US2690059A - Absorption refrigeration system - Google Patents

Description

p 28, 1954 s M. BACKSTROM 2,690,059

ABSORPTION REFRIGERATION SYSTEM Original Filed Dec. 15, l945 INVENTOR.

Patented Sept. 28, 1954 ABSORPTION BEFRIGERATION SYSTEM Sigrd Mattias Backstrom, Stockholm, Sweden,

assignor to Aktiebolaget Elektrolux, Stockholm, I

Sweden, a corporation of Sweden Original application December 15, 1945, Serial No.

635,152. Divided and this application April 18,

1951, Serial No, 221575 Claims priority, application Sweden December 19, 1944 9 Claims.

This invention relates to absorption refrigeration, and more particularly to absorption reirige eration systems employing evaporation of refrigerant fluid in the presence of inert gas. This application is a division of application Serial No. 635452, filed December 15, 1945, now Patent No. '2,585,908.

It is an object of the invention to improve the' places of evaporation, flowin inert gas through the low temperature place of evaporation and thence through the higher temperature place of evaporation, and diverting part of the inert gas passing from the low temperature place of evaporation to another place in the gas circuit so as to byspass the higher temperature place of evap or-ation. r

In addition, the inert gas, which is enriche in refrgerant under different temperature conditions in the several places of evaporation, is conducted in separate gas streams through different paths of flow into the same passage of a gas h'eat exchanger to form a single gas stream in such manner that one or more of the separate gas streams at a higher temperature will flow into the gas heat exchanger at a point or points removed from and spaced from the entry of the lowest temperature gas stream, each such point constituting a zone where the enriehed inert gas passing through the gas heat exchanger is at a temperature which is substantially the same as that of the entering separate gas stream.

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 pecfcation, and of which:

1 more or less diagrammatically illustrates an absorption refrigeration system embodying the invention, such system being associated with a refri erator shown vertical section;

Fig, 2 is an enlarged fragmentary view of the refrigeration system shown in Fig. 1 to illustrate the invention more clearly; and

Fig. 3 is a'fragmentary view similar to Fig. 2 illustrating another embodiment of the invention. e

Referringto Fig. 1, the invention is shown in connection with a refri erator eomprising a cabinet 30 having an inner metal shell 4! arranged to be supported with an outer metal shell 31 and insulated therefvrom with any suitable insulating material 40. The inner metal shell 4! defines athermally insulated stora e space 32 for storing frozenfood packages and free'zing meat, fruit, vegetables and other foods. Access to the storage space 32 is had through the open top thereof which is adapted to be closed by a removable closure member or lid 33 containing a suitable insulating material.

The ora e pa e 3215 ar an d to be coo d by' a plurality of evaporatorsl and 43 in the form of coils which are disposed about the inner metal shell 4 I, the coil 5! along its length being in good thermal contact with the shell, as by welding, and the coil 43 being spaced from the shell and retained within a plate or shield 42 of annular form which is provided with a bottom and embedded in the insulating material 40 between the inner and outer shells4l and 3l, respectively.

'The evaporator 5! is connected to a condenser 34 which is in heat exchange relation with a low temperature cooling element 50, and the evaporator 43 is connected to a condenser 35 which is in heat exchange relation with a higher temperature cooling element 44. Each evaporator and condenser connected thereto forms a secondary heat transfer system, the evaporators being of he ood d t p and l cated, wer els th h condei er The e a ra o 5,! n ndenser 34 form a closed fluid circuit which is partly filled with a suitable volatile fluid which evaporates in 'the evaporator 51 andtakes up heat thereby producing cold. The `vapor flows from the evaporator 5! into condenser 34 in which the' nd ccndensed byccoling .element M an the condensate returning by gravity through a conduit 31 to evaporator 43.

The low and higher temperature cooling elements and 44 form art of a primary refrigeration system of an absorption type containing an inert gas or pressure equalizing agent. In such a system refrigerant expelled from solution in a generator 45 by heating and liquefied in a condenser 48 ows through a connection 60 into cooling elements 44 and 50 in which the liquid evaporates and diffuses in the presence of an inert gas, thereby producing a refrigerating effect for condensing vapor in the condensers 34 and 35.

The resulting gas mixture of refrigerant and inert gas fiows from the upper cooling element 44 through a Conduit 62, gas heat exchanger 49 and conduit 63 into the lower part of an absorber coil 4l in which refrigerant vapor is absorbed into liquicl absorbent. Inert gas Weak in refrgerant is returned to the lower end of cooling element 50 through gas heat exchanger 49. Although the absorption liquid circuit is not illustrated, it is understood that such liquid enriched in the absorber passes into an absorber vessel 46 from which enriched solution flows to the generator 45 where it is heated and refrigerant vapor is again expelled out of solution. The Weakened absorption liquid from which refrigerant has been expelled fiows from generator 45 to the absorber coil 41 to again absorb refrigerant vapor.

Since inert gas flows first through cooling element 53 and then through cooling element 44, the partial vapor pressure of refrigerant vapor is higher in cooling element 44 than in cooling element 50, and evaporation of liquid refrigerant takes place at a higher temperature in the upper cooling element than in the lower cooling element. In order to simplify the drawing, the refrigeration system has only been shown diagrammatically, systems of this type well known in which upward flow of inert gas through the coolingelements 50 and 44 is effected in counterflow to liquid refrigerant.

It may be assumed that the temperature of the storage space 32 is to be maintained at about 25 C. and that the temperature of the plates or shields 42 is to be maintained at about -l0 C. Under these conditions it will be apparent that the quantity of heat which must be transferred from the storage space 32 to the low temperature cooling element 50 will be materially less than in an arrangement in which the refrigeration of the insulation 40 by the evaporator 43 is not employed.

According to the invention it is very advantageous to provide an inert gas circuit in which extremely intensive gas circulation through the high temperature cooling element 44 is avoided. Fig. 2 diagrammatically shows the manner in which parts of the inert gas circuit illustrated in Fig. 1 preferably should be connected, similar parts in Figs. l and 2 being referred to by the same reference numerals. As indicated by the arrows in Fig. 2 liquid refrigerant flowing through Conduit 60 passes through the high temperature cooling element 44 and thereafter through the low temperature cooling element 50. On the other hand, inert gas flows from absorber 41 through the gas heat exchanger 49, low temperature cooling element 50 and then partly through the high temperature cooling element 44 and partly in a path of flow which includes conduits 6! and 62, the outer passage of gas heat exchanger 49 and conduit 83 to the lower part of absorber 47.

The inert gas flowing through the high temperature cooling element 44 passes through the conduit 62, gas heat exchanger 49 and Conduit 63 back to the lower part of absorber 4?. The diverted inert gas flowing into the Conduit E! lay-passes the high temperature cooling element 44, thereby avoiding an extremely intensive circulation of inert gas through the upper cooling element.

It may be desirable in certain instances to provide an inert gas circuit in which the parts thereof are connected according to Fig. 3 which diagrammatically shows a modification in which parts similar to those shown in Fig. 2 are referred to by the same reference numerals. In Fig. 3 conduit 54 replaces the Conduit 62 in Fig. 2. The upper end of conduit 64 is connected to the lower end of the condenser connection E@ which is in communication with the upper end of the cooling element 44. The lower end of Conduit 64 is connected to a point in the gas heat exchanger 45 at which the temperature of the gas therein corresponcls to that of the gas passing through the Conduit 64 upon entering the gas heat exchanger. The concluit 65 i, in which the colder gas passes, is connected with the end of the gas heat exchanger in the same manner as shown in Fig. 2.

It Will now be understood that cooling element 50 operates at a sufliciently low temperature to maintain storage space 32 at a temperature of about 5 C. and that cooling element 44 operates at a higher temperature to maintain the plates 42 at a temperature of about -l0 C. The partially enriched inert gas passes from the low temperature cooling element 58 at a temperature in the neighborhood of -25 C. and its temperature is raised to about -l0 C. in the higher temperature cooling element 44. By diverting part of the low temperature inert gas from the high temperature cooling element 34, the necessity of raising the temperature of all of the inert gas from -25 C. to 1c C. is avoided.

In Fig. 3 the point at which enriched inert gas passes from Conduit t into the gas heat exchanger 49 is selected so that the temperature of the inert gas in the gas heat exchanger, at the connection of Conduit 54 thereto, as substantially the same as that of the inert gas introduced into the gas heat exchanger at that point. When the enrichecl inert gas from the higher temperature cooling element 44 is introduced into a colder portion of the gas heat exchanger, the temperature of enriched inert gas at the colder portion of the heat exchanger would be raised at the expense of refrigeratng efiect which otherwise could be advantageously utilized to effect cooling of weak inert gas owing through the inner passage of the gas heat exchanger from absorber 41.

In View of the foregoing, it will now be understood that, in the embodiment of Fig. 3, enriched inert gas flows from the higher temperature cooling zone 44 through Conduit 64 and all of such enriched inert gas is introduced into the outer passage of the gas heat exchanger 49 in a region thereof at which the enriched inert gas flowng only from the low temperature cooling zone 5!) and approaching such region is at a temperature substantially the same as that of the inert gas initially entering the outer passage of the gas heat exchanger 49 through the Conduit 64 at the point the latter is connected to the gas heat ex- 'inert gas which' has completed its circulation through the' cooling elements' 50'- and 44 i's' con du'ct'ed" through the con'diits' B' and 643 respect'i'v'ely, to the oute'r passage of' the* gas heat exchanger 49. Further, the Conduit Bl is connected to the in et end or'- point of entry of' the* outer passage of" the gas heat' exchanger' 49 while the conduit- 64' is connectedto the* outer-` gas heat' exchanger' passage at a Zone at which the enriched:

inert gas stream passing through the gas" heat exchanger and approachingsuch zone is at" a temperature substantially' the same as that of the gas stream entering the out'er gas heat exch'anger passage through the conduit 64% Modifications of the embodime-nts ofthe invention which have been described will occur, to those skilled intheart', so that it' is' desired not 'to-'be limited to the' particular'arrangements' s'et iorth; Moreover, certain' featuresof the' i`nventioncan be advantageo-usly employed independently of other features. 'Ihereforeit is intended in the claimst'o cover all those modifications and features which-donot depar t fromthe spirit and' scope of the invention.

What is claimed is:

1 In` a method' of refrigeration withthe aid of' a' system having a ci'rcuit for circulation of iiiert gas including a place of absorption, a= gas heat exchanger and-apl'urality of places of evaporat'ionin which refrigerant fluid* evaporates in the presence of inert gas a't difierent temperatures, said gas heat exchanger'havinga plurality of passages for passing in heat' exchange relation inert gas flowing from and returning to said ert gas flowing in another' passage of the gas'` heat exchanger, and flowing inert gas at a higher temperature from another of said places of evapo-ration to said place of absorption and initially iit'roducing all of theinert gas in' such path of flow to said one gas heat exchanger passage in a zone thereof at which the inert' gas'returning only from said lower or lowest temperature place of evaporation and approaching such zone is'` at a, temperature substantially the same, as that of the inert gas initially entering said' one' gas heat exchanger passage at said zone.

2-.` In* a method of refrige'ration with the aid of a system having a circuit for circulation of an i nert gas including aplurality'of cooling' zones ih which refr-gerantfiuid evaporates in thepresence of inert gas at difierenttemperaturs and a gas heat' exchanger having afirst pass'age'- for flowing inert gas-to said coolin'g zones and a second passage having an inlet and an outlet for fiowing inert gas from said cooling zones, the improvement which comprises fiowing inert gas to said cooling zones after passing through said first gas heat exchanger passage and before flowing through said second gas heat exchanger passage, flowing inert gas only from the lower or lowest temperature cooling zone to the inlet of said second gas heat exchanger passage for flow therethrough, and fiowing inert gas from another higher temperature cooling zone in a path of flow and initially introducing all of the ZIP iiir t gas:: sii'cl pathof floww said second: gas

heat ex'chager passage in: a region thereof at whicli the inert gas flowing only from' said lower' or lowesttemperature' place of evaporation and approaching such region' is at a temperature substantially the* same as that of the inert gas i'nitially entering' said second gas heat exchanger passage Y at said region.

32 A refrigeration system including evaporatorstructure, means to conduct liquid refrigerant to' said evaporator structure, said evaporator' structure' having one portion in` which refrigerant evaporates in the presence of inert gas at the lower' oi' lowest temperature in the system and another portion i'n which refrigerant evapoi ates in the presence of inert gas at a higher t'emperat'ure,` connections including a gas heat; exchanger for circulation of inert gas' through Said evaporator structure, saidgas heat ex'- changer having a first' passage for conductin'g' warm inert gas to said evaporator structure and a second passage'for conducting cooler inert gas' nom said' evaporator structure, said connections p including Conduit' means for conducting to said second" gas heat exchanger passage only cool iher-t gas which has completed its circulation through-said evaporator structure, and said conduit means' including provisions for conducting inert gas oni-'y from said' lower or lowest temperat'ure evaporator portion to one region of said secondpassageand for conducting inert gas from said other higher temperature' evaporator portion toariother region of said second passage at which the i'ner t' gas flowing only from said lower or lowest temperature evaporator portion and approachihg. said other regionis at a temperature substaitially the same as that of the inert gas iiiiti'a-lly ent'ering said other'region from said' higher temperature evaporator portion.

45; A-refr-igeration system including evaporator structure, meansto conduct liquid refrigerant to' said` evaporator structure, said evaporator structu re' having' one portion in which refrigerant evaporates in the presence of inert gas at the lower or lowest temperature in the system and another-'pot'rion in which refrigerant evaporates ih the presence of inert gas at a higher temperat`ure", connections including a gas heat exchanger for circulation of inert gas through said evaporat'orstructure, said gas heat exchanger having a first passage for conducting warm inert gas to said' evaporator structure and a second passage having an' inlet and' outlet for conducting cooler inert gas-ironisaidevaporatbr structure in counterfiowj to warm inert gas, said connections including Conduit means for conclucting to said second' gas* heat exchanger passage only cool inert gas which has completed its circulation through said evaporator structure, and said cond-'-i't means including provisions for conducting inert gas" only from said lower or lowest temper at-ure evaporator portion tothe inlet of said second-passage andor conducting inert gas from said other higher temperature evaporator portion to a region of said second passage intermediate the inlet and outlet thereof and at which the inert gas flowing only from said lower or lowest temperature evaporator portion is at a temperature substantially the same as that of the inert gas initially entering said region from said other higher temperature evaporator portion.

5. In absorption refrigerating apparatus of the continuous cycle inert gas type provided with an evaporator divided into separate elements having difierent temperatures adapted for different re- 7. frigerating purposes, a heat exchanging process which includes the steps of introducing inert gas enriched in refrigerant under different conditions of temperature in the different evaporator elements through two or more separate gas passages into a gas heat exchanger to form a common gas stream, completing the enrichment of the inert gas With refrigerant in all of the different evaporator elements in the apparatus before initially introducing the enriched gas into the gas heat exchanger to form said common stream, owing only the enrichecl gas from the lower or lowest temperature evaporator element to a point of entry of said gas heat exchanger, and fiowing enriched gas of a higher temperature into said exchanger at a second point which is spaced from the point of entry of the lower or lowest temperature enriched inert gas and constitutes a zone at which the enriched gas stream passing through the heat exchanger and approaching said. zone has a temperature substantially the same as that of the entering gas stream.

6. An absorption refrigerating apparatus of the inert gas type having evaporator elements of different tenperatures and a gas heat exchanger which includes separate conduits leading inert gas enriched in refrigerant respectively from each evaporator element to the gas heat exchanger, all of said separate conduits initially intrcducing to said gas heat exchanger inert gas whose enrichment with refrigerant in said evaporator elements has been completed, and the conduit from each evaporator element of higher temperature opening into the rich gas stream of the gas heat exchanger at a point which is spaced from the entry of the Conduit conveying only the gas stream from the lower or lowest temperature evaporator element and constitutes a zone at which the enriched gas stream passing through the heat exchanger and approaching said zone is at substantially the same temperature as that of :e enriched inert gas entering said zone through said Conduit from the higher temperature evaporator element.

7. An absorption refrigeration system comprising an inert gas circuit including a low temperature evaporator coil at a first level and a higher temperature evaporator coil at a higher level and a gas heat exchanger having first and second passages, each coil having the opposing ends thereof at different levels, said low temperature evaporator coil constituting the lower or lowest temperature evaporator portion in the system, means for supplying liquid refrigerant to the upper end of said higher temperature coil for gravity flow therethrough, means including said first gas heat exchanger passage for supplying inert gas to the lower end of said low temperature coil, connecting means or flowing inert gas from the upper end of said. low temperature coil to the lower end of said higher temperature coil and for conducting unevaporated liquid rerigerant from said higher temperature coil to said low temperature coil for gravity flow therethrough, and Conduit means for fiowing inert gas from the upper end of said low temperature coil and from the upper end of said higher temperature coil to said second gas heat exchanger passage.

8. An absorption refrigeration system as set forth in claim 7 in which said Conduit means includes a first branch for conducting only inert gas from the upper end of said low temperature coil to one end of said second gas heat exchanger passage and a second branch for conducting inert gas from the upper end of said higher temperature coil to a region of said second gas heat exchanger passage intermediate the ends thereof and removed from said one end to which inert gas in conducted by said first branch.

9. In a method of refrigeration with the aid of a system having a circuit for circulation of inert gas including a place of absorption, a gas heat exchanger and a plurality of places of eVaporation in which refrigerant fluid evaporates in the presence of inert gas at different temperatures, said gas heat exchanger having a plurality of passages for passing in heat exchange relation inert gas fiowing from and returning to said place of absorption, the improvement which comprises conducting to said places of evaporation inert gas fiowing from said place of absorption after passing through only one passage of the gas heat exchanger, returning inert gas only from the lower or lowest temperature place of evaporation in the system to said place of absorption in a path of fiow including at least a portion of another passage of the gas heat exchanger in which the temperature of such returning inert gas progressively increases from one temperature level to a higher temperature level due to heat exchange with inert gas flowing in said one gas heat exchanger passage, flowing inert at a higher temperature from another of said places of evaporation in a path of flow to said place of absorption and initially introducing all of the inert gas in such path of flow said other gas heat exchanger passage at a zone thereof at which the inert gas returning only from said lower or lowest temperature place of evaporaticn and approaching such zone is at a temperature substantially the same as that of the inert gas entering said zone from the higher temperature place of evaporation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,996,094 Backstrom Apr. 2, 1935 2,059,877 Kogel Nov. 3, 1936 2,072,1 l4 Ullstrand Mar. 2, 1937 2,210,509 Ullstrand Aug. 6, 1940 2,256,519 Grubb sept. 23, 194 2267283 Lenning Dec. 23, 1941 &2691701 Ullstrand Jan. 13, 1942

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