocean, said liquid exiting from said cooler (9) being at a lower temperature and being disposed of in any convenient way, including sen¬ ding said liquid back to its source, said energy, after being transfered to the HSHE of said heat pump then being used as a source of heat, said heat being used for any purpose, including space heating, snow melting, mine heating, etc.

34- A method according to claim 1 in which said cooler (9) is the CSHE of a liquid chiller, said chiller being capable of chilling any liquid (5), said liquid exiting (6, 23) from said cooler being at any temperature including supercooling temperatures, said liquid (5) being of any type, said chilled liquid (6, 23) being used for any purpose. 35- A method of cooling liquids comprising a cooler (9), said cooler (9) being the CSHE of a heat pump, said heat pump being used for heating or cooling purposes, said heat pump being of the VCHP type, the refrigerant circulating in said heat pump circuit being of the non-azeotropic mixture type, said heat pump being characterized by the presence in the cycle of a reformer LPR, said reformer being a reservoir capable of containing said re¬ frigerant in liquid and vapor phases, said vapor from the top of said reformer (LPR) being entrained, compressed, condensed, and expanded in the hot side portion of the said circuit, said liquid from the bottom part of said reformer (LPR) being entrained, circu¬ lated and evaporated in the cold side portion of said heat pump circuit, said circulation in said cold side being produced by a refrigerant pump P , said pump P being capable of pro¬ ducing an overfeeding of said cooler EV, the overfeed rate having any value including one, said pump P having a fixed or a variable speed, said cycle featuring said reformer (LPR) being an improvement over conventional cycles in that the composition of said re¬ frigerant vapor circulating in said hot side is rich in the more volatile, higher density, component(s) of said mixture while the composition of said refrigerant liquid, circulating in said cold side, is rich in the less volatile, higher latent heat, component(s) of said mix¬ ture, said modified cycle thus providing at the same time higher system efficiency and larger system capacity.

36- A method according to claim 35 in which said condensation is performed using an overfed condensing system, said system comprising a high pressure reformer HPR, a blower B and a condenser CR, said blower B being capable of overfeeding said condenser CR in such a way that refrigerant (79) out of said condenser CR is part liquid and part vapor, said liquid accumulating at the bottom of HPR, said vapor on top of said liquid being recirculated by blower B into said condenser CR, said liquid being sent to low- pressure reformer LPR, via expansion device FL (and optional subcooler S), said vapor on top of HPR also coming from compressor C, said system being characterized by the fact that it is capable of partially separating the volatile and non-volatile (dense and light) component(s) of non-azeotropic refrigerant mixture, volatile-rich vapor going back into high-pressure loop L3_f which results in a better HTC in condenser CR, while volatile- poor liquid goes to reformer LPR and to low pressure loop L-j , which results in a higher efficiency for the system.

37- A method according to claim 36, in which said condensation is performed using an overfed condensing system, said system comprising a high pressure reservoir HPR, a blower B and a condenser CR, said blower B being capable of overfeeding said condenser CR in such a way that refrigerant (79) out of said condenser CR is part liquid and part vapor, said liquid accumulating at the bottom of HPR, said liquid accumulating at the bot- torn of HPR, said vapor on top of said liquid being recirculated by blower B into said con¬ denser CR, said liquid being sent to low-pressure reservoir LPR, via expansion device FL (and optional subcooler S), said vapor on top of HPR also coming from compressor C, said system using instead a pure refrigerant or an azeotropic mixture of refrigerant, said re¬ servoirs LPR and HPR then acting as simple accumulators and not as reformers, such a full-overfeed system (evaporator plus condenser overfeed) being characterized mainly by its higher COP and its smaller size.

38- A method according to claim 36 or 37, in which said condensation is performed using an overfed condensing system, said system comprising a high pressure reservoir HPR, a blower B and a condenser CR, said blower B being capable of overfeeding said condenser CR , said condenser overfeed system being used in a system having a conven¬ tional (non-overfed) evaporator.

39- A method according to claim 35 or 36 in which said cycle, comprising a condenser divided in two or more parts ( CR-| , CR2), is further modified by the addition of an ex¬ traction circuit comprising reservoirs ER and SR-_] ; said circuit being capable of storing, in receiver ER, the liquid refrigerant mixture extracted from CR-) and accumulated in SR-j , said liquid mixture being rich in light, non-volatile, component(s), capacity of said cycle being increased by said storage in ER; said circuit also being capable of condensing and storing in receiver ER the refrigerant vapor extracted from the top of receiver HPR, said vapor being rich in dense, volatile, component(s), capacity of said cycle being de¬ creased when said mixture rich in volatile component(s) is stored in ER; said capacity being gradually restored when said mixture rich in dense component(s) in ER is gradually reintroduced into the circuit through valve V-| .

40- A method according to claim 35 or 36 in which said cycle is modified by the addition of a liquid (5)-to-refrigerant (75) heat exchanger (S) acting as a subcooler for the con¬ densed liquid coming from condenser or high pressure receiver (HPR); said subcooler S also being capable of modifying the composition of the said refrigerant vapor going to the said hot side circuit and modifying the composition of the said iiquid going to the said cooler EV said subcooler (S) providing control over temperature glide of said refrigerant (R) and over system capacity.

41- A method according to claim 35 or 36 in which said improved cycle is modified by the addition of a continuous extraction circuit comprising refrigerant conduit means, re¬ servoir SR2 and expansion device CP, said circuit capable of sending directly to reformer

LPR, via expansion device CP, the already condensed refrigerant accumulating at the

SUBSTIT bottom of reservoir SR2, located between CR-j and CR2, said extraction improving sys¬ tem capacity and performance and modifying • refrigerant temperature glide along the condenser CR.

42- A method according to claim in which said cycle is modified by the addition of a continuous extraction circuit comprising refrigerant conduit means, reservoir ER3, said circuit capable of sending directly to reformer LPR, the already evaporated refrigerant accumulating at the top of reservoir ER3, located between EV-j and EV2, said extraction improving system performance and modifying refrigerant temperature glide along cooler EV.

43- A method according to claim 42 in which said cooler EV comprises three or more parts, EV-) to EVj, instead of two, as well as two or more extraction reservoirs ER ins¬ tead of one, said continuous extraction circuit being capable of sending directly to re¬ former LPR, the already evaporated refrigerant accumulating at the top of said reser¬ voirs ER, said extraction system thus being more efficient at improving system perfor¬ mance.

44- A method according to claim 42 in which said cooler EV is modified in such a way as to offer total and continuous extraction of the already evaporated refrigerant, the refri¬ gerant vapor at all points along said cooler being extracted from said cooler as soon as it is vaporized and sent to LPR, said extraction system thus being more efficient at impro¬ ving system performance.

45- A method according to claim 41 in which said condenser CR comprises three or more parts, CR-j to CRj, instead of two, as well as two or more extraction reservoirs

SR instead of one, said continuous extraction circuit being capable of sending directly to reformer LPR, via expansion device CP, the already condensed refrigerant accumulating at the bottom of said reservoirs CR, said extraction system thus being more efficient at improving system capacity.

46- A method according to claim 41 in which said condenser CR is modified in such a way as to offer total and continuous extraction of the already condensed refrigerant, said refrigerant being extracted from said condenser as soon as it is condensed, said extrac¬ tion system thus being more efficient at improving system performance and modifying refrigerant temperature glide along condenser CR.

47- A method of making artificial snow in which a continuous flow of supercooled liquid water (93), is changed to a flow of supercooled droplets (98) using any method, each of said supercooled droplets (98), because of the perturbation, then rapidly becoming dro¬ plets containing a mixture of dendritic ice and water, said ice part in said droplets (98) then growing in ambiant cold air until said droplets become 100% ice crystals (i.e. snowflakes); or said droplets (98) possibly used as seeders for larger cold or supercoo¬ led water droplets which will then grow into large snowflakes.

48- A method according to claim 47 in which said change from continuous flow (93) to supercooled droplet flow (98) is simply done with the action of turbulent viscous forces between a high speed supercooled water jet and static ambiant air, action of said turbu¬ lence also being capable of initiating crystallization within each droplet (98), said dro¬ plets then containing a mixture of dendritic ice and water; ice portion in said droplets (98) then increasing due to contact with ambiant cold air (heat and mass transfer) until said droplets become snowflakes.

49- A method according to claim 47 in which the change from continuous flow (93) to supercooled droplet flow (98) is done with an atomizer, said atomizer using compressed air (94), said compressed air generating a high speed jet of air (97) with the help of a nozzle (96); said jet (97) being subsonic, sonic or supersonic; said jet of air (97) also being at a very low temperature; said jet of air (97) mixing with said jet of water (93); said mixing having the effect of generating a very high turbulence, which helps said su¬ percooled water jet (93) in becoming a flow of supercooled droplets (98); said high tur¬ bulence also having the effect of initiating crystallization inside said droplets (98); said mixing with cold air also having the effect of accelerating said crystallization inside said droplets (98); angle between said water jet (93) and said air jet having any value; said jets (93), (97) having any shape, including the circular and annular shapes; said jets (93), (97) having any of the possible positions relative to one another, including the con¬ centric position; ice portion in said droplets (98) then increasing due to contact with ambiant cold air (heat and mass transfer) until said droplets become snowflakes.

50- A method according to claim 47, 48 or 49, in which said droplets of supercooled water (98) are first sent into a large flow of artificially cooled air before being sent into ambiant air, said air cooling being performed using any method including going through an air cooler of the heat-pump type, this system permitting the fabrication of snow when ambiant wet-bulb temperatures are at or slightly above the "freezing point".

51- A method according to claim 47, 48 or 49, in which the flow of supercooled water (90) is obtained through a heat exchange between water and cold ambiant air, said heat

SUBSTITUTE SHEET exchange being obtained using an air-to-water heat exchanger built according to the gene¬ ral principles regarding the generation and handling of supercooled liquid explained above.

52- A method of generating ice in which cooler (9) is the CSHE of a liquid chiller, said chiller being capable of cooling any liquid, said liquid (23) being cooled down to super¬ cooling temperatures, said exiting supercooled liquid (23) being made to partially change phase, said phase change providing a mixture of solid and cold liquid at the phase-equili¬ brium temperature, said change of phase being provoked by any convenient method, in¬ cluding seeding with already formed crystals and/or giving a mechanical or a thermal shock to flow of said supercooled liquid (23), said mechanical shock being of any kind, including sonic or ultrasonic, or simply an abrupt change of direction, said mixture, and/or said solid, and/or said cold liquid being used for any purpose.

53- A method according claim (52) in which the operating conditions of the chiller is mo¬ dulated in order to modify the type of solid material generated during said phase change of said supercooled liquid, said conditions being mainly the temperature of supercooled liquid (23), a slight supercooling (e.g. at temperatures between 0°C and about -0,5°C for pure water) favouring the generation of hard crystals; a "deep" supercooling (e.g. at temperatures below about -1,2°C for pure water) tending to generate fine crystals (24); a medium supercooling (e.g. at temperatures between about -0,6°C and about -1°C for pure water) tending to generate medium size crystals.

54- A method according to claim 53 in which a slightly supercooled liquid flow (23), is used to build a block of solid material, said block slowly growing due to the fact that part of said supercooled liquid flow (23) changes phase when its hits already solidified mate¬ rial, initial crystallization having been obtained by any convenient method, including a mechanical shock, said blocks having any size, being used for any purpose and having any shape.

55- A method according to claim 54 in which large blocks of hard ice are produced, said blocks being built up onto any supporting structure including a metallic plate, said blocks being made by sending slightly supercooled water, preferably as jets at relatively low velocity, onto said structure, said liquid partially changing phase upon contact with al¬ ready formed ice, initial crystallization having been obtained using any convenient method including a mechanical shock, said blocks being used for any purpose and having any shape, including artistic forms.

56- A method according to claim 52, 53, 54 or 55 in which said crystals or solid blocks of material, when cleaned, e.g. by washing, become a solid which is purer than the liquid from which it was made, said method being used for any purpose including the puri¬ fication of water and the concentration of solutions.

57- A method of removing a slurry (24') of crystals (24) and liquid (25) from within a reservoir (26) and bringing said slurry (24'), via conduit means (28), towards another location where said slurry (24) is used or disposed of, said method using a Coanda-effect wall-jet ejector (42), said ejector (42) being characterized by the fact that said wall jet (46), has enough kinetic energy to be capable, because of the Coanda effect, of following bellmouth-shaped entrance (27) and penetrate into said conduit means (28), its turbulent eddies thus being capable of breaking agglomerations of solid particles near said entrance (27), said wall jet being also capable of entraining said slurry (24') into said conduit means (28), thus moving said slurry (24') to said other location.

58- A method of breaking up crystal agglomerations inside a reservoir (26) containing a liquid (25) and said crystals (24), said breaking up being performed for any reason, in¬ cluding improving entrainment of said crystals (24) into an outlet (42) towards slurry conduit means (28), said method being characterized by the installation, partly inside said outlet (42) of a "self-propelled" rotor, said rotor being made in such a way that it can be partly located inside conduit means (28) and partly inside reservoir (26), the part of said rotor located at least partly inside said conduit means (28) acting as a turbine capable of driving any device, said device being the part of said rotor protruding inside said reservoir (26), the purpose of said device being mainly the breaking-up of ice- crystal agglomerations and also the entrainment of crystals towards said outlet (42); said turbine being designed approximately like one of the well known types (e.g. axial type); device being made approximately like a propeller, an axial flow pump or any component that can at the same time break-up said agglomerations and entrain said crystals; said method using relatively little external energy.

59- A method of breaking up crystal agglomerations inside a reservoir (26) containing a liquid (25) and said crystals (24), said breaking up being performed for any reason, in¬ cluding improving entrainment of said crystals (24) into an outlet (42) towards slurry conduit means (28), said breaking up being performed by the action of several liquid jets (49), said liquid jets (49) exiting from conduit means (48) and originating from any convenient source including the liquid (25) at the bottom of said reservoir (26), said se¬ veral jets generating a vortex inside said reservoir (26), axis of rotation of said vortex passing through (or close to) said outlet (42), said vortex being generated because axes of said jets (49) are not parallel with one another and do not meet at a point, path of

BSTITUTE SHEET every individual jet (49) crossing said axis of said vortex at approximately identical angles smaller than 90°, preferably of the order of 30°, said crossings being made at a small and preferably identical distance from said axis of said vortex, said crossings all being approximately in the same plane, said plane being approximately perpendicular to said axis of said vortex, said jets (49) creating entrainment of said agglomerations towards said outlet (42), said jets (49) also creating rotation of said agglomerations, said jets (49) then acting as so many jet saws capable of cutting through said agglome¬ rations and moving broken up pieces towards said outlet (42).

60- A method of breaking up crystal agglomerations inside a reservoir (26) containing a liquid (25) and said crystals (24), said breaking up being performed for any reason, in¬ cluding improving entrainment of said crystals (24) into an outlet (42) towards slurry conduit means (28), said breaking up being performed by the action of a giant "egg-bea¬ ter" type of device, said device being installed close to said outlet (42) in such a way that the resulting slurry (24') (composed of the liquid (25) and the broken up agglomera¬ tions of said crystals (24)) is directed towards said outlet (42).

61- A method of joining flows of supercooled liquid from two or more individual conduit means (10), in order to create a larger flow of supercooled fluid inside another larger conduit means (33), by making sure that said flows of supercooled liquid between said individual conduit means (10) and said larger conduit means (33) does not have to endure any important mechanical or thermal perturbation, said perturbations being of any type, including abrupt changes in velocity.

62- A method according to claim 61 in which said two or more conduit means (10) are extended past the tubesheet (7'a) which are fitted with other extensions (31), the free end of said other extensions (31) being brought close together and positioned in such a way that the flows exiting from all of said extensions (31) be essentially parrallel, ends of said extensions (31) being preferably close to one another, possibly pressed one against the other, side-by-side, and introduced into said other larger conduit means (33) or into a special fitting (32) attached to said other larger conduit means (33).

63- A method of cooling liquids (80) down to or below their phase equilibrium tempera¬ ture using a hybrid multiple-cascade heat pumping system comprising preferably 3 ab¬ sorption heat pumps (AHP-j to AHP3), said AHPs using any working pair, including LiBr- H2O, said system also using preferably 2 vapor-compression heat pumps (VCHP2 and VCHP3), said AHPs being normally unable to attain the low temperature necessary for providing desired final liquid states, said AHPs being helped here by VCHPs installed in cascade fashion with said AHPs; warm liquid (80) coming from load first being cooled by AHP-J ; then chilled liquid (81) entering VCHP2 where it is cooled a few more degrees, said VCHP2 being installed in series with AHP-j ; said liquid (82) finally entering VCHP3, installed in series with VCHP2; said liquid, now cooled, coming out (83) at final desired low temperature and going back to load; AHP2, installed in cascade with VCHP2, being used as a source of cooling water (CW2) for the condenser of VCHP2; AHP3, installed in cascade with VCHP3, also being used as a source of cooling water (CW3) for the con¬ denser of VCHP3; compressors of said VCHPs being driven by any type of motor, inclu¬ ding combustion engines; this method of generating deeply cooled or supercooled liquids being characterized by the fact that the system, while remaining essentially an absorp¬ tion system (most of the outside driving power (Q-j to Q3) still coming in as heat energy while only a small percentage has to come in as mechanical energy (W and W3)), permits the use, as components, of AHPs which are unable by themselves of deeply cooling liquids.

64- A method according to claim 63 in which VCHP2 and VCHP3 do not have their own condenser, the condensation of the refrigerant circulating in VCHP2 being carried out di¬ rectly in the evaporator of AHP2, and the condensation of the refrigerant in VCHP3 being carried out in the evaporator of AHP3, such an arrangement improving appreciably the overall COP and saving the expense and space of two VCHP condensers.

65- A method according to claim 63 in which only two AHPs are used, AHP-j and AHP2, and only one VCHP is used, AHP-j providing part of the liquid cooling, the other part of said cooling being provided by the CSHE of said VCHP, said VCHP also having a HSHE, said HSHE being cooled by cooling water, said cooling water being provided by AHP2.

66- A method according to claim 63 in which only one AHP and one VCHP are used, the CSHE(s) of said VCHP being capable of cooling the liquid exiting (81) from AHP down to low temperatures (83), the capacity of AHP being large enough to provide chilled liquid (81) both for HSHE of VCHP (81") and for CSHE(s) (81") of VCHP; said low temperature liquid (83) being sent to load and coming out as warmed iiquid (85); the cooling liquid coming out of said HSHE as a warm liquid (84); warm liquids flows (84) and (85) being joined into a larger flow (80) of warm liquid which is sent back into the CSHE of the AHP for chilling purposes.

67- A method according to claim 1 in which individual fluid conduit means (10) are ex¬ tended (20) past an exterior tubesheet (7'a) at the outlet end of said cooler, thus protru¬ ding from said tubesheet (7'a) into a cooler head (14b) in such a way that said cooler (9),

E SHEET capable of generating cold liquids down to their solid-liquid equilibrium temperature, can easily be converted, when desired, into a cooler capable of generating supercooled li¬ quids.

68- A method according to claim 6 in which individual fluid conduit means (10) are ex¬ tended (20) past an exterior tubesheet (7'a) at the outlet end of said cooler, thus protru¬ ding from said tubesheet (7'a) into a cooler head (14b) in such a way that said cooler (9), capable of generating cold liquids down to their solid-liquid equilibrium temperature, can easily be converted, when desired, into a cooler capable of generating supercooled li¬ quids.

69- A method of generating artificial snow independently of weather conditions in which a continuous flow of supercooled liquid water (23) at about -0,8°C is changed into a mix¬ ture of ice crystals (24) and water (25) by any convenient method, said ice crystals being separated from mixture and accumulated by any convenient method, said crystals having the look and feel of natural snow.

70- A method according to claim 69 in which artificial snow is produced by generating said mixture of ice crystals (24) and liquid water (25) in a reservoir (26), recirculating said water (25) from said reservoir (26) into cooler (9), operating the supercooling chiller for a long period of time, until there is practically no liquid water (25) left in said reservoir (26), said crystals (24) remaining in said reservoir (26) having the look and feel of natural snow.

71- A method of generating very fluid ice slurries, ice-crystals in said slurry being ex¬ tremely fine, in which a continuous flow of "deeply" supercooled liquid water (23) (i.e. said water being at temperatures of about -1 ,6°C, or lower) is changed into a mixture of ice crystals (24) and water (25) by any convenient method, said ice crystals being ac¬ cumulated (e.g. in a reservoir (26)) until the desired percent solid/liquid ratio is achie¬ ved, said slurry then being used for any purpose, including the cooling of buildings.

72- A method of storing a supercooled liquid in reservoir (26) in which said supercooled iiquid is simply sent to reservoir (26) via tubes or pipes (20, 21 or 36), outlet of said tubes or pipes being above or below liquid level of said reservoir (26), always making sure that crystallization is not induced by mechanical or thermal perturbations.

73- A method of storing a supercooled liquid in reservoir (26) in which said supercooled liquid is simply sent to reservoir (26) via tubes or pipes (20, 21 or 36), outlet of said

BSTITUTE SHEET tubes or pipes being directed in such a way that supercooled-liquid jets (23) are not sub¬ jected to large mechanical perturbations, e.g. hitting internal side walls of said reservoir (26) at low speed and/or with an angle much smaller than 90°, preferably below 30°.

74- A method according to claim 69 or 70 in which different qualities of snow are pro¬ duced by varying the temperature of the outlet flow of supercooled liquid water (23), lower temperatures (e.g. -0,6°C) providing larger and drier crystals, higher tempera¬ tures (e.g. -1°C) providing much finer crystals; said crystals , in both cases, looking and feeling a little less natural than when produced from supercooled water at -0,8°C.

75- A method of solid/liquid separation whereby slightly supercooled liquid (25) inside reservoir (26) is forced through a porous membrane (52) of any type (e.g. a perforated- metal plate, a piece of tissue, etc.), ice then starting to build up all over said membrane (52), said membrane (52) then acting as a crystallizer.

76- A method according to claim 75 in which said ice building up over said membrane (52) being relatively hard and porous, is easily harvested and washed clean, the pheno¬ menon becoming the basis for a simple freeze-concentration system, said system being used for any purpose including purifying water or concentrating solutions.

77- A method of conditioning water in fish hatcheries and other similar applications in which heating (or cooling, in summer) is mostly performed passively in a heat exchanger HX and also partly by the HSHE (or CSHE, in summer) of a heat pump, said heat pump being of any type, including the VCHP type; in winter, cold fresh water (100) at 0°C (or more) being circulated (101), e.g. by a pump (P1), into said heat exchanger HX where it picks up energy, said warmed water (103) then going through HSHE of said heat pump where it picks up more energy and from which it exits (104) at the proper temperature and enters fish reservoir (105); overflowing warm gray water (106) then flowing out of fish reservoir (105), being circulated (107), e.g. by a pump (P2), through said HX where it loses some of its energy to incoming fresh water (102); colder gray water (108) out of said HX then going through CSHE of said heat pump; coming out (109) of said CSHE and then being disposed of; said gray water then being at about the same temperature (0°C or more) as when it first came in (101) as fresh water; with system in normal operating conditions in winter, said CSHE thus possibly having to cool water down to the "freezing point" of water; with system in start-up conditions, said CSHE then possibly having to supercool water, said CSHE thus being designed according to invention; positions of said CSHE and HSHE in water circuit being inversed during summertime, in order to be capable of cooling efficiently warm fresh water (100) before its entrance (104) into said reser-

SUBSTITUTE SHEET voir (105).

78- A method according to claim 16 in which individual liquid conduit means extensions (21) are transporting supercooled liquid to a reservoir, said supercooled liquid (23) being used to manufacture ice crystals (24); ends (22) of said extensions (21) being positioned above said reservoir (26) and jets of said supercooled liquid (23) being directed in such a way that ice generation is distributed uniformly across the surface of the reservoir (26).

SUBS