US2648204A - Absorption refrigeration system - Google Patents

Description

Aug. 11, 1953 G. A. GRUBB 2,648,204

ABSORPTION REFRIGERATION SYSTEM Filed June 24, 1949 INV TOR.

Patented Aug. 11, 1953 ABSORPTION REFRIGERATION SYSTEM Gunnar Axel Grubb, Bromma, Sweden, assignor to Aktiebolaget Elektrolux, Stockholm, Sweden,

a corporation of Sweden Application June 24, 1949, Serial No. 101,005 In Sweden June 28, 1948 6 Claims.

My invention relates to refrigeration, and is especially concerned with absorption refrigeration systems of the kind employing an inert as 01' pressure equalizing agent.

In absorption refrigeration systems of this typ it is usually the practice to employ a gas heat exchanger in the gas circuit to effect heat exchange between warm gas flowing from an absorber to an evaporator and cold gas flowing from the evaporator to the absorber. When an evaporator of such a system is employed to effect cooling of a thermally insulated space of a household refrigerator cabinet, the gas heat exchanger is often arranged so that it projects through the wall of the cabinet. In order that cold gas flowing from the evaporator can be utilized most advantageously for cooling purposes, the gas heat exchanger desirably is connected in the gas circuit so that the cold gas contacts the outer wall of the exchanger. In this way the part of the heat exchanger within the cabinet may be utilized to aid the evaporator to obtain the greatest possible cooling effect. However, the part of the gas heat exchanger outside of the cabinet desirably is protected from the atmosphere, because objectionable condensation of moisture in atmospheric air tends to take place on the relatively cold outer surface of the heat exchanger.

It is an object of my invention to provide an improvement for protecting the outer projecting part of a gas heat exchanger with the aid of heat given up in other parts of the refrigeration system. More particularly, it is an object of the invention to shield the outer projecting part of the gas heat exchanger from the atmosphere by transferring heat thereto from the condenser. I

accomplish this by thermally blank-eting the part of the gas heat exchanger outside the cabinet with the aid of condensed refrigerant flowing from the condenser to the evaporator. Such blanketing can be readily eifected by utilizing a jacket about the outer projecting portion .of the heat exchanger as a part of the path of flow for relatively warm condensed refrigerant passing from the condenser to the evaporator.

Not only is condensed refrigerant effectivel employed to prevent atmospheric air contacting relatively cold parts of the refrigeration system and thereby avoid condensation of water vapor, but effective precooling of condensed refrigerant is obtained before entering the evaporator, so that the average or mean temperature of the evaporator is lowered. Further, condensed refrigerant passing from the jacket may be arranged to flow in thermal relation with the part (Cl. Gil-119.5)

of the heat exchanger within the cabinet, whereby further heat transfer can be effected between condensed refrigerant and cold gas. In order o supplement heat derived from condensed refrigerant for thermally shielding the outer projecting part of the gas heat exchanger, heat may also be transferred to the blanketing body of fluid from other places in the system. In accord with the invention this may be accomplished, for example, by transferring heat from weak absorption liquid, before the latter enters the absorber, to condensed refrigerant utilized to thermally shield the outer projecting part of the heat exchanger from atmospheric air.

The invention, together with the above and other objects and advantages thereof, will be better understood from the following description and accompanying drawing forming a part of this specification, and in which the single figure illustrates more or less diagrammatically an absorption refrigeration system embodying my invention.

In the drawing I have shown the invention embodied in an absorption refrigeration system of ,a type .employing a pressure equalizing agent. Such a system includes a vapor expulsion unit It, a condenser ll, an evaporator 12 and absorber I4 which are connected to one another in a manner well known in the art and which will be described briefly. The system contains a solution of refrigerant in absorption liquid, such as ammonia in water, for example, and also an auxiliary agent or inert gas, such as hydrogen.

The vapor expulsion unit [0 is heated in any suitable manner, as by a gas burner [5, for example, whereby refrigerant vapor is expelled from solution therein. Hence, fluid undergoes a change of state from liquid to vapor phase in the vapor expulsion unit It which may be referred to as a ,heat receiving part. The refrigerant vapor flows upwardly through a conduit t6 and air-cooled rectifier I! to the air-cooled condenser H in which such vapor is liquefied. Any vapor of absorption liquid accompanying refrigerant vapor is condensed in the rectifier I! and flows back to the vapor expulsion unit I0. Liquid refrigerant flows from condenser H to the evaporator I: in a manner to be explained presently, and such liquid introduced into the evaporator evaporates and diffuses into the inert gas which enters through a conduit 18 from an inner passage I9 of a gas ,heat exchanger 2t. Due to evaporation of refrigerant fluid into inert gas, a refrigerating effect is produced with consequent absorption of heat from the surroundings. As diagrammatically 3 shown, the evaporator i2 is disposed in a thermally insulated space 2| of a refrigerator cabinet which is defined by insulated walls 22.

The rich gas mixture of inert gas and refrigerant vapor formed in evaporator 12 flows from the upper part thereofthrough a conduit 23, outer passage 24 of gas heat exchanger 20, conduit 25 and absorber vessel 26 into the lower end of absorber Hi. In absorber l4, which is in the form of a looped coil, the rich gas mixture flows counter-current to downwardly flowing absorption liquid which enters through a conduit 21. The absorption liquid absorbs refrigerant vapor from inert gas, and inert gas weak in refrigerant flows from absorber M in a path of flow including conduit 28 inner passage l6 of gas heat exchanger 20 and conduit l8 into the lower part of evaporator l2.

The circulation of gas in the gas circuit just described is due to the difference in specific weight of the columns of gas rich and weak, respectively, in refrigerant vapor. Since the column of gas rich in refrigerant vapor and flowing from evaporator [2 to the absorber i4 is heavier than the column of gas weak in refrigerant vapor and flowing from the absorber M to evaporator I2, a force is produced or developed within the system for causing circulation of gas in the manner de scribed.

Absorption solution enriched in refrigerant flows from the absorber vessel 26 through a conduit 28' and an inner passage or pipe of a liquid heat exchanger 29 to a coil 36 disposed about the lower end of a heating flue 31 which extends upwardly through the vapor expulsion unit I0.

Liquid is raised by vapor-lift action from coil through a tube 32 into the upper part of the vapor expulsion unit it). Refrigerant vapor expolled out of solution in vapor expulsion unit l0, together with refrigerant vapor entering through tube 32, flows upwardly through conduit [5 into condenser H, as explained above. Absorption liquid from which refrigerant has been expelled flows from vapor expulsion unit [0 through a conduit 33, outer passage of liquid heat exchanger 29 and conduit 2'! into the upper part of absorber :4. This circulation of absorption liquid is effected by raising of liquid in tube 32 by vapor-lift action.

The outlet end of condenser l l is connected by an upper extension of a conduit 34, vessel 35 and conduit 36 to a part of the gas circuit, as to the conduit 25, for example, so that any inert gas which may pass through the condenser can flow into the gas circuit. Refrigerant vapor not liquefled in the condenser I l flows through the upper part of conduit 34 to displace inert gas in vessel 35 and force such gas into the gas circuit. The effect of forcing gas into the gas circuit in this manner is to raise the total pressure in the entire system whereby an adequate condensing pressure is obtained to insure condensation of refrigerant vapor in condenser I l.

The evaporator [2 may be formed of piping and includes an upper section [2a and a lower section [2b. Although the several evaporator sections are diagrammatically shown as looped coils disposed in a vertical plane, it is to be understood that the evaporator sections may be formed in any suitable manner. Inert gas weak in refrigerant flows through conduit l8 into the lower evaporator section 121) which can be eifectively employed as a freezing section. The inert gas flowing from the lower evaporator section l2b to the upper evaporator section In is partially enriched in refrigerant vapor, so that evaporation of refrigerant takes place at a higher temperature in evaporator section l2a than in section I21). Hence, the upper evaporator section l2a can be most effectively employed for space cooling, and as diagrammatically shown, may be provided with fins 3'[ to obtain a relatively ex-'- tensive heat transfer surface.

Liquid refrigerant flows from condenser H to the upper part of evaporator section l2a in a path of flow including conduit 38, and gravity fiow of such refrigerant takes place successively through evaporator sections 12a and [217. Any unevaporated refrigerant passing from the lower evaporator section l2b flows into a conduit 39 whose upper open end is immediately ahead of a dam or barrier 59 with respect to the direction of flow of liquid. Such unevaporated liquid refrigerant flows into the outer passage 24 of gas heat exchanger 20 and passes therefrom through conduit 25 to the absorber vessel 26.

The gas heat exchanger 23 comprises an elongated outer shell having the tubes [9 extending lengthwise thereof in spaced apart relation. The ends of tubes (9 are snugly held in openings in end plates ll and 42, respectively, and are secured to such plate-s at the regions of the openings. The end plates 4| and 42 are spaced from the end walls of the heat exchanger shell to form end spaces 43 and 44, respectively, which are in communication with the tubes [9.

It will now be understood that inert gas weak in refrigerant flows from absorber M to the lower end of evaporator section I2?) in a path of flow which includes conduit 28, end space 44, tubes It, end space 43 and conduit [8, the tubes [9 forming the inner passage of the gas heat exchanger Inert gas rich in refrigerant flows from the upper end of evaporator section 1211 to the absorber l4 in a path of flow which includes conduit 22;, the intermediate portion of the heat exchanger shell enveloping the tubes I9, conduit 25 and absorber vessel 26. Hence, the portion of the heat exchanger shell between the end plates 44 and 42, and through which inert gas rich in refrigerant flows, constitutes the outer passage 24 of the gas heat exchanger.

In absorber hi heat is liberated with absorpt on of refrigerant vapor into absorption liquid, so that warm weak gas passes from the end space 44 into the outer ends of the tubes l9. Heat exchange is effected between such warm weak gas and cold rich gas flowing from the evaporator section l2a into the outer passage 24 of the gas heat exchanger 23. The cool rich gas also passes in contact with the outer shell of th heat exchanger to effect cooling there-of. In this manner the portion of the gas heat exchanger disposed within the thermally insulated space 2| may b advantageously utilized to abstract heat therefrom.

In accordance with my invention the portion of the gas heat exchanger 20 outside of the thermally insulated wall 22 of the cabinet is thermally protected from atmospheric air by condensed refrigerant flowing from the condenser II to evaporator I2. I accomplish this by providing a jacket 45 which is spaced from and envelops the end space 44 and outwardly extending portion of the outer gas heat exchanger passage 24. If desired, the jacket 45 may extend inwardly and also envelop the portion of the outer gas heat exchanger passage 24 within the insulated wall 22. The jacket 45 is provided with a downwardly extending portion which is disposed about the upper part of conduit 25 and may be referred to as a secondary jacket 46.

In the condenser II heat of condensation is liberated when refrigerant vapor flowing thereto is condensed and liquefied. Hence, fluid in condenser ll undergoes a change of state from vapor to liquid phase and heat is liberated by the condenser during operation of the system. The warm condensed refrigerant flows from condenser ll through conduit 34 into secondary jacket it and jacket 45. From the upper part of jacket 45 condensed refrigerant then flows through conduit 38 into the upper part of evaporator section I211. The conduit 34, jackets 46 and 45 and conduit 38 essentially form a U- shaped liquid trap leading from the condenser H to the evaporator 12, the upper overflow end of conduit 33 being at a level below the region at which the outlet end of condenser II is connected to the conduit 3d.

During operation of the refrigeration system, therefore, the jackets 45 and 46 are completely filled with condensed refrigerant, thereby shielding the outer projecting part of the gas heat exchanger from the atmosphere and preventing atmospheric air coming in contact with relatively cold portions of the gas heat exchanger. Since the warm condensed refrigerant supplied through conduit 34 completely fills the jackets 45 and 45 and contacts the inner surfaces thereof, the likelihood of condensation taking place at the exterior surfaces of the jackets is avoided.

The secondary jacket 46 shields the upper part of conduit 25 from atmospheric air and is sufficiently long so that, when the rich gas passes into the lower portion of the conduit not enveloped by the secondary jacket, its temperature is sufficiently high to avoid condensation even though atmospheric air can come in direct contact with the conduit. The length of the secondary jacket 46 will depend, of course, upon several factors including the operating temperature of evaporator l2 and the relative humidity of the air encountered at the place of use.

Since the condensed refrigerant in jackets 46 and 45 comes in contact with relatively cool portions of the conduit 25 and gas heat exchanger shell, its temperature is lowered by heat exchange with cool rich gas. Further, cooling of condensed refrigerant can also be effected by arranging conduit 38 in thermal relation with the outer shell of the gas heat exchanger, as indicated at 41. If desired, further cooling of condensed refrigerant can be effected by arranging conduit 33 in thermal relation with conduit 23. Such heat exchange may be accomplished by thermally connecting conduits 23 and 34 directly to one another or by a suitable heat conductive block or connection 48 which extends lengthwise of the conduits for the desired distance.

If desired, heat may be transferred to condensed refrigerant from other places in the refrigeration system so that the blanketing body of liquid in jacket 45 will be maintained at a sufficiently high temperature under the most adverse conditions encounterd. Thus, conduit 28 may be arranged in thermal relation with conduit 25 or secondary jacket 46. These parts may be in direct thermal contact or a suitable heat conductive member 41' may be provided therebetween. In such case not only is the heat of condensation developed in condenser ll utilized to protect the outer projecting part of gas heat exchanger 20, but additional heat is 6 transferred to the warm condensate by warm gas passing upwardly in conduit 28 from the upper end of absorber [4.

Further, additional heat may be transferred to the condensed refrigerant entering jacket 46 from weak absorption liquid flowing through conduit 21. This may be accomplished by arranging conduits 25 and 21 in thermal conductive relation, as indicated at 48', for example. By selecting a liquid heat exchanger 29 of ap-' propriate size, the desired extent of heat transfer effected between the fluids in conduits 25 and 21 can be obtained, thereby reducing the temperature of weak absorption solution flowing to the absorber l4 and increasing the temperature of conduit 28 and secondary jacket 46. To promote transfer of heat from the condenser l I and conduits 26 and 21 to the blanketing liquid in the jackets 45 and 46, the conduits 34, 25, 26 and 21 may be provided with a covering of suitable insulating material.

Modifications of the embodiment of my invention which I have described will occur to those skilled in the art. For example, under certain operating conditions encountered the outer projecting part of the gas heat exchanger may be adequately protected with the aid of heat transferred from one or both of the conduits 21 and 28. In such case the outer projecting part of the gas heat exchanger and conduit 25 may be formed with Walls which are relatively thick, or the heat conductivity of these parts may be improved by a metallic coating formed of aluminum or zinc, for example. When this is done, the metallic coated parts desirably may be jacketed to provide spaces which are evacuated or filled with a suitable insulating material. Therefore, I intend in the claims to cover all modifications which do not depart from the spirit and scope of my invention.

What is claimed is:

1. A refrigerator having a thermally insulated space, a refrigeration system including .a condenser, an evaporator arranged to abstract heat from said space and in which refrigerant evaporates in the presence of inert gas, conduit means for conducting liquid refrigerant from said condenser to said evaporator, first means providing a first path of flow for gas flowing to said evaporator, second means providing a second path of flow for gas flowing from said evaporator, at least a part of said first means being disposed within said second means to form a heat exchanger, a part of said heat exchanger being disposed outside said space, and structure forming an enclosure about the part of said heat exchanger outside said space, said enclosure forming a part of said conduit means for conducting liquid refrigerant from said condenser to said evaporator.

2. A refrigerator as set forth in claim 1 in which said conduit means for conducting liquid refrigerant from said condenser to said evaporator includes a trap normally filled with liquid during operation of the system, and said enclosure forming a part of said conduit means constitutes a portion of such trap.

3. A refrigerator as set forth in claim 1 in which said system includes a circuit for absorption liquid, and structure providing a solid heat conductive path for transferring heat from said absorption liquid circuit to liquid in said enclosure.

4. A refrigerator including a cabinet having thermally insulated walls defining a space, a re- 7 frigeration System employing a pressure equalizing fluid which comprises a plurality of parts including a heat exchanger forming a circuit for circulation of such fluid, said system including high temperature parts at a temperature above that of surrounding atmospheric air during operation of the system, said high temperature parts including a heat receiving part and another part in which fluid undergoes a change of state from vapor to liquid phase and heat is liberated during operation of the system, said heat exchanger having an outer portion exteriorly of said space which is at a temperature below that of surrounding air during operation of the system, and structure to transfer heat to the outer portion of said heat exchanger in a manner to protect the latter from atmospheric air, said structure comprising means forming an enclosure about the outer portion of said heat exchanger and conduit means including such enclosure providing a path of flow from liquid from said other part in which fluid undergoes a change of state from vapor to liquid phase, said enclosure providing a trap in said conduit means which is normally filled with liquid during operation of the system.

5. A refrigerator including a cabinet having thermally insulated walls defining a space, a re frigeration system employing a pressure equalizing fiuid which comprises a plurality of parts including a condenser in which refrigerant vapor is condensed, an evaporator arranged to abstract heat from said space and a circuit for circulation of said equalizing fluid including said evaporator and a heat exchanger, said system comprising high temperature parts including said condenser at a temperature above that of surrounding atmospheric air during operation of the system, said heat exchanger having an outer portion exteriorly of said space which is at a temperature below that of surrounding air during operation of the system, and structure to transfer heat to the outer portion of said heat exchanger in a manner to protect the latter from atmospheric air, said structure comprising means forming an enclosure about the outer portion of said heat exchanger and conduit means including such enclosure providing a path of flow for condensed refrigerant from said condenser to said evaporator, said enclosure comprising a trap in such path of flow which is normally filled with liquid during operation of the system, and said conduit means including a region in thermal relation with the portion of said heat exchanger within said space and into which condensed refrigerant flows from said enclosure.

6. A refrigerator having a thermally insulated space, a refrigeration system including an evaporator arranged in thermal transfer relation with said space and in which refrigerant evaporates in the presence of an inert gas, said system embodying provisions to provide at a place at a first level liquid having a relatively high concentration of refrigerant, means including an absorber and a gas heat exchanger having an inner passage to provide a first path of fiow for conducting gas from said absorber to said evaporator and an outer passage to provide a second path of flow for conducting gas from said evaporator to said absorber, a part of said gas heat exchanger being outside said space and above said absorber, structure providing an enclosure enveloping substantially the entire portion of said heat exchanger disposed outside said space, first conduit means for conducting by gravity from the place at said first level to said enclosure liquid having the relatively high concentration of refrigerant, and second conduit means for conducting said liquid from the upper part of said enclosure to maintain liquid in the latter in physical contact with the portion of said heat exchanger disposed outside said space during operation of the system.

GUNNAR AXEL GRUBB.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,181,376 Lynger Nov. 28, 1939 2,229,697 Grubb Jan. 28, 1941 2,242,282 Bergholm May 20, 1941 2,267,283 Lenning Dec. 23, 1941 2,267,893 Bergholm Dec. 30, 1941 2,489,752 Coons Nov. 29, 1949 2,533,031 Miller Dec. 5, 1950 2,536,342 Ashby Jan. 2, 1951

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