US2715819A - Absorption refrigeration - Google Patents

Description

1955 c. T. ASHBY ET AL 2,715,819

ABSORPTION REFRIGERATION Filed Dec. 28, 1951 a 4 7' ram/v5 y United States Patent Ofilice 2,7 15,8 1 9 Patented Aug. 23, 1955 ABSORPTION REFRIGERATION Carl T. Ashby and Charles A. Miller, Evansville, Ind.,

assignors to Servel, Inc., New York, N. Y., a corporation of Delaware Application December 28, 1951, Serial No. 263,732

3 Claims. (Cl. 62119.5)

This invention relates to the art of refrigeration and particularly to absorption refrigerating systems of the three fluid or uniform pressure type wherein an inert gas is used to maintain an equal pressure throughout the system. More particularly this invention relates to refn'gerating systems of the above type wherein two or more liquid drains in the form of liquid traps are used for flowing liquid refrigerant from the condenser to the evaporator of such system and wherein the condenser is vented to an inert gas circuit.

When two or more condenser drains are used on a refrigerating system of the above type it is necessary that the drain from the last part of the condenser, that is the part of the condenser that is last to receive refrigerant vapor from the generator, always contains liquid refrigerant when the system is operating in normal or below normal room temperatures even though liquid refrigerant is not supplied to this drain by the condenser during such normal operation. With a refrigerating system wherein inert gas is used to maintain a uniform pressure, should the drain from the last part of the condenser go dry it may cause a short circuit around the inert gas circuit. Then, when hot room temperature conditions are encountered, and refrigerant vapor is supplied to the last part of the condenser and is condensed therein, a second gas circuit may be set up through the drain which will cause the liquid refrigerant flowing thereinto to evaporate and diffuse into the inert gas in the drain and thus prevent such liquid refrigerant from ever reaching the evaporator.

It is therefore an object of our invention to provide means for preventing short circuiting of inert gas in refrigerating systems of the uniform pressure type.

It is a further object of our invention to provide improved means for precooling liquid refrigerant en route from the condenser to the evaporator, and for precooling inert gas en route from the absorber to the evaporator of a refrigerating system of the above type.

Further objects and advantages of our invention will be apparent from the following description considered in connection with the accompanying drawing in which:

Fig. 'l is a more or less schematic illustration of a refrigerating apparatus embodying our invention; and

Fig. 2 is a detail section of a part of the apparatus illustrated in Fig. 1.

Referring to the drawing, reference character 10 designates a generator divided by a partition 11 into a circulating chamber 12 and a weak liquid chamber 13. A standpipe 14 extends upward from chamber 13, and a vapor lift conduit 15 extends from within pump chamber 12 to the upper part of standpipe 14. The lower end of conduit 15 projects below the level of liquid maintained within chamber 12 and is provided with apertures 16 near its lower end. A conduit 17 connects the upper end of standpipe 14 to an analyzer 18. A partition 19 divides the analyzer into an upper chamber 20 and a lower chamber 21. A vapor lift conduit 22 and a drain 23 connect the analyzer chambers 20 and 21.

A conduit 26 communicates with the upper part of chamber 20 and leads upward to a rectifier 27 which may comprise a section of conduit provided with air cooled fins 28. A conduit 29 connects the rectifier to the upper part of a condenser 30. The condenser is formed of an upper section 31 and a lower section 32, each of which sections is provided with air cooled fins 33.

A conduit 34, in the form of a liquid trap, connects section 31 of the condenser to an evaporative precooler 36, and the precooler is connected by a liquid trap 37 to an upper section 38 of an evaporator. The upper section of the evaporator is connected by a conduit 39, having a liquid trap 40 in the lower portion thereof, to one end of a second evaporative precooler 41 and the opposite end of this evaporative precooler is connected by a liquid trap 42 to one end of an intermediate section 43 of the evaporator. The opposite end of the intermediate section of the evaporator is connected by a conduit 44 to the upper part of a lower section 45 of the evaporator. The liquid and gas outlet end of section 38 of the evaporator is provided with a dam 46.

The upper and intermediate sections, 38 and 43, of the evaporator are formed as fiat coils and are placed in good thermal contact with the top and bottom, respectively, of a chamber 35 located within a refrigerator cabinet (not shown), and the lower section 45 of the evaporator is located in a food storage compartment of such cabinet. The top wall of the freezing chamber and the upper evaporator coil 38 are inclined slightly for downward flow of liquid refrigerant therethrough from right to left, as viewed in the drawing. However, the bottom wall of the freezing chamber, which may be termed a freezing shelf or plate in that it is adapted to support ice trays or the ilke for freezing the contents thereof, should be substantially level and some provision should be made for downward flow of liquid refrigerant through the attached section 43 of the evaporator. This section rna, for example, be formed as a tapered coil with a flat plate secured thereto similar to that described and claimed in application Serial No. 164,969 of Charles A. Miller, filed May 29, 1950.

The lowermost part of section 45 of the evaporator is connected by a liquid trap 4'7 to an outer passage 48 of a gas heat exchanger 49, and the opposite end of this passage is connected by a conduit 50 and an absorber vessel 51 to the lower part of an air-cooled absorber 52. The upper part of the absorber is connected by a conduit 53 to an inner passage 54 of the gas heat exchanger. As shown, portions of conduits 50 and 53 are placed in good thermal contact with each other, as by a weld 54 A conduit 55 connects the inner passage of the gas heat exchanger to the gas inlet end of section 38 of the evaporator. As shown, a portion of conduit 55 is placed in thermal contact, as by a weld 56, with a portion of the evaporative precooler 41. The gas outlet end of section 38 of the evaporator is connected by a conduit 57 to the gas inlet end of section 43 of the evaporator, and as stated, the gas outlet end of section 43 is connected by conduit 44 to the upper portion of section 45 of the evaporator. The lower portion of section 45 is connected by a conduit 58 to one end of the evaporative precooler 36, and the opposite end of this evaporative precooler is connected by a conduit 59 to the gas inlet end of the evaporative precooler 41. The opposite end of this evaporative precooler is connected by a conduit 69 to the outer passage 48 of the gas heat exchanger.

The lower section 32 of the condenser is connected by a conduit 51 to the liquid trap 40 at the lower end of conduit 39. For reasons to be described hereinafter, conduit 61 is in the form of a liquid trap which receives liquid refrigerant from conduit 39 as well as from the lower section of the condenser. A portion of conduit 61 is placed in thermal contact as by a weld '62, with the outer passage 48 of the gas heat exchanger. A vent conduit 63 connects the outlet of section 32 ofthe condenser to the gas line 50 between the outer passage of the gas heat exchanger and the absorber vessel 51.

A conduit 64 connects the lower portion of the absorber vessel 51 with one end of an outer passage 65 of a liquid heat exchanger 66, and the opposite end of such passage is connected by a conduit 67 to the lower chamber 21 of the analyzer. A conduit 68 connects the lower chamber of the analyzer to chamber 12 of the generator, and a conduit 69 connects chamber 13 of the generator with one end of an inner passage 70 of the liquid heat exchanger, the opposite end of which passage is connected by a conduit 71 to an upper portion 52A of the absorber. A conduit 72 connects the liquid outlet end of section 52A of the absorber with the next lower section 52B thereof. The upper portion of conduit 69 is connected by vent conduit 73 to the upper end of conduit 17 leading from the standpipe 14. The generator may be heated by any suitable heating element, as by a gas burner 74.

The operation of the apparatus incorporating our invention is as follows:

The generator is filled with an absorption liquid, for instance water, in which is dissolved a suitable refrigerant, as ammonia. The portion of the system not occupied by the ammonia-water solution is originally charged with a gas inert with respect to ammonia and insoluble in water. This gas is preferably hydrogen.

Application of heat to the generator 10 causes ammonia to be expelled from solution in the form of vapor. This vapor collects in the upper part of chamber 12 and passes through the apertures 16 in conduit and entrains slugs of liquid within the conduit and lifts them to the upper part of standpipe 14 in well known manner. Ammonia vapor driven from the solution contained in chamber 13 passes upward through the standpipe 14. Some water vapor necessarily passes along with the ammonia vapor and the mixture of ammonia and water vapors from both chambers 12 and 13 passes from the upper part of standpipe 14 through conduit 17 to the lower chamber 21 of the analyzer.

Chamber 21 of the analyzer is supplied with enriched absorption liquid from the absorber, that is absorption liquid in which refrigerant gas has been absorbed, and

the vapor in chamber 21 passes through the apertures in vapor lift conduit 22 and lifts a portion of the enriched liquid through conduit 22 to the upper chamber 20, in a manner similar to that described in connection with vapor lift conduit 15. The hot vapor mixture of ammonia and water is brought into intimate contact with the cooler strong absorption liquid during the passage through conduit 22 so that water vapor which accom panics the ammonia vapor from the generator is condensed and returns with the solution through drain conduit 23 to the lower chamber 21. The enriched absorption solution flows from the analyzer through conduit 68 into chamber 12 of the generator; and the refrigerant vapor passes upward through conduit 26 to the rectifier 27. In the rectifier the Vapor is cooled sufficiently to condense most of the remaining water vapor and this condensate drains back through conduit 26 to the analyzer. The ammonia vapor passes from the rectifier through conduit 29 to the upper section 31 of the condenser.

Assuming that the ambient temperature is normal, say about 70 F., then all ammonia vapor supplied to section 31 of the condenser is condensed therein and the liquid ammonia flows therefrom through conduit 34 to the liquid inlet end of the evaporative precooler 36. A small portion of this liquid refrigerant evaporates and diffuses into inert gas flowing through the evaporative precooler, which evaporation results in absorption of heat from the remaining liquid whereby the remaining liquid is cooled and flows through trap 37 into section 38 of the evaporator. In this section of the evaporator the liquid refrigerant flows in concurrent relation with weak inert gas entering the evaporator through conduit 55. Part of the liquid refrigerant evaporates and difiuses into the inert gas, which evaporation results in absorption of heat from the freezing chamber 35. Ordinarily, liquid refrigerant would flow out of section 38 through conduit 57 into the intermediate section 43 of the evaporator.

With our invention however, the dam 46 prevents the liquid refrigerant from flowing into conduit 57 but sends such refrigerant through conduit 39 and trap 40 into the second evaporative precooler 41. In this precooler, the liquid refrigerant and inert gas flow in countercurrent relation and again a small amount of liquid refrigerant evaporates and diffuses into the inert gas, which evaporation results in absorption of heat from the remaining liquid refrigerant and from inert gas flowing through conduit 55. From the second evaporative precooler, liquid refrigerant flows through trap 42 into the liquid inlet end of section 43 of the evaporator. In section 43 of the evaporator, the liquid refrigerant and inert gas flow in concurrent relation and part of the liquid refrigerant evaporates and diffuses into the inert gas, which evaporation results in absorption of heat from the bottom or freezing plate of chamber 35. The remaining liquid refrigerant and the partially enriched inert gas flow from section 43 cf the evaporator through conduit 44 into the upper portion of section 45 of the evaporator.

In section 45, the liquid refrigerant evaporates and diffuses into the inert gas, which evaporation results in absorption of heat from the food compartment (not shown) of the refrigerator in which this section of the evaporator is located. Any excess liquid refrigerant that passes through section 45 of the evaporator flows therefrom through trap 47 into the outer passage 48 of the gas heat exchanger, and the enriched inert gas flows from the lower portion of this section of the evaporator through conduit 58 into and through the evaporative precooler 36. From the opposite end of the precooler 36, the enriched inert gas flows through conduit 59 into and through the second precooler 41, and from there this enriched inert gas flows through conduit 60 into the outer passage 48 of the gas heat exchanger.

From the outer passage of the gas heat exchanger the enriched inert gas flows through conduit 50 into the absorber vessel 51, and from there this rich inert gas flows into the lower portion of the absorber 52 wherein the gas is brought into intimate contact with weak absorption liquid flowing downward through the absorber in counter-flow relation with the upward flowing inert gas. In the absorber, the ammonia is absorbed by the weak absorption liquid, while the hydrogen gas passes from the upper part of the absorber through conduit 53 into the inner passage 54 of the gas heat exchanger. In passing through the vertical portion of conduit 53 the relatively warm inert gas gives up heat to the relatively cold inert gas flowing through conduit 50, and in passing through the inner passage of the gas heat exchanger, the inert gas again gives up heat to the cold inert gas flowing through the outer passage. From the inner passage 54 of the gas heat exchanger, the inert gas flows through conduit 55 into the gas inlet end of section 38 of the evaporator. In passing through conduit 55 this inert gas in further cooled by transfer of heat therefrom to the second'evaporator precooler 41.

From the lower portion of the absorber, the strong absorption solution flows into the absorber vessel 51,

and from there it passes through conduit 64, the outer.

passage of the liquid heat exchanger and conduit 67 into the analyzer, wherein the strong solution is brought into intimate contact with refrigerant vapor from the generator and flows therefrom through conduit 68 into chamber 12 of the generator, as explained above. Weak absorption liquid flows from chamber 13 of the generator through conduit 69, the inner passage of the liquid heat exchanger and conduit 71 into section 52A of the absorber. The Weak absorption liquid flows downward in section 52A in concurrent relation with inert gas and forces the inert gas into conduit 53 thereby initiating and maintaining the flow of inert gas in the proper direction in the inert gas circuit. From section 52A, the absorption liquid flows through conduit 62 into section 52B, and from there, the absorption liquid flows downward through the remainder of the absorber in counter fiow relation with the upwardly flowing inert gas, as explained above.

Assuming now that the ambient temperature has risen to a point, say 90 to 100 F., such that the first section 31 of the condenser is no longer capable of condensing all refrigerant vapor that is supplied thereto by the generator. Under these conditions refrigerant vapor will pass from the outlet of section 31 into section 32 of the condenser. Except for small quantities of inert gas that may find their way into the generator-condenser side of the system and be vented therefrom through section 32 of the condenser and through vent conduit 63 into the active gas circuit, the fluid in section 32 of the condenser and in vent conduit 63 will, under normal operating conditions, be more or less dormant and will consist of inert gas containing a small amount of refn'gerant vapor. Now then, with a substantial flow of refrigerant vapor into section 32 of the condenser, the dormant gas mixture contained therein will be forced therefrom through the vent 63 into the active gas circuit thereby raising the total pressure in the system with the result that refrigerant vapor will be condensed in section 32 of the condenser and flow therefrom through circuii 61 and trap 40 into the evaporative precooler 41, as liquid refrigerant.

With our invention, by having conduit 39 arranged to discharge liquid refrigerant through trap 40 into the precooler 41, it is always assured that the liquid trap in conduit 61 will be filled with liquid refrigerant before such refrigerant can overflow from trap 40 into the precooler. This is so even though, under normal room temperature conditions, no liquid refrigerant is discharged into conduit 61 from section 32 of the condenser. Otherwise, if liquid refrigerant be discharged through conduit 57 from section 38 into section 43 of the evaporator, which heretofore has been the practice, the liquid trap in conduit 61 may, under normal room temperature conditions, be void of liquid refrigerant. If the liquid trap i1 conduit 61 does go dry, a short circuit will be established around the main gas circuit and when hot room temperature conditions are encountered the short circuit may become a secondary gas circuit in which all of the liquid refrigerant that flows into conduit 61 from section 32 of the condenser will evaporate and diffuse into the inert gas and thus prevent such refrigerant from ever reaching the precooler 41 and/or the evaporator section 43. With our invention, however, the liquid trap in conduit 61 is always filled with liquid and, under hot room temperature conditions, liquid refrigerant will always flow from section 32 of the condenser through conduit 61, trap 40, precooler 41 and trap 42 into section 43 of the evaporator. The operation of the system under hot room conditions is otherwise the same as that described above in connection with the operation under normal room temperatures.

While we have illustrated and described a more or less specific embodiment of our invention, it is to be understood that variations thereof fall within its scope as set forth in the following claims.

What is claimed is:

1. A refrigerating system including a generator, a condenser including an upper and a lower section, an evaporator including an upper and a lower section, an absorber and conduits interconnecting said elements and forming therewith a first circuit for flow of refrigerating medium, a second circuit for flow of inert pressure equalizing gas and a third circuit for flow of absorption solution, said second circuit being connected between said evaporator and said absorber in a manner that inert gas weak in refrigerant from the absorber flows first through the upper section of the evaporator and then through the lower section thereof whereby said upper section of the evaporator operates at a lower temperature than the lower section, and said conduits including a first conduit connecting the upper section of the condenser to the upper section of the evaporator, a second conduit formed with a liquid trap therein connecting the lower section of the condenser to the lower section of the evaporator, and a third conduit connecting the upper and lower sections of the evaporator and having a-portion thereon in open communication with said second conduit at a point below the connection of the second conduit with the second evaporator for discharging liquid refrigerant into said liquid trap prior to discharge of liquid refrigerant into said second evaporator.

2. A refrigerating system as set forth in claim 1 in which each of said first and second conduits is formed with an evaporative precooler therein for precooling liquid refrigerant flowing from the upper and lower sections of the condenser to the upper and lower sections of the evaporator, respectively.

3. A refrigerating system as set forth in claim 2 in which the evaporative precooler in said first conduit is connected to the inert gas circuit in a manner so as to receive inert gas flowing from the lower section of the evaporator toward the absorber, and in which the evaporative precooler in said second conduit is connected to the inert gas circuit and to the upper section of the evaporator in a manner so as to receive inert gas flowing from the first evaporative precooler and to receive liquid refrigerant flowing from the upper section of the evaporator.

References Cited in the file of this patent UNITED STATES PATENTS 2,194,505 Kogel Mar. 26, 1940 2,252,791 Ullstrand Aug. 19, 1941 2,256,519 Grubb Sept. 23, 1941 2,267,283 Lenning Dec. 23, 1941 2,269,102 Lynger Jan. 6, 1942 2,314,064 Ashby Mar. 16, 1943

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