US2631443A - Absorption refrigeration - Google Patents

Description

March 17, 1953 s, BACKSTROM 2,631,443

ABSORPTION REFRIGERATION Filed Feb. 26, 1949 2 SHEETS-SHEET l j INlfENTOR. A9 I 3-? 'BY M Patented Mar. 17, 1953 UNITED STATES OFFICE ABSORPTION REFRIGERATION SigurdMattias Backstrom; Stockholm. Sweden, assignor to Aktiebolaget Elektrolu-x, Stockholm, Swedema corporation: of Sweden.

ApplicationFbruary 26, 1949, Serial No. 78,511 In Sweden March 2, .1948

81ClaimSr (Cl; GEM-119.5)-

and accumulate on such-lowtempera-ture cooling element.

Another object of my invention 'is to provide an improved refrigerator in which an absorption refrigeration system having one or more cooling elements is employed for maintaining a freezing section-at a desired low temperature,

and utilizing such refrigeration systemto effect coolin of a thermallysegregatedspace with the aid .of a secondary heat transfer system in such manner that, whenheatis suppliedto the cooling. element. or elements of the freezing section:

to meltfrost whichxmay form thereon, substantially no heat is supplied to the evaporationportion. of. the secondaryheat transfer system. arranged. to: abstract h-eat'sfrom such other space.

The novel features which Lbelieve to :becharacteristic of my invention are set forth with .particularity in the claims. The invention, both as to organization and method, together with the above and other objects and advantages thereof, will be better understoodby reference tothe following description taken in connection with the accompanying drawings forming a part of this specification, and of which Fig. 1 more. or less diagrammatically illustrates anabsorption refrigeration system embodying the invention; Fig. 2 isan enlarged fragmentary sectional view taken at line 2-2 of Fig. 1.; and Fig. .3isavvertical sectional view of a refrigerator cabinet schematically illustrating one manner in which parts of the refrigerationsystemof Fig. 1. may be incorporated therein in accord withthe invention.

In'Fi'g. 1 I have shown my invention inconnection with an absorptionrefrigeration system of a uniform pressure type which is well known in the art and in which an inert pressure'equalizing gas is employed. Such a refrigeration system comprises a generator or vapor expulsion unit'ia including a boiler or pipe ll containing. a refrigerant, such as'ammonia, in a bodyoi absorption liquid, such as water. 'Heat issupplied to the boiler" l them a heating tube or'fiue l2 thermally connected therewith, as by welding, forexample; The heating tube i2 may be heated in any suitable manner, as by an electrical heating element disposed within the lower part of the tube-l2 or by a liquid or gaseous fuel burner which is adapted to project its flame into the-lower heat input 'end of the'tube.

The heat supplied to the boiler H and its contents expelsrefrigerant' vapor out of solution and such vapor passes upwardly from the'vapor expulsion uni-t H! into air cooled condensers l5 and I in which. it is condensed and liquefied. Liquidrefrigerant flows from condensers ltzand ll through conduits-t8- and it into cooling elementsor eVapQratOrs'Z-EB and 2!, respectively, in

which it evaporates and diffuses into an inert pressure equalizing gas, such as hydrogen, which enters througha conduit 22.. Due to evaporation of refrigerant'fiuid into inert .gas, a refrigerating effect is-produced by cooling elements 20 and 2| with consequent. absorption of heat from the surroundings.

The rich .gas mixture .of refrigerant vaporiand inert gas formed in cooling elementszZfl and 2| merge or come together at 2%.andflowsthrough a. conduit 24, one passage of a gas heat exchanger 25, conduit'zliv and absorber'vessel. 21 intothe lower endof an absorber coil 28. In absorber coil 28 therich gas mixture flows counter-current to. downwardly flowing absorption liquidwhich enters-through.a.conduit 29. The

absorption liquid absorbsref-rigerant vapor from inert.gas,.andinertlgas weak in refrigerant flows from absorber coilzZB .in apathof flow including conduit 5d, another passage of gas heat exchanger 25' andconduit ZZ-into the upper parts of the cooling elements 20 and 2-1.

Absorption solution enriched in refrigerant flows from the absorber vessel 2-7 through a conduittl andaninner passage .iZofla liquidiheat exchanger 33- into the lower end ofa lift tube or pump pipe 3 6. The pump pipe-3 lisin thermal exchange relation with the heating tube 82, as-by welding, for example, and liquidis raised therethroughby vapor-liquid lift action to the upper partofthe boiler I-l. The-vapor'expelled out of solution in-boiler H, together with vapor entering-the latter from the pumppipe 3 1 flows upwardly'from the-vapor expulsionunit 10 to the condensers lt'and H; as previously explained. Theabsorption liquid from which refrigerant has been expelled flows from the boiler ll through the-outer passagetfi of theliquid heat 3 exchanger 33 and conduit 29 into the upper part of the absorber coil 28.

The outlet ends of the condensers l6 and I! are connected by a conduit 36, vessel 31 and conduit 38 to a part of the gas circuit, as at one end of gas heat exchanger 25, for example, so

that any inert gas which may pass through the condensers I6 and I! can flow into the gas circuit. Refrigerant vapor not liquefied in the condensers flows through conduit 36 to displace inert gas in vessel 31 and force such gas through conduit 38 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 condensers I6 and II.

The vessel 31 in effect serves as an extension of the air cooled condensers l6 and H. Refrigerant condensed in the vessel 31 flows therefrom through conduit 36 at the lower end of which a liquid divider may be provided in any suitable manner. As shown in Fig. 2, the lower end of conduit 36 may be formed with branches or arms 39 at the upper ends of which a baffle or divider 40 is disposed to divide any liquid flowing downwardly in conduit 36 into two streams, one of which is conducted through conduit l8 to cooling element 20 and the other through conduit H) to the cooling element 2|.

In order to increase the temperature of cooling elements 2|) and 2| when it is desired to melt frost which may accumulate thereon, provision is made for raising warm absorption solution from the boiler through a riser conduit 4| into the vessel 31. The raised warm absorption solution flows from vessel 3? through conduit 36, such solution being divided into two streams at the lower end of conduit 36 and passing into the cooling elements 26 and 2|. In this manner rapid defrosting is efiected due to the relatively high temperature to which the solution is heated in the vapor expulsion unit H3. The absorption solution passes from the cooling elements through conduit 24 and gas heat exchanger 25 to the absorber vessel 21.

The riser conduit 4| constitutes a vapor lift tube or pump pipe through which absorption solution is raised when desired by heat derived from the heating flue |2 with the aid of a controllable secondary heat transfer system. As shown in Fig. 1, such a system may include a vertical conduit 43 and a U-tube 44 having one arm connected to the lower end of conduit 43 and the other longer arm 46 in thermal relation with the heating tube |2 at 46. The upper part of the arm 45 is also in thermal relation with the riser conduit 4| at 41, and the extreme upper end thereof is connected to the upper part of conduit 43. A bulb 48 is flexibly connected at 49 to the upper end of the conduit 43.

The heat transfer system is hermetically sealed and is charged with a volatile fluid substantially all of which is held in the bulb 48 when the latter is in the position shown in Fig. 1. When it is desired to effect defrosting of the cooling elements 23 and 2|, the bulb 48 is raised from the position shown, so that fluid will flow therefrom by gravity to the U-tube 44. The longer arm 45 of the U-tube 44 constitutes the vaporization portion of the heat transfer system in which fluid is vaporized by heat taken up from the heating tube l2. The vapor formed in this manner is partly condensed in the arm 45 and gives up heat to the conduit 4| and its contents to raise absorption,

solution by vapor lift action from the boiler II to the vessel 37. Such lifting of absorption solution continues until all of the vapor is condensed in the bulb 4-8 which previously has been returned to its lower position shown in Fig. 1. In this way substantially all of the volatile fluid is held back from the lower vaporization portion of arm 45, and heat transfer to the conduit 4| is reduced to terminate raising of solution therein.

In Fig. 3 is shown a refrigerator comprising a cabinet 59 having thermally insulated walls defining a storage space 5|. In the upper part of space 6| is provided a freezing section comprising a shell 52 having thermally insulated walls defining a chamber 53 within which the cooling elements 26 and 2| of the refrigeration system of Fig. l are disposed. Although not shown, it is to be understood that closure members or doors are provided to close an access opening of the space 5| and a similar access opening of the chamber 53.

One of the coolin elements 26 may be employed for ice freezing and provided with suitable supporting surfaces upon which ice trays 54 can be positioned. The other cooling element may be employed primarily to cool the freezing chamber 53 in which frozen foods, meat and other matter may be stored. Hence, it is desirable to insulate the chamber 53 effectively from the storage space 5|.

The parts of the refrigeration system shown in Fig. 2 are similar to those illustrated in Fig. 1, like parts being indicated by the same reference numerals. In the operation of the refrigerator of Fig. 2, liquid refrigerant is conducted to the upper parts of cooling elements 26 and 2| through conduits l8 and I3, respectively, as previously explained in describing the refrigeration system of Fig. l. Inert gas weak in refrigerant flows from the absorber through conduit 36, one passage of gas heat exchanger 25 and conduit 22 whose upper end communicates with the upper ends of cooling elements 2|] and 2|. Refrigerant evaporates and diffuses into inert gas in the cooling elements 26 and 2|, and such gas mixture from the cooling elements 26 and 2| merge at 23. All of the gas mixture then flows through the conduit 24, one passage of the gas heat exchanger 25 and conduit 26 to the absorber. Any unevaporated refrigerant also flows from the cooling elements 26 and 2| and meet at 23 from which region all of the refrigerant flows through conduit 24 and gas heat exchanger 25 and eventually finds its way to the absorber vessel.

In accordance with my invention the absorption refrigeration system having the cooling ele ments 26 and 2| is advantageously employed to effect cooling of storage space 5i with the aid of a secondary heat transfer system 55 which is so arranged that, when heat is supplied to the cooling elements 20 and 2| to melt frost accumulated thereon, substantially no heat is supplied to the evaporation portion of the secondary heat transfer system which is arranged to abstract heat from the storage space 5|.

The secondary heat transfer system 55 includes an evaporation or vaporization portion 56 in the form of piping which desirably is distributed thermal exchange relation with the conduit 24,

as by a plurality of heat transfer plates or fins 53, for example. The heattransfer system 55 is herego-321,443

'n'q'etically sealed and ispartly filled'with a suitable 'volatile fluidor heat transfer agent having a relatively lowboiling temperature. In certain instances the heat-transfer system 55 may also be chargediwith asuitable quantity of inert gas in: addition to the volatile heat transfer fluid.

During operation of the refrigerator the volatile fiuid-evaporates in the lower part of the vaporization-portion eie and also partly in the vertically extendin partsthereof, thereby taking up heat fromair in the storage space 54. To promote such taking-up ofheat from the storage space oi, the vaporization'portion 56 desirably is provided with-heat absorbing members to provide a relatively extensive heat transfer surface. The vapor flows from the vaporization portion 53 to the-condensation portion 5-7 in which the vapor ifs-condensed and liquefied, such condensate then returning by gravity to the vaporization portion 56.

The heat ofcondensation resulting from condensa-tion of vapor in the condensation portion is given up to fluid flowin through the conduit 2 4: Since the gas mixture formed in the cooling elements wand 21 andpassing through the conduit 2 1* is relatively cold, such gas mixture can be effectively utilized to take up the heat of condensation resulting from condensation of vapor in the' condensation portion 5? of the secondary 'heattransfer system. When unevaporated refrigerant from the cooling elements 29 and 22 flows through the conduit 24', the latter in effect acts as an auxiliary cooling element in which refrigerantevaporates and diffuses into inert gas, thereby effectively taking up heat of condensation libera't'ed by the secondary heat transfer system.

Itwill now be understood that therefrigeration system of which the cooling elements so and 2i form a part is employed to cool storage space 5% with-the aid of'the secondary heat transfer system 55. With such arrangement the storage space 5 is maintained at a useful refrigerating temperature which, however, is higher than that at whichthe freezing chamber 53 is maintained by the cooling elements 2i! and ill.

Theconduit 2 3, condensation portion 5'? of the secondary heat transfer system 55 and heat trans- 'fer plates 58 thermally connecting these parts essentiallyconstitute a heat exchanger. In order to obtain efficient operation of such heat exr changer and take full advantage of conduit as and thefluids il'owing therethrough to take up heat of condensation, the conduit 2%, condensa- 'tion portion 5'! and plates 58 desirably are emrbeddedin a body of suitable insulating material, asindicated at (it in Fig. 3.

During defrosting periods Warm absorption solution'is supplied to cooling elements it and '21 to melt frost thereon, as previously explained.

' f Su'ch absorption solution passes from cooling eleents 2'3 and 2! through conduit 24 and gas heat exchanger 25 and eventually finds its way to the absorber vessel. Under such conditions the temperature of conduit-2e rises sufficiently so that condensation of vapor can no longer take place inthe condensation portion of the secondary heat "transfer system. When this occur the natural circulation of volatile fluid in the heattransfer system 5'5 stops, and heat temporarily is not abstracted from the storage space 5%. Under these conditions the body of insulation disposed about the conduit 24 thermally shields the latter from the storage space 5!, so that the increase in temperature in the space 5| due to how of absorption solution through-theconduit 21i is negligible and 6 only dependent upon the extent of heatleakage through the insulation Although not shown, it is also advantageous for the reasons justgiven to embed the gasheat exchanger 25 in suitable insulation when the latter is. located .inthe storage space 5 l, as illustrated in Fig. 3.

In view-of the foregoing, itwiil now be understood thatwhen heat is supplied to cooling elements 2i! and 2! to effect defrosting, no heat to any appreciable" extent is supplied. to the vaporization portion at employed to effect cooling of the higher temperature storage space 5i. Since f-rostonly forms and accumulates on the low temperature cooling elements employed for freezing purposes, and substantially no frost forms inla higher temperature cooling space like the spaceifiii in Fig. 3 by reason of the relatively extensive heat transfer surface provided to abstract heat there'- from, it is of distinct advantage to supply defrosting heat only to the cooling element or elements upon which frost tends to form audaccumulate, thereby making it possible to continue to store food and other matter at a safe refrigerating temperature in the higher temperature storage space which frost normally does not form and accumulate.

Modifications of the embodiment of my inventi n which I have describedwill occur to those slcilled in the art, so that I desire my invention not to be limited to the particular arrangement forth. For example, provision may be. made supply a heating fluid other than warm absorption solution to the cooling element or elements upon which frost tends to form. Thus, refrigerant vapor flowin from the generator unit may be arranged to pass directly into one or more cooling elements in a heated state to eifect defrosting. Also, the inner liner definin the space with which the secondary heat transfer system is associated may be double-walled to provide a space therebetween which can be employed as the vaporization portion of the secondary heat transfor system, thereby avoiding the necessity of providing a vaporization portion formed of tubing or piping. Therefore, I intend in the claims to cover all those modifications which do not depart from the spirit and scope of my invention.

What is claimed is:

1. In a refrigerator comprising a cabinet having segregated compartments, an absorption refrigeration system including an absorption solution circuit and a gas circuit comprising an absorber and one or more cooling elements in which refrigerant fluid evaporates in the presence of an inert gas and conduit means for conducting inert gas enriched in refrigerant from the latter to said absorber, at least one of said cooling elements being arranged to abstract heat from one of said compartments which is employed for freezing purposes and may cause formation of frost due to the refrigerating effect produced thereby, a system for heat transfer iiuid having a vaporization portion arranged to abstract heat from another of said compartments and a heat rejecting'portion in heat conductive relation with said conduit means, said refrigerationsystem including means for supplying warm absorption solution to said one cooling element which is operable to cause melting of any frost which may be formed, said conduit means serving to conduct such absorption solution from said one cooling element to said absorption solution circuit, and said conduit means at the region said heat rejecting portion is in heat conductive relationtherewith being thermally segregatedfrom said other compartment, said heat conductive relation being so constructed and formed that any increase in temperature of said other compartment resulting from flow of absorption solution through said conduit means is substantially negligible.

2. A refrigerator as set forth in claim 1 in which said heat rejecting portion is in heat conductive relation with a portion of said conduit means disposed in said other compartment.

3. A method of refrigeration which includes evaporating a first refrigerant fluid in the presence of an inert gas in one or more places of vaporization thermally segregated from the surroundings to produce refrigeration which may cause the formation of frost, flowing relatively cool inert gas enriched in refrigerant from the first-mentioned place or places of vaporization in a path of flow to a region removed therefrom which is at a lower level and serves as an auxiliary place of vaporization, flowing excess unevaporated refrigerant by gravity in such path of flow to said auxiliary place of vaporization from the first-mentioned place or places of vaporization, flowing inert gas enriched in refrigerant from the auxiliary place of vaporization to a place of absorption, evaporating a second refrigerant fluid in a place of vaporization thermal ly segregated from the surroundings and also segregated from said first-mentioned place or places of vaporization to produce refrigeration substantially free of frost formation, condensing the second vaporized fluid at a place of condensation in thermal relation with said region and returning condensate therefrom to said place of vaporization for second refrigerant fluid, intermittently effecting rapid heating of said place or places of vaporization for first refrigerant fluid by a medium at a temperature level above the ambient temperature of the surroundings to cause melting of any frost which may have been formed, the temperature of said place of vaporization for second refrigerant fluid being substantially unaffected by heated fluid received by said region or auxiliary place of vaporization from said place or places of vaporization for first refrigerant fluid when heating of the latter is effected, and thermally segregating said place of condensation and region in thermal relation therewith from the surroundings and from said place of vaporization for second refrigerant fluid.

4. A method of refrigeration which includes evaporating a first refrigerant fluid in the presence of an inert gas in one or more places of vaporization thermally segregated from the surroundings to produce refrigeration which may cause the formation of frost, flowing relatively cool inert gas enriched in refrigerant from the first-mentioned place or places of vaporization in a path of flow to a region removed therefrom which is at a lower level and serves as an auxiliary place of vaporization, flowing excess unevaporated refrigerant by gravity in such path of flow to said auxiliary place of vaporization from the first-mentioned place or places of vaporization, flowing inert gas enriched in refrigerant from the auxiliary place of vaporization to a place of absorption, evaporating a second refrigerant fluid in a place of vaporization thermally segregated from the surroundings and also segregated from said first-mentioned place or places of vaporization to produce refrigeration substantially free of frost formation, condensing the second vaporized fluid at a place of condensation in thermal relation with said region and returning condensate therefrom to said place of vaporization for second refrigerant fluid, intermittently supplying a heated fluid to said place or places of vaporization for first refrigerant fluid to effect rapid heating of the latter and cause melting of any frost which may have been formed, the temperature of said place of vaporization for second refrigerant fluid being substantially unaffected by any heated fluid received by said region or auxiliary place of vaporization from said place or places of vaporization for first refrigerant fluid when heating of the latter is effected, and thermally segregating said place of condensation and region in thermal relation therewith from the surroundings and from said plac of vaporization for second refrigerant fluid.

5. In a refrigerator comprising a cabinet having segregated compartments, an absorption refrigeration system comprising a circuit for inert gas including one or more cooling elements in which refrigerant fluid evaporates in the presence of an inert gas and an absorber, at least one of said cooling elements being arranged to abstract heat from one of said compartments which serves as a freezer and may cause formation of frost due to the refrigerating effect produced thereby, conduit means for conducting inert gas enriched in refrigerant from said one or more cooling elements to said absorber, said conduit means including a conduit section intermediate said absorber and freezer into which enriched inert gas flows after leaving said one or more cooling elements, said conduit section being below said freezer and into which unevaporated refrigerant passes by gravity from said one or more cooling elements, heating means operable to provide at said one cooling element, at a region removed from said conduit section, a medium which is at a temperature level above the ambient temperature of the surroundings for rapidly heating said one cooling element to cause melting of any frost which may be formed, and a system for heat transfer fluid having a vaporization portion at one level arranged to abstract heat from another of said compartments and a heat rejecting portion at a higher level in heat conductive relation with said conduit section, and means for thermally insulating said condensation portion and at least the part of said conduit section in heat conductive relation therewith.

6. In a refrigerator comprising a cabinet having segregated compartments, an absorption refrigeration system including a gas circuit comprising an absorber and one or more cooling elements in which refrigerant fluid evaporates in the presence of an inert gas, at least one of said cooling elements being arranged to abstract heat from one of said compartments which is employed for freezing purposes and may cause formation of frost due to the refrigerating effect produced thereby, conduit means for conducting inert gas enriched in refrigerant from said one or more cooling elements to said absorber and into which unevaporated refrigerant passes by gravity from said cooling element or elements, and a system for heat transfer fluid having a vaporization portion arranged at one level to abstract heat from another of said compartments and a heat rejecting portion at a higher level in heat conductive relation with said conduit means, said refrigeration system including a connection for conducting a heated fluid to said one cooling element which is operable to cause melting of any frost which may be formed, means for controlling flow of such heated fluid through such connection, and means including insulation enveloping said condensation portion and at least the part of said conduit means in heat conductive relation therewith.

7. In a refrigerator comprising a cabinet having segregated compartments, an absorption refrigeration system including a gas circuit comprising an absorber and one or more cooling elements in which refrigerant fluid evaporates in the presence of an inert gas and conduit means for conducting inert gas enriched in refrigerant from the latter to said absorber, at least one of said cooling elements being arranged to abstract heat from one of said compartments which is employed for freezing purposes and may cause formation of frost due to the refrigerating effect produced thereby, a system for heat transfer fluid having a vaporization portion arranged at one level to abstract heat from another of said compartments and a heat rejecting portion at a higher level in heat conductive relation with said conduit means, said refrigeration system including a connection for conducting warm absorption solution to said one cooling element which is operable to cause melting of any frost which may be formed, means for controlling flow of such absorption solution through such connection, said conduit means serving as a path of flow for absorption solution from said one or more cooling elements to said absorber, and means including insulation enveloping said condensation portion and at least the part of said conduit means in heat conductive relation therewith.

8. In a refrigerator comprising a cabinet having segregated compartments, an absorption refrigeration system including a circuit for inert gas having one or more cooling elements in which refrigerant fluid evaporates in the presence of an inert gas and conduit means for conducting therefrom inert gas enriched in refrigerant and through which unevaporated refrigerant passes by gravity from said cooling element or elements, at least one of said cooling elements being arranged to abstract heat from one of said compartments which serves as a freezer and may cause formation of frost due to the refrigerating effect produced thereby, a system for heat transfer fluid having a vaporization portion arranged to abstract heat from another ofusaid compartments and a heat rejecting portion in heat conductive relation with said conduit means, said refrigeration system including a connection for conducting to said one cooling element heated liquid having a higher boiling point than the refrigerant, such heated liquid being operable to cause melting of any frost which may be formed, means for controlling flow of such heated liquid through such connection, said conduit means also serving as a path of flow for such liquid which passes therethrough by gravity from said one cooling element, and means for thermally insulating said condensation portion and at least the part of said conduit means in heat conductive relation therewith.

SIGURD MATTIAS- BACKSTROM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,976 Dailey Feb. 24, 1948 1,798,951 Munters Mar. 31, 1931 1,986,638 Knight Jan. 1, 1935 2,035,573 Smith Mar. 31, 1936 2,239,583 Schmieding Apr. 22, 1941 2,261,682 Hedlund Nov. 4, 1941 2,357,612 Soroka Sept. 5, 1944 2,402,415 Kogel et a1 June 18, 1946 2,487,662 McCloy Nov. 8, 1949

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