US2635438A - Absorption refrigeration apparatus - Google Patents

Description

April 21, 1953 AK. G... BOREN ABsoRPTIoN REFRIGERATION APPARATUS.

Filed Nov. 15, -1948 .fvlllalllllllllnz rllltlrllllllllllvvlf W mfr/vir April 21, 1953 K. G. BOREN 2,635,438

ABSORPTION REFRIGERATION APPARATUS Filed Nov. l5, 1948 A5 Sheets-Sheet 2 @47 J7 effi! MV da 9'? J INVENTOR.

April 21, 1953 K. G. BoRi-:N 2,635,438

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Patented Apr. 21, 1953 UNi'iED STATES NT OFFICE Karl Gunnar Boren, Stockholm, Sweden, assigner to Aktiebolaget Elektrolux, Stockholm, Sweden,

a corporation of Sweden Application November 13, 1948, Serial No. 59,870 In Sweden November 1S, 1947 (Cl. (i2-103) 4 Claims.

This invention relates to refrigeration and is particularly concerned with cooling of a relatively large supporting surface with the aid of an absorption refrigeration system employing evaporation of refrigerant fluid in the presence of an inert gas or auxiliary agent.

In absorption refrigeration systems of this type the evaporator is formed of tubing or piping which is bent to provide a coil having a number of straight portions and connecting bends. When such an evaporator coil is employed to effect cooling of a plate having an extensive area, such as, for example, a partition which is adapted to subdivide a refrigerator storage space into several compartments, diiiiculty is usually encountered to obtain a good thermal connection between the coil and plate. Since the supporting plates are often formed of sheet metal, such plates are not perfectly flat. The evaporator coil is of considerable length and essentially disposed in a single horizontal plane. Such evaporator coils are not perfectly fiat, and this is especially true of evaporator coils for absorption refrigeration systems of the inert gas type which are bent into shape from steel tubing or piping. Evaporator coils of this type are essentially rigid and cannot be readily worked to conform to a particular shape of a supporting plate to which it is to be iXed and obtain a good thermal connection therebetween.

Further, in large scale manufacturing operations, it is difficult to produce satisfactory flat evaporators because the flat supporting plates and evaporator coils adapted to be thermally connected thereto often become deformed during fabrication. This is particularly true when plates and coils are subjected to heating, and any deformation resulting therefrom requires time consuming straightening operations.

In accordance with this invention, the foregoing objections and difficulties are avoided by mechanically anchoring the evaporator coil to a plate having a relatively extensive area, and providing a good thermal connection between the plate and coil, along the entire length of the latter, by a metallic binding agent which also forms a corrosion protective layer for the evaporator structure.

It is, therefore, a primary object of the invention to provide in absorption refrigeration apparatus of the inert gas type an improved flat evaporator structure having a relatively eXtensive area which is eiicient in operation and also readily fabricated.

The above and other objects and advantages of the invention will be more fully understood from the following description taken in conjunction with the accompanying drawings froming a part of this specification, and of which:

Fig. l illustrates more or less diagrammatically an absorption refrigeration system of the inert gas type to which the invention is applied;

Fig. 2 is a fragmentary front elevation, partly broken away and in section, looking toward the rear of a storage space of a refrigerator diagrammatically illustrating evaporator structure in accord with the invention which is embodied in a refrigeration system like that diagrammatically shown in Fig. 1;

Fig. 3 is a fragmentary side vertical View, partly broken away and in section, of the refrigerator shown in Fig. 2 to illustrate the evaporator structure and connections thereto more clearly;

Fig. 4 is a top plan View of the evaporator structure shown in Figs. 2 and 3, the rear wall part of the refrigerator with which it is associated being omitted; and

Figs. 5 and 6 are detailed views of the upper and lower parts of the evaporator structure shown in Figs. 2, 3 and 4.

Referring to Figs. 2 and 3, a household refrigerator I0 having a storage space II is subdivided into a plurality of compartments I2 and I3 one above the other and arranged to be cooled by a plurality of evaporators I4 and I5 operable at different temperatures. The subdivided compartments I2 and I3 extend between the lateral side Walls It of the storage space, and one such subdivided compartment is adapted to be maintained at a low temperature for freezing water and other matter as well as for storing frozen food packages.

In absorption refrigeration systems of the inert gas type having evaporators i4 and I5 adapted to operate at different temperatures, such evaporators are generally formed of piping which are shaped as coils and connected by conduits to other parts of the system for circulation of inert gas as well as to supply liquid refrigerant to the evaporators. When such an absorption refrigeration system is employed in the cabinet of a household refrigerator, the evaporators Id and I5 and connections thereto are usually inserted into the storage space Il through an opening in a wall il of the cabinet adapted to be closed by an insulated closure member I8, as shown in Fig. 3.

An absorption refrigeration system of the inert gas type to which the invention is applied is more or less diagrammatically shown in Fig. l.

In order to simplify Fig. 1 the evaporators I4 and I5 have been illustrated apart from a household refrigerator having subdivided compartments one above the other. The absorption refrigeration system shown in Fig. 1 is of a uniform pressure type in which an inert gas or auxiliary pressure equalizing uid is employed.

In a system of this type a refrigerant uid, such as liquid ammonia, for example, is introduced through a conduit I9 into the evaporators I4 and I5. The refrigerant fluid evaporates and diffuses in evaporators I4 and I5 into an inert gas, such as hydrogen, for example, to produce a refrigerating effect and abstract heat from the surroundings. The resulting gas mixture of refrigerant and inert gas flows from the evaporators I4 and I5 through an outer passage 20 of the gas heat exchanger 2| and vertical conduit 22 into an absorber comprising a vessel 23 and a looped coil 24. In the absorber vessel 23 and coil 24 refrigerant vapor is absorbed by a suitable absorbent, such as water, for example, which is introduced into coil 24 through a conduit 25. The hydrogen or inert gas, which is practically insoluble and weak in refrigerant, is returned to the evaporators I4 and I5 through an inner passage 26 of the gas heat exchanger 2I and a conduit 2T.

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 evaporators I4 and I5 to the absorber coil 24 is heavier than the gas Weak in refrigerant and flowing from such coil to the evaporators I4 and I5, a force is produced or developed within the system for causing circulation of inert gas in the manner described.

From the vessel 23 enriched absorption liquid flows through a conduit 28 and an inner passage 29 of a liquid heat exchanger into the lower end of a vapor lift tube 30 of a generator unit 3|. The generator unit 3I comprises a heating flue 32 having the vapor lift tube 30 and a boiler pipe 33 in thermal exchange relation therewith, as by welding, for example. By heating generator unit 3l, as by a gas burner 34, for example, liquid from the inner passage 29 of the liquid heat exchanger is raised by vapor lift action through tube 30 into the upper part of the boiler pipe 33. The liberated refrigerant vapor entering boiler pipe 33 through the tube 3D, and also vapor expelled from solution in the boiler pipe, flows upwardly into an air cooled condenser 35 provided with a plurality of cooling fins 36.

Refrigerant vapor is liquefied in the condenser 35 and returned to the evaporators I4 and I5 through the conduit I9 to complete the refrigerating cycle. The lower end of condenser 35 is connected by a conduit 31 to the gas circuit, as to the upper part of absorber coil 24, for example, so that any non-condensable gas that may pass into the condenser will flow to the gas circuit and not be trapped in the condenser. The weakened absorption liquid, from which refrigerant vapor has been expelled, is conducted from boiler pipe 33 through a conduit 38, the outer passage 39 of the liquid heat exchanger and conduit 25 into the upper part of the absorber coil 24.

It will be understood that the evaporators I4 and I5 in Fig. l are diagrammatically shown in the form of a continuous coil, and that in Figs. 2 to 6 a practical form of the evaporator structure in accord with the invention is illustrated in which the evaporators I4 and I5 comprise horizontally disposed coils at different levels. As shown in Figs. 3 and 4, the evaporator coils I4 and I5 are connected in series relation with inert gas from point 21a flowing through evaporator coil I4 in the presence of and in parallel Aflow with liquid refrigerant which is introduced through conduit I9. From the evaporator coil I4 inert gas then passes through a vertical connecting conduit 40 for flow through the lower evaporator coil I5. Unevaporated liquid refrigerant is conducted from the upper evaporator coil I4 through the vertical connection 49 into the lower evaporator coil I5. Such liquid refrigerant flows in the presence of and in parallel flow with the inert gas in the lower evaporator coil I5. In order to obtain good distribution of liquid refrigerant in the evaporator coils I4 and I5 and promote evaporation and diffusion of refrigerant fluid into the inert gas, the coils may be provided with suitable inserts, such as wire coils, for example.

As shown in Fig. 4, inert gas rich in refrigerantpasses from the evaporator coil I5 at 4I into one end of the outer passage of the gas heat ex changer 2I, the opposite end of which communicates with the vertical conduit 22 connected at its lower end to the absorber vessel in the manner shown in Fig. 1. Inert gas weak in refrigerant and flowing from the absorber coil, like the coil 24 in Fig. 1, for example, passes through a conduit 42 disposed about the conduit 22. From the upper end of conduit 42 weak gas passes through the inner passage of the gas heat exchanger 2I and to the upper evaporator coil I4 at 21a.

In order to precool liquid refrigerant passing through conduit I9 to the upper evaporator coil I4, the conduit I9 at spaced apart regions is connected by conduits 43 and 44 to the outer passage 20 of the gas heat exchanger 2I through which inert gas rich in refrigerant flows from the lower evaporator coil I5 to the absorber. In this way natural circulation of a part of the rich gas takes place through a local circuit including conduits 43 and 44 and a portion of conduit I9. Liquid refrigerant in conduit I9 evaporates and diffuses into rich gas above the liquid surface level thereof, thereby taking up heat from the liquid refrigerant. Liquid refrigerant precooled in this manner passes to the upper evaporator coil I4 through a part of conduit I 9 provided with a liquid trap 45. The liquid trap 45 prevents weak gas from conduit 2'I entering the conduit I9 and flowing into the gas heat exchanger 2I through conduits 43 and 44.

In order to provide a maximum amount of usable storage space in the subdivided compartments I2 and I3, the evaporator coils I4 and I5 desirably are associated with the partition providing such compartments. As best shown in Figs. 2, 3 and 4, the partition comprises a boxlike container 46 which extends substantially over the entire width and depth of the storage space II, whereby circulation of air between the upper and lower compartments I2 and I3 is substantially prevented.

The upper evaporator coil I4 is in thermal exchange relation with the underside of the top horizontal wall 41 of the container 46, and the lower evaporator coil I5 is in thermal exchange relation with the top surface of the bottom horizontal wall 48 of the container. Since the inert gas ows successively through the evaporator coils I4 and I5, the gas in the upper evaporator coil I4 contains a lesser amount of refrigerant vapor than the gas in the lower evaporator coil I5. The partial vapor pressure of the refrigerant is a gradient, so that the temperature of. liquid refrigerant in the evaporator coils is also a gradient, the evaporating temperature of liquid being lower in the upper evaporating coil I4 which constitutes the freezing portion of the evaporator structure.

The refrigerating effect produced by the upper evaporator coil I4, which is adapted to be operated at temperatures below freezing, is utilized to effect cooling of the upper compartment I2 which is dened by the partition 46 and the thermally insulated walls of the refrigerator IIJ. Accordingly, the upper compartment I2 serves as a freezing space which is adapted to receive ice trays, frozen food packages and other matter to be frozen. The refrigerating effect produced by the lower evaporator coil I5, which is adapted to be operated at a higher temperature than that of evaporator coil I4 and desirably above freezing, is utilized to cool air in the lower cornpartment I3.

In accordance with this invention the upper evaporator coil I4, which is formed of piping including spaced apart straight portions and connecting bends, is fixed in heat conductive relation with the underside of the top horizontal wall 41 of the container 46 by a number of U- shaped clamps or bracket members 49 having flanges 56 which are secured, as by spot welding, for example, to such wall. Similarly, the lower evaporator coil I5 is fixed in heat conductive relation with the top surface of the bottom horizontal wall 4S of the container 46 by a number of U-shaped clamps or bracket members 5I having anges 52 secured to such wall. As best seen in Figs. 5 and 6, the U-shaped clamps 49 and 5I are provided at the straight portions of the evaporator coils Ill and I5 and arranged relatively olose to one another. Further, the coil straight portions and connecting bends are distributed over the entire surfaces of the horizontal Walls 41 and 48 between the lateral side walls 53 of the container 46.

The top horizontal wall 41, opposing side walls 53, front wall 54 and rear plate 55 of the container 46 are desirably formed by a single sheet metal stamping. Such sheet metal stamping is shaped to provide a forward or front ledge 56, a rear ledge 51, side ledges 58 and a ledge 5S midway between the side ledges and parallel thereto. These ledges form two pockets or recesses 60 and 6I in the top horizontal wall 41 at opposite sides of the ledge 59, the recess 6I being of greater depth than the recess 68. Hence, one part of the top horizontal wall 41 is at a slightly higher level than the other part, and the upper evaporator coil I4 is xed to the underside thereof in such a manner that the portion of the coil nearer the region liquid refrigerant is supplied thereto is positioned at the higher located part of the top horizontal wall. With such step down in level between two portions of the upper evaporator coil I4, satisfactory circulation of fluids in the evaporator structure is always assured.

The bottom horizontal wall 48, front ilange 62, side anges 63 and rear plate 6i are also formed by a single sheet metal stamping. As shown in Figs. 2 and 3, the sheet metal stamping providing the bottom horizontal wall 48 snugly nts within the sheet metal stamping providing the top horizontal wall 41, the flanges 62 and 63 of the former being disposed adjacent the lower edge portions of the side and front walls 53'and 54 of the latter and secured thereto at l65, as by welding, for example.` To provide a `relatively extensive heat transfer surface at the underside of the bottom horizontal wall 48, a plurality of heat transfer members 66 may be fixed thereto, as by Welding, for example. The heat transfer members 66, which are U-shaped in section and have the spaced apart sides thereof extending downwardly, are arranged more or less parallel to the lateral side walls 53 of the container 45.

In order to drain water and other liquid which may collect on the top horizontal wall 41 in the recesses 60 and 6I, hollow tubes 61 are provided within the container 46 which are secured `at their upper and lower ends to the top and bottom horizontal walls 41 and 48, respectively, at the regions of vertically aligned openings 68 and 69 in the walls. One or more hollow tubes 61 maybe provided at each side of the ledge 59 for conducting water and the like from the top horizontal wall 41 to regions below the container 46, and suitable vessels (not shown) may be provided in the lower compartment I3 for collecting such water.

The sheet metal stamping providing the bottom horizontal wall 48 of the container 46 is formed with a groove or channel 10 which is adjacent to the rear plate 64 and extends from one lateral side wall 53 to the opposite side wall, as best shown in Figs. 3 and 6. The bottom wall 48 at the region of the groove 1I) is provided with one or more openings 1I for conducting from the interior of the container 46 any water which may collect therein. The water discharged from the opening or openings 1I may be collected in suitable vessels (not shown).

In Fig. 3 it will be seen that the rear plates 55 and 64 of the upper and lower parts of the partition or container 46 are disposed in the same vertical plane and utilized as the inner liner of the insulated closure member I8. Hence, the container 46 and closure member I8 form a unitary structure which vcan be inserted into position as a unit when .the evaporator structure is placed within the storage space II of the refrigerator I0.

When the evaporator coils I4 and I5 are in thermal exchange relation with the opposing horizontal walls 41 and 48 of the container 46, a gap is formed between the coils. It has been found that even when no insulating material is provided in the container 46, the upper and lower coils I4 and l5 are thermally shielded from one another adequately to maintain a satisfactory temperature differential between the opposing horizontal walls 41 and 48, this being due to the poor heat conductive path formed by the front wall 54 and side walls 53 of the container.

In constructing an absorption refrigeration system provided with an evaporator structure like that illustrated and just described, the upper evaporator coil I4 is positioned at the underside of the sheet metal stamping providing the upper horizontal wall 41, and, after the U-shaped clamps 49 are placed over the straight portions of the coil, the flanges 58 are spot Welded to the wall 41 to hold the coil firmly against the wall. The lower evaporator coil I5 in a similar manner is clamped firmly in position to the sheet metal stamping providing the lower horizontal wall 48. The two parts of the container 46 are then assembled so that the anges 62 and 63 snugly fit within the front and side walls 54 and 53 adjacent the lower edge portions thereof, and these contacting regions are secured together along their lengths at 65, as by spot Welding.

Before the two parts of the container 46 are assembled in the manner just described, the connecting conduit 40 is welded to one of the evaporator coils I4 and I5. After the container parts are assembled, the connecting conduit 40 is welded to the other evaporator coil, as at the joint indicated at 12 in Fig. 3, for example. The gas heat exchanger 2| is then connected by welding to the upper and lower evaporator coils I4 and I5 and also to the liquid refrigerant conduit I9, and the latter is connected by welding to the upper evaporator coil I4.

The container 46 and evaporator coils I4 and I5 fixed therein are next subjected to hot galvanizing treatment, whereby molten zinc or other suitable corrosion protecting agent penetrates into and fills the minute spaces or gaps between the coils and opposing walls 41 and 48. In this way a good heat conductive connection is obtained between the Walls 41 and 48 and evaporator coils along the entire length of the coils including not onlf,7 the straight portions but also the connecting bends.

To facilitate dipping of the container 46 into a body of molten zinc or other like corrosion protecting agent, the front wall 54 of the container is formed with openings 13, as shown in Fig. 2. This permits the molten metal to flow from the interior of the container 46 when the latter is removed from the body of molten metal into which it has been dipped. The openings 73 may thereafter be closed in any suitable manner, as by closure members (not shown) adapted to snap into position, for example.

After subjecting the evaporator structure to anti-corrosive treatment, the liquid refrigerant conduit I9 is connected by welding to the condenser 35 and the gas heat exchanger 2I to the absorber, these parts in turn being connected to other parts of the refrigerating system. In this manner the welding operations effected after the evaporator structure is fabricated, are sufficiently removed from the latter so that the thermal connection between the coils and walls of the container will not be impaired.

When the containeri46 is positioned in the storage space II of the refrigerator I0, the upper compartment I2 may be provided with a suitable closure member (not shown) at the front wall 53 of the container to provide access to the freezing space.

In view of the foregoing, it will now be understood that an improved evaporator structure has been provided in which an evaporator coil is mechanically anchored to the underside of a plate or supporting surface of relatively great area and also in good thermal connection therewith by a metallic binding agent. Such metallic agent not only provides a good thermal connection along the entire length of the evaporator coil which is essentially disposed in a single horizontal plane, but also forms a corrosion protective layer for the evaporator structure. When the plate or supporting surface to which the evaporator coil is mechanically anchored forms the top wall of a container which is employed to subdivide a storage space of a refrigerator into several compartments, the metallic binding agent not only improves the thermal connection of the evaporator coil to the top wall of the container but also provides a corrosion protective layer in the interior as well as at the exterior of such container.

While a particular embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

1. A refrigerator comprising a cabinet having thermally insulated walls forming a space, one of said walls having a normally closed opening, absorption refrigeration apparatus employing evaporation of refrigerant fluid in the presence of an inert gas, said refrigeration apparatus comprising a plurality of interconnected parts including a plurality of cooling elements and a gas heat exchanger for gas fiowing to and from said cooling elements, and structure providing a chamber for housing said gas heat exchanger and said cooling elements, one part of said structure serving as a removable closure member for the wall opening and within which at least a major portion of said gas heat exchanger is disposed, insulation in said one part enveloping said gas heat exchanger, another part of said structure projecting inwardly into said space, said cooling' elements being arranged in thermal exchange relation with the opposing top and bottom horizontal walls of said other part and unobstructedly facing each other, the top and bottom walls of said other part having openings and a vertically extending tubular member joined to said walls at the openings and having the upper end thereof flush with the top wall to drain water collecting on said top wall.

2. In absorption refrigeration apparatus employing evaporation of refrigerant fluid in the presence of an inert gas, evaporator structure comprising first and second members each including an essentially flat portion, a rst looped coil extending over a face of the fiat portion of said first member, a second looped coil extending over a face of the flat portion of said second member, means including fastening elements fixed to said first and second members for mechanically anchoring said coils against the faces thereof, means for connecting said rst and second members to one another, said members including additional portions besides said fiat portions which together form a hollow shell within which said coils are disposed when said first and second members are connected to one another, said looped coils being formed of ferrous metal, and means including a non-ferrous agent within said hollow shell at the regions said coils are anchored to said members to provide a thermal conductive path therebetween, said agent possessing corrosion resisting properties and providing a protective coating on said coils.

3. In absorption refrigeration apparatus employing evaporation of refrigerant fiuid in the presence of an inert gas, evaporator structure comprising a flat metallic container subject to corrosive action and adapted to serve as a partition in a storage space of a refrigerator cabinet, a pair of looped coils of ferrous metal comprising a plurality of straight portions and connecting bends, said coils being disposed essentially in horizontally extending planes, members fixed to the interior of said container for mechanically anchoring said coils to the inside surfaces of the opposing top and bottom horizontal Walls of said container, said top wall constituting a shelf for supporting matter to be refrigerated, said coils and container walls while mechanically held together having gaps therebetween, and means including a non-ferrous metallic agent within said container at the regions said coils are anchored to said walls which lls said gaps and adheres to said coils and walls to provide a good thermal conductive path therebetween, said non-ferrous metallic agent possessing corrosion resisting properties and providing a protective coating on said coils and interior surfaces of said container.

4. A refrigerator comprising a cabinet having thermally insulated walls forming a space, one of said walls having a normally closed opening, absorption refrigeration apparatus employing evaporation of refrigerant fluid in the presence of an inert gas, said refrigeration apparatus comprising a plurality of interconnected parts including a plurality of cooling elements and a gas heat exchanger for gas owing to and from said cooling elements, and structure providing a chamber for housing said gas heat exchanger and said cooling elements, one part of said structure serving as a removable closure member for the wall opening and within which at least a major portion of said gas heat exchanger is disposed, insulation in said one part enveloping said gas heat exchanger, another part of said structure constituting a hollow partition Which is disposed in said space, said cooling elements being arranged Within said hollow partition in thermal exchange relation with the Opposing top and bottom horizontal walls thereof and un- 10 obstructedly facing each other through yan air space, said top horizontal wall providing a supporting surface for matter to be refrigerated, and said hollow partition including provisions for draining any water collecting on a surface thereof, such draining provisions including a groove or depression formed in said bottom wall and in which water may collect, said bottom Wall having an opening at the region of said depression for draining Water collecting therein.

KARL GUNNAR BOREN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,706,982 Murray et al, Mar. y26, 1929 1,982,075 Smith Nov. 27, 1934 1,987,422 Steenstrup Jan. 8, 1935 1,987,707 Replogle Jan. 15, 1935 2,064,141 Askin Dec. 15, 1936 2,211,713 Bergholm Aug. 13, 1940 2,271,437 Lewis Jan. 27, 1942 2,345,453 Brace Mar. 28, 1944 2,363,385 Bixler Nov. 21, 1944 2,371,214 Beach Mar. 13, 1945 2,386,889 Furry Oct. 16, 1945 2,407,733 Ashby Sept. 17, 1946 2,450,305 Shoemaker Sept. 28, 1948 2,550,512 Woolvich Apr. 24, 1951

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