CA1285398C - Absorption refrigeration and heat pump system - Google Patents

Abstract

ABSTRACT

This invention relates to a cooling and heating system which operates on the absorption and phase change heat exchange principle. More particularly it relates to a continuous heat actuated, air cooled, double effect generator cycle, absorption system. In further aspects, this invention relates to a system constructed for use with an absorption refrigeration solution pair consisting of a nonvolatile absorbent and a highly volatile refrigerant which is highly soluble in the absorbent. A
disclosed refrigerant pair are ammonia as the refrigerant and sodium thiocyanate as the absorbent.
An absorption cycle is disclosed using the thermo physical properties of sodium thiocyanate/ammonia, absorption/refrigerant pair. Also disclosed is the construction and configuration of a reverse cycle air cooled double effect generator absorption refrigeration system for use with the sodium thiocyanate/ammonia refrigeration pair, as well as subcompositions, subsystems and components that improve the system efficiency and reduce cost.

Description

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This is a division of copending commonly owned Canadian Patent Application No. 494,837 filed on November 7, 1985.

FI~LD OF T~E INV~NTION
This invention relates to a cooling and heating system ~hich operates on the absorption and phase change heat exchange principle. More particularly it relates to a continuous heat actuated, air cooled, multiple effect generator cycle, absorption system.
In further aspects, this invention relates to a system constructed for use with an absorption refrigeration solution pair comprising a nonvolatile absorbent and a highly volatile refrigerant which is highly soluble in the absorbent. A disclosed refrigerant pair are ammonia as the refrigerant and sodium thiocyanate as the absorbent.

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1 1 BACKGROUND OF THE INVE~TION
. __ There are two major types of absorption refrigeration equipment in commercial use: (1) air cooled systems using ¦ ammonia as the refrigerant and water as the absorbent, and ¦ (2) water cooled systems using water as the refrigerant ¦ and lithium bromide as the absorbent.
~ Although these are the major types in commercial use, _ ~ I and there are many patents relating to these and other ¦ types, variations have been patented from these general principles and the following are typical examples of such patents: U. S. 4,055,964 - Swenson et al. and U. S.
2,350,115 - Katzow.
Others ~ave demonstrated air cooled absorption ~ refrigeration systems uslng other absorbent, refrigerant : 15pairs. The following patents relate to these systems: U.
S. 4,433,554 - Rojay et al. and U. S. 3,4~3,710 - Bearint.
Still others have patented water cooled refrigeration ~; systems using other salts or other salts in co~bination - , with lithium bromide as the absorbents. The following are `~` 20examples of these: U. S. 3,609,086 ~lodahl et al. and U.
; I S. 3,541,0~3 - ~acriss et al.
: ¦ Water cooled refrigeration circuits using the double ¦ effect generator are also in commercial use and have been ¦ patented as seen in the following patents: U. S. 495,420 -¦ Loweth et al., U. S. 3,389,573 - Papapanu et al., U. S.
4,183,228 - Saito et al., and U. S. 2,182,453 - Sellew.
¦ In absorption refrigeration and/or heating systems, ¦ the generator, sometimes called desorber, is a very ¦ important part of the system and contri~utes significantly ¦ to the overall efficiency. Much attention has been given ¦ to the construction of ~hese devices, and various ~ arrangements are shown in the following patents: U. S.
¦ 3,323,323 - Phillips, U. S. 3,608,331 - Leonard, and U. S.
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¦ 4,127,993 - Phillips, and U. S. 4,4~4,688 - WilXinson~
! These existing air cooled absorption refrigeration circuits have demonstrated cooling coefficients of I performance as h igh as 0. 50 using various ¦ absorbent/refrigerant pairs. These systems have also been demonstrated as heating only heat pumps with a coefficient of performance of up to 1.3.
As used herein, coefficient of performance, i.e. COP, is defined as the energy transferred at the load in ¦ 3TU/unit of time over the energy provided to the system in I BTU/unit of time which is well understood by those skilled ¦ in the art.
¦ Air cooled refrigeration circuits have also been ¦ demonstrated which can be reversed to provide either ¦ heating or cooling to an air conditioned space (a load) by ¦ switching the flow of an intermediate heat transfer solution typically consisting of water and antireeze ¦ solutions such as ethylene glycol, etc.
¦ Liquid cooled absorption refrigeration circuits using ¦ the double effect generator cycle to achieve high ¦ ef~iciency are co~mercially available. However, these ¦ systems are not suitable or use in heating a conditioned ¦ space (the heating load) since the refrigerant freezes at ¦ 3~F and therefore cannot be used in a space heating ,~ ~ 25 ¦ system at ambient tempera~ures below approximately 40~F.
,"`, ~ J ¦ Absorption refrigeration and heat pump systems are well known in their basic operating characteristics and need little further description except to establish the definitions and context in which this invention will be later described.
In a typical system a refrigerant, water or other phase change material is dissolved in a absorbent ¦ (typically lithium bromide or other salts) and these are ¦ often called the "solution pair". The refrigerant is .--, ~.y ,~ .

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l . ~ l I absorbed or desorbed (expelled) in or out of solution with the absorbent to varying degrees throughout the system and the heat of absorption is added or extracted to produce ~ heating and cool-ng ef~ects.
5 ~ The solution pair ente~s a generator where it is subjected to heat and the applied hea~ desorbs (expells) l the refrigerant water in the form of a vapor which is : , conveyed to ~he condenser. There, external ambient .~ cooling condenses the refriserant vapor to liquid, which is conveyed through an expansion valve/ into an evaporator where heat is gained. In the refrigeration system operation the heat gained in the evaporator is from the cooling l~ad.
¦ - The low pressure vapor then passes to an absorber ¦ where ambient cooling allows the absorbent solution to l absorb the refrigerant vapor. The solution is then ¦ conveyed to a recuperator by a pump. The recuperator is a counterflow heat exchanger where heat ~rom the l absorbent/refrigerant solution, flowing from the gP~erator ¦ to the absorber, heats the returning solution pair f~owing from the absorber to t~e generator. In the heating cycle, the cooling applied at the absorber and/or the condenser i5 the heat delivery to the heating load.
l As a matter of convenience and terminology herein, 1 each part of the absorption sys~em which operates at the ;~ I same pressure is termed a chamber.
¦ Conventional absorption refrigeration/heating systems ¦ are two chamber systems although three chamber systems ¦ appear in th pr~or ~Ft and have seen limited use. When : ! . , , .. . ~

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1 1 operated as a heat pump two chamber systems give ¦ respectable heating performance but give poor cooling i¦ performance.
¦ Using ammonia ~NH3) as the refrigerant and water ¦ (H20) as the sorbent, heat pumping can occur from an ambient air source which is at temperatures below freezing. ln a theoretical assessment where the air is treated as if it were dry so that no defrosting is l necessary, the typical two chamber ~H3/H2O heat pump would l, represent a significant improvement over what would be ~ expected of a simple furnace. ~owever, since heat pumps ¦ are more expensive than furnaces, cooling season performance benefits are needed to justify the added expense. In other words, the heat pump must act as an air conditioner also to offset the cost of a separate installation of an air conditioner with the furnace.
.~J~:il For cooling, an N~3/H20 system is predicted to have a ¦ COP equal to about 0.5. This low per~ormance index causes ¦ unreasonable fuel (or energy) costs from excessive fue].
¦ ~or energy) use. This low performance of the ammonia/water ¦ system results from the poor performance characteristics ¦ of the ammonia/water solution at the higher temperature ¦ ranges, if the heat is supplied to the absorption system at higher temperatures.
25 ¦ Three-chamber systems of various types have been suggested which would improve the performance by staging the desorption process into effects. This would allow for increasing the actual temperature at which the driving ¦ heat is added to the system (cycle). The reference Carno~
¦ cycle efficiency would be increased and the real cycle ¦ would follow suit. Until the present invention it was ¦ thought that this increase in temperature would represent ¦ an unreasonably high pressure, especially for .1 . "~' '~ l I - .

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~ ¦ ammonia/water systems, and would force the system to ~l operate in regions for which data is not readily available.
l In addition the pressure has tended to rule out ¦ ammonia/water in a three chamber system. The search for organic material such as halogenated hydrocarbons and j other refrigerants as a replacement for the ammonia has been limited by fluid stability at these higher 9 temperatures. ~ormal organic refrigerant stability tests have indicated that it is necessary for oil to be present for operation in vapor compression refrigeration syste.~s.
I These high operating temperatures rule o~t most of the common refrigerants~ partieularly being heated directly by ¦ combustion products which often cause local hot spots, ¦ which result in working fluid degradation and/or corrosion ¦ of components.
; ¦ U. S. Patent 4,441,332 - Wilkinson is an example of a four-chamber absorption refrigeration system to provide ¦ refrigeration and/or heat pump total capability. This prior art patent employs two chemically separated two-chamber sys~ems ~hich are mechanically integrated into ¦ a total system to take advantage of the high performance ¦ of one solution pair in a low temperature range for ¦ cooling and the advantages of the other solution pair in a ¦ high temperature range when the total system is heat ¦ pumping in the heating mode.
¦ The invention described herei-n is an integrated ¦ three-chamber system having one solution pair using an ¦ organic materia~ of unusual fluid stability at higher temperatures when manipulated in an apparatus and system ¦ to take advantage of its properties. The typical ¦ preferred solution pair for operation as part of the ¦ system and components of this invention is ammonia as the .,~ ¦ refrigerant and sodium thiocyanate as the absorbent.
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,~.,.., 39~3 Others have given consideration to this solution pair , as examplified by the ASME publication "Performance of A
¦¦ Solar Refrlgeration System Using Ammonia - Sodium 1~ Thiocyanate", by Swartmen et al., in November 1972 and the 5 ¦¦ publication entitled "A Ccmbined Solar ~eating/Cooling System", by Swartmen and presented 28 July-l August 1975 at the 1975 International Solar Energy Congress and Exposition and U. S. Patent 3,458,445 - Macriss et al.
The heat actuated, air cooled, double effect generator cycle absorption refrigeration system of this invention overcomes limitations of the existing prior art technology. The air cooled system of this invention l eliminates the need for cooling water and the use of ¦ ammonia as the refrigerant avoids refrigerant freezing ¦ during heating operation. The double effect generator l cycle permits high efficiency through internal heat - ¦ recovery in the absorption refrigeration circuit. The use ;^~i~ I of sodium thiocyanate as the absorbent eli~inates the need for analyzers and rectifiers to purify the refrigerant 1 stream. Internal refrigerant flow reversal, to achieve heat/cool switching and defrosting, eliminates the need for intermediate water/antifreeze heat transer loops to switch from heating to cooling operatlon.
SUMMARY OF ~HE I~VE~'rION
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25 ¦ A combination oi a double effect generator absorption cycle, the thermo/physical properties of which are enhanced by th e app lication of the sodium thiocyanate/ammonia absorbent/refrigeration pair, with the ¦ arrangement of a reverse cycle air cooled double effect ¦ refrigeration circuit with generator and heat exchanger i~
¦ a stacXed coil configuration including tube in tube ¦ concepts, together with the combination of energy recovery ¦ motors to contribute ~o the power requirement of the ¦ solution pump and means for positioning the refrigerant d . ~2 8 53 98 reversing valve(s) to provide warm refrigerant ~apor through the re~rigerant to air heat exchanger while still producing heat from the system as a way of de~rosting the refrigerant to air heat exchanger when outside air temperatures are low.

The invention includes an absorption refrigeration and/or heating process wherein a highly volatile chemically and thermally stable refrigerant (ammonia) is alternately absorbed in and expelled from an absorbent (sodium thiocyanate~ with the process conducted as a double effect system in the generator section.

The present invention ma~ therefore be considered as providing, in a multiple effect absorption refrigeration and/or heating system including a plurality of generators and a plurality of heat exchanging recuperators, the impro~ement comprising: (a) a source o~ external heat in proximity to at least one of the generator means; (b) a first generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite ~orm, with the ~irst generator means surrounding the source of heat; (c) a first recuperator means ¢omprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the recuperator means surrounding the first generator means; ~d) a second generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with a second generator means surrounding the first recuperator means; and (e) a second recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the second recuperator means surrounding the second generator means.

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~ ~8~3~3 Furthermore, the present invention may be considered as providing, in a multiple effect absorption refrigeration and/or heating system including a plurality of generators and at least one heat exchanging recuperator, the improvement comprising: ~a) a source of external heat in proximity to at least one of the generator means; (b) a first generator means and at least one second generator means constructed as a plurality of coils with the coils juxtaposed one to the next in a generally annular composite form, with th~ first generator means surrounding the source o~ heat; and ~c) at least one recuperator means comprising a plurality oE coils with the coils juxtaposed one to the next, in a generally annular composite form, with the recuperator mean~ surrounding the first generator means.

It is an object of this invention to provide in combination an absorption reErigeration and/or heating system which may be operated either in a heating mode or a 12685/LcM:l~J

l~ ~ /o cooling mode by interchanging the use of various of compone~ts by me~ns af valves and/or controls. Another object of the invention i5 to operate such a system using a specific solution pair, ammonia as the refrigerant and sodium thiocyanate as the absorbent in a double effect system.
A further object of the invention is to increase the efficiency of an absorption refrigeration and/or heating system by passing the operating solutions through motive units to augment the solution pump and reduce the external power requirements of the system. Still a further object of the invention is to operate an absorption refrigeration and/or heating system. A further object of this invention is to maintain a major portion of the space heating capacity at the system during the defrost cycle. S~ill a further object is to use the hot working fluid from the absorber in the heating and cooling modes, and the hot working fluid from the second heat exchanger in the heating mode, to preheat domestic hot water. Still a further object is to use the heat pump to preheat domestic water when there is no space heating or space cooling demand. A further object of this invention is to provide an air cooled absorption heat pump with a coo~ing~COP
greater than O. a and a heating COP greater than 1.5.
,,~ 25 ¦ The foregoing and other advantages of the invention will become apparent from the following disclosure in which a preferred embodiment of the invention is described in detail and illustrated in the accompanying drawings.
It is contemplated that variations and structural features and arrangement of parts may appear to the person sXilled in the art, without departing from the soope or sacrificing any of the advantages of the invention which is delineated in the included Claims.
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1 1 BRIEF DESC~IPTIo~ OF THE DRAWINGS
Figure 1 is a diagram of typical double effect ¦ absorption refrigeration cycle system.
Figure 2 is a diagram of the double effect absorption system of this invention in the cooling mode.
Figure 3 is a diagram of the double effect absorption ¦ system of this invention in the heating mode.
¦ Figure 4 is a cross-sectional elevation view of the ~ generator/recuperator apparatus of this invention.
¦ Figure 5 is a cross-sectional plan view taken on tne line 5-S of Figure 4.
Figure 6 is a schematic diagram for the absorption ¦ cycle of this invention.
¦ Figure 7 is a heat versus solution concentration ¦ diagram for the double effect absorption cycle of this ¦ invention using ammonia as the refrigerant and sodium ¦ thiocyanate as the absorbent.
¦ Figure 8 is a perspective view, partially broken r ¦ away, of a solution pump and energy recovery motor ¦ apparatus of this invention.
Figure 9 is a schematic elevational sectional view o~
one embodiment of the apparatus and system of this invention as it could be constructed for installation adjacent to a building having a cooling and/or heating ,~i 25 load.
Figure 10 is a graph of exposure time versus corrosion rate for a solution pair of-this invention, with and without the additive material of this invention~
DETAILED DESC~IPTION OF THE INVE~TION
In the description of this invention, it is important that there is a clear understanding of the meanings of the terms used herein. Otherwise, because of the complexity of the entire system and the use of components from r.; various fields of mechanical, chemical, and electrical .. . ..

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1 arts, the terminology could be confusing in some cases.
Therefore, as used herein the term "strong solution", when speaking of the solution pair refers to that soLution that has picked up refrigerant in the absorber and is in progress toward the generator and carries a higher ratio of refrigerant to absorbent than solution which has been desorbed and partially expelled of refrigerant in the generator(s) of the system. Solution from which refrigerant has been expe~led is, by contrast, a "weak" or weaXer solution holding a lesser ratio of refrigerant to absorbent in solution In the three chamber system of this i~vention, a sol~tion of "intermediate" strength is employed between the generator means. This solution is by definition, weaker than strong solution and stronger than weaX
solution.
The terms "generator" and "desorber" are synonymous.
The term "heat exchanger" defines an apparatus where fluids are passed in close proximity to each other separated only by a usually impervious wall through which the heat from the warmer is conducted to the cooler.
¦ Conventionally, it is understood that heat passes from the ¦ hot fluid to the cold fluid.
¦ As used herein, the term "heat exchanger" defines .~,25 ¦ apparatus which exchanges heat into or out of the system, ¦ i.e., with an external fluid such as ambient outdoor air, ~ or ground water, or air conditioned indoor living space ¦ environmental air. Those apparatus which exchange heat ¦ within the system are termed "recuperators".
¦ Referring to Figure 1, and as a point of reference, a ¦ double effect absorption refrigeration system, is provided ¦ with a first effect generator means 30 and a second effect ¦ generator means 31, depicted schematical~y as vessels.
~-¦ The generator means 30 contains a vapor phase of a ~.. ~, .. ~

~ . 13 1 ¦ refrigerant 32 in the system, and a strong liquid phase ¦ solution 35 or intermediate solution 36 of the refrigerant ¦ with an absorbent. Heat is applied from an external ¦ source, such as a gas flame, to the vessel 30 which raises ¦ the temperature of the strong solution 35 above the ¦ vaporization point at the first pressure in the vessel 30 ¦ and provides latent heat of vaporization. Refrigerant ¦ vapor 32 is desorbed from the solution 35 and expelled ¦ through a connecting conduit 29 to a heat transfer means ¦ 37 in the second effect generator means 31.
¦ A weaker, intermediate solution 36 remains in the ¦ generator means 30, from which it is conveyed in heat ¦ exchange relationship, through a recuperator 38, where ¦ heat is transferred to the strong solution 35 that is ¦ being conveyed through a connection 39 to the generator ¦ means 30. From the recuperator 38, the intermediate ;` ';:'''t ¦ solution 36 is conveyed by means of a connection 40 ~._,~...~.,~
¦ through a throttling valve 41 where the pressure is ¦ reduced to a second intermediate pressure and is ¦ introduced into the vesse~ of the second generator means 31 by means of a connection 45.
In the vessel 31 additional heat is transferred to the liquid intermediate solution 36 by means of the heat transfer unit 37. This further raises the temperatura of . 25 the intermadiata solution 36 and adds heat sufficient to expell further vaporous reErigerant 46, leaving a weak solution 47 of tha refrigerant and absorbent in the second effect generator means 31.
Although double ef~ect generator systems are the most usually disclosed in tha prior art, succassive additional genarators ara also shown, and thus a "multiple" effact system may be considered as an extension of the concepts involved.
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In a typical multiple effect absorption refrigeration ¦ system, further external heat need not be supplied to the second or successive generators. Beneficial effects can be obtained by further heating of the intermediate solution 5 ¦ ~hrough heat exchange with the refrigerant vapor 32 from the first effect generator 30. However, external heat depicted in phantom in Figure 1 may be applied to the ¦ vessel 31. Also external heat can be applied to l recuperators 38 and 67.
10 ¦ Partially condensed, refrigerant 32, at the pressure of the first (high pressure) chamber is conveyed from the heat transfer unit 37 through a connection 48 and ¦ expansion valve 49 into a condenser 55, depicted ¦ schematically as a closed pressure vessel in Figure 1, 15 ¦ where heat i5 transferred to a cooler surrounding medium, ¦ which may be the surrounding outside air or water from a ~i ~ ¦ cooling tower. Refrigerant vapor 46 which is expelled in O~ ¦ generator means 31 is conveyed to the condenser 55 through ¦ a connection 56. Condensed liquid 57 is conveyed to a 20 ¦ recuperator 58 by means of connection 59 and then by ¦ connector 60 to an expansion valve 61. From the expansion ¦ valve 61 the refrigerant sprays into a third, low pressure ¦ environment of an evaporator 62 where the refrigerant ¦ returns to the vapor state by extracting heat from an 7 ¦ external fluid medium which is in contact with the ;:~ ¦ evaporator 62. Low pressure refrigerant vapor 63 is ¦ conveyed through recuperator 58 where heat is recouped ¦ from the liquid S7 passing to the evaporator 62. From the recuperator 58 the low pressure vaporous refrigerant 63 is conveyed through a connec~ion 64 to an absorber 65 where the weak solution 47 has been collected.
After expelling further refrigerant vapor in the second effect generator means 31, the weak solution 47 is ¦ conveyed by a connection 66 through a recuperator 67 and a ~i I

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1 connection 68 to a throttling valve 69. In the recuperator 67 heat is transferred to strong solution 35 as it is conveyed to the first effect generator 30.
lIn the absorber 65 the refrigerant vapor 63 is ¦ absorbed in the weak solution 47 to produce the strong ¦ solution 35. In the process, heat is rejected to a ¦ surrounding medium, or a working fluid in contact with the '~? ¦ absorber.
¦A solution pump 70 conveys the strong solution through a connection 71, and connections 72, 73, and 39, and through recuperators 67 and 39 to the first effect generator 30.
A double effect absorption system, as shown in Figure 1, is a three-chamber system, since the second e~fect generator 31 operates at a pressure intermediate between the higher pressure of the first generator means 30 and the lower pressure of the evaporator 62 and absorber 65.
As described in the Background of the Invention ¦ portion of this disclosure, for many years a large variety ¦ f proposals have been made for employing a three-chamber system usins? a single refrigerant pair. Numerous problems ¦ exist which have defied satisfactory solution prior to the ¦ present invention. One problem not heretofor ¦ satisfactorily solved was the identification of an , 25 ¦ appropriate solution pair in which the pair could operate ¦ at the higher temperatures to which the refrigerant could ¦ be driven at reasonable pressures in a double effect ¦ system. Although ammonia has remained the best prospect ¦ for the refrigerant, its absorption in water has proven 3~ ¦ unattractive because it is difficult to adequately I separate the refrigerant and absorbent vapors from the ¦ generators of the double effect system without ¦ unreasonably complicated equipment.
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- l ¦ In this invention ammonia as a refrigerant and sodium thiocyanate as the sorbent are conceived to be an appropriate solutio~ pair in the double effect system.
This is especially true in combination with the other features of the applicants' invention to be later described. For instance, the combination refrigera~ion and/or heating system can be located externally of a l living enclosure in an air conditioning/space conditioning .. ,. I
¦ useage.
¦ Double Efect Generator Absor~tion Cycle W _h Switchin~
Between Coolin~, Heatin~ and Defrosting An absorption heat pump designed to provide both space heating and space cooling must be able to be ¦ reversed bètween the heating and the cooling modes without ¦ adversely effecting the operation of the absorption refrigeration cycle. In this invention this reversal may l be accomplished by using switching valves in the ... ,,-....... I
refrigerant ~ines in the heat pump. The location and operation of the switching valves is shown in Figures 2 and 3, which illustrate the cooling and heating mode valve functions, respectively, Switching may be accomplished by ¦ one six~way valve.
¦ Refrigerant switching permits direct refrigerant heat ¦ transfer to the ambient conditions. This approach results ¦ in higher heat transfer eficiency because of the higher i ¦ temperature difference between the refrigerant and the ¦ heat source or heat sink and reduces the weight and cost ¦ of the heat pump by eliminating the intermediate heat ¦ transfer loop. This concept of refrigerant switching ¦ avoid~ any change in the effective working volume of the heat pump when switching from one mode to the other.
Referring to Figure 2, in a m~nner similar to the system described in Figure l, a fixst generator me~ns 80 desorbs a vapor re~rigerant 82 from a strong solution 83 ~i .

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by the application of heat from a source 84, such as a gas flame. A solution of intermediate strength 85 remains in the vessel and is conveyed to a first recuperator means 86 and through a throttling valve 87 to a second generator means 81. Heat from the refrigerant vapor 82 is exchanged with the intermediate solution 85 in the vessel 81 through ¦ a heat conduction means 88, and additional vapor 82 is ¦ desorbed from the intermediate solution 85 leaving a weaX
¦ solution 89 in the vessel 81.
¦ Additional heat may be supp~ied from the same source ¦ 84 or a second source 90, to further enhance the ¦ desorption process.
l In the manner described for the system of Figure 1, ¦ the weaX solution 89 passes through a second recuperator ¦ means 95, and a throttling valve 96 into an absorber means ¦ 97. Weak solution 89 absorbs vaporous refrigerant 82 ¦ becoming a strong solution 83 which is pumped by a ¦ solution pump 98 successively through recuperator 95 and ¦ 86 back to the first generator means 80.
20 ¦ Operating in t~e cooling mode, refrigerant vapor 82 is conveyed to a first heat exchanger means 100 through a first two-way valve means 101 and an isenthalpic expansion valve 102, from the first effect generator means 80 af~er passing through the second effect generator means 81.
Refrigerant vapor 82 is also conveyed from the second e~fect generator 81 to the first heat exchanger means 100 through a second two-way valve means g9 and a third ¦ two-way valve means 103. Operating as a condenser the ¦ first heat exchanger 100 is cooled by surrounding ambient ¦ c~nditions, such as outside air, at a lower temperature.
¦ Cooling may also be provided by ground water, earth or a ¦ cooling tower. Condensed liquid refrigerant 105 is ¦ conveyed from the first heat exchanger 100 through a r~ ¦ fourth two-way valve 106, a third recuperator 107, fifth ,~

S3~8 l , 1~ 1 1 j and sixth two-way valves 108 and 109 and an isenthalpic expansion valve means 110 to a second heat exchanger means 115. Through the expansion valve 110, the pressure is reduced and refrigerant 116 is evaporated in the second 5 heat exchanger 115 by gaining heat from a cooling load.
Refrigerant vapor at low pressure is conveyed from the heat exchanger 115 through seventh and eighth two-way valves 117 and 118 to the absorber 97 passing through the recuperator 107.
An accumulator 205 is provided between valYe 118 and recuperator 107 for the collection of excess refrigerant 82. Excess refrigerant may ~ccur as a sesult ~ changes in the amount of refrigerant contained in the first and second heat exchangers at difere~t operating conditions, especially differences between coling, heating and defrost modes of operation.
~ his permits the system to operate at the optimum solution concentration in whichever mode the system is operating by storing a small mass of refrigerant as vapor or a greater mass o~ rerlgerant as li~uia. This preYents a loss of efficiency due to the inability of the system to efectively absorb and desorb under various operating temperatures and pressures.
It is an important feature of this invention that an accumulator is provided in combination with the refrigerant switching concept that allows for changing from the cooling to the heating mode and vice versa.
Conventionally, accumulators are not provided in an absorption refrigeration system because the operat;ng system conditions remain unchanged and sufficiently within the designed or controlled parameters.
Referring to Figure 3, in the heating mode the apparatus remains substantially the same, except that the . two-way valves 99, 101, 103, 106, 108, 109, 117, and 118 ,,:

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~ S39~3 ~ q 1 are reversed. Since the apparatus does not change, the numerals designating the various components are the same.
¦ Liquid refrigerant 82 under high pressure is reversed in the valve 101 and is connected through the valve 109 and the expansion valve 110 to the second heat exchanger 115 (which is operating as the condenser in the system).
Additional vaporous refrigerant 82 from ~he second generator 81 at lower pressure is reversed through the l valves 99 and 117 and conveyed to the second heat ¦ exchanger 115 where it is condensed to liquid refrigerant ¦ 105, joining the refrigerant from the first generator 80.
¦ The li~uid refrigerant lOS is conveyed throush the valve ¦ 108, which has been reversed, and ~hrou~h the recuperator 1~7 and valve 106 to an isenthal~ic expansion val~e 120 and valve 103. ~eaving the expansion valva 120, refrigerant 105 enters the first heat exchanger 100 ~which ; : is operating as the evaporator in the system). Upon .
- pressure reduction the liquid evaporates by absorbing heat from the outside air and is conveyed as a vapor through valve lla, and recuperator 107 in~o the absorber 97 where it i5 absorbed in the weak sol~tion ag and is pumped back to the first generator means by tne pump 98.
In the heating mode shown in ~igure 3, heat is transferred ~o the loaa in the second heat exchanger llS
by condensing refrigerant directly in the condensing process. In addition, the absorption of the vapor refrigerant in the absorber 97 is a-subprocess generating heat, and in the process of this invention a substantial , portion of the transfer to the load is carried out from the absorber.
In the residential air conditioning embodiment of this invention, the space conditioning load is transferred to and from heat exchanger 115 by means of an antifreeze ~,~ working solu~ion flowing in a conduit 78, which is ~ ~53~
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1 ¦ conveyed from a conventional heat exchanger in the air ¦ transfer ducts of the residence (not shown) to the second ¦ heat exchanger 115 in both the heating and the cooling ¦ mode and to the absorber in the heating mode. Any problems ¦ associated with the toxicity of either the refrigerant or ¦ the absorbent are avoided within the conditioned space ¦ and/or the residence structure.
The composition of the working solution may be ¦ alcohol and water, or glycol and water or other antifreeze ¦ fl~id.
¦ As shown in Figure 3, an additional cond~it 79 ¦ provides another connection for conveyance of working ¦ fluid in heat transfer relationship through the absorber ¦ 97. The conduit 79 is connected for use in heat transfer ¦ with the load, and may be combined with the flow of ¦ working fluid from the conduit 78 conveying working fluid ¦ from the heat exchanger 115. T~pically, a valve 76 may ~C~ f Jil i ¦ modulate the flow of working fluid in the conauit 79 and ¦ by this means heat trans~er from the absorber 97 may be ¦ controlled.
l In the heating mode, because the first heat exchanger ¦ 100 has been reversed to act as the evaporator in the ¦ system, heat is added to the absorber by heat pumping from ¦ the ambient surrounding source. The use of this heat by r~25 ¦ heat transfer in the absorber 97, through the conduit 7g, -~¦ is an important addition to the efficiency Of the unit as ¦ well as providing an important source of recovered heat for other domestic uses in the living space. For instance, the worXing fluid conveyed in the conduits 78 and 79 may be combined and transferred to the air conditioning heating load during the wintertime. During the summertime, the warm worXing fluid from the absorber 97 may be conveyed through a domestic hot water prehea~er .~.~providing savings in that part of the operation of living 39~
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1 space. Because of the switching arrangement, with appropriate valves, various combinations of uses of the heat energy from the absorber 97 and the second heat exchanger 115 may be employed.
The following Table A shows the source of working fluid that may be directed to the various uses in the living space. It is especially significant to note the large number of circumstances, under which water heating capability is provided while the space cooling and space heating loads are being simultaneously satisfied. There is additional flexibility, in that flow through the conduit 79 may be arranged to add the heat to the flow through conduit 78 with no flow to the water heating use.
"
TABLE A

SYS~EM WATERSPACE SPACE
MODE HEATI~GCOOLI~G _ATI~G_ Cooling 97 115 ~
Heating 97 ~ 115 - -Heating 97 - 115 Heatlng 115 ~ -~ ~ 97 Heating 97 +115 ~ 97 ~ 115 _ __ . _ ~.i Heating ~ ~ 97 + 115 .,,;......................... --- ' The Defrost Cycle One of the features of this invention is a ~nique defrosting method or cycle which is provided by the refrigerant switching arrangements.
Referring further to Figure 3, when the system is operating in the heating mode the first heat exchanger 100 is operating as an evaporator absorbing heat from the ..... ~
~ .

1 surrounding outside ambient air environment. Under certain conditions the exterior surface of the evaporator 100 will collect frost from the moisture in the surrounding environment. An accumulation of frost on the evaporator reduces its heat exchange efficiency hindering heat pumping operations and reducing the overall system l efficiency.
: ¦ Various solutions have been proposed and are used in ¦ prior practices to overcome this problem, although not all ¦ have been entirely s~lccessful or convenien~. However, in ¦ the operation of the system of this invention, defrosting ¦ is accomplished by reversing all of the two-way valves 99, ¦ 101, 103l 117, 109, 106, 108, and 118 temporarily, in the ¦ institution o a defrost cycle.
¦ Air flow across the heat exchanger 100 is interrupted ¦ by shutting off the fan 170 and/or closing shutters 75, -~o; ¦ (see Figure 9). The warm refrigerant vapor 82 ~lowing in ~ A.A l ¦ the heat exchanger 100 is condensed and the latent heat ¦ rejected by the condensing reErigerant melts the frost.
20 ¦ The liquid water is then collected and carried away.
l The worXing solution 78 ~lowing through the second ¦ heat exchanger 115 (conveying heat to and from the living ¦ space conditioning load) is interrupted by a valve ll9 ¦ during the defrosting cycle which causes the worXing . 25 ¦ solution to flow only through the absorber 97, through the ¦ connection 79, where heat is removed from the absorber and ¦ transmitted to the living space environment, at a reduced ¦ rate.
l It is a feature of this invention that heat continues 30 ¦ to f low to ~he load through the conduit 79 from the ¦ absorber during the defrost cycle. In the conventional arrangements that have been provided to answer the frosting problsm of air cooled (heated) heat pumps, it is .. the practice to cut off the heat pump completely and use _.. , ; ~

5~9~3 I
1 ¦ electrical resistance heaters (with the attendant lowest COP) ~o provide heating during defrosting. This invention, to the contrary, maintains heat flow from the ~ heat pump during defrosting; or to use hot gas defrostins, ¦ which causes the space conditioning load to be cooled and ¦ to offset this cooling 'effect and provide heating with resistance coils. This invention, to the contrary, . ¦ maintains heat flow from the heat pump during defrosting ¦ and in most circumstances defrosting can be completed ¦ before heat is required in excess of that available during ~ defrost operation.
¦ At the end of the defrost cycle, all the refrigerant ¦ reversing valves are returned to their normal heating mode -: '' ¦ position, the air flo~ over the heat exchanger 100 is ¦ restored, and the working solution flow through the heat ¦ exchanger 115 is also restored.
: '.; ¦ Conventional controls are provided to sense the loss ¦ of efficiency resulti~g from frost buildup and the defrost r ¦ cycle is operated automaticall~.
¦ A uni~ue feature of this defro~t cycle is that the ¦ heat pump can continue to provide heat to the conditioned ¦ space during the defrosting process. Vapor compression ¦ cycles cannot do this and if they use "hot gas defrosting"
¦ they actually cool the conditioned space. The heat ¦ delivered during defrosting will be more than fifty '-` r~ ¦ percent of heat delivered when not defrosting at the same ¦ con~itions in the process of this invention.
The space heating capacity of the double effect absorption refrigeration cycle illustrated in Figure 3 is approximately 68000 btu/hr. at design conditions of 47F
ambient and a minimum space heating capacity o 36000 btu/hr. at low outdoor temperature conditions.
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This space heating can be incrsased, if necessary, by adding additional heat to the working solution circuit.
This can be done eithe- in a separate gas burner under and/or around the second heat exchanger (see Figure 9), a gas fueled water heater, or by installing an additional worXing solution heater in the generator/recuperator subsystem, downstream of the second recuperator 95.
Absor~tion Refri~era ~ at Pumping_ S~stem Containin~ Ammonia and Sodium Thiocyanate While others have worked with the solution pair ammonia (~H3) as refrigerant and sodium thiocyanate (~aSCN) as absorbent in single effect absorption systems, as previously stated in the Background of the Invention portion of this disclosure, the applicants have conceived the double effect and reversible heatin~ and cooling system using this solution pair. The advantages of this system permit high efficiency through internal heat recovery and mechanical energy recovery in the absorption refrigeration circuit; and the use of sodium thiocyanate as the a~sor~ent eliminates the need for analyzers and rectifiers to purify the refrigerant stream. The refrigerant pair ammonia/sodium thiocyanate is uniquely suited to the system of this invention.
Referring to Figure 6, an operational diagram is shown for the refrigerant and solution for operation in the refrigeration cycle (values are approximately stated).
This set of operating conditions would be expected to result in a refriqeration circuit coefficent of performance of approximate~y lØ
30 ¦ At a temperature of about 350F, strong solution 83 enters the first generator 80 at a pressure of about 1200 psia where it is heated to a temperature of about 370F by ~he external source of heat 84 and refrigerant is desorbed and conveyed into heat exchange relationship with ;~

1 ~ inter~ediate strength solution 85 in the second generator ¦ 81 which is at a pressure of about 270 psia.
The intermedlate solution 85 leaves the first l generator at a tempera~ure of abo~t 370F having been the S recipient of dlrect heat from the source at a rate of about 33,000 btulhr. and passes throu~h the recuperator 86 where i~ exchanges heat to the strong solution at a rate r~ of about 56,000 btu/hr. and leaves at a temperature of ,. - 220~ a pressure of 1200 psi. Leaviny the recuperator 86 the temperature of the intermediate solution is 220F
where it is throttled subst~ntially isenthalpically through valve 87 and arrives in the secondary generator 81 at a temperature of 220F and a pressure of 270 psia.
,~ In the se~ond generator high pressure vapor is 15 condensed and cooled to 240F before entering valve 102 where it is expanded to a saturated vapor and liquid mixture. Approximately 17,000 btulhr. liberated in this condensation, along with an additional about 6,000 btu/hr.
from the flue gases external to the second generataor 20 cause additional refrigerant to be desorbed in the second senerator, which when mixed with refrigerant from valve 102 go ~o the condenser at ~50~F and 265 psi~.
The condenser expells about 24000 btu/hr., and the refrigerant temperature is reduced to about 85F after 25 leaving the recuperator and before entering the expansion valve 110 where its temperature is further reduced to about 42F while its pressure is reduced to about 76 psia in the evaporator. The evaporator 115 absorbs 36000 btu/hr., evaporating the refrigerant which enters the : 30 recuperator 108 at a temperature of about 50F and leaves at a temperature o llO~F on the way to the absorber 97 which is operating at the lower system pressure of about 70 psia.
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1 1 Weak solution leaves the second generator 81 at a ¦ pressure of 270 psia and a temperature of 240F passing through the recuperator 95, and transmitting 39000 btu/hr.
l to the strong solu~ion 82, which is on the way to the 5 ¦ recuperator 86.
I Referring to Figure 7, an enthalpy diagram for the ammonia/sodium thiocyanate solu~ion is provlded showing the component by component changes in solution ¦ concentration ana enthalpy in the refrigeration circuit.
~ In the cooling mode, the strong solution 83, at a ¦ concentration of about 45 percent ammonia refrigerant, is ¦ pumped to the first generator 80 where it is heated by the ¦ outside source 84 expelling vapor refrigerant ammonia 82 ¦ at an enthalpy of about 350 btu/lb~ which is conveyed to ¦ the entrance of the second generator 81. The heat content ¦ is at its highest point as the intermediate solution 85 enters the recuperator 86 exchanging heat with the strong ¦ solution 83 passing from the pump 98 to the first ¦ generator 80.
¦ Upon entering the second generator 81 heat is added ¦ as fur~her vaporous ammonia i5 expelled at an enthalpy of ¦ about 310 btu/lb.
¦ The further heat added results primarily from heat ¦ exchanged from the refrigerant 82, but additional heat I from exhaust gas or from another source 90 may also be ¦ added.
l Heat is extracted in the first or second heat ¦ exchanger 100 or 115, which ever is operating as the ¦ condenser in the system. The concentration then increases ¦ from its lowest level of about 39 percent bacX to its ¦ strong solution concentration of 45 percent in the ¦ absorber 97 and is conveyed to the inlet of the solution ~5~9 ,~
- 1 pump 98.
Other investigators have demonstrated air cooled absorption refrigeration systems using other absorben~/refrigerant pairs.
Existing air cooled absorption refrigeration circuits have demonstrated cooling coefficients of performance as high as 0.5 using various absorbent and refrigerant pairs.
:~ ~hese systems have al o been demonstrated as heating only heat pumps with a coefficient performance of up to 1.3.
This invention uni~uely combines a double effect system using ammonia and an absorbent in a system capab~e ¦ of switching by reversing the funtions of the condenser and evap orator heat exchangers 100 and 115.
Sodium-thiocyanate is the uniquely preferred absorbent.
This system is an air cooled absorption refrigeration system having a demonstrated cooling coefficient as high :. as 0.85 using the NH3 and ~aSCN refrigerant pair with a burner efficiency of 0.85. Using the double effect generator cycle a high efficiency is provided.
Sodium ~hiocyanate and Ammonia with Triethylenetetramine (~ET~) as Corrosion Inhibitor The hi~h temperatures and pressures reached in double and multiple effect absorption refrigeration systems is known to produce corrosion problems with the use of the recognized absorbent salts such as lithium bormide.
Corrosion inhibitors in absorption refrigeration systems have been sought and used under certain conditions. These prior inhibitors met a measure of success in certain specific operating situations.
Ammonia is well known for its reactivity which in combination with sodium thiocyanate makes for a potentially troublesome solution pair from a corrosion standpoint.

~ ~53~318 I , ~ I
1 ¦ It has been found in the practice of this invention that the addition of TETA (~l~C6N4) in the solution with sodium thiocyanate and ammonia provides a means for inhibiting and controlling corrosion in the high temperature, double effect absorption refrigeration system. The system comprises an absorber, first and second generators, a condenser and evaporator that form a closed, substantially anaerobic system.
The addition to the solution of a TETA corrosion resistor in an amoun~ between about 3.0 to about 0.5 percent by weight has been conceived and found to be very . beneficial in results.
As a system of this invention operates in the cooling mode, the absorbent/refrigerant/inhibitor solution ¦ composition of about 99 percent absorbent and refrigerant ¦ and 1 percent TETA absorbs and desorbs ammonia as shown in Figure 7 in a range between about 39 to about 45 percent ammonia by weight. The surprisingly favorable results in the operation of the absorption refrigeration system are 0 ¦ further enhanced by the corrosion resisting additive. The increase in corrosion r~sistance has been demonstrated according to the evaluation depicted in Figure 10.
Corrosion in the double effect absorption refrigeration system results in the liberation- of 1 non-condensible gases (predominating hydrogen)which ¦ interfere with the efficient operation of the refrigeration circuit and in the separation of particu}ate ¦ corrosion products from the corroding surfaces which can ¦ plug flow restrictors and throttling valves and cause , 30 I rapid wear of pump, motor and valve parts, and ultimately I can compromise of the structural strength of the vessels ¦ and piping which comprise the sealed refrigeration ¦ cicruit.
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1 ¦ Referring to Figure 10, which is a plot of corrosion ¦ rate versus time, the corrosion rate in the system ¦ inhibited with one~half percent TETA declines more rapidly ¦ (and reaches a lower stable level) than is the case with ¦ the same steel without the inhibitor.
The tests which produced the results shown in Fiqure 10 were conducted on an AISI 9260 steel in corrosion induclng contact with a solution pair of ammmonia (45 l percent by weight) and sodium thiocyanate. The curve 195 ¦ discloses data from the tests of the uninhibited solution pair. The curve 196 shows the results of tests conducted in the same conditions except that the solution pair contained the additive T~TA as an inhibitor in the amount of one-half percent by weight.
The TETA inhibitor is effective in the vapor space occupied by the refrigerant, and in the liquid space :~ occupied by ~he solution, as well as at the active surface interface between the spaces, in the autoclave tests ~ summarized in Figure 10, which simulate conditions in the first efect generator 80.
The TETA inhibitor also improves the lubricity of the solution pair, which ex~ends the life of pump, motor and valve parts.
The following Table B is a table of test results ~ ~ 25 showing the results of three button wear test experiments ;. to demonstrate the increased lubricity of the solution pair when the additive TETA is included. A comparison with generally well known lubricating materials is also shown.

3~3 I
~ ~, l I TABLE ~
R~SULTS OF THREE-BUTTON WEAR EXPERI~ENTS
Contact Running Wear l Test Material Pressure, Time, Rate(d) 5 1 No. Buttons Environment psi ,min 8uttons 7 440C Heat Transfer 2100 30 0.72 ~ Fluid ~3/~aSCN
-- ¦ 21 440C Heat Transfer 2100 60 0.35 l Fluid NH3/~aSC~
lO ¦ Plus Add~tive(b) ¦ 20 440C ATF~a) llOo 12 78 1 22 440C SAE 30(c~ 1100 4 150 ¦ (a) Automatic transmission fluid I ~b) Addition of three percent triethylenetetramine ¦ (TETA) ¦ (c~ Automotive engine oil 12 ¦ (d) In. Wear/In. Sliding/Pound ~oad, X 10 ~ The test results of Table B were o~tai~ed on AISI 440C
¦ high carbon martensitic stainless steel quenched and ¦ tempered with a hardness o RC58-60.
Double Effect Generator and ~ec~erator Apparatus i~ Referring to Figures 4 and 5 an embodiment of the ' 25 ¦ double eff~ct generator means is shown in apparatus which ¦ integrates in one interrelated assembly the various ¦ components of the apparatus which are associated with the ¦ use of the heat generated in the driving heat source. To ~ facilitate understanding, numeral designations are the ~ame as and refer to like components in the system shown in Figures 2 and 3, where appropriate.

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3~8 ~3 1 ~¦ A dri~ing heat sQurce 84, typically a gas burner is centrally positioned substantially on a central axis lZ0 af the annular components including a first effect generator means 80, a recuperator means 86, a second effect generator means 81~ and a recuperator means 95.
Each component is constructed as a substantially annular coil, or coils and/or plurality of vertically positioned toruses or helical tubings. Each co~ponent is juxtaposed . ~ tc, the next, and radially more, or less, distant from the ¦ central axis 120.
l The recuperators 86, 95, and the second effect ! generator 81 comprise an inner tube and an outer tube, often referred to as tube-in-tube construction. The ¦ materials are conventional, being chosen for good heat I transfer through the walls of the tubings. Metals could ~ ¦ be suitable.
- ¦ In the preferred embodiment, the first effect ¦ generator 80 comprises a helical coil of tubing into which ¦ the strong solution 83 enters from the high te~perature ¦ recuperator 86 through a connection 137. Heat and ¦ combustion products from the source 84 impinge upon the ¦ walls 131 of the tubular generator 80. ~affles 132 may be provided to cause the combustion products to ~low more or ¦ less radially through the generator package and therefore ¦ through the gaps between the coils of components 80, 86, ¦ 81, and 95. At the top of the generator 80, intermediate ¦ solution 85 is transferred to a header/vessel 133 where ¦ expelled vaporous refrigerant 82 is conveyed to an inner ¦ tube of second generator 81 by connection 138, while ¦ intermediate solution 85 is conveyed through the outer tube of the tube-in-tube heat exchange coil structure o~
the recuperator 86. An inner tube 135 carries the strong solution 83 in counter-current airection to the intermediate solution 85 being conveyed in the outer ' , ' ,, , , 3~
l tubing. However the location of 85 and 83 may be reversedO
At the end of the recuper~tor 86 the inner tubing 135 is connected to the beginning end of the first generatcr 80 through a connection 137.
S Refrigerant vapor 82 is connected to the inner tube ! of the second effect generator means through a connection 138. Passing down through the inner tube 139 of the second effect generator 81, the refrigerant 82 passes in counter current heat exchange relationship with the intermediate strength solution 85 passing upward in the outer tube 140. At the lower end of the second effect generator 81, the condensed vapor a2 is conveyed through a ¦ connection 144 to the two-way valve lOl where it is ¦ switched to the heat exchanger 100 or 115, after ¦ isenthalpic expansion in the valve 102 or valve llO.
¦ Heated inter~ediate strength solution 85 rises in the ¦ outer tube of the second effec~ generator 81 and e~pells ¦ additional refrigerant 82 at a header 141, which also ¦ transfers the weak solution 89 to the outer tube 142 of ¦ the second recuperator 95. The additional refrigerant 82, . ¦ is connected through the two way valve 99 to the heat ¦ exchanger 105 or 100 by a connection 146. The weaX
¦ solution returns to the absorber through throttling valve 1 96.
¦ S~rong solution a3 enters the inner tube 143 of the ¦ recuperator 95 through a connection 145 from the pump 98 ¦ (shown in Figures 2 and 3). The location of weaX solution ¦ 89 and strong solu~ion 83 may be reversed, i.e., 83 in the ¦ outside and in 89 insi~e.
¦ The generator unit 18S efficiently combines the ¦ various components 80, 86, 81, and 95 that are used in the double effect absorption system of this invention. The temperature gradient through these components decreases progressively outward in the operation of the double ~.

?~ 98 1 effect absorption cycle; With the arrangement of components in a series of coils which surround a component of higher temperature in the gradient, and with the burner in the center, the heat and combustion products naturally ¦ radiate outward in decreasing magnitude. The burner is ¦ centrally positioned on the axis and closest to the first ¦ effect generator, which is the point in the cycle of ~" ¦ highest temperature, and provides the most effective heat ¦ transfer from the source. In addition with the provision ¦ of suitable spacing ver~ically among the coils, the ¦ combustion products move radially outward and impinge on other components of the unit thereby increasing the efficiency. For instance, some of the heat from the ,,, r' source 84 will be conducted directly to the second effect generator 81 carrying out the effect of the second direct source of heat 90 shown in Figures 2 and 3.
~- The tube-in-tube concept further renders the unit more compact in carrying out the natural heat gradients which are necessary in the absorption cycle as used in the system of this invention.
Although the preferred embodiment is shown and described, other arrangements may be suitable for different operation conditions - ~or example, the second ef~ect generator 81 and high temperature recuperator 86 may be interchanged.
~-f<~;; Such an interchange, which would position the second effect generator closer to the source of heat 84, will in some circumstances be advantageous since its temperatures will be higher, and higher direct heat input may be obtained. On the other hand a tradeoff in efficiency will be incurred since the high temperature recuperator ~6 will be operatin~ at a lower heat input from the source and a lower temperature.
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In certain circumstances, it may be worthwhile to operate the outermost recuperator means 95 in a condensing mode wherein a portion of the products of combustion from the burner 84 are caused to condense on the outside surface of the outer tube of the recuperator means 95.
This is accomplished by increasing the surface area of the outer tube by means of fins 200 shown on a portion of the recuperator 95 in Figure 5. 3y the use of fins, the latent heat of condensation of the combustion gas will be imparted to the outer surface of the recuperator 95 raising the temperature of the strong solution passing therethrough. The construction of the recuperator means 95 to operate in the condensing mode is expected to increase the overall efficiency of the process and apparatus of this invention of between about four to eight percent. The particular construction wherein the generators and recuperators are constructed of coils at increasing radial dis~ances from the centrally located source of heat makes the use of this efficiency enhancing condensing mode particularly inexpensive to include in an apparatus and process of this kind.
Solution Pump/Ener~Y Recovery Motors In the operation of the absorption refrigeration cycle of the type of this invention a mechanical energy input is necessary in addition to the thermal energy input. Mechanical energy necessary is primarily required to operate the solution pump which circulates the solution pair through the system. In Figures 1, 2, and 3 solution pumps 70 and 98 are shown conveying the strong solution from the absorber to the first effect generator thro~gh the second and first recuperators. In the operation of the typical system described for Figures 6 and 7, the mechanical energy required to raise the solution pressure to about 1200 psia is approximately 670 watts. Providing .~ .

39~3 this mechanical energy using a conventional electric mator and pump requires consumption of approximateiy 1200 watts of electrical power which would reduce the refrigeration cycle COP by approximately 11 percent.
In the embodiment of the system of this invention having the maximum COP the energy available at the five isenthalpic throttling valves 87, 96, 102, 120 and 110 is used by constructing the valves in the form of hydraulic or expansion motors connected to augment and be additive to the input to solution pump 98 or other mechanical energy input components such as for the motor 171 and worXing fluid pump(s). By this means about 1000 watts of mechanical energy, in the typical system under consideration, as shown in Figure 8, is saved increasing lS the efficiency in an important degree. In the hydraulic motors the high pressure solution is reduced in pressure ;~ by moving pumping elements as motors.
These may be expansion motors, in which the entering pressurized liquid expands to move turbine-like rotary impellers which are connected to the shaft of the electric motor. Other types o~ hydraulic motors also may be employed, such as gear motors, piston motors, or scroll ¦ motors. Thus, as the solution and refigerant str~ams are ¦ reduced in pressure, the requirement of the electric motor ¦ is reduced.
~, ¦ Referring to Figure 8, the energy recovery motor I subsystem is shown as a rs~ary device including a housing ¦ 150 which is broken away on the si~e lSl so that the ¦ inside can be seen. The subsystem 149 includes rotary 3~ ¦ motor means 152, shown as an electric ~otor connected ~y a ¦ common shaft to rotary turbine-like expander motors 1 153-156.
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1 Also connected on the common shaft 160 with the motors is the solution pum~ 98 comprising three stages 157~ 15~, and 159.
¦ In additional reference to Figures 2, 3, and 4, 5 ¦ strong solution 83 enters an inlet 164 to pump 9~ and is ¦ conveyed fro~ an outlet 165, on the way to the first ¦ effect generator 80 through the recuperators 86, 95.
¦ Intermediate solution 85 enters the motor 153, through .. ,,,~....... l ¦ inlet 166, and exits through outlet 167. Refrigerant 82 10 ¦ enters the motors 154 and 155, through inlets 168 and ¦ exits through outlets 169. Weak solution 89 enters ¦ hydraulic motor 156 through inlet 147 and exits through _. ¦ outlet 148.
¦ Through their interconnection in the common dri~e ¦ means 160, the several hydraulic motors 153 156 and the ¦ electric motor 152 combine to provide the mechanical energy necessary to raise the pressure of the strong ¦ solution and move the strong solution through the system l at the pressure of the first effect generator 80. At the ¦ same time, the solution and refrigerant pressures are reduced to those as necessary in the absorption cycle.
When the several hydraulic motors 153-156 and the ¦ electric motor 152 are combined to provide the mechanical ¦ energy necessary to operate the system, the system has the I advantage of being self-governing to a surprisingly ¦ greater degree than when the various pumps are operated ¦ separately. This measure of controlling the system results ¦ from the natural cause and effect when the demands of the ~ system increase and decrease.
39 ¦ When the hea~ pump is operating with an electric motor driven so~ution pump in the cooling mode, as the temperature aE the ambient heat sinX increases. the pressure in the high pressure chamber of the heat pump must also increase, increasing the differential pressure i39~3 ~'1 over which the solution pump must operate. As the differential pressure across the pump increases, pump flow decreases, the quantit~ of refrigerant desorbed from the solution decreases with constant thermal energy input causing the cooling capacity of the heat pump to decrease, with a corresponding decrease in heat pump coefficient of ¦ performance. When the heat pump is operating in the .~ ¦ heating mode, as the temperature of the ambient source ¦ decreases, the pressure in the low pressure chamber of the ¦ heat pump must decrease, which also increases the ¦ differential pressure over which the solution pump must ¦ operate. The heat pump response to increasing differential ¦ pressure across the solution pump is the same as in the : ¦ cooling mode.
¦ When the system is operated with the solution pump ¦ and its electric drive motor connected in common with the solution motors and/or the refrigera~t motors, as the ¦ temperature difference between the heat source or sinX and ¦ the load increases the pressure in the high pressure ¦ chamber of the heat pump increases, and the differentia:L
pressure over which the solution motors and refrigerant ¦ motors operate also increases. This causes the energy input to the solution pump from the solutio~ and ¦ refrigerant ~otors to increase, largely offsetting the ¦ effect of increasing differential pressure on the pumping .;,- . . l . I solution pump and maintaining solution flow relatively ¦ constant. -¦ As a result of the insensitivity of the absorbent¦ solution and refrigerant flow rates to external ¦ conditions, control of this system is easier and simpler than similar systems without the direct coupled recovery motors.

.

391~3 1 1 The common mechanical linkage between the various components in the eneryy recovery motor systern inherently provides this measure of control stability in the system.
Without the mechanical linkage each component operates independently according to other external controls which ¦ must be provided and operated, such as valve modulation ¦ and electrical relays, etc.
I Since the solution flow remains essentially constant, I
¦ the energy required to desorb refrigeran~ from the solution also remains constant and the refrigerant flow, cooling capacity and COP of the machine remain largely unchanged.
¦ Referring to Figure 4, when the energy recovery ¦ system 149 is employed, hydraulic motor 153, is connected ¦ between the o~ter tube passages of the first recuperator 86 and the second effect generator 81 at an insertion in connection 77.
, ¦ Hydraulic motor 156 is connected between the outer ¦ tube passage of the second recuperator 95 and the inlet to ¦ the absorber 97 replacing valve 96 in Figures 2 and 3.
¦ Hydraulic motors 153 and 154 in Figure 8 replace valves ¦ ¦ 102, 120 and 110 in Figures 2 and 3, respectively.
¦ A Living Space Environmental Conditioning AE~aratus ¦ A concept for a living space - residential air ¦ conditioning and heating embodiment of this invention is ¦ shown semi-schematically in Figure 9. Other constructions ¦ and arrangements of physical apparatus~components may also ¦ be conceived without departing from the spirit or the ~ scope of the invention.
¦ Referring to Figure 9, an air conditioning and ¦ heating unit 165 is generally symmetrically constructed ¦ about a substantial vertical central axis, and includes a ¦ housing 166 (which may be circ~lar or other shape in the ¦ p}an view, not shown) which is constructed on a frame base ~539f~

1 ~ 167 that may be placed on a concrete foundation or ot.her support. The housing 166 includes an upper shroud 168, ¦ havlng an aperture 169. The aperture is positioned above an ambient air inductive motive means, such as a fan 170, that is driven by an electric motor 171 which is suspended from the shroud 168 by a frame 172 or other means. The fan and motor rotatively operate on the central axis.
An additional frame 173 provides a housing or a compartment 174 for controls, a compartment 175 for refrigerant switchihg valves, a compartment 176 for an electric motor to drive the solution pump, and compartment 177 for the pump and motors; as well as a compartment 178 for fluid working valves, and power supply switching, etc.
In a lower section surrounded by insu}ation 180, the recuperator 107 surrounds the second heat exchanger means 115~ An inlet 181 and an outlet 182 are provided for the entrance and exit of working solution 78 which is in communication with the heat exchanger in the environment of the living space. The gas burner 84 is positioned on the central axis in the generator unit 185, which includes the first effect generator 80, the recuperator 86, the second effect generator 81, and the recuperator 9S (see ¦ Figure 4).
Absorber 97 (shown in cross-section) is a coil of ~5 ¦ tubing extending around the internal periphery of the :~;,¦ housing 166 positioned on the central axis~ Tube-in-tube ¦ construction is preferably employed. The first heat ¦ exchanger 100 is similarly positioned above the absorber 1 97.
¦ Apertures 186 and 187 are provided to admit outside ¦ air inducted to pass across the first heat exchanger 100 j and the absorber 97 drawn by the fan 17~. This expells ~ outside air ~rom the unit through the aper~ure 169.
¦ Shutter 76 is provided to control the outside air flow 53~1~
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1 ¦ across the absorber as conditions require as previo~sly i described in this disclosure. A flue 190 is provided or the exhaust of combustion products from the burner 84.
To provide additional heat, additional burners 206 may be provided beneath the second heat exchanger 115. In this construction, an additional flue 207 is located above the second heat exchanger 115 to carry the produc~s of combustion to the aperture 169. Additional insulation 208 is provided between the recuperator 107 and the second heat exchanger llS.
¦It will be apparent that this invention meets the objective of provlding an efficient and convenient living space environmental conditioning unit using the absorption cycle without directly interfacing toxic, noxious, or flammable chemicals within the living space. By the : switching arrangements the number of components is reduced - I and the apparatus is rendered more compact and efficient.
¦ It is herein ~nderstood that although the present ¦ invention has been specifically disclosed with the ¦ preferred embodiments and examples, modificatiQns and ; ¦ variations of the concepts herein disclosed may be ¦ resorted to by those skilled in the art. Suc~
¦ modi~ications and variations are considered to be within ¦ the scope of the invention and the appended claims.

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53~38 SUPPL~MENTARY DISCLOSURE
A further embodiment of this invention, particularly a double effect absorption system, represents a logical extension of the basic invention pre~iously described. This embodiment will be described herein with reference to the additional drawings wherein:

~ igure lOAis a diagram of another embodiment of the double effect absorption system of this invention in the cooling mode.
Figure 11 is a diagram of the embcdiment shown 10in Figure loAof the system of this invention in the heatiny mode.
Figure 12 is a cross-sectional elevation view of the generator/recuperator apparatus of the other embodiment of this invention shown in Figure lOA.
Figure 1 is a schematic diagram for the other embodiment of this invention shown in Figure 10 A .
Figure 14 is a schematic elevational section view o~ the other embodiment shown in Figure lOAof the apparatus and systems of this invention.
20Figure 15 is a schematic plan view of the other embodiment shown in Figures lO~and 14.

Referring to Figure 10~ another simplified embodiment of this invention is disclosed with the valves arranged in the cooling mode~ As described in Figure 2, a first generator means 80 desor~s refrigerant ~apor 82 by the application of heat from a source 84. Heat from the refrigerant vapor 82 is exchanged with the intermediate solution 85 in the vessel 81 through conduction means 88. In this 30embodiment, the conduction ~eans 88 is connected to the recuperator 95 by a conduit 210 having heat exchange tubing 211. The tubing 211 is connected back to the expansion valve 102. From valve 102 the cooled and expanded mixture of re~rigerant liqu~d and vapor passes through conduits 213, mixes with desorber refrigerant vapor 82, and enters a two-way reversing valve 214 that is positioned to convey the refrigerant to the first heat exchanger 100 which is operating as a condenser. In the manner of the embodiment shown in Figure 2, the liquid refrigerant 105 is conveyed through the recuperator 1~7, accumulator 205, and expansion valve 110 to the second heat exchanger 115 which is operating as an 1~ evaporator. Having been heated and vaporized by conduction from a working fluid in ~onduit 78, the refrigerant passes as a vapor through a valve 2~4 to the recuperator 107 where it is heated, and conYeyed to a third heat exchanger 215 which is operati~g as an absorber. Third heat exchanger 215 is cooled by the ambient air as shown in Figure 14. Valve 76 is closed so that working fluid from the load does not pass through the absorber 97 which is operating as a holding tanX in this cooling mode.
Weak solution enters the third heat exchanger - 215 by way of expansion valve 96 and two-way valve 216 which is turned to bring the weak solution together with the refrigerant 82 Pntering from recuperator 107. --As will be apparent by a comparison of the diagrams of Figures 2 and lOAthe second embodiment is simplified by a reduction in the number of valve means to two, 214 and 216 respectively. T h i s eliminates three two-way reversing valves. In this embodiment the absor~er 97 remains structurally the same although it is operating as a holding tank only, since absorption takes place in the third heat exchanger 215 in this cooling mode. Valve 119 in working fluid conduit 78 is open.
In the heating mode of the embodiment of this invention shown in Figure 11, the two-way valve 214 is rotated to connect the conduits 213 with the second heat exchanger 115 which is operating as a 4~

condenser, conveying heat to the load by means of the worXing fluid in conduits 78, with valve lls in the open position. Condensed refrigerant is . expanded through .expansion valve llO and passes through accumulator 205 and recuperator 107 before being conveyed to the first heat exchanger 100 which is operating as an evaporator in this heating mode.
Comparatively warmer ambient outside air evaporates the refrigerant and the vapor 82 passes throu~h two-way ~alve 214 and recuperator 107 to third heat exchanger 215. From the third heat exchanger 215, which is operating as an evaporator heated ~y comparatively warmer am~ient outside air, the refrigerant vapor is conveyed to absorber 97 where it is absorbed in weak solution from expansion valve 96 a~ter the solution passes through two-way valve 216 which has been set to by-pass third heat exchanger 215. Heat is conveyed to the load ~rom absor~er 97 ~y means of the working ~luid in conduit 79. Valve 76 is in the open position in this mode.
In addition to the advantage of reduction in valves and associated conduits and connections, the second embodiment has the advantage of having an increased COP both in the cooling-~nd the heating modes. This is brought a~out by the additional recuperati~e heat transfer in the recuperator 95 by the connection 210 and tubing 211. ~his increased ef ficiency is the result of additional heat ~eing transferred to the low te~perature weak solution being conveyed to the recuperator 86.
Additional advantages are provided thraugh the use o~ the third heat exchanger ~15 as an air-cooled absorber in the.cooling mode with switchover to the liquid-cooled absorber 97 in the heating mode.
There is no need for dampers or insulation on the outside surface of the air-cooled t~ird heat exchanger 215, since it functions as an air-heated evaporator in the heating mode.
A further advantage of the multiple absorber in series construction in the embodiment of this invention shown in Figures lOAand ll is that the air cooled first heat exchanger 100 is smaller, since the air cooled third heat exchanger 215, ls used as an evaporator in the heating mode. The air-cooled first heat exchanger 100 can therefore be sized to supply only the condensing load in the cooling mode and only part of the evaporative load in the heating mode.
Still a further advantage of this embodiment is that there is a constant inventory of solution in the system with none being stored external to the system in going from one mode to the other. The need for changing ammonia concentrations from the cooling to the heating mode only requires storing a certain amount of refrigerant which can be handled easily in the accumulator 205. This further advantage is reduced by a few percentage points in the cooling mode because of the reverse flow of ammonla through the recuperator 107 and the low pressure ammonia letdown valve 110. However, the COP in the heating mode is exceptionally high and more than adequate to compensate for this.
~eferring to the e~odiment af Figure 11, when defrosting is required in the heating mode, two-way valve 214 is rotated to the position of t~e cooling mode. This conveys warm refrigerant to the first heat exchanger 100 amd the third heat exchanger ~15 on which the frost has collected. This cools the second heat exchanger 115 temporarily but this is not transferred to the load because the shutoff valve 119 is closed during defrosting. Heat continues to be conveyed to ~he load from the absor~er 97. During the defrosting period which is of only short duration.

A~

As previously stated in the description of the embodiment or Figure 3 defrosting is greatly simplified over prior practices and even more so in the embodimen~ of Figure 11.
Referring to the embodiment of the invention shown in Figure 13f condensed refrigerant leaving the second generator at 240F is conveyed to the recuperator 9S where it is cooled to a temperature of 150F. Leaving the recuperator 95 it is reduced in pressure to 265 psia through expansion valve 102.
At this temperature and pressure it is conveyed to the first heat exchanger lO0 or the second heat exchanger 150, in accordance with the setting of the two-way valve 214.
As shown in Figure 13 the refrigerant leaves the second heat exchanger 115 passing through recuperator 107 on the way to the third heat exchanger 215, which is operating at the ~ower ~ system pressure of ahout 70 psi.
; 20 Referring to Figure 12, in the embodiment of this invention shown in Figures 10 and 11, the cond~its 211 of the recuperator 9S are interposed in the tu~in:g 143 to provi~e a further tube-in-tube-in-tube construction. Conduits 211 enter at the top by a connection 210 from the inner tubing 139 of the second effect generator 81 conveying refrigerant liquid 820 ~efrigerant 82 is conveyed from the bottom through the valve 102 on the way to the first heat exchanger 100 in the coolin~ mode.
Referring to Figures 14 and 15, a rectangular shaped unit 28~ is constructed to house the components of the system that have been previously described including the ~irst heat exchanger lO0 at the periphery and the third heat exchanger 215 positioned above, a cylindrical liquid cooled absorber 97, the fan 170, and the generator unit 185. A refrigerant solution pump 98 and a working solution pump 217.
As shown in Figures 14 and 15, in the embodiment of this invention shown in Figures 1~ an~
11, the third heat exchanger 21S may be positioned in vertical symmetry above the first heat exchanger 100 in the air ~low compartment space around the periphery of a unit 285. In this embodiment shutters are not required on the periphery of the unit 2a5 and are not necessary since the absorber 57 is a liquid cooled unit in the heating mod~, receivin~ its cooling from the wor~ing solution through conduits 79, when the valve 76 is open.
The rectangular configuration of the unit 285 has the advantage of compactness since the occupied space volume of the apparatus is less. This configuration i5 feasible because the addi~ion of the third heat exchanger 215 pre~ents the use of absorber 97 as a water cooled unit so that air flow is not required across the heat exchange surfaces.
It will be apparent that this invention meets the objective of pro~iding an efficient and convenient living space environmental conditioning unit using the absorption cycle without directly interfacing toxic, noxious, or flammable chemicals within the living space~ B y t h e s w i t c h i n g arrangements the number of components is reduced and the apparatus is rendered more compact and efficient.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a multiple effect absorption refrigeration and/or heating system including a plurality of generators and a plurality of heat exchanging recuperators, the improvement comprising:

(a) a source of external heat in proximity to at least one of the generator means;

(b) a first generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with the first generator means surrounding the source of heat;

(c) a first recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the recuperator means surrounding the first generator means;

(d) a second generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with a second generator means surrounding the first recuperator means; and (e) a second recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the second recuperator means surrounding the second generator means.

12685/LCM:?

2. The improvement according to Claim 1 wherein the coils are constructed as helices.

3. The improvement according to Claim 1 wherein the recuperator coils comprise tube-in-tube heat transfer members.

4. The improvement according to Claim 3 wherein a strong solution is conveyed through the inner tubes of the recuperators.

5. An improvement according to Claim 1 wherein the second generator comprises tube-in-tube heat transfer members.

6. In a multiple effect absorption refrigeration and/or heating system including a plurality of generators and at least one heat exchanging recuperator, the improvement comprising:

(a) a source of external heat in proximity to at least one of the generator means;

(b) a first generator means and at least one second generator means constructed as a plurality of coils with the coils juxtaposed one to the next in a generally annular composite form, with the first generator means surrounding the source of heat; and (c) at least one recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with the recuperator means surrounding the first generator means.

12685/LCM:?

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

7. The improvement according to Claim 4 wherein the refrigerant is conveyed through the innermost tube of the second recuperator means.

8. In a multiple effect absorption refrigeration and/or heating system including a plurality of generator means, a plurality of heat exchanging recuperator means, and a plurality of heat exchanger means comprising a first, a second, and a third, heat exchangers alternately operating as condensers, evaporators, and absorbers, the improvement comprising:

(a) a source of external heat in proximity to at least one of the generator means;

(b) a first generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with the first generator means surrounding the source of heat;

(c) a first recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the recuperator means surrounding the first generator means;

(d) a second generator means constructed as a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, with the second generator means surrounding the first recuperator means; and 12685/LCM:? 49 (e) a second recuperator means comprising a plurality of coils with the coils juxtaposed one to the next, in a generally annular composite form, and with the second recuperator means surrounding the second generator means, wherein the recuperator means comprise tube-in-tube heat transfer members and refrigerant is conveyed from the second generator means through the tubes of the second recuperator means.

9. The improvement according to Claim 8 wherein the refrigerant is conveyed through the innermost tube of the second recuperator means.

10. A system according to Claim 6 wherein the recuperator means surrounds and is in proximity to the at least one second generator means.

11. A system according to claim 6 wherein the at least one second generator means surrounds and is in proximity to the first generator means.

12685/LCM:? 50