WO2008122714A2

WO2008122714A2 - Improvements in gas/sol or liquid/sol exchangers

Info

Publication number: WO2008122714A2
Application number: PCT/FR2008/000233
Authority: WO
Inventors: Denis Consigny
Original assignee: Climatisation Par Puits Canadiens
Priority date: 2007-03-07
Filing date: 2008-02-21
Publication date: 2008-10-16
Also published as: WO2008122714A3; FR2913487A1; FR2913487B1; WO2008122714A9

Abstract

The invention can be used for heating and air-conditioning equipments in living premises. The invention more particularly relates to equipments including one or more heat exchangers buried in the ground about the building. The invention comprises providing fins (4 or 14) in thermal contact with the outer walls of buried ducts (1 or 10), wherein said fins include drills capable of receiving at least one pole (5 or 15) having a lower portion that can be urged into the ground and an upper portion provided with a large mass head in thermal contact with the fins. The fins and the poles of the invention allow the mass and the average depth of the earth concerned by the calories or frigories transfers with the buried exchanger to be increased.

Description

The invention aims to provide an optimized solution from the point of view of energy control and environmental impacts for heating and air conditioning of living quarters and activity. It relates more particularly to an improvement of the gas / soil or liquid / soil heat exchangers used for the heating or air conditioning of the premises or for the preheating or for the cooling of the air of renewal of the habitable volumes. It is known that the heating or cooling needs of buildings come partly from the need to compensate for the losses of the walls of the volume built and secondly from the obligation to bring the renewal air to an acceptable temperature. Many of the heating and cooling solutions on offer include reversible heat pumps, which include winter heating and summer cooling. Also known are facilities designated by the names of "Canadian wells" or "Provençal wells", installations intended to temper the air of renewal of the premises.

Most heat pump heating or cooling systems use underground heat exchangers located near the building. These exchangers are constituted by small diameter tubes, typically between 10 and 40 mm, deployed in closed circuit under the ground at depths between 40 and 120 cm and covered with earth. These closed circuit heat exchangers are traversed either directly by the refrigerant gas supplying the compressor of the heat pump, or by a liquid, typically water or antifreeze mixture, circulating in a heat exchanger itself traversed by the refrigerant gas put circulated by the compressor of the heat pump. Similarly, Canadian wells consist of buried tubes, generally between 120 and 300 mm in diameter in which the air of renewal of the premises circulates. The burial depth of the tubes is generally a little larger than that of the circuits supplying the heat pumps, namely of the order of 200 to 300 cm.

In the current state of the art, the realization of these exchangers involves major earthworks and have a large reserved area of private land in the immediate vicinity of the heated or air-conditioned buildings. By reserved area is meant lawn-covered or slightly vegetated surface, it being understood that plants developing deep root systems are incompatible with the presence of such exchangers in the subsoil. In general, the performance of the heat exchangers and therefore the heating and / or air conditioning systems they supply are directly proportional to the depth of burial and the length of the tubes deployed. However, a significant length of pipe causes significant losses that must be countered by high power circulators which compromises the performance of the facilities. Similarly, a large depth of burial is not always feasible, at least under acceptable economic conditions. In particular, legislation requires that trenches be shielded or tarred when their depth exceeds 150 cm, so that the costs of earthworks quickly become a deterrent. In practice, the limits imposed by the length of the feasible pipelines and by the possibilities of burial result in heating installations which are limited to a so-called "boiler up" operation, that is to say installations which do not can provide all the heating needs by very low outdoor temperatures; similarly, the Canadian well installations currently being carried out most often require auxiliary devices, whether for preheating or cooling the renewal air.

It is also noted that the gas / ground or liquid / ground heat exchangers produced according to the state of the art have a significant winter operating limit: these exchangers can be traversed by fluids carried at low temperatures. At negative temperatures, the conduction of the walls of the pipes causes the formation of an ice sheath around said walls, this sheath of ice resulting from the solidification of the water contained in the earth in contact with these walls. When a period of mild weather occurs, the fluid passing through the pipes is brought to positive temperatures, causing the ice sheath to melt, giving way to an annular space filled with low density air or soil, which space permanently degrades the pipe exchange performance. The invention proposes to solve these difficulties. Its main objective is to improve the performance and reliability of liquid / soil or gas / soil heat exchangers.

An ancillary objective is to enable performance levels to be achieved such that the exchangers provided with the devices according to the invention can make it possible to operate thermodynamic or direct heating or cooling systems which ensure the entirety of the needs without it being necessary. necessary to add extra facilities.

Another objective is to make possible the realization of such exchangers, including when the private lot adjoining the buildings is of small surface or a composition poorly suited to performing earthworks. A complementary objective is to reduce the cost price of the production of the liquid / soil or gas / soil heat exchangers, while also reducing the lead time for producing such exchangers.

These objectives, as well as others that will appear in the following description are achieved by the use of accessories designed and made to improve heat transfer between the outer wall of the pipes and the soil in which the said pipes are buried. These accessories are also ancillary function to protect the pipes during backfilling and throughout their life. Experience shows that the performance limits of gas / soil or liquid / soil heat exchangers come mainly from the outer wall surfaces of pipes in contact with the earth. In order to reduce these limits, it has been proposed to replace, at the time of backfilling operations, the earth present on the site with a more conductive material, for example sand, a lean mortar or bentonite. This type of development actually improves the performance of the exchangers, but in proportions that remain relatively low.

The accessories according to the invention will be formed by profiled fins having a cylindrical female portion which will be placed in thermal contact with the outer wall of the pipes and a flat portion extending laterally with respect to the pipe. The accessories will be designed in such a way that they have the largest possible surface contact with the ground. They will advantageously have recesses facilitating their gripping and increasing their contact surface.

In addition to these profiled fins, whose function is to considerably increase the surface area of material in contact with the earth, the invention proposes to place a plurality of piles comprising a lower part provided with devices allowing them to sink into the ground and a part upper comprising means for providing thermal contact with said profiled fins. It will be understood that the fins will cooperate with the piles to transfer the calories (or, in certain operating phases, the frigories) from the outer walls of the pipes to a mosaic of soil much larger than that which is concerned when the buried pipes are not not equipped with such accessories. It is also understood that the average depth of the earth mass concerned by the heat exchange with the outer wall of the tubes (and therefore, thanks to the action of the fluid passing through these pipes with the building itself) will be greater than that surrounding the pipeline itself. Thus the devices according to the invention allow: - A performance equal to divide by at least 2 the length of the pipes necessary for the realization of a gas exchanger / ground or liquid / soil.

- Always with equal performance to significantly reduce the actual burial depth of the pipes, and thus reduce the magnitude and cost of earthworks.

Preferably, the fins will be profiled so that their female part can be fixed at the periphery of the pipes by simple clipping operations. Also preferably, these fins will be made of recycled plastic materials, preferably loaded with particles improving their thermal conductivity, for example particles of metal or carbon. In a variant, these fins may be made of metal, for example cast iron, steel or aluminum. In a preferred embodiment, the piles will be provided with a large helical thread pitch, said screw pitch facilitating on the one hand the driving of the piles into the earth and on the other hand the heat transfer between the piles. piles and the ground in which they will be implanted. They will also be provided with an upper part or large mass head, said upper part or head being in thermal contact on a large surface with the fin that they contribute to fix in the ground.

In an alternative embodiment, these piles may comprise a hollow central part capable of containing a liquid or a gas in a sealed cylindrical reservoir, which may make it possible to improve the heat transfer from the earth to the fin by a method known in the art. name of heat pipe. The exchangers gas / soil or liquid / soil according to the invention are intended for heating or cooling of living quarters either live or through a heat pump. They are of the type comprising at least one buried pipe, and are remarkable that they comprise a plurality of fins in thermal contact with the buried pipe and in that said fins are provided with at least one piercing adapted to receive at least a stake comprising a lower part capable of sinking into the ground and an upper part provided with a large mass head in thermal contact with said fin.

For the air / ground exchangers the fins will be provided with a female part having a shape such that it can be fixed by clipping around a cylindrical pipe having an outer diameter of between 120 and 300 mm.

For the liquid / soil exchangers according to the invention, the fins will be provided with a female part having a shape such that it can be fixed by clipping around a cylindrical pipe having an outside diameter of between 15 and 50 mm.

In a preferred embodiment, the fins will be made of plastic material made conductive by inclusion of metal particles or carbon. To reduce their cost while ensuring optimum performance, these fins can be manufactured by extrusion or roto molding.

Advantageously, the piles will be provided with a helical screw pitch of large width adapted to facilitate the insertion of said piles into the ground and to increase the contact surface between said piles and earth. In a preferred embodiment, the piles will consist of a plurality of segments that can be assembled by screwing, the upper segment comprising a large mass head provided with means for exerting a rotation torque being used several times for the establishment of successive segments. Furthermore, the piles will comprise a hollow cylindrical inner part, said hollow cylindrical inner part being able to be filled with a heat conducting liquid or, preferably, by a heat pipe tube which will facilitate the transfer of frigories or calories between the earth. in which is immersed the pile and the massive head, itself in thermal contact with the fin and thus with the buried pipe. More generally, the invention applies to residential space heating installations comprising a heat pump, in which the heat pump is fed by a liquid / ground heat exchanger whose exchange surface with the ground is increased by a plurality of fins preferably fixed by clipping on the buried pipe and connected to the ground by buried piles passing through said fins. The invention also relates to installations for preheating or cooling the air for the renewal of living quarters, insofar as these installations will comprise at least one buried pipe equipped with accessories, that is to say with fins. and piles as described above. Other advantages and characteristics of the invention will become apparent on reading the following of a preferred embodiment of the invention, given for information only, and the appended drawings in which:

FIG. 1 schematically represents a view of a building equipped with a water / water heat pump heating installation and a facility for preheating and cooling the renewal air by Canadian wells, said installations being carried out according to FIG. the known technique prior to the invention.

Figure 2 schematically shows a view of a building equipped with facilities identical to those illustrated in Figure 1 but benefiting from the modifications and improvements proposed by the invention. Figure 3 shows a side view and a top view of a fin according to the invention, fin intended to improve the performance of gas / soil heat exchangers and more particularly air / ground type heat exchangers Canadian. Figure 4 shows a side view of a fin as shown in Figure 3 equipping a portion of Canadian well pipe. Figure 5 shows a side view and a top view of a fin according to the invention, fin for improving the liquid / soil heat exchangers used in primary heat pump.

Figure 6 shows a side view and in section of pipes constituting a liquid exchanger / sol equipped with fins according to the invention. Figure 7 illustrates the implantation of air / ground or liquid / ground heat exchangers included in the prior art.

FIG. 8 illustrates the implantation of air / ground or liquid / ground heat exchangers equipped with devices according to the invention. It can be seen in FIG. 1 that the building shown is equipped on the one hand with a heating system for the living volumes of the water / water heat pump type and on the other hand with a preheating and cooling plant for the water / water heat pump. renewal air by a Canadian well or provencal well installation. The heating installation comprises in particular a liquid / ground type primary heat exchanger comprising a pipe (1) of great length in a closed circuit buried at a depth (HL1) of several tens of centimeters below the ground level (represented by a line dotted line). This primary heat exchanger supplies a heat pump (2) which, during the heating period, will cool the liquid or, in certain cases, the gas contained in the pipe (1) to heat a secondary circuit (2). The Canadian well has an air inlet (12) through which air is sucked and then descends into a manhole (11) to a depth (HG1). The air then travels a pipe (10) buried at this depth (HG1) and enters the living space under the action of a fan (13) or a central dual flow. With respect to the installations described in FIG. 1, the installations according to the invention represented in FIG. 2 are distinguished: for the heating installation by the setting up of several fins (4) in thermal contact with the pipe (1), fins (4) whose action is completed by that of several piles (5) themselves in thermal contact with said fins (4). With respect to the installation of Canadian wells, it differs from that illustrated in Figure 1 by a plurality of fins (14) in thermal contact with the pipe (10), piles (15) in thermal contact with the fins (14) complete the action of said fins (14). In both cases, the pipes (1 or 10) have a shorter length and are implanted at a lesser depth (HL2 less than HL1 and HG2 less than HG1) in the case of the installations according to the invention shown. in Figure 2 that in the case of installations according to the state of the prior art shown in Figure 1.

Figure 3 shows a fin specifically designed to equip an air / ground heat exchanger for Canadian wells type installations. This fin (14) has a female portion that can be pressed against the outer wall of a Canadian well pipe; this female part will be adapted to the outer diameter of the pipes, diameter most often between 150 and 300 mm; it will be designed in such a way that close contact is ensured between said female part and the outside part of the pipe, for example by means of a clipping device. This fin, which will preferably be produced by extrusion, molding, rotational molding or thermoforming, will be made of a conductive material, for example a plastic material doped by inclusion of particles of metal or carbon. It may also be made of metal material, not or not very sensitive to corrosion. In all cases, it will represent a significant mass, greater than or equal to that of the portion of pipe that it is intended to cover. This fin will have two plane parts symmetrical with respect to the female part; the planar parts will be provided with recesses and holes through which may be placed piles (15) as shown in Figure 4. The piles (15) have a pointed lower end. They will be equipped with a helical screw pitch facilitating the penetration and driving of the piles into the ground and increasing the contact surface between the piles and the ground. In the upper part, these piles will have a head having a large mass, the head being provided for housing, once the pile driven into the earth in the recesses and holes formed in the fins.

FIG. 5 shows a fin (4) more specifically intended for equipping liquid / ground heat exchangers able to operate heating or air conditioning systems comprising heat pumps or simple exchangers on the renewal air as described in the application French Patent No. 0503640 filed April 12, 2005. This fin has a female portion having a diameter adapted to fit on the outer wall of a pipe, diameter usually between 15 and 40 mm. A clipping device will advantageously be provided to ensure optimum contact between the female part of the fin and the outer wall of the pipe. The fin will comprise bores and recesses (6) through which will be placed, as shown in Figure 6, piles (5) fixing the fin (4) in the earth and improving the heat transfer between said fin (4) and the soil. The piles (5), the fin (4) and the pipe (1) will cooperate to ensure a heat exchange between the fluid passing through the pipe (1) and a ground mass as large as possible. To increase these exchanges, we can choose to increase the length of the piles (5) which may consist of several segments adding to each other by screwing.

FIG. 7 represents a pipe buried in an installation included in the state of the prior art. This pipe is buried under a depth of earth symbolized by the dimension (HL1). Its implementation required earthworks to a depth represented by the dimension (HT1) and fill the trench to the ground level represented by the dotted line. It can be seen that the mass of earth with which thermal exchanges occur, the mass represented by the gray zone, is limited to a ring at the periphery of the pipe constituting the heat exchanger.

Figure 8 shows a pipe identical to that shown in Figure 7, provided with improvements according to the invention. This pipe (1) is equipped with a fin (4) in thermal contact with said pipe. The fin (4) is traversed by two piles (5) implanted in the ground. It can be seen that the depth represented by the dimension (HL2) to which the pipe (1) is placed is substantially less than the implantation depth (HL1) made for an ordinary pipe shown in FIG. 7. Similarly, the earthworks necessary, namely a disbursement to the coast (HT2) and backfilling to ground level are significantly less than those required for installations in accordance with prior techniques. We notes also that, thanks to the presence of the fins (4) and the piles (5) in thermal contact with the pipe (1) the mass of earth concerned by the heat exchange with the fluid passing through the pipe (1), mass of earth represented by the shaded area, is significantly larger. Moreover, by varying the length of the piles, it can be obtained that the average depth of this earth mass participating in the heat exchange with the ground is located on average at a depth comparable to or greater than that of a pipe constituting a heat exchanger compliant at the state of the prior art, and this by means of earthworks limited to disbursements of lesser importance and therefore significantly less expensive.

The invention therefore makes it possible to very significantly improve the performance of the liquid / soil or gas / ground heat exchangers with equivalent depth of burial and pipe length, regardless of the end use of the fluid passing through the buried pipes. A fortiori, the invention can significantly reduce the length of the pipes and / or the burial depth for the realization of a liquid exchanger / soil or gas / soil having a given exchange capacity. Consequently, it allows significant savings on the cost of producing such exchangers. In addition, by the compactness it allows, it opens the way to the realization of gas exchanger / soil or liquid / soil for buildings located on privately owned land of small area compared to their living volumes. Finally, thanks to the increase in the mass and volume of earth involved in heat exchange, and the action of the piles to perform these exchanges at great depths without having to carry out expensive earthworks, the invention makes it possible to realize heat pump space heating systems with buried primary heat exchangers that can operate autonomously throughout the heating season, including low or very low outdoor temperatures. In this sense, the invention makes it possible to produce, even in regions with a continental climate, heating installations using exclusively heat pumps without additional heat. electrical or boiler resistances: the provisions of the invention make it possible in fact to avoid, by distributing the flow of frigories dispersed by the exchanger on a very large mass of earth and located at a significant average depth, the icing phenomena of primary heat exchangers which constitute the main limit of operation of heat pumps. Of course, improving the performance of underground heat exchangers will make it possible to improve proportionally the efficiency (represented by the coefficient of performance) of the heat pumps equipped. In the same way, the invention will make Canadian well performing wells, without requiring excessive earthworks. In particular, it will be sufficient to make trenches of low depth, for example less than or equal to 1 m 30 that is to say, to overcome the requirement to shield or calibrate the trench, to ask the pipes at the bottom of this trench and to provide them with a plurality of fins itself equipped with piles of great length, which will achieve the same performance in terms of winter preheating and summer cooling of the air renewal than those provided by a pipe buried at a depth of 2 meters which would have required earthworks and embankment delicate and expensive. The descriptions are given for information only and other embodiments of the fins and / or piles may be chosen without departing from the scope of the invention.

Claims

Claims:

- 1 - Gas / soil or liquid / soil heat exchanger for heating or cooling of living quarters either directly or via a heat pump of the type comprising at least one buried pipe, characterized in that it comprises a plurality of fins in thermal contact with the buried pipe and in that said fins are provided with at least one hole adapted to receive at least one pile having a lower part capable of sinking into the ground and a part upper provided with a large mass head in thermal contact with said fin.

- 2 - gas / ground heat exchanger according to claim 1, characterized in that the fins are provided with a female portion having a shape such that it can be fixed by clipping around a cylindrical pipe having an outer diameter of between 120 and 300 mm.

- 3 - liquid / soil exchanger according to claim 1, characterized in that the fins are provided with a female portion having a shape such that it can be fixed by clipping around a cylindrical pipe having an outer diameter between 15 and 50 mm.

- 4 - exchanger according to claim 1, characterized in that the fins are made of plastic material made conductive by inclusion of metal particles or carbon.

- 5 - exchanger according to any one of the preceding claims, characterized in that the piles are provided with a helical screw pitch capable of facilitating the insertion of said piles into the ground and to increase the contact surface between said pious and earth.

- 6 - exchanger according to claim 5, characterized in that the piles consist of a plurality of segments that can be assembled by screwing. - 7 - exchanger according to claim 1, characterized in that the piles comprise a hollow cylindrical inner portion, said hollow cylindrical inner portion being filled with a conductive liquid.

- 8 - exchanger according to claim 1, characterized in that the piles comprise a hollow cylindrical portion in contact with the solid head, said hollow cylindrical portion being filled by a heat pipe.

- 9 - Residential heating installation comprising a heat pump, characterized in that the heat pump is supplied by a liquid / soil heat exchanger according to at least one of the preceding claims.

- 10 - Installation for preheating or cooling the renewal air of living quarters, characterized in that it comprises a buried pipe equipped with accessories according to at least one of claims 1 to 8.