US2728201A - Absorption refrigerator of the inert gas type - Google Patents

Description

G. A. GRUBB 2,728,201

ABSORPTION REFRIGERATOR OF THE INERT GAS TYPE Dec. 27, 1955 Filed Oct. 20, 1951 2 Sheets-Shea; l

w .73 J7" a4 45 2&2

wzf M Dec. 27, 1955 e. A. GRUBB 2,728,

ABSORPTION REFRIGERATOR OF THE INERT GAS TYPE Filed Oct. 20, 1951 2 Sheets-Sheet 2 BY I Qb/I; M

4 ATTORNEY United States Patent a.

ABSORPTION REFRIGERATUR OF THE TNERT GAS TYPE Gunnar Axel Grnbb, Bromzna, Sweden, assignor to Aktiebolaget Elektrolnx, Stockholm, Sweden, a corporation of Sweden Application October 20, 1951, Serial No. 252,312

Claims priority, application Sweden October 25, 1950 Claims. (U. 62-95) My invention relates to absorption refrigeration systems of the inert gas type, and more particularly relates to such a refrigeration system having plural temperature evaporator structure.

It is an object of my invention to provide an improved evaporator structure in which several cooling elements operable at different temperatures may be effectively employed to cool the thermally insulated interior of a refrigerator cabinet and a freezing section disposed therein. I accomplish this by providing an inert gas circuit having low and higher temperature evaporators which are formed of piping and disposed in the interior of a refrigerator, the low temperature evaporator having a plate-like supporting surface and piping associated therewith which is essentially disposed in a single horizontal plane, and the higher temperature evaporator having a relatively extensive heat transfer surface and piping including a horizontally extending portion at a higher level than the horizontal plane of the piping forming the low temperature evaporator. The higher temperature avaporator is closely adjacent to the low temperature evaporator and provides an arrangement which assures gravity flow of liquid refrigerant successively through the higher and low temperature evaporators, respectively, even though an elongated path of flow for liquid refrigerant is provided by the low temperature evaporator piping which is disposed essentially in a single horizontal plane.

The invention, together with the above and other objects and advantages thereof, will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a fragmentary front view of the interior of a refrigerator embodying the invention;

Fig. 2 is a fragmentary side vertical section of the refrigerator shown in Fig. 1 to illustrate details more clearly;

Fig. 3 is a fragmentary perspective view of parts shown in Figs. 1 and 2; and

Fig. 4 illustrates more or less diagrammatically the type of refrigeration system with which the parts shown in Figs. 1, 2 and 3 are associated.

Referring to Figs. 1 and 2, a household refrigerator is provided with a low temperature freezing section 11 which is disposed in a higher temperature food storage space 12. The freezing section 11 and storage space 12 are arranged to be cooled by a plurality of evaporators or cooling elements 14 and 15 which are operable at different temperatures. The evaporators 14 and 15 form part of an absorption refrigeration system of the inert gas type and are usually inserted into the storage space 12 at the rear of the refrigerator in any suitable manner, such as, for example, through an opening in the rear insulated wall which is adapted to be closed by an insulated closure member 16. A refrigeration system of this type is more or less diagrammatically shown in Fig. 4 in which the evaporators 14 and 15 are illustrated apart from a household refrigerator.

The system illustrated is of a uniform pressure type employing an inert gas or pressure equalizing agent. In Fig. 4 a refrigerant fluid, such as liquid ammonia, for example, is introduced through a conduit 17 into the evaporators 14 and 15.

The refrigerant fluid in evaporators 14 and 15 evaporates and diffuses 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 evaporators 14 and 15 through an inner passage 18 of a gas heat exchanger 19 and vertical conduit 20 into an absorber comprising a vessel 21 and a looped coil 22. In the absorber vessel 21 and coil 22 refrigerant vapor is absorbed by a suitable absorbent, such as water, for example, which is introduced into coil 22 through a conduit 23. The hydrogen or inert gas, Which is practically insoluble and Weak in refrigerant, is returned to the evaporators 14 and 15 through an outer passage 24 of the gas heat exchanger 19 and a conduit 25. 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 14 and 15 to the absorber coil 22 is heavier than the gas weak in refrigerant and flowing from such coil to the evaporators 14 and 15, a force is produced or developed within the system for causing circulation of ineit gas in the manner described.

From the vessel 21 enriched absorption liquid flows through a conduit 26 and an inner passage 27 of a liquid heat exchanger 28 into the lower end of a vapor lift pump 29 of a generator unit 31). The generator unit 30 comprises a heating tube 31 having the vapor lift pump 29 and a boiler pipe 32 in thermal exchange relation therewith, as by welding, for example. By heating generator unit 30, as by an electrical heating element within the lower part of heating tube 31 or by a fluid fuel burner, for example, liquid from the inner passage 27 of the liquid heat exchanger is raised by vapor lift action through pump 29 into the upper part of the boiler pipe 32. The liberated refrigerant vapor entering boiler pipe 32 through the pump 29, and also vapor expelled from solution in the boiler pipe, flows upwardly into an air cooled condenser 33 provided with a plurality of cooling fins 34.

Refrigerant vapor is liquefied in the condenser 33 and returned to the evaporators 14 and 15 through the conduit 17 to complete the refrigerating cycle. Gravity flow of liquid refrigerant is effected through the evaporators, the lower evaporator 14 receiving liquid refrigerant from the upper evaporator 15. The outlet end of condenser 33 is connected by a conduit 35 to the gas circuit, as to the upper part of the absorber coil 22, 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 32 through a conduit 36, the outer passage 37 of the liquid heat exchanger 28 and conduit 23 into the upper part of absorber coil 22.

It will be understood that the evaporators 14 and 15 in Fig. 4 are diagrammatically shown in their relation to. other parts of the system, and that in Figs. 1, 2 and 3 a practical form of the evaporator structure in accord with the invention is illustrated in which the evaporator 14 comprises a horizontally disposed coil located essentially in a single horizontal plane, and evaporator 15 comprises a vertically disposed coil projecting upwardly from the horizontal plane of evaporator 14. The evapa) orator coils 14 and are connected in series relation, and, while all of the conduit connections associated with the coils may not be immediately evident in Figs. 2 and 3, it is to be understood that such connections are generally liketlrose' diagrammatically shown in Fig; 4.

Accordingly, flow of fluids takes place the evaporator coils 14 and 15 of Figs. 1, 2- and' 3 in the manner shown in Fig; 4, whereby inert gas from conduit enters the horizontal evaporator coil 14 at one end of aconduit 33 which is positioned parallel to the lateral sides of the refrigerator cabinet and more or less serves as a continuation of the horizontal portion of conduit 25. From conduit 38 the inert gas passes rearwardly through successive looped portions of the horizontal evaporator coil 14 and then flows upwardly through the vertically disposed evaporator coil 15. From theupper end of evaporator coil 15 inert gas flows to the inner passage 18 of gas heat exchanger 19 through a conduit 39 to which the liquid refrigerant supply line 17 is connected, the conduit 39 being inclined downwardly toward the evaporator coil 15 or provided with a dam therein (not shown) to cause all of the liquid entering conduit 3? to flow toward the upper end of evaporator coil 15". Hence, liquid refrigerant passes vertically downward through evaporator coil 15 and then flows through the horizontal part of the evap orator structure formed by the coil 14, With this arrangement liquid refrigerant flows in the presence of and in counterfiow to inert gas in both the vertical evaporator coil 15 and horizontal evaporator coil 1 In order to obtain good distribution of liquid refrigerant in the evaporator coils 1d and 15 and promote evaporation and diffusion of refrigerant fluid into the inert gas, the coils may be provided with suitable inserts, such as fine Wire coils or screens, for example.

Since the inert gas flows successively through the evaporator coils 14 and 15, the gas in the horizontal evaporator coil 14 contains a lesser amount of refrigerant vapor than the gas in the vertical evaporator coil 15. The partial vapor pressure of the refrigerant is a gradient, so that the temperature of liquid refrigerant in the evaporator coils also is a gradient, the evaporating temperature of liquid being lower in the horizontal evaporator coil 14 which constitutes the freezing portion of the evaporator structure.

The refrigerating effect produced by the horizontal evaporator coil 14, which is adapted to be operated at temperatures below freezing, is primarily adapted to effect cooling of the freezing section 11 As shown in Fig. 1, the freezing section 11 comprises a vessel or shell 40 which extends substantially from one lateral side 41 to the opposite lateral side 42 of the storage space 12. The shell 40 is provided with a front access opening adapted to be closed by a cover plate or closure member 43 hinged at 44 in any suitable manner. A shelf or plate-like member 45 is provided within shell 40 to the underside of which is heat conductively connected the horizontal evaporator coil 14, the space between the shelf 45 and bottomof the shell 40 holding a body of suitable insulation 46, so that evaporator coil 14 will efficiently transmit cooling effect to matter placed on the shelf, such as trays 47 containing water to be frozen, for example. The top 48 of the freezing section 11 is spaced from the ceiling or roof of the storage space 12 to form a storage chamber 49.

In the preferred embodiment illustrated, the vertical evaporator coil 15 is located between the freezing section 11 and the rear insulated wall 50 of the refrigerator cabinet. In order to provide a relatively extensive heat transfer surface, a number of heat transfer members or fins 51 are fixed to the upper and lower horizontally extending arms of the coil 15. If desired, a vertical evaporator coil may be employed in which the horizontally extending arms are inclined to a marked. degree. In such case a separate bundle of fins or heat transfer members may be individually fixed to each arm, the arrangement in other respects permitting the use of tubing which is of smaller size in cross-section, because of the inherent ability of liquid to flow more readily through the different parts of the evaporator tubing. The refrigerating effect produced by the vertical evaporator coil 15, which is adapted to be operated at a higher temperature than that of evaporator coil 14 and desirably above freezing, is primarily utilized to cool air in the storage space 12, the relatively extensive heat transfer surface provided by the fins 51 promoting such air cooling.

As best shown in Fig. 2, the piping 15 and fins 51 form an air-cooling unit which is positioned in a gap between the freezer unit 11 and the rear insulated wall 50 of the space 12, the freezer unit 11 in the vertical direction having a major portion of its height coextensive with that of the air-cooling unit. The opposing vertically extending imperforate wall sections of the freezer unit 11 and inner liner of the storage space 12, at the immediate vicinity of the gap, provide a vertically extending passage which is always open and completely unobstructed at the top and bottom ends thereof for flowing air in the space 12 in thermal exchange relation with the air-cooling unit. It will be evident that the passage at the rear of the freezer unit 11 extends vertically for a major portion of the vertical height of the air-cooling unit. I

It will now be understood that the freezing section 11 and higher temperature cooling element, comprising the vertical evaporator coil 15 and fins 51 fixed thereto, divide the storage space 12 into the upper compartment 49 and another lower compartment beneath the freezing section. in Fig.2 it will be seen that the bottoms of the freezing section 11 and air-cooling unit at the rear thereof are essentially at the same level to provide a food storage compartment which extends downwardly therefrom at substantially all regions thereof between the lateral side walls 41 and 42 of the storage space 12. 48 of the freezing section 11 may be constructed as a removable plate or support, and formed either of sheet metal or a synthetic resinous material which is less heat conductive than metal. While in the preferred embodiment the freezing section 11 extends substantially across the entire width of the storage space 12, it will be evident that in refrigerators of small size the freezing section may extend only part of the distance across the space;

It has already been pointed out that liquid refrigerant flows successively through evaporator coils 15 and 14, re-

spect'ively. Since the partial pressure of refrigerant vapor in the gas mixture in the vertical evaporator coil 15 is less than the vapor pressure of the warm liquid refrigerant entering conduit 39 through conduit 17, liquid refrigerant evaporates and diffuses into the gas mixture with consequent absorption of heat from liquid refrigerant in the evaporator coil 15. Hence, the higher temperature evaporator coil 15 not only functions to abstract heat from air in storage space 12 but also effectively serves as a precooler for liquid refrigerant. frigerant then flows to the horizontal evaporator coil 14 into the presence of inert gas which is Weaker in refrigerant vapor, whereby etfective low temperature cooling below the freezing temperature is effected in the freezing section 11.

Since liquid refrigerant entering the horizontal evaporator coil 14 from the vertical evaporator coil 15 flows by gravity through the horizontal coil, it is desirable to arrange successive straight portions and turns in the direction of liquid How in such a manner that gravity flow of the liquid is promoted from the region 52 to" a lower region at 53. In such arrangement, it is desirable, of course, to provide a connection 54 having aliquid trap 55 for draining excess liquid from the lower end of the evaporator structure to the gas circuit, as shown in Fig. 4.

In Fig. 2 the condenser 33 is positioned in an apparatus space'56 at the-rear of the refrigerator 10. The absorber coil 22 (not shown) desirably is also positioned in the space 56 beneath the condenser, both of these parts con-- stituting heat rejecting parts which are cooled by natural The top plate Such precooled liquid redraft circulation of air in the space 56 which serves as a flue for inducing upward circulation of cooling air therethrough. While the COHdflRlII' 33 in Fig. 2 comprises four straight sections and connecting bends disposed essentially in the same horizontal plane, such straight pipe sections may be disposed in two or more horizontal planes relatively close to one another. In any event, each straight section in the direction of fluid flow is at a slightly lower level than the preceding straight section or slopes downwardly sufficiently to enable liquid condensed therein to flow by gravity toward the outlet end of the condenser and thence through the conduit 17 to the upper vertical coil 15 of the evaporator structure.

Even though the overall vertical height of the condenser 33 is relatively small, the arrangement and construction of the evaporator structure is such that the evaporator coils l4 and 15 may be located closely adjacent to the roof or ceiling 57 of the thermally insulated interior of the refrigerator and still provide a vertically extending path of flow of adequate height for liquid refrigerant from condenser 33 to the evaporator structure. Stated another way, an adequate liquid head will be produced in the vertically extending path of flow for liquid refrigerant condensed in condenser 33, so that gravity flow of liquid refrigerant through evaporator coils 14 and 15 will be promoted even when the latter are located near the ceiling 57. In such case, of course, no provision is made for an upper compartment 49, as shown in Fig. 2. However, under all conditions a small space or gap should be provided in the cabinet interior adjacent the ceiling 57, so that natural draft circulation of air will be effected over the surfaces of the evaporator coil 15 and heat transfer members 51 fixed thereto.

The cabinet interior arrangement shown in Figs. 1 and 2, in which the compartment 49 is provided above the freezer section 11, possesses several advantages. One important advantage is that a place is provided for preserving foodstuffs and liquids, such as butter, lard, shortening and bottled beverages, for example, at a relatively high temperature level. A temperature range of 11 to 16 C. is particularly suitable for the compartment 49 and can be attained by providing an apertured top 48 for the freezer section 11 and a cooperating movable plate to regulate the size of the apertures and hence the extent of cooling effect transmitted to the compartment 49 by the freezer section 11.

Modifications of the embodiment of my invention which I have described will occur to those skilled in the art. For example, the top edges of heat transfer members 51, which are fixed to the U-shaped coil of the higher temperature evaporator 15, may be substantially at the same level as the top member 48 of the freezing section 11, so that matter to be refrigerated can be placed on the member 43 and project toward the rear of the storage compartment and occupy the region immediately above the higher temperature evaporator 15. Therefore, I intend in the claims to cover all those modifications which do not depart from the spirit and scope of the invention.

What is claimed is:

1. A refrigerator including a cabinet having an inner liner defining a thermally insulated storage space having a ceiling and an absorption refrigeration system associated therewith having a circuit for inert gas including piping in said storage space forming low and higher temperature evaporator sections in which refrigerant fluid evaporates in the presence of the gas, a freezer unit in the storage space comprising wall means including a horizontal plate to provide a compartment substantially segregated from the remainder of the storage space to restrict circulation of air therebetween, substantially all of the piping of said low temperature evaporator section being disposed essentially in a single horizontal plane, the piping of said low temperature evaporator section being in thermal exchange relation with said plate which provides a supporting surface for matter to be refrigerated, an air cooling unit in the storage space comprising means providing a relatively extensive heat transfer surface, the piping of said higher temperature evaporator section being in thermal exchange relation with heat transfer surface and" including a horizontally extending portion which is nearer to the ceiling of said storage space than the piping of said low temperature evaporator section disposed in said single horizontal plane, means for conducting liquid refrigerant to said higher temperature evaporator section for gravity flow therethrough and from the latter to said low temperature evaporator section for gravity flow therethrough, said freezer unit and a vertical wall of said inner liner having a gap therebetween in which said air-cooling unit is disposed alongside of said freezer unit with the latter in the vertical direction having a major portion of its height coextensive with that of said air-cooling unit, and means including opposing vertically extending imperforate wall sections of said freezer unit and inner liner at the immediate vicinity of said gap to provide a vertically extending passage which is always open and completely unobstructed at the top and bottom ends thereof for flowing air in said space in thermal exchange relation with said air-cooling unit, said passage extending for a major portion of the vertical height of said air-cooling unit.

2. A refrigerator as set forth in claim 1 in which said freezer unit is adjacent to and spaced from the ceiling of the storage space to provide a top compartment and the wall means of said freezer unit provides a supporting surface for matter to be refrigerated in such top compartment.

3. A refrigerator as set forth in claim 1 including a partition in the storage space to divide the latter into upper and lower compartments, said partition comprising said freezer and air cooling units.

4. A refrigerator as set forth in claim 3 in which said air cooling unit is at the rear of said freezer unit and the heat transfer surface thereof includes a plurality of vertically extending heat transfer fins which are in spaced relation and fixed to the piping of said higher temperature evaporator section.

5. A refrigerator including a cabinet having an inner liner defining a thermally insulated storage space having a ceiling and lateral side walls and an absorption refrigeration system associated therewith having a circuit for inert gas including piping forming low and higher temperature evaporator sections in which refrigerant fluid evaporates in the presence of inert gas, conduit means in said circuit including said piping for effecting circulation of inert gas solely by the difference in specific weight of columns of inert gas rich and weak, respectively, in refrigerant vapor, a freezer unit in the storage space comprising wall means to provide a compartment substantially segregated from the rest of the storage space to restrict circulation of air therebetween, the piping of said low temperature evaporator section being in thermal exchange relation with said wall means which provides a supporting surface for matter to be refrigerated, an air cooling unit in the storage space comprising means providing a relatively extensive heat transfer surface and the piping forming said higher temperature evaporator section which is in thermal exchange relation therewith, means for conducting liquid refrigerant to said higher temperature evaporator section for gravity flow therethrough and from the latter to said low temperature evaporator section for gravity flow therethrough, said freezer unit and a vertical wall of said liner having a gap therebetween in which said air-cooling unit is disposed alongside of said freezer unit at the vinicity of the ceiling of the storage space, the bottoms of said freezer and air-cooling units being essentially at the same level to provide a food storage compartment which extends downwardly therefrom at substantially all regions thereof between the lateral side walls of the storage space, and means including opposing vertically extending imperforate wall sections of said freezer unit and inner liner at the immediate vicinity of said gap to provide a vertically extending passage which is always open and completely unobstructed at .the top and bottom ends thereof for flowing air in said space in thermal exchange relation with said air-cooling unit, said passage extending tor a major portion of the vertical height of .said air-cooling unit.

Refexenges Cited in the file of this patent UNITED STATES PATENTS Bergholm Aug. 13, 194i) Acheson V Sept. 29, 1942 Bixler Nov. 2 1943 Beach Mar. 13, 1945 Hedlund May 8, 1945 Ashby Apr. 18, 1950 Miller Dec. 5, 1950

Images