US3399542A - Method and apparatus for cooling compressor recycle gas - Google Patents

Description

Sept. 3, 1968 v BRACKEN ET AL 3,399,542

METHOD AND APPARATUS FOR COOLING COMPRESSOR RECYCLE GAS Filed May 25. 1967 no L I 1 1 .5 1 SURGE I I I6 l I5 20 30 l3 l4 ACCUM. I2 I 2| 25o 25b 25c 25d 25 INVENTORS R. C. BRACKEN E. D. LEA H. J. JOBE DE WAYNE MADDOX United States Patent O 3,399,542 METHOD AND APPARATUS FOR COOLING COMPRESSOR RECYCLE GAS Robert C. Bracken, Eugene D. Lea, Howard J. Jobe, and

De Wayne Maddox, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed May 25, 1967, Ser. No. 641,270

3 Claims. (Cl. 62-117) ABSTRACT OF THE DISCLOSURE In a refrigeration system having constant-capacity compressor and varying refrigerant demand, a portion of hot compressed refrigerant vapor stream is bypassed'during period of light demand to the novel mixing valve wherein a liquid refrigerant is flashed into the hot vapor stream to reduce its temperature to normal compressor suction temperature so as to maintain substantially constant temperature to the compressor.

Background of the invention This invention relates to a method and means for operating and controlling a compressor refrigeration system so as to keep the compressor running fully loaded during varying demand rates by bypassing discharge vapors to the compressor suction and holding a constant temperature of the suction by cooling with liquid refrigerant. In another aspect, this invention relates to a novel sparger or mixing valve adapted to efficiently mix fluids responsive to a process variable. In accordance with a further aspect, this invention relates to means for effecting direct heat exchange and mixing between the super heated compressor recycle gas of a refrigeration apparatus and a liquid refrigerant responsive to the temperature of the compressor suction.

A refrigeration apparatus usually consists essentially of a compressor, a condenser and an evaporator. Normally, refrigerant gas is compressed, cooled, condensed and then expanded in an evaporator or other refrigeration load Where heat is absorbed in the expansion of the liquid into gas. The cycle is continuously repe'ated. lt is commonplace to operate a refrigeration apparatus so that the compressor operates intermittently or on demand. Such systems are usually thermostatically controlled and do not operate to a point Where the vapor pressure in the ev-aporator is lower than that desired for compressor suction pressure. Homerefrigerators and home air conditioners are examples of such systems.

There are syst ems wherein refrigeration apparatus is employed and wherein the compressorruns continuously. In such systems, it is necessary to provide means for recycling compressor discharge gases to the compressor suction during varying demand rates in order to maintain adequate suction pressure. One application of such refrigeration apparatus is the chilling of absorption oil .in a gas liquid absorption plant. In such systems, there is necessarily means to recycle gas from the compressor discharge to the compressor suction.

Accordingly, it is an object of this invention to provide method and means for cooling compressor recycle gas in a refrigeration system.

It is a further object of this invention to provide method and means for contacting the compressor recycle gas in a refrigeration system with liquid refrigerant.

Another object of this invention is to provide suction gas to a compressor at substantially constant temperature wherein the compressor is kept running susbtantially fully loaded during varying demand rates.

Another object of this invention is to provide method and means for providing constant temperature suction gas 3,399,542 Patented Sept. 3, 1968 to a constant-capacity compressor operating on a variable refrigeration load.

I Other aspects, objects and the several advantages of this invention will be apparent to one skilled in the art upon study of this disclosure, the drawing, and the appended claims.

Summary of the invention In accordance with the present invention, improved method and means are provided for cooling the recycle gas passed directly from the compressor discharge to the compressor suction by cooling the hot compressed gas by mixing with a portion of the liquid refrigerant whereby the amount of liquid refrigerant introduced into the recycle gas is controlled responsive to suction temperature.

Alsoaccording to the invention, a novel sparger or mixing valve is provided for flashing liquid refrigerant under controlled conditions into the recycle hot vapor stream being returned to the compressor suction which comprises an outer valve body having disposed therein a tubular element provided with a plurality of radial holes and "an inner reciprocal hollow sleeve which uncovers the holes responsive to a condition change elsewhere in the system. Preferably, valve structure is in combination with a conventional diaphragm assembly or topworks.

Description of preferred embodiments A better understanding of the invention will be obtained upon reference to the following figures, wherein:

FIGURE 1 is a schematic flow diagram of a refrigeration system having incorporated therein the sparger valve of the invention, and

FIGURE 2 is a schematic drawing, partially in crosssection, of the novel sparger valve of the invention.

Referring now to FIGURE 1, the refrigeration system set forth therein comprises compressor 10, cooler 15, accumulator 20, refrigeration loads 250, b, c, d, and e, sparger 30, and accumulator 35. Liquid refrigerant is evaporated in loads 25a-e and passed to surge tank 35 as vapors through line 26. Refrigerant vapors travel through line 27 and are passed as the suction gas to compressor 10. Within compressor 10, the gases are compressed and discharged from the compressor by way of line 11, and passed by way of line 12 through cooler 15, and introduced into liquid accumulator 20. A portion of the hot compressed gases discharged from compressor 10 is passed by way of line 13 to sparger valve 30, to be described in more detail below.

Line 13 contains control valve 14, which is connected to flow recorder 16, which senses the flow of compressor discharge through line 11. Flow recorder 16 is set so as to increase the flow through line 13 when the flow rate decreases at the flow recorder, as sensed in line 11. This instrument senses lower flow caused by reduced demand for liquid refrigerant at loads 25a-e. The constant speed compressor continues to run, delivering hot compressed vapors, part of which flow through the bypass valve 14 to compressor suction 27 by way of sparger 30 and surge tank 35.

Liquid refrigerant is removed from accumulator 20 by way of line 21 and passed by way of line 22 to loads 25ae, wherein the refrigerant is expanded and evaporated to refrigerate fluid or other material circulated through loads ZSa-e. Line 23 is connected to the liquid withdrawal line 21 from accumulator 20 for introduction of liquid refrigerant into sparger valve 30. Control valve 24 is provided in line 23. Control valve 24 and sparger valve 30 are both connected to temperature recording controller 28, which senses the temperature in suction line 27. Upon an increase in compressor suction temperature in line 27, temperature controller 28 responds by opening valve 24 in the liquid refrigerant bypass line 23 to the sparger valve 30, and by opening the sparger valve to blend liquid refrigerant with the hot bypass vapors introduced therein by way of line 13.

The invention will now be described with reference to a refrigeration system wherein substantially pure propane is the refrigerant in refrigeration apparatus utilized to chill absorption oil in a gas liquids absorption plant. The liquid refrigerant passed through line 23 is at about 175 p.s.i.g. and 98 F. The hot propane vapors in conduit 13 are at atmospheric pressure and about 140 F. The cooled recycle refrigerant vapors in line 29 are passed to the suction of the compressor at about atmospheric pressure and in the temperature range of to 30 F. The temperature in line 27 is preferably maintained at about 0 F.

As indicated above, when the refrigeration system has a constant-capacity compressor as described above, and a varying refrigeration load in accordance with the invention, a portion of the hot compressed refrigerant vapor stream in line 13 is passed to valve 30 during periods of light load wherein liquid refrigerant in line 23 is flashed into the hot vapor stream to reduceits temperature to normal compressor suction temperature and thence to the compressor suction. Flow controller 16 senses lower flow caused by reduced demand for liquid refrigerant at loads 25a-e. However, the constant speed compressor continues to run, delivering hot compressed vapors, parts of which flow through the bypass valve 14 to the compressor suction. Simultaneously, the temperature recorder 28 senses a rise in the compressor suction temperature and responds by opening valve 24 is the liquid refrigerant bypass line to the sparger valve 30, and by opening the sparger valve to blend liquid refrigerant With the hot bypass vapors.

Referring now to FIGURE 2, the sparge-r valve 30 is illustrated in more detail. Valve 30 comprises body portion 35, having a side outlet 36 and an inlet 37, which is connected to conduit 13. Valve body 35 also comprises a reducer section 38, which is connected to flange element 39. Side outlet 36 is connected to line 29 in FIG- URE 1.

Disposed within valve body 35 is tubular element 40, which is closed by end 41. Tubular element 40 is connected to T 42. T element 42 is connected through a flange to conventional type diaphragm element 43. Valve 24 is connected to T 42, and conduit 23, as illustrated in FIGURE 1.

Disposed within tubular element 40 is valve stem 45, which is connected to diaphragm element 43 and sleeve 46. Near end 41 of tubular element 40 are multiple circumferential rows of holes 47a-e. Upon movement of sleeve 46 away from closed end 41, an increasing number of holes are uncovered so as to permit flow of fluid through line 23, valve 24, T 42, through tubular element 40, out through holes 47a-e into the valve body 35.

Tubular element 40, illustrated in FIGURE 2, can be cylindrical or any other suitable shape, including square, elliptical, etc., provided sleeve 46 conforms to the same configuration. With respect to holes 47a-e, it should be realized by those skilled in the art that these could be disposed anywhere along tubular element 40, as long as sleeve 46 covers the holes in a normally closed position. Thus, upon moving the holes nearer the inlet of tubular element 40, sleeve 46 could be reciprocated either to the right or to the left. As illustrated in FIGURE 2, movement of sleeve 46 to the right closes the valve, and movement to the left provides an increasing number of openings for passage of fluid into valve body 35.

It is also within the scope of the invention to have any number of rows of holes which can be symmetrically spaced or it is within the scope of the invention to use a spiral row of holes to gradually increase the number of openings or any other configuration desired.

In actual operation, as illustrated in FIGURE 1, hot

compressor effiuent vapors are introduced into the valve by way of conduit 13 through'valve body 35 and outside outlet 36. Liquid refrigerant used to cool the vapors is introduced through line 23, valve 24, into tubular element 40, and out through holes 47a-e. The movement of sleeve 46 so as to expose the openings is controlled responsive to temperature in the suction inlet by way of controller 28 by actuating diaphragm element 43 and opening valve 24.

The above system and control valve have operated successfully in a commercial installation for chilling absorption oil in a gas liquids absorption plant.

A similar system has operated successfully utilizing commercial propane containing varying amounts of butane and ethane as impurities.

The invention, by maintaining essentially constant suction temperature at the refrigeration compressor, minimizes the likelihood of shutdown of an entire gasoline plant due to excessive suction temperature at the refrigeration compressor. Unexpected shutdowns of this type have occurred in the past. A plant shutdown in a very large plant causes loss of profit at a rather high rate of dollars per day. The invention will also save the cost of operating one cooling water circulating pump for the refrigerant condenser when the invention is operating. Less condenser water is required because the invention achieves improved flashing of the refrigerant into the hot bypass recycle gas stream. With reference to the sparger valve, the invention valve allows easy removal of the topworks and inner valve without the necessity of removing the entire valve from the piping. This is a very useful advantage for cleaning purposes or for inspection. Also, as illustrated in FIGURE 2, the greater number of holes that are provided along the body of tubular element 40 give a much better control of flow through the opening.

We claim:

1. The method of maintaining a predetermined, substantially constant temperature on the suction of a constant-capacity compressor having a varying refrigeration load in a cyclic refrigeration system comprising a compressor, condenser and evaporator, which method comprises:

- (a) recycling a portion of the hot compressed refrigerant vapors to the suction of the compressor responsive to a decrease in the flow rate of vapors in the compressor discharge caused by reduced demand for liquid refrigerant at the load,

(b) introducing a portion of the liquid refrigerant into said hot compressed refrigerant vapor stream to reduce its temperature to normal compressor suction temperature, and

(c) controlling the amount of said liquid refrigerant introduced into said vapor stream responsive to the temperature of said compressor suction whereby upon an increase in suction temperature the amount of liquid refrigerant introduced into vapor stream is increased so as to maintain a substantially constant suction temperature passed to the compressor.

2. The method of claim 1 wherein said vapor stream and said liquid refrigerant are mixed together in a proportioning section of a control valve operated in response to the temperature sensed in said compressor suction, and wherein a mixed stream of hot vapor and liquid refrigerant are mixed with recycle refrigerant vapor from the load prior to said temperature sensing point and introduction into said compressor.

3. A method according to claim 2 wherein the refrigerant is substantially pure propane.

References Cited UNITED STATES PATENTS 2,551,666 5/1951 Gilmore 62-l17 3,318,102 5/1967 Henderson 62196 X 3,320,758 5/ 1967 Harper 62-117 LLOYD L. KING, Primary Examiner.

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