US3273350A

US3273350A - Refrigeration systems and methods of refrigeration

Info

Publication number: US3273350A
Application number: US409339A
Authority: US
Inventors: Robert S Taylor
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-09-14
Filing date: 1964-09-14
Publication date: 1966-09-20
Anticipated expiration: 1983-09-20

Description

Sept. 20, 196% R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 7 Sheets-Sheet 1.

INVENTOR Robert S. Taylor WWW 2s ATTORNEYS p 1966 R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 7 Sheets-Sheet 2 INVENTOR Robert S. Taylor ATTORNEYS p 1966 R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 7 Sheets-Sheet 5 INVENTOR Rob art 5. Taylor ATTORNEYS Sept. 20, 1966 R. S. TAYLOR REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION 7 Sheets-Sheet 4 Filed Sept.

INVENTOR Robert S. Taylor ATTORNEYS Sept. 20, 1966 R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 7 Sheets-Sheet 6 INVENTOR Robert SToylor ATTORNEYS Sept. 20, 1966 R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 '7 Sheets-Sheet 5 Q n g & 3 &

INVENTOR Robert S. Taylor ATTORNEYS Sept. 20, 1966 R. s. TAYLOR 3,273,350

REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Filed Sept. 14, 1964 7 Sheets-Sheet 7 FIG.7

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' INVENTOR Robert S. Taylor BY WW ATTORNEYS United States Patent 3,273,350 REFRIGERATION SYSTEMS AND METHODS OF REFRIGERATION Robert S. Taylor, 2906 edarview Drive, Austin, Tex. Filed Sept. 14, 1964, Ser. No. 409,339 (Ilaims. (Cl. 62-101) This application is a continuation-in-part of my copending application Serial No. 216,368, filed August 13, 1962, now abandoned.

This invention relates to new and useful improvements in refrigeration systems and methods of refrigeration.

The invention is particularly concerned with absorption refrigeration, especially systems in which water is the refrigerant and lithium bromide, lithium chloride, mixtures of the two, or any other suitable water absorbing material is the absorbent. Consequently, as utilized herein, a dilute absorption solution signifies a solution rich in refrigerant, and a concentrated absorption solution designates a solution poor in refrigerant or having its capacity for absorbing refrigerant substantially increased.

In lithium bromide-water refrigeration systems, it has been proposed to utilize a two stage refrigerant generator in which the refrigerant vapors from one stage, which is directly heated, are used to heat the second stage by means of a heat exchange relationship. The dilute lithium bromide-water solution from the absorber section is employed in one stage which enables the use of lower temperatures in that stage and at least a theoretical reduction of internal corrosion rates. At the same time, the system has a disadvantage from the viewpoint of efliciency in that the strongest absorption solution should receive heating at the highest temperature level and the refrigerant vapors from this stage employed for heating or boiling the more dilute absorption solution. In these prior systems, the evaporator operated at only a single pressure or temperature and the absorber correspondingly operated at a single pressure.

It is therefore, the primary objective of this invention to provide improved refrigeration systems and methods of refrigeration in which, whether or not the refrigerant generator operates in one or several stages, at least two stages of evaporators are employed and at least two stages of absorbers so that cooling or heat absorption is furnished at two levels. Thus, in an air conditioning system in which the return air from the air conditioned space is at a temperature of usually at least 75 F., the high temperature evaporator may operate at a temperature level of 55 F. to 60 F., and the low temperature evaporator may operate at a temperature level of around F. In this manner, the return air may be initially cooled by the high temperature evaporator and may receive its final cooling from the low temperature evaporator. This staging of the absorbers and the evaporators lessens the quantity of absorption solution circulated and produces part of the refrigeration at a higher temperature with a corre sponding reduction in losses and a gain in the coefficient of performance.

A further object of the invention is to provide refrigeration systems and methods of refrigeration in which any desired number of stages may be employed in the refrigerant generator, the evaporators and the absorbers, Within practical limits as to space and initial cost, in which more dilute absorption solutions may satisfactorily be employed to minimize problems of crystallization occurring in the absorption solution, which may be water cooled or air cooled, and in which provision may be made in several fashions for the prevention of internal corrosion and for elimination of the problem of salt crystallization.

A still further object of the invention is to provide improved refrigeration systems and methods of refrigeration in which one or more of the higher temperature evaporators may be utilized in aiding in the cooling of one or more of the lower pressure absorbers.

A construction designed to carry out the invention will be hereinafter described, together with other features of the invention.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings, wherein examples of the m vention are shown, and wherein:

FIG. 1 is a diagrammatic view of a refrigeration system constructed in accordance with this invention and adapted to carry out the methods thereof,

FIG. 2 is a schematic view of a modification of the invention in which the high temperature evaporator is utilized to aid in cooling the low pressure absorber,

FIG. 3 is a diagrammatic view of a further modified form of the invention utilizing a single stage generator,

FIG. 4 is a diagrammatic view illustrating a still further modification of the invention in which. the generator, the evaporators, and the absorbers are all divided into three stages,

FIG. 5 is a diagrammatic view illustrating another form of the invention in which refrigerant passes first to the low temperature evaporator and then to the high temperature evaporator,

FIG. 6 is a view similar to FIG. 5 and showing a form in which the refrigerant flows first to the high temperature evaporator, and

FIG. 7 is a diagrammatic view of a modification in which the high temperature evaporator is in heat exchange with the low pressure absorber.

In the drawings, in FIG. 1, the numeral 10 designates a refrigerant generator including a heating kettle or pot 11 having associated therewith a natural gas burner 12 or other suitable economical heating means. A vapor lift riser 13 extends upwardly from the pot 11 into a surge and separation enclosure 14 provided internally with a baflie or mist extractor 15 and an upwardly extending refrigerant vapor discharge conductor 16. This is: the first stage or heating stage of the generator which receives an absorption solution into the pot 11 relatively rich in absorbent and discharges from the chamber 14 through an outlet conductor 17 a concentrated absorption solution rich in absorbent.

The second stage of the generator includes an entrance chamber 18 for reception of a dilute absorption solution through an inlet conductor 19, a vapor lift riser 20 extending upwardly from the chamber 13 through a heat exchange jacket 21 and opening at its upper end into a surge or separation chamber 22 again provided with a baflie or mist extractor 23 and having an upwardly extending refrigerant vapor discharge conductor 24. The refrigerant vapor conductor 16 from the first stage of the generator opens into the upper end of the jacket 21, and a discharge conductor 25 extends from the lower end thereof. The surge chamber 22 has an outlet pipe 26 extending therefrom through a pump 27 into the pot 11 of the first stage of the generator, the conductor 26 conveying a partially or intermediately concentrated absorption solution from the chamber 22 to the pot 11. There is also a short riser 28 extending from the upper end of the chamber 18 upwardly above the pump 27 and being connected into the conductor 26 on the intake side of the pump 27.

The dilute absorption solution, containing lithium bromide and water, enters the chamber 18 through the conductor 19 and passes upwardly into the riser 20. Within the riser 20, the dilute solution receives heat from the hot refrigerant vapors in the jacket 21, condensing the vapors for discharge through the pipe 25 and vaporizing refrigerant from the dilute solution, the refrigerant vapors passing upwardly through the riser into the chamber 22 for outlet through the conductor 24 and creating a vapor lift arrangement carrying partially concentrated absorption solution into the chamber 22 for discharge through the conductor 26. At the same time, the pump 27 is drawing partially concentrated absorption solution from chamber 18 and the chamber 22 for delivery under pressure of the pump 27 as well as the hydrostatic head created in the conductor 26, into the pot 11 for reception of heat from the burner 12. The burner 12 functions to vaporize additional quantities of refrigerant from the absorption solution which flow upwardly through the riser 13, carrying therewith concentrated absorption solution into the chamber 14 for discharge through the conductor 17. The vaporized refrigerant from the first stage passes through the pipe 16 into the jacket 21 for condensation therein. Thus, the second stage refrigerant vaporizer functions as the condenser for the first stage vaporizer. At times there may come into existence the problem of hydrogen evolution caused by reaction between the hot water and hot solutions and the metal of the several generator parts, and provision is made for removal of such hydrogen through a riser 29 extending upwardly from the conductor and opening through a float box 30 into the conductor 24. The hydrogen may then be moved from the system by a conventional palladium trap 31 or in other usual and conventional manners.

The refrigerant vapor conductor 24 passes through a water cooled condenser 32 for condensation of the refrigerant vapors which then pass through a suitable orifice, restricting means, expansion valve or the like 33 into the low temperature evaporator 34 for absorption of heat. The expanded refrigerant vapors, and whatever liquid refrigerant may be present, flow from the evaporator 34 through a conductor 35 into a water cooled low pressure absorber 36 wherein the refrigerant is absorbed in absorption solution. The concentrated absorption solution passes from the chamber 14 of the first stage of the generator through the conductor 17 and into a heat exchanger 37 wherein the solution is cooled by the incoming dilute absorption solution passing through the conductor 19, and then passes through a conductor 38 into a float valve box 39 and thence into the absorber 36. The low pressure absorber 36 and in particular the float valve box 39 are placed at a higher elevation than a surge chamber 14 and accordingly function to maintain the first stage of the generator at a higher pressure than the low pressure absorber 36 due to the difference in vertical elevation and the hydrostatic head necessarily resulting.

The refrigerant from the first stage condensed in the jacket 21 passes through the conductor 25 into a second heat exchanger 40, where it is cooled by the dilute absorption solution entering through the conductor 19 and then flows through a conductor 41 and a float valve box 42 into the high temperature evaporator 43 for absorption of heat at a level higher than that of the evaporator 34.

The expanded refrigerant flows from the high temperature evaporator 43 through an outlet conductor 44 into a water cooled, high pressure absorber 45, partially diluted absorption solution from the absorber 36 also entering the absorber 45 through a U-tube trap 46 or through any other suitable means for permitting the maintaining of the absorber 45 at a higher pressure level than the absorber 36. The now reconstituted dilute solution of refrigerant and absorbent then flows by gravity from the absorber 45 and the conductor 19 into the entrance chamber 18 of the second stage of the generator.

The hydrostatic head in the conductor 26 and the pressure exerted by the pump 27 causes the first stage of the generator to operate at an elevated pressure, and this pressure is sufficient to lift the concentrated absorption solution to the float valve box 39. At the same time, this pressure obtains within the jacket 21 and is suflicient to elevate the refrigerant condensed in the jacket 21 to the float valve box 42. The absorber 36, receiving concentrated absorption solution, functions effectively to absorb refrigerant from the evaporator 34, permitting the evaporator 34 to operate at a low pressure and low temperature, while at the same time, the evaporator 34 receives condensed refrigerant from the condenser 32. The evaporator 43 is also functioning under a reduced pressure, although higher than that of the evaporator 34 and thus maintains the evaporator 43 at a reduced pressure, again, however, higher than that of the evaporator 34 and consequently at a higher temperature, while the absorber 45 is elevated vertically sutficiently above the second stage of the generator for the dilute absorption solution to return thereto by gravity from said absorber 45. Again, the U-tube trap 46 protects and maintains the pressure differential between the absorber 36 and the absorber 45.

The float box 30 carries a float actuated valve 47 for preventing the passage of the high pressure refrigerant upwardly through the conductor 29 into the conductor 24.

In some instances in the lithium bromide-water systems there may be a tendency for the lithium bromide to crystalize, particularly from the more concentrated solutions and at the times when such solutions are not under appreciably elevated temperatures. This problem becomes more severe in air cooled units in which more concentrated solutions are sometimes needed for obtaining proper absorbing at the air cooled temperatures of the absorbers. One solution of this problem, which usually arises during times the unit is not refrigerating, is to supply heat to the areas of crystallization by low temperature, low voltage electric heaters or the like, but a preferred solution is illustrated in FIG. 2 in which an air cooled embodiment of the invention is shown and in which the high temperature evaporator is utilized for obtaining enhanced cooling of the low pressure absorber. In this modification, the dilute absorption solution returns from an air cooled high pressure absorber 48 through a condoctor 49 leading heat exchangers 50 and 51 for preheating and connected to a leveling pot or chamber 52 surrounding the jacket 21 of the second stage of the generator and having a drain conductor 53 leading downwardly into the chamber 18 along with a vent conductor 54 opening upwardly into the chamber 22. Otherwise, the generator is constructed in the same fashion as that of the first described form of the invention and the same numerals have been applied to the same respective elements and parts.

The vaporized refrigerant from the second stage of the generator passes through the conductor 24 to an air cooled condenser 55 and thence into a conductor or coil 56 disposed in an enclosure 57 for the high temperature evaporator and the low pressure absorber for additional cooling. Thereafter, the condensed refrigerant passes through the orifice, expansion valve or restricting means 33 into the low temperature evaporator 34. The condensed refrigerant from the jacket 21 passes through the conductor 25 to the heat exchanger 50 for cooling by the incoming dilute absorption solution and then passes through the pipe 41 to the float valve box 42 for expansion and discharge into the interior of the enclosure 57, passing over a tray 58 in the upper end thereof. Thus, the refrigerant within pipe 56 is further cooled, and the low pressure absorber 59 which is disposed within the enclosure 57 is also cooled. The concentrated absorption solution passes, of course, from the chamber 14 through the conductor 17 to the float valve inlet box 39 for pressure reduction and discharge into the low pressure absorber 59. The low temperature evaporator 34 is connected by the pipe 35 to the low pressure absorber for absorption of the expanded refrigerant vapors from the low temperature evaporator, the absorption solution then passing through the U-tube trap 46 into the air cooled high pressure absorber.

The utilization of the high pressure refrigerant for cooling the interior of the enclosure 57 thus furnishes additional cooling facilities for the refrigerant passing to the low temperature evaporator 34, and also enhances.

the cooling of the low pressure absorber 59, enabling the assembly to function with air cooling and to function with solutions of refrigerant and absorbent sufficiently dilute as to eliminate the problem of crystallization. At the same time, refrigeration in sufficient amount and at sufiiciently low levels is provided to enable the use of the system for air conditioning purposes without necessitating resorting to water cooling.

A third form of the invention is illustrated in FIG. 3 in which a single stage generator is utilized and in which the staging of the evaporators involves the passage of the refrigerant through first one evaporator and through the second evaporator in series flow. In this modification the generator includes a lower pot or kettle provided with a gas burner or other suitable heating means 61 and having an upwardly extending vapor lift riser 62 entering at its upper end a surge or separator chamber 63. The chamber 63 is provided with a bafiie or mist extractor 64 and a refrigerant vapor outlet pipe 65 having connected thereinto a conventional palladium cell or other means 66 for disposing of any hydrogen which may be evolved in the generator. The vapor outlet pipe 65 extends through a water cooled condenser 67 and a heat exchanger 68 to a restricting valve, expansion valve, orifice or other similar means 69 and thence into a first low temperature evaporator 70.

A drain line 71 for expanded and unexpanded refrigerant extends downwardly from the evaporator into a downwardly concave section 72, the outlet leg 73 of which extends through the heat exchanger 68 and into a first, low pressure, water cooled absorber 74. From the lowermost point of the downwardly concave section 72, a U-tube trap 75 extends downwardly and is connected into a second or high temperature evaporator 76, the outlet 77 of which communicates with a high pressure water cooled absorber 78. The other end of the absorber 78 is connected to the absorber 74- and to the conductor 73 by a U-shaped trap 79. A dilute absorption solution drain conductor 80 extends from the conductor 77 through a heat exchanger 81 into a leveling pot 82 surrounding the medial portion of the vapor lift riser 62 of the generator. A discharge conductor 83 extends downwardly from the pot 82 into the pot 60, and a vent or equalizing line 84 extends from the pot 82 upwardly into the chamber 63. A concentrated absorption solution conductor 85 extends from the chamber 63 through the heat exchanger 81 and into the inlet of the low pressure absorber 74.

In the operation of this form of the invention, the dilute absorption solution entering through the conductor 80 is preheated in the heat exchanger 81 and passes into the leveling pot 82 for flow downwardly through the conductor 83 into the heating pot 60. In the pot or kettle 60, the dilute absorption solution is heated by the burner 61 or other heating means, driving off refrigerant vapors which pass upwardly through the riser 62 and function to vapor lift concentrated absorption solution upwardly into the chamber 63 from which the concentrated solution passes outwardly through the conductor 85 and into the heat exchanger 81 for partial cooling. The refrigerant vapors pass upwardly through the conductor 65 and are condensed in the water cooled condenser 67, then passing through the heat exchanger 68 for additional cooling before expanding through the orifice or valve 69 into the first or low temperature evaporator 70. From the evap' orator 70, refrigerant vapors and unexpanded refrigerant exit through the conductor 71, the unexpanded refrigerant tending to accumulate in the section 72 and pass downwardly through the trap 75 for expansion into the second or high temperature evaporator 76. The expanded refrigerant vapors from the evaporator 70 pass onwardly through the conductor 73, being partially warmed in the heat exchanger 68 and then flowing into the absorber 743-. The concentrated absorption solution flows through the pipe 85 and the heat exchanger 81 into the absorber 74, which is water cooled, and therein the 6 refrigerant vapors are absorbed in the concentrated solution to form a partially concentrated or intermediate absorption solution which drains downwardly through the trap 79 into the high pressure absorber 78. Refrigerant from the evaporator 76 passes through the conductor 77 into the absorber 78, therein being absorbed to reconstitute the dilute absorption solution which drains through the conductor 80 back into the leveling pot 82. Again, the elevations of the various components with respect to one another and the pressure trap means between both the evaporators and the absorbers, maintain the desired pressure and temperature levels and create the desired flow of the several bodies of refrigerant and absorption solutions.

A fourth form of the invention is shown in FIG. 4, this form utilizing three-stage refrigerant generation, threestage evaporation and three-stage absorption. In this fourth form of this invention the three-stage generator includes a first-stage 86 having at its lower end a heating pot or kettle 87 with a gas burner or other suitable heating means 88 therebelow, a vapor lift riser 89 extending upwardly from the pot 87 to a surge and separation chamber 90. The chamber 90 has the usual baffle or mist extractor 91 and an outlet conductor 92 for concentrated absorption solution. A refrigerant vapor conductor 93 extends from the upper portion of the chamber 90 into the upper end of the heat exchange jacket 94 of the secend-stage 95 of the generator. The second stage has a reception chamber 96 at its lower end and a vapor lift riser 97 extending upwardly through the jacket 94 and in heat exchange relationship therewith, terminating in an upper surge and separation chamber 98 having therein the usual baffie 99. An absorption solution outlet conductor 100 extends from the chamber 98 through a pump 101 into the heating pot or kettle 87 of the first-stage 86.

The second stage of the generator has a refrigerant vapor outlet conductor 10.2 extending into the heat exchanger jacket 103 of the third stage 104 of the generator, the third stage also having a receiving chamber 105 at its lower end with a vapor lift riser 106 extending upwardly through the jacket 103 into an upper surge and separation chamber 107 having therein the usual baifie or mist extractor 108. A flow conductor 109 extends downwardly from the chamber 107 through a pump 110 into the chamber 96 of the second stage of the generator, and an additional flow conductor 111 extends from the lower chamber 105 of the third stage into the conductor 109 on the intake side of the pump 110.

The third heating or heat exchanger stage 104 of the generator has a vapor outlet conductor 112 extending upwardly from the chamber 107 into a water cooled con denser 113 for condensation of the refrigerant vapors. The third stage also has an outlet conductor 114 at the lower end of the jacket 103 for discharge of the condensed refrigerant from the second stage, the conductor 114 having connected thereto a vapor vent'115 extending through a float and valve box 116 into the conductor 112 for discharge thereinto of any hydrogen evolved in the third stage of the generator, there being provided in the conductor 112 the usual palladium cell or other conventional means for disposing of such evolved hydrogen. The heat exchange jacket 94 of the second stage 95 also has an outlet conductor 118 extending from its lower end for discharge of the condensed refrigerant from the first stage of the generator, the conductor 118 also having a vent riser 119 connected through a float valve box 120 with the conductor 102 for discharge of hydrogen evolved in the second stage, a second palladium cell or the like 121 being also connected into the conductor 102.

There is provided what may be termed a triple heat exchanger which includes a central heat exchange conductor 122 surrounded by a heat exchange jacket 123 which, in turn, is surrounded by a pair of secondary heat exchange jackets 124- and 125. The central conductor 122 is connected into the receiving chamber 105 of the third stage 104 of the generator for delivering dilute absorption solution thereto, the solution having been heated in its passage through the multiple heat exchanger. The concentrated absorption solution conductor 92 of the first stage of the generator is connected into the heat exchange jacket 123 from which a conductor 126 leads to the absorption stages. The condensed refrigerant outlet conductor 118 of the second stage of the generator is connected into the secondary heat exchange jacket 124 from which an outlet conductor 127 leads to the evaporator stages. In addition, the condensed refrigerant outlet conductor 114 from the third stage 104- of the generator is connected into the heat exchanger 125 and an outlet conductor 128 also leads therefrom to the evaporator stages.

The condensed refrigerant from the third stage of the generator, having been liquified in the condenser 113 is conducted through an orifice, expansion valve or other restricting means 129 into a first evaporator 130 from which the refrigerant vapors are discharged through a conductor 131 to a first, water cooled absorber 132. The condensed refrigerant from the second stage of the generator is passed through the conductor 128 through a float restriction valve 133 into a second evaporator 134 from which the refrigerant passes by a conductor 135 into a second water cooled absorber 136. In addition, the condensed refrigerant from the first stage of the generator flows via the pipe 127 to a float restriction valve 137 and into a third evaporator 130 from which the refrigerant is discharged through a conductor 139 into a third water cooled absorber 140. The concentrated absorption solution conductor 126 is connected into the first absorber 132 through a float valve assembly 141. In addition, the conductor 131 is connected through a U-tube trap 142 to the second absorber 136, and the conductor 135 is connected to the third stage absorber 140 through a U-tube trap 143. The conductor 139 has connected thereinto the absorber 140 and dilute absorption solution conductor 122.

In the operation of this three-stage modification of the invention, dilute absorption solution enters the receiving chamber 105 of the third stage of the generator through the conductor 122 and passes upwardly through the riser 106 to receive heat from the condensing refrigerant within the jacket 103, vaporizing refrigerant from the dilute solution, the vaporized refrigerant passing upwardly through the conductor 112 for condensation through the condenser 113. At the same time, a partially concentrated absorption solution is formed which passes downwardly through the pipe 109 and also through the conductor 111 through the pump 110 into the receiving chamher 96 of the second stage of the generator, Herein, again, the solution moves upwardly through the riser 97 to receive heat from the refrigerant within the jacket 94 to condense said refrigerant and vaporize refrigerant from the partially concentrated solution. The refrigerant vapors pass upwardly through the conductor 102 into the jacket 103 of the third stage for condensation, while the additionally concentrated absorption solution passes downwardly from the chamber 98 through the conductor "and the pump 101 to the heating kettle or pot 87 of the first stage of the generator. Here, the additionally concentrated solution receives heat from the heating means 88 to drive refrigerant vapor and concentrated absorption upwardly through the riser 89 into the chamber 90, from which the vaporized refrigerant is discharged through the conductor 93 and to the jacket 94 of the second stage of the generator, while concentrated absorption solution is discharged through the conductor 92 for passage to the heat exchange jacket 123. In all three stages of the generator, the volatilizing of refrigerant vapors which pass upwardly through the vapor lift risers result in the simultaneous lifting of the absorption solution therefrom into the upper surge and separation chambers.

Within the triple heat exchanger, the incoming dilute absorption solution is preheated while the outgoing concentrated absorption solution is cooled, and the condensed refrigerants from the second and third stages are also cooled. The refrigerant vapor condensed in the condenser 113 expands into the evaporator 130 which is at the lowest temperature and lowest pressure of the three evaporators and then drains into the first absorber 132 wherein it is contacted by the concentrated absorption solution for absorption therein while simultaneously being cooled by the water jacket. The less concentrated solution thus formed drains through the trap 142 to the second a'bsorber 136.

The refrigerant from the second stage of the generator is condensed in the jacket 103 of the third stage thereof and passes through the secondary heat exhange jacket 125 and the conductor 128, through the restriction or expansion valve 133 and to the second evaporator 134 which is at a higher temperature and higher pressure than the evaporator 130. Refrigerant from the evaporator 134 drains through the conductor 135 into the second absorber 136 for absorption in the less concentrated absorption solution entering through the trap 142. From the second absorber 136, the still less concentrated absorption solution drains through the trap 143 and to the third absorber 140.

The refrigerant vaporized in the first stage of the generator and condensed in the jacket 94 of the second stage flows through the conductor 11% and the secondary heat exchanger 124- to the conductor 127 from which it enters the third evaporator 130 through the restriction or expansion valve 137, the third evaporator 13? being at a higher temperature and pressure than either the first or second evaporators. From the third evaporator, the refrigerant drains through the conductor 139 through the absorber 140 wherein it contacts the still less concentrated absorption solution being delivered from the second evaporator and is absorbed therein to reconstitute the dilute absorption solution which drains through the conductor 122 into the receiving chamber of the third stage of the generator. Again, the vertical spacings and relative elevations of the several components ensure the desired flows of the refrigerant and absorption solutions, only the pumps 101 and being required for maintain- 1ng such flow as well as the several pressure differentials. The first stage of the generator produces refrigerant at the highest pressure and highest temperature, and at the same time, produces the most concentrated absorption solution for maintenance of the first absorber 132 and the first evaporator at the lowest temperature and the lowest pressure, the successive stages producing refrigerant at lower temperatures and lower pressures, and the successive absorbers utilizing still less concentrated solutrons to maintain the second and third evaporators at progressively higher pressures and higher temperatures. In all forms of the invention, any suitable fan or pumpmg means may be utilized for passing air or water in heat exchange with the several evaporators for progressive cooling thereof and extraction of heat therefrom. The absorbers and condensers may be air cooled or water cooled depending upon the performance requirements involved, and in general, in the water cooled modifications more dilute solutions may be utilized. As illustrated in FIG. 2, however, one of the evaporators may be employed for supplemental cooling of the first stage or low pressure evaporator and quite effict'ent performance obtained using relatively dilute solutions and air cooling of the several components, In all forms of the invention, various corrosion inhibitors such as the chromates and certain of the nitrites and molybdates may be employed for minimizing internal corrosion. Also, low voltage and low power electrical heaters may be employed at various points throughout the several systems wherein crystallization tends to occur in the case of the lithium chloride and lithium bromide units. Obviously, the usual and conventional thermal insulation and heat shielding may be employed throughout the several systems as well as the conventional pressure and temperature controls, safety devices and the like. The pumps utilized may be of the sealed type, the magnetically driven type or of any other suitable or desirable nature. In all forms of the invention, the heat introduced is utilized most effectively and completely, and increased efiiciency of refrigeration is provided with relatively dilute refrigerant-absorbent solutions and with most effective extraction of heat by the several series arranged evaporators. Further, the maximum absorption properties of the absorption solutions is approached if not attained.

The temperatures and pressures in the various modifications of the invention described in the foregoing de scription will, of course, depend on the solution chosen, its concentration, rate of solution circulation, cooling water or air temperatures, refrigeration temperatures required, heat input, etc. Some typical figures for a specific set of conditions are given herewith. These cover first the water cooled modification shown in FIG. 1 and second the air cooled version in FIG. 2.

An air conditioning application is assumed in both instances. The assumed evaporator temperatures are F. for the low temperature evaporator and F. for the high temperature for the version shown in FIG. 1. Under these conditions the low pressure refrigerant will evaporate under a pressure of 6.3 mm. of mercury absolute and the high pressure refrigerant pressure in the high temperature evaporator will be 11 mm. Hg abs. Assume the temperatures of the low and high pressure absorbers to be F. and F. respectively. The equilibrium concentration of the intermediate solution leaving the low pressure absorber would then be 51% lithium bromide and the corresponding concentration of the reconstitute-d dilute solution would be 48% lithium bromide. This corresponds to a circulation rate of 16.8 pounds of concentrated solution (54% lithium bromide) per pound of water evaporated in the two evaporators. In practice more concentrated solution than 54% lithium bromide can be used for the concentrated solution. Assuming 56% lithium bromide fo rthe concentrated solution and F. condenser temperature, the second or heat exchange stage of a two stage generator will operate at F. (pressure 36 mm. Hg abs.) and the first or high pressure generator will operate at 213 F. (pressure mm. Hg abs.).

In the case of the air cooled modification in FIG. 2, the low temperature evaporator is assumed to operate at 50 -F. with an evaporator pressure of 9 mm. Hg abs. A temperature of 90 F. is assumed for the low pressure absorber (in heat exchange relationship with the high temperature evaporator). The equilibrium solution concentration having a vapor pressure of 9 mm. Hg abs. at 90 F. is 51% lithium bromide which then is the strength of the intermediate concentration solution. Assume the cooling air is such that the high temperature absorber operates at a temperature of 125 F., then 48% lithium bromide solution leaving the high pressure, 125 F. absorber will support a 90 F. high temperature evaporator and the low pressure absorber in heat exchange relationship with it. The concentrated solution entering the low pressure absorber then would have an equilibrium concentration of about 54%. In practice equilibrium conditions are not reached. Hence again, the strong solution entering the low pressure absorber will be assumed to be 56% lithium bromide. Assuming a 125 F. condenser temperature also, the condenser pressure will be 100 mm. Hg abs. This corresponds to a second generator temperature of 180 F. and a leaving concentration of 52% lithium bromide. The first generator would then have a maximum temperature of 260 F. to give off vapor from a 56% solution at a pressure (400 mm. Hg abs.) which will condense at 180 F. and thus heat the second generator.

In FIG. 5 of the drawings there is shown a modification of the form of the invention that was presented in FIG. 1, in which two generators are used to produce a single a single stream of refrigerant which is passed in series through the two evaporators and then into the two absorbers from each evaporator.

The first generator pot 143 receives the most dilute absorption solution through an inlet conductor 144, the solution being heated in the pot 143 by a gas burner or other suitable heating means 141-5. The evolved refrigerant vapors and partially concentrated absorption solution pass up through the vapor lift fiume 146 from the pot 163 into the usual separating chamber 147 from which the refrigerant vapor passes upwardly and through a conductor 146 to the heating jacket or heat exchanger jacket 149 of the second generator 150. Separated liquids are drained from the chamber 147 through a conductor 151 to the interior chamber 152 of the second generator through a heat exchanger 153 in heat exchange relationship with the conductor 144 and then through a restricter or expansion valve 154. Within the chamber 152, the partially concentrated absorption solution is further concentrated by receiving heat from the refrigerant vapors condensing in the jacket 149 and passes upwardly through the vapor lift conductor 155 into the separating chamber 156 of the second generator. The refrigerant vapors pass upwardly from the chamber 156 through a conductor 157 to a condenser 158 and are joined therein by a conductor 159 extending from the jacket 149 through a restricter or expansion valve 160 into the conductor i157.

The condensed refrigerant flows from the condenser 158 through the restricter or expansion valve 161 and into the low temperature evaporator 162. The unvaporized liquid refrigerant then passes from the low temperature evaporator 162 through a U-tube trap 163 and into the high temperature and higher pressure evaporator 164. Vaporized refrigerant passes from the low temperature evaporator 162 into the low pressure absorber 165 wherein it is joined by the concentrated absorption solution flowing from the separating chamber 156 through a conductor 166 leading to a heat exchanger 167 in heat exchange relationship with the conductor 144 and thence through a conductor i168 and an expansion valve 169 into the low pressure absorber through a conductor 170.

From the low pressure absorber, the partially diluted absorption solution fi'ows through a U-tube trap 17-1 into the high pressure absorber 172, uncondensed refrigerant passing from the high temperature evaporator 164 through a conductor 173 to the absorber 172 for absorption in the partially concentrated absorption solution. The absorption solution passes from. the absorber 172 through an outlet conductor 174 into which is connected a condensed refrigerant conductor 175 extending from the high temperature evaporator, the commingled and reconstituted dilute absorption solution then being forced by the solution pump 176 through the conductor 144 and into the first generator pot 143.

A slight variation of the form of the invention shown in FIG. 5 is illustrated in FIG. 6 and in which the condensed refrigerant passes through a first restricter or expansion valve 177 to the high temperature evaporator 178, and then unevaporate-d refrigerant passes from the high temperature evaporator through a second restricter or expansion valve 179 into the low temperature evaporator 1'80. Refrigerant vapor from the low temperature evaporator and unevaporated refrigerant passes to the low pressure absorber 181 where it commingles with concentrated absorption solution from the conductor 1170 to form a less concentrated absorption solution which passes through the U-tube trap 182 to the high pressure absorber 183. Refrigerant vapor from the high temperature evaporator 178 flows through a conductor 184 to the high pressure absorber 183, the reconstituted dilute absorption solution then leaving the absorber 183 through a conductor 185 leading to the solution pump .176. The other components of the modification shown in FIG. 6 are the same as those of FIG. 5 and the same numerals have been applied thereto.

The form of the invention shown in FIG. 7 differs 1 i from that of FIG. 6 in that the high temperature evaporator is in heat exchange relationship with the low pressure absorber. Otherwise, the structure is the same as that of FIGS. 5 and 6 and the same numerals have been applied to corresponding parts or elements.

In FIG. 7, the liquid refrigerant from the condenser 158 passes through the restricter or expansion valve 186 into the high temperature evaporator 187, the unvaporized refrigerant then flowing from the high temperature evaporator 187 through a second restricter or expansion valve 188 to the low temperature evaporator 189. Refrigerant vapor and liquid from the low temperature evaporator 189 is delivered through a conductor 190 to the low pressure absorber 191 which, it will be noted, is in heat exchange relationship with the high temperature evaporator 187, the concentrated absorption solution from the separating chamber 156 being delivered through the conductor 166 and heat exchanger 167 to the conductor H2 having therein the expansion valve 193 and which leads to the low pressure absorber 191. Partially diluted absorption solution drains from the low pressure absorber 191 through the U-tube trap 194 into the high pressure absorber 195, the dilute absorption solution then passing through the conductor 1% to the solution pump 1'76. Refrigerant vapor from the high temperature evaporator 187 flows through the conductor 197 to the high pressure absorber 195.

A particular feature of the modification shown in FIG. 7 is that it enables lower overall concentrations of the absorption solutions with higher temperatures for the condenser and the absorber cooling media and yet maintains the desired temperatures at the low temperaure evaporator. This facilitates more successful air cooling as compared to the modifications of FIGS. 5 and 6 which are better adapted for water cooled systems. Of course, in the modification of FIG. 5, it would be possible and sometimes advantageous to place the high temperature evaporator in heat exchange relationship with the low pressure absorber as shown in the modification of FIG. 7.

'The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A refrigeration system including,

a generator for receiving a dilute solution of a refrigerant and an absorbent,

means for heating the generator to drive off refrigerant from the dilute solution to form a concentrated absorption solution,

means for condensing the driven off refrigerant,

a low temperature evaporator,

means for flowing the condensed refrigerant into the low temperature evaporator while restricting such flow, a low pressure absorber, means for flowing refrigerant vapor from the low temperature evaporator to the low pressure absorber,

means for flowing the concentrated absorption solution from the generator to the low pressure absorber to absorb refrigerant vapor therein,

a high temperature evaporator,

means for flowing a condensed refrigerant from the generator to the high temperature evaporator, a high pressure absorber, means for flowing the refrigerant from the high temperature evaporator to the high pressure absorber,

means for flowing the absorption solution from the low pressure absorber to the high pressure absorber to absorb the refrigerant from the high temperature evaporator and reconstitute the dilute solution of the refrigerant and the absorbent,

and means for flowing the reconstituted dilute solution from the high pressure absorber to the generator.

2. A refrigeration system as set forth in claim 1 wherein the means for flowing a refrigerant from the generator to the high temperature evaporator is means for flowing a condensed refrigerant directly from the generator to the high temperature evaporator.

3. A refrigeration system as set forth in claim 1 wherein the means for flowing a refrigerant from the generator to the high temperature evaporator is means for flowing a refrigerant from the generator through the low temperature evaporator and then to the high temperature evaporator.

4. A refrigeration system including,

a first generator for receiving a partially concentrated absorption solution of an absorbent and a refrigerant,

means for heating the first generator to drive off a high pressure refrigerant from the partially concentrated solution and produce a concentrated absorption solution,

a second generator for receiving a dilute absorption solution,

means for passing the high pressure refrigerant in heat exchange relationship with the dilute absorption solution in the second generator to condense the high pressure refrigerant and to drive off from the dilute absorption solution a low pressure refrigerant and so produce a partially concentrated absorption solution,

means for flowing the partially concentrated absorption solution from the second generator to the first generator,

means for condensing the driven off low pressure refrigerant,

a low temperature evaporator,

means for flowing the condensed low temperature refrigerant into the low temperature evaporator while restricting such flow,

a low pressure absorber,

means for flowing the low pressure refrigerant from the low temperature evaporator to the low pressure absorber,

means for flowing the concentrated absorption solution from the first generator to the low pressure absorber to absorb therein the low pressure refrigerant and produce an intermediate absorption solution,

a high temperature evaporator,

means for flowing the condensed high pressure refrigerant from the second generator into the high temperature evaporator,

a high pressure absorber,

means for flowing the high pressure refrigerant from the high temperature evaporator to the high pressure absorber,

means for flowing the intermediate absorption solution from the low pressure absorber into the high pgssure absorber to absorb therein the high pressure refrigerant and reconstitute the dilute 55.65am solution,

and means for flowing the reconstituted dilute absorption solution from the high pressure absorber to the second generator.

5. A refrigeration system as set forth in claim 4,

means for maintaining a pressure differential between the first generator and the low pressure absorber,

means for maintaining a pressure differential between the first generator and the high temperature evaporator,

and means for maintaining a pressure differential between the high pressure absorber and the low pressure absorber;

6. A refrigeration system as set forth in claim 4 wherein the high temperature evaporator is in heat exchange relationship with the low pressure absorber.

7. A refrigeration system including,

a generator for receiving a dilute absorption solution of a refrigerant and an absorbent,

means for heating the generator to drive off a refrigerant and produce a concentrated absorption solution,

means for condensing the driven-off refrigerant,

a low temperature evaporator,

means for flowing the condensed refrigerant into the low tempeature evaporator while restricting such flow,

a low pressure absorber,

means for flowing at least a portion of the refrigerant from the low temperature evaporator into the low pressure absorber,

a high temperature evaporator,

means for flowing the remainder of the refrigerant from the low temperature evaporator into the high temperature evaporator,

a high pressure absorber,

means for flowing refrigerant from the high temperature evaporator to the high pressure absorber,

means for flowing the concentrated absorption solution from the generator to the low pressure absorber to absorb therein the portion of the refrigerant from the low temperature evaporator and to produce an intermediate absorption solution,

means for flowing the intermediate absorption solution from the low pressure absorber to the high pressure absorber to absorb therein the refrigerant from the high temperature evaporator and reconstitute the dilute absorption solution,

and means for returning the dilute absorption solution from the high pressure absorber to the generator.

8. The method of producing refrigeration including,

heating in a heating zone a dilute absorption solution containing a refrigerant and an absorbent to drive off refrigerant and produce a concentrated absorption solution,

condensing the driven-off refrigerant,

expanding the condensed refrigerant into a low temperature evaporator to absorb heat,

absorbing the expanded refrigerant from the low temperature evaporator in the concentrated absorption solution to produce an intermediate absorption solution,

flowing condensed refrigerant from the heating zone to a high temperature evaporator and therein expanding such refrigerant to absorb heat,

absorbing the expanded refrigerant from the high temperature evaporator in the intermediate absorption solution at a pressure higher than that at which the expanded refrigerant from the low temperature evaporator is absorbed to reconstitute the dilute absorption solution,

and returning the dilute absorption solution to the heating zone.

9. The method of producing refrigeration including,

condensing the driven-off refrigerant,

flowing condensed refrigerant directly from the heat ing zone to a high temperature evaporator and therein expanding such refrigerant to absorb heat,

absorbing the expanded refrigerant from the high temperature evaporator in the intermediate absorption solution at a pressure higher than that at which the expanded refrigerant from the low temperature evaporator is absorbed to reconstitute the dilute absorption solution, I

and returning the dilute absorption solution to the heating zone.

10. The method of producing refrigeration including,

heating in a heating zone a dilute absorption solution containing a refrigerant and an absorbent to drive of)? refrigerant and produce a concentrated absorption solution, condensing the driven-off refrigerant, expanding a portion of the condensed refrigerant into a low temperature evaporator to absorb heat,

flowing unexpanded refrigerant from the low temperature evaporator to a high temperature evaporator and therein expanding such refrigerant to absorb heat,

and returning the dilute absorption solution to the heating zone.

11. The method of producing refrigeration including,

heating in a heating zone a partially concentrated absorption solution containing a refrigerant and an absorbent to drive off refrigerant and produce a concentrated absorption solution, flowing the driven off refrigerant to a heat exchange zone and into heat exchange relationship with a dilute absorption solution to condense the driven off refrigerant and drive off refrigerant from the dilute solution while producing a partially concen trated absorption solution, flowing the partially concentrated absorption solution from the heat exchange zone to the heating zone,

condensing the refrigerant driven off from the heat exchange zone and expanding the condensed refrigerant into a low temperature evaporator to absorb heat, absorbing the expanded refrigerant from the low temperature evaporator in the concentrated absorption solution to produce an intermediate absorption solution, i

expanding the condensed refrigerant driven off from the heating zone into a high temperature evaporator to absorb heat,

and returning the dilute absorption solution to the heat exchange zone.

12. The method of producing refrigeration as set forth in claim 11 wherein the expanded refrigerant from the low temperature evaporator is absorbed in the concentrated absorption solution in heat exchange relationship with the high temperature evaporator.

'13. A refrigeration system including,

a generator for receiving a dilute solution of a refrigerant and an absorbent,

means for condensing the driven off refrigerant,

a low temperature evaporator,

means for flowing the condensed refrigerant into the low temperature evaporator while restricting such flow,

a low pressure absorber,

means for flowing refrigerant vapor from the low tempera-ture evaporator to the low pressure absorber,

a high temperature evaporator,

means for flowing condensed refrigerant from the generator to the high temperature evaporator,

a high pressure absorber,

means for flowing the refrigerant from the high temperature evaporator to the high pressure absorber,

14. A refrigeration system including,

a generator for receiving a dilute solution of a refrigerant and an absorbent,

means for condensing the driven off refrigerant,

a first evaporator,

means for flowing the condensed refrigerant into the first evaporator while restricting such flow,

a first absorber,

means for flowing the refrigerant vapor from the first evaporator to the first absorber,

means for flowing the concentrated absorption solution from the generator to the first absorber to absorb refrigerant vapor therein,

a second evaporator,

means for flowing condensed refrigerant to the second evaporator,

a second absorber,

means for flowing the refrigerant from the second evaporator to the second absorber,

means for flowing the absorption solution from the first absorber to the second absorber to absorb the refrigerant from the second evaporator and reconstitute the dilute solution of the refrigerant and the absorbent,

and means for flowing the reconstituted dilute solution from the second absorber to the generator.

15. -A refrigeration system including,

a generator for receiving a dilute solution of a refrigerant and an absorbent,

means for condensing the driven off refrigerant,

at least two evaporators in series and the same number of corresponding absorbers,

means for flowing the condensed refrigerant into the first evaporator and the remaining unevaporated refrigerant into each succeeding evaporator,

means for flowing the concentrated absorption solution from the generator to a first absorber and to each succeeding absorber in series,

means for flowing refrigerant vapor from each evap orator to its corresponding absorber,

and means for flowing the reconstituted dilute solution from the last absorber to the generator.

16. A refrigeration system as set forth in claim 1 wherein the high temperature evaporator is in heat exchange relationship with the low pressure absorber.

17. A refrigeration system including, a first generator for receiving a partially concentrated absorption solution of an absorbent and a refrigerant,

a second generator for receiving a dilute absorption solution,

means for passing the high pressure refrigerant in heat exchange relationship with the dilute absorption solution in the second generator to condense the high pressure refrigerant and to drive off from the dilute absorption solution a lower pressure refrigerant vapor and so produce a partially concentrated absorption solution,

means for condensing the refrigerant driven off from the second generator,

a low temperature evaporator,

means for flowing the condensed refrigerant driven off the second generator into the low temperature evaporator while restricting such flow,

a low pressure absorber,

means for flowing the concentrated absorption solution from the first generator to the low pressure absorber to absorb therein the refrigerant from the low temperature evaporator and produce an intermediate absorption solution,

a high temperature evaporator,

means for flowing the refrigerant generated in the first generator and condensed in the second generator into the high temperature evaporator through a controlling restricter,

a high pressure absorber,

means for flowing the intermediate absorption solution from the low pressure absorber into the high pressure absorber to absorb therein the high pressure refrigerant and reconstitute the dilute absorption solution,

18. A refrigeration system as set forth in claim 4, and

including,

means for maintaining a pressure differential between the high pressure absorber and the low pressure absorber,

and means for transferring reconstituted solution from the high pressure absorber to the second genera-tor and then to the first generatorv 19. A refrigeration system including,

a generator for receiving a dilute absorption solution of a refrigerant and an absorbent and having a heating stage and at least one additional heat exchange stage,

means for heating the heating stage to drive off refrigerant from the dilute absorption solution and form a concentrated absorption solution,

means for condensing the refrigerant driven oif from the heating stage by passing it in heat exchange relationship in a heat exchange stage of the generator with an absorption solution to increase the concentration of the absorption solution and drive off there from a refrigerant,

means for condensing the refrigerant driven off from the heat exchange stage,

means for flowing absorption solution from the heat exchange stage to the heating stage,

at least two evaporators and an equal number of corresponding absorbers,

means for flowing condensed refrigerant from one stage of the generator to one of the evaporators,

means for flowing condensed refrigerant from another stage of the generator to a second evaporator,

means for flowing refrigerant vapor from each evaporator to its corresponding absorber,

means for flowing concentrated absorption solution from the heating stage of the generator to a first absorber and thence to each succeeding absorber in series to absorb the refrigerant vapor from the evapora-tors and reconstitute the dilute absorption solution,

and means for returning the dilute absorption solution from the last absorber in the series to the generator.

20. A refrigeration system including,

a refrigerant generator having first, second and third stages,

first, second and third evaporators,

first, second and third absorbers corresponding to the evaporators,

means for flowing an additionally concentrated absorption solution of a refrigerant and an absorbent from the second stage of the generator to the first stage,

means for heating the first stage to drive off refrigerant from the absorption solution and form a concentrated absorption solution,

means for passing the refrigerant driven off from the first stage in heat exchange relationship with partially concentrated absorption solution in the second stage to condense the refrigerant driven off in the first stage and drive off refrigerant from the second stage while additionally concentrating the absorption solution in the second stage,

means for passing the refrigerant driven off in the second stage in heat exchange relationship with dilute absorption solution in the third stage to condense the refrigerant driven off in the second stage and drive off refrigerant from the third stage while partially concentrating the dilute absorption solution in the third stage,

means for flowing the partially concentrated solution from the third stage to the second stage,

means for condensing the refrigerant driven off from the third stage,

means for flowing the condensed refrigerant from the third stage into the first evaporator while restricting such flow,

means for flowing the condensed refrigerant from the second stage into the second evaporator while restricting such flow,

means for flowing the condensed refrigerant from the first stage into the third evaporator while restricting such flow,

means for flowing refrigerant vapor from the first, second and third evaporators to their corresponding absorbers,

means for flowing concentrated absorption solution from the first stage of the generator to the first absorber to absorb refrigerant vapor from the first evaporator and from a less concentrated absorption solution,

means for flowing the less concentrated absorption solution from the first absorber to the second absorber to absorb refrigerant vapor from the second evaporator and form a still less concentrated absorption solution,

means for flowing the still less concentrated absorption solution from the second absorber to the third absorber to absorb refrigerant vapor from the third evaporator and reconstitute the dilute absorption solution,

and means for flowing the dilute absorption solution from the third absorber to the third stage of the generator.

References Cited by the Examiner UNITED STATES PATENTS 2,027,106 1/ 1936 Knight 62-484 X 2,283,213 5/ 1942 Katzow 62484 X 2,290,532 7/ 1942 Buffington 62-484 X 2,932,958 4/1960 Johansson et al. 6 24 84 3,126,720 3/ 1964 Stubblefield 62476 X LLOYD L. KING, Primary Examiner.

Claims

1. A REFRIGERATION SYSTEM INCLUDING, A GENERATOR FOR RECEIVING A DILUTE SOLUTION OF A REFRIGERANT AND AN ABSORBENT, MEANS FOR HEATING THE GENERATOR TO DRIVE OFF REFRIGERANT FROM THE DILUTE SOLUTION TO FORM A CONCENTRATED ABSORPTION SOLUTION, MEANS FOR CONDENSING THE DRIVEN OFF REFRIGERANT, A LOW TEMPERATURE EVAPORATOR, MEANS FOR FLOWING THE CONDENSED REFRIGERANT INTO THE LOW TEMPERATURE EVAPORATOR WHILE RESTRICTING SUCH FLOW, A LOW PRESSURE ABSORBER, MEANS FOR FLOWING REFRIGERANT VAPOR FROM THE LOW TEMPERTURE EVAPORATOR TO THE LOW PRESSURE ABSORBER, MEANS FOR FLOWING THE CONCENTRATED ABSORPTION SOLUTION FROM THE GENERATOR TO THE LOW PRESSURE ABSORBER TO ABSORB REFRIGERANT VAPOR THEREIN, A HIGH TEMPERATURE EVAPORATOR, MEANS FOR FLOWING A CONDENSED REFRIGERANT FROM THE GENERATOR TO THE HIGH TEMPERATURE EVAPORATOR, A HIGH PRESSURE ABSORBER, MEANS FOR FLOWING THE REFRIGERANT FROM THE HIGH TEMPERATURE EVAPORATOR TO THE HIGH PRESSURE ABSORBER,