CA1221844A - Absorption refrigeration and heat pump system - Google Patents
Absorption refrigeration and heat pump systemInfo
- Publication number
- CA1221844A CA1221844A CA000449951A CA449951A CA1221844A CA 1221844 A CA1221844 A CA 1221844A CA 000449951 A CA000449951 A CA 000449951A CA 449951 A CA449951 A CA 449951A CA 1221844 A CA1221844 A CA 1221844A
- Authority
- CA
- Canada
- Prior art keywords
- subsystem
- heat
- higher temperature
- refrigerant
- load
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A30/00—Adapting or protecting infrastructure or their operation
- Y02A30/27—Relating to heating, ventilation or air conditioning [HVAC] technologies
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/62—Absorption based systems
Abstract
ABSTRACT
An absorption refrigeration and heat pump system in which a higher temperature subsystem and a lower temperature subsystem are combined with the desorber means of the higher temperature subsystem in heat exchange relationship with the condenser means of the lower tempertaure subsystem, and in which the evaporators of each subsystems are in heat exchange relationship with either the load in one mode of operation or the heat sink in another mode of operation, and the absorbers and condenser of the lower temperature subsystem are in heat exchange relationship with the heat sink in the first mode of operation and with the load in the other mode of operation. Means are provided to balance the system including a condensate pump between the higher temperature condenser and the higher temperature desorber Alternate means are provided to improve lower temperature heat pumping by restricting the refrigerant flow through one of the expansion valves and diverting it to the solution pump.
An absorption refrigeration and heat pump system in which a higher temperature subsystem and a lower temperature subsystem are combined with the desorber means of the higher temperature subsystem in heat exchange relationship with the condenser means of the lower tempertaure subsystem, and in which the evaporators of each subsystems are in heat exchange relationship with either the load in one mode of operation or the heat sink in another mode of operation, and the absorbers and condenser of the lower temperature subsystem are in heat exchange relationship with the heat sink in the first mode of operation and with the load in the other mode of operation. Means are provided to balance the system including a condensate pump between the higher temperature condenser and the higher temperature desorber Alternate means are provided to improve lower temperature heat pumping by restricting the refrigerant flow through one of the expansion valves and diverting it to the solution pump.
Description
l.'ZZ~ 4 1 TI~L~: A~SORPTION REFRIG~RATIO~ EAT PU~P SYS~EM
S~IARY 0~ T~E INVE~TION-This invention relates to an absorption refrigeration/heat pump system which comprises a higner temperature subsystem ana a lower temperature su~system with various components of the subsystems in heat exchange relationship with one another to provide greater performance than usually obtainable in such systems and/or ~o permit the use of fluids that have been unsatisfactory in conventional systems~ ~ore particularly, it relates to an absorption refrigeration or heat pump system comprising a higher temperature subsystem and a lower temperature SuDSyStem in which the higher temperature condenser is in a heat exchange relationsnip with the lower temperature desorber an~ the heating and/or cooling loads are arrangea to exchange heat with various combinations of the other components of the system Briefly and in summary, the invention comprises an absorption refrigeration and heat pump system constructed to provi~e heat to or remove heat from a load when the ambient heat sink or source of heat is aDove about 45F comprising at least one first subsystem for operation at higher temperature and at least one second subsystem for operation at lower temperature relative to the first subsystem, each subsystem having components of absorber means, desorber means, con~enser means, ana evaporator means operatively connectea together, with a conaenser means of the higher temperature subsystem in heat exchange relatlonsnip witn the desorber means of the lower temperature subsystem; with the evaporator of the higher temperature subsystem ana the evaporator of the lower temperature subsystem in series heat excnange relationship with the load in the cooling moae or with the ambient in the heating moae; ana with the absor~er . r4~
~;~2~
l of the higher temperature subsystem, the condenser of the lower ~emperature subsystem, and the absorGer of the lower temperature subsystem in series heat exchange relationshi~
with the sink in the cooling mode and the loaa in the heating mode When operated with the heat sink or source of heat below 45F, the evaporator of the higher temperature su~system is placed in heat excnange relationship with the conaenser of the lower temperature subsystem and n,eans is providea to balance the system.
An aaditional feature of the invention includes means to pump li~uid refrigerant from the conaenser of the higner temperature subsystem to the desorDer of the higher temperature subsystem to balance the evaporator of the higher temperature subsystem heatins requirement with tne heating requirement of the condenser of the lower temperature subsystem.
Absorption refrigeration and heat pump systems are well known and their basic operating characteristics need little further aescription except to establish the definitions and context in which this invention will be later aescribed In a typical system water is a refrigerant dissolved in a lithium bromide/water solution, often called the "solution pair"~ Water is absorbea in the lithium bromide solution to varying degrees throughout the sytem and the heat of absorption is added or extractea to produce heating ana cooling effects The solution pair enters a generator where it is subjected to heat~ The appliea heat aesorbs the refrigerant water in the form of vapor which is conveyed to the condenser. There, external ambient cooling condenses the water vapor to liquid, which is conveyea through an expansion valve, into an evaporator where neat is absorbed.
In the refrigeration system the heat absor~ed in the evaporator is from the cooling loaa~
~z~
1 The lo~- pressure vapor then Qasses to an absorber where ambient cooling allows the lithium bromide solution to absorb the water vapor The solution pair is then conveyea to a recuperator by a pu~,p The recuperator is a counter flow heat exchanger where heat from the absorbent, li~hiurr, bromiae~water solution, flowing from the generator to the absorber, heats the returnins solution pair flowing from the absorber to the generator In the heating cycle, the cooling appliea at the absorber and/or the condenser is the heat delivery to the heating loaa As a matter of convenience and terminology, each ~art of the aborption system, which operates at the same pressure, is termed a chamber Conventional absorption refrigeration anà heat systems are two-chamber systems~ ~hen operated as a heat pump they give respectable heating performance but give extremely poor cooling performance Using ammonia (N~3) as the refrigerant and water (H20) as the sorbent, heat pumping can occur from an ambient air source which is at temperatures below freezing. In a theoretical assessment where the air is treated as if it were dry so that no aefrosting is necessary, t~e typical two chamber NH3/~2O heat pump would represent a significant improvement over what would be expected of a simple furnace However, since heat pumps are more expensive than a furnace, cooling season performance benefits are needea to justify the aaaed 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 conaitioner with the furnace For cooling, an NH3~2u system is predicted to have a performance factor, PF (PF =
cooling effect/combustion heat input) equal to aDout 0~46.
This low performance index causes unreasonable fuel (or ener~y) costs from excessive fuel (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 3 ~Zl~
1 supplied to the absorption system at higher ~emperatures Three-cham~er systems of various types have been suggested which would improve the performance Dy staging the desorption process into effects. T~lis woulQ allow for increasing the actual tempeeature in which the ariving heat is aaded to the system (cycle)~ The reference Carnot cyc'e efficiency would be increased and the real cycle would follow suit~ However again this increase in temperature would represent an unreasonably high pressure foc ammonia/water systems anà woula force the system to operate in regions for which aata is not readily available.
Extrapolations estimate a peak cycle temperature of about 400F for an air conditioning case with a 35F evaporator and much higher for a heat pump case with a lower evaporator temperature.
In aadition the pressure ano toxicity tena to rule out ammonia/water in a three-chamber system. The search for organic material such as halogenatea hyarocarbons ana other refrigerants as a replacement for the ammonia has been limitea by fluid stability at these higher temperatures.
Normal organic refrigerant stability tests anticipate that it is necessary for oil to be present for opera~ion in vapor compression refrigeration systems. These high operating temperatures rule out most of the common refrigerants, particularly when being heated directly by combustion products which often cause local hot spots, which result in working fluid degradation and/or corrosion of components~
The subsystem of this invention employes four char,bers Two chambers are operatively connectea in one two-chamcer subsystem ana two other chambers are operatively connectea in another subsystem.
One subsystem employes a higher temperature solution pair having good higher temperature performance properties, preferably lithium bromide/water with water as the refrigerant ana lithium bromide as the absorbent. The other subsystem employes a aifferent solution pair, preferably 12Z~
1 ammonia/water, with ammonia as the refri~erant ana water as the a~sorbent, The first mentionea su~system is operatea at higher temperatures and the system configuratiGn allows the pair to be selectea to avoi~ freezing ana cr~stalization proble~s, The other, secona, s~bsystem employes a lower temperature solution pair having yood low te,nperat~re perfomance properties and is operated at lower temperatures in the ranse wnere an oryanic shouia be expectea to operate successfully without toxicity corrosion or stability problems and where t~mperatures below freezing are acceptable, The first subsystem ana the secona subsystem; i,e,, higher ten~perature and the lower temperature subsystem respectively, are operatively combinea anà connected by placing the higher temperature condenser in heat exchange relationship with the lower temperature aesor~er with other conlponents of the total system also combinea in a new and novel way as will be later described, In the prior art, others have associated various components of absorption refrigeration/heat pump systems in various ways with the purpose of improving the performance or otherwise enhancing the operation of these systems, These other prior art systems have met with varying aegrees of success but have apparently not obtained all objectives and are capable of further improvement as proviaed by this invention, In the prior art, U, S, Patent 2,350,115 - Katzaw describes what may be termed a four-chamber system that employes some of the characteristics o~ the applicant's 3G invention but which fails to recognize the advantages of proviains an arrangement that recombines and reairects the heating and cooling effects of the uncontrolled amDient atmosphere, as well as the controlled/ conditioned atmospheres or loaas, 3~4 1 ~ S Patent 3,4~3,710 - ~earint, is another exa~.ple oi a prior art version of a four-cnamber system that combines a higher temperature subsystem with a lower temperature subsystem As aisclosed in the previous patent to ~atzaw, although the advantage of placing the higher temperature conaenser in heat exchange relationship with lower temperature aesorber is revealed, tne interrelationships between other components are not the same or arranged to the same advantage as the applicant's invention This is especially to be noted in connection with the arrangement of various elements with regara to ambien~ atmosphere conditions ana the conditioned atmosphere/or loa~
It is a purpose of this invention to comoine the co~ponents of the separate subsystems of the four-chamber 1~ system to provide an absorption refrigeration and/or heat pump total system that is capable of either a higher coefficient of performance or of being manufacturea with efficiencies without reàucing performance, and without resorting to continued search for an ideal fluid pair.
Other objectives ana features of the invention will be apparent and unaerstood from the detailed description anà
the accompanying drawings wnich follow l.~Z'~
1 DESC~IPTIO~ OF THE DRA~INGS
Figure 1 is a schematic representation of the arrangements of the various components of the system of this invention in the air conditioning and warm ambient neat pump mode of operation Figure 2 is a schematic representation of the various components of the system of this invention in the cold am~lent heat pump moae of operation~
Fig~re 3 is a schematic representation of the various components of the system of this invention in another embodiment of the cold ambient heat pump mode of operation.
Fiyure 4 is an air flow diagram of the various - components of the system of this invention when operated in the air conditioning mode shown in Figure 1.
15Figure 5 is an air flow diagram of the various components of the system of this invention when operated in the warm heat pump mode shown in Figure l Figure 6 is an air flow diagram of the various components of the system of this invention when operated in the moae shown in Figure 2.
Figure 7 is an air flow aiagram of the various components of the system of this invention when opera~ed in the moae shown in Figure 3 Figure 8 is a P-T-x diagram illustrating the thermodynamic operation of the system when operated in the moaes shown in Figure 1~
Figure 9 is a F-T-x aia~ra~. illustratin~ the thermoaynamic performance of the system when operated in the modes shown in Figures ~ ana 3~
DETAILED DESCRIPTION OF THE INVENTION
In a aescription of this invention, it is important that clear distinction be made between solutions entering ana leaving various components. Therefore, adopted herein is the notation of the standard setting body on absorption systems in the U~ S~, the ASHRAE Technical Committee (8.3) on Absorption ~achines~ Their notation is given in the ~Z211~
d 1 following quote from the ASHRAE 1979 Equipment ~andDook, Cha~ter 14:
"To avoid confusion of terminology in the absorption field, AS~RAE Technical Committee (~.3) recommenas the following standaraizea terms for the absorDent-refriseran~ solution.
Weak absorbent is that solution which has picked up refrigerant in the absorber and is then weak in its affinity for refrigerant Strong a~sorbent is that solution which has had refrigerant driven from it in the generator and, therefore, has a strong affinity for refrigerant "
In the schematic representation o~ Figure 1~ the hexagonal blocks represent the components of the first subsystem of the invention and the circles represent the components of the second subsystem~ The first subsystem may ~e interchangeably termed the "high" subsystem and the second, the "low" subsystem. Components of each may be termed in the same manner, respectively In the preferred embodiment of the invention, in the first (high) subsystem the water is the refrigerant and lithium bromide (LiBr) is the absorbent.
The higher temperature desorber 30 of the first su~system is heatea by a flame 31 or other means such as electricity. The desorber 30 is connected by a suitable conduit 32 to a higher temperature condenser 33 The conduit 32 carries superheated refrigerant vapor to the condenser 33. Heat extracted from the con~enser causes the refrigerant to conaense to a liquid.
The condenser 33 is connected to an expansion valve 34 Dy a conauit 35 which carries the conaensea liquid refrigerant~
Expansion valve 34 is connectea to a high evaporator 36 where the low pressure refrigerant vaporizes ~s it extracts heat from the ambient surroundings The vaporized l refrigerant is conveyed by conauit means 37 to a high abso~ber 38 where it wea~ens the strong solution suppliea to the aosorber 38 from conduit 43 through expansion valve 42 In the nigh subsyste~" the desorber 30 is connected to 5 a recuperator 40 by conduit means 41 The recuperator 40 is connected to an expansion valve 42 ana to the absor~er 3~ by a conàuit ~eans 43 The absorber 38 is connectea through a pump 44 to the recuperator 40 by a conduit means 45 ana ~he recuperator 40 is connectea back to the aesorber 3C by a conduit ~eans 46 In this part of the subsystem strons absorbent solution is carried from the desorber 30 through the recuperator 40 to the absorber 38 where it absorbs refrigerant ana the resulting weak solution is pumpea through the recuperator 40 to the desorDer 30. Heat is exchanged between the strong absorbent and the weak absorbent solutions in the recuperator 40.
In the above described manner the two-chamDer I,II, higher temperature, first subsystem operates in a typical generally conventional manner.
The solution pair used in chambers III and IV of the second (lower temperature) subsystem is prefecably ammonia ana water, with ammonia as the refrigerant and water as the sorbent.
Combined with the conaenser 33 in heat exchange relationship is a desorber 50 which is connected to a conaenser 51 by conduit means 52. Conduit 52 may include rectifier sections as typically needea when a volatile sorbent, such as water, is usea in a lower tem~erature solution system, comprising chambers III and IV.
Condenser 51 is connected through an expanslon valve 53 to an evaporator 54 by a conauit means 55. Evaporator 54 is connecteà to an absorber 59 by a conduit means 56 ana the exit from the aesorber 50 is connected to recuperator 56 by a conauit 57 whicn continues through an expansion valve 58 to the absorber 59. Through a pump 60 r the exit from the absor~er 59 is connectea through the recuperator 56 to the ~2~ 4 1 desorber 50 tnrough conduit means 61~
In operation, ammonia refrigerant vapor is driven from the desorber 5~ by heat from the conàenser 33 ana passes through the cona~it means 52 to the condenser 51. In condenser 51 heat is given up to a cooling medium, and the liquic refrigerant is carried to the expansion valve 53 where it expands into the evaporator and becomes vapor as it receives heat from an external source. The re~rigerant vapor is carried to the absorDer 59 where heat is given up to a sink and refrigerant is absorbea in a strong absorDent solution supplied to the absorber S9 from expansion valve 5~ The weakened absorbent solution is pumpea Dac~ to the desorber 50, being warmed by heat exchange in the recuperator 56~
Throughout the continuea aetailea description, the invention is described in the context of refrigeration and heat pumping for the purpose of heating ana cooling the environmental atmosphere of living space in a building or other shelter~ This "heating and air conditioning"
application of the invention is an essential and impor~ant use but it should be understood that in the broader sense the invention may be applicable in any circumstance where cooling or heating is desired and it may be aavantageous to use an a~sorption multi-purpose system.
Air Conditionin Mode of Operation In the air conditioning moae high evaporator 36 and the low evaporator 54 are connected in series heat excnange relationship with the flow of air from the conditioned livins space environment (the load) As shown in Figure 1, components operating at higher temperatures are snown to tne right and components operating at lower temperatures are shown to the left, relative to eacn other. The loaa is progressively cooled as it passes across the evaporators 36 and 54 respectively~ As shown in Figure 4, a fan 120 draws air from a living space return auct 121, and with dampers 122 and 124 in the "A" position, i~Z~
1 forces Lhat air throu~h a duct 123 to the high evaporator 36 hith aampers 127 ~na 128 in the "~" position, house air leaves evaporator 36 and passes through a duct 126, low evaporator 54, ana a àuct 12~ from which it is returnea to the conaitioned living space.
Outside air is drawn into the system through a duct 101 t and with a damper 102 in the "A" position, throuyh duct 103 to high absorber 3~. Damper 106 isolates the outsiae air inlet duct 103 from the interior plenum 125 to nigh 10 evaporator 36. Flow continues through duct 112 to the low absorDer 59, duct 113, ana low conaenser 51 to duct 11~
Damper 109 placed in the "A" position connects auct 114 with the discharge duct 110 which contains the fan 111, that induces the flow of outsiae air.
As seen in Figures 1 and 4, heat from the absorber 38, condenser 51, and absorber 59 is re~ected to the outside air (the heat sink) by means of the air flow pattern establishea across these ~omponents.
Referring to Figures 1 and 8, in the air conditioning mode of the preferred emboadiment, a saturation temperature of 254F establishes the pressure at 32 psia for operations in chamber I. The desorber 30 receives weak absorbent solution (57 % LiBr.) after being heatea in the recuperater 40 by the strong absorbent solution leaving the desorber 30 25 at 60~ Li~r ana 363F. In the total system in this moae~
only the desorber 30 receives heat from the external source 31.
Saturation conaitions at the evaporator 36 esta~lish the pressure of 0.18 Psia and a temperature 50F In the absorber 38, the strong absrobent solution enters at a temperature of 121F and 60% LiBr equilibrium condition.
Heat is rejected to the heat sink which in an air conditioning system, may be the outside ambient atmospnere.
Because the solution pair has been selected for its performance under these conditions, operations are below tne crystalization limit and especially aàvantageous for the 1 heat exchange relationship between the conàenser 33 ano the desorber 50.
A saturation tempera~ure of 140F in condenser 51 esta~lisnes the pressure at 350 Psia for operations in chamber III with NH3/H2O as the lower temperature fluid pair The desorber 50 receives weak absorbent solution (42 8% NH3) at a temperature of 237F ana the desorber 50 receives heat from the condenser 33 Saturation conaitions at the evaporator 54 establishes the pressure at 71 psia at temperature 40F. The absorber 59 receives strong solution at 39 ~% ~H3 ana a temperature of 131F, discharges weak solutiorl at approximately 121F, ana gives up heat to the heat sink in heat exchange relationship The theoretical performance of this cycle is preaictea to be: COP = 0.96. Taking loses into the account, the actual coefficient of performance is estimated to be 0 8~ with a high performance combustor 31 Warm Ambient Heat Pump Operation When the outside ambient air conaitions are about 45F
and above, heat pump operations are carried out in the same system except that the roles of the ambient and load are reversed as shown in Figure 5 for a system which is heating or air conaitioning.
With dampers 122 ana 109 in the "B" position, return air from the living space supplied by fan 120 is aiverted to duct 103, high absorber 38, low absorber 59, ana low condenser 51 and then returned to the conditionea air exit duct 129~ With dampers 102 and 128 also in the "B"
position, outside air passes from inlet 101 through high evaporator 36 ana low evaporator 54 before being arawn to exit duct 110 by fan 111. Dampers 124 ana 127 remain in the "A" position ana da~,per 106 remains closea.
In this circumstance, the ambient outside air as a source of heat is causea to flow across the evapora~ors 36 ana 54 which are arrangea in series heat exchange 211~
1 relations~i,? with the air passing across the evaporator 36 of the hisner temperature su~system first. Retaining the series nature of the flow of air across the two evapo~ators allows the outside air to oe cooled to temperatures Delow freezing without freezin~ the higher temperature evaporator At the same time, imposing the return air from the livins space atmosphere on the high absor~er first allows it to be operated away from crystalization region. Subsequent hea~ins of the living space atmosphere by the aDsorber 59 and the con~enser 51 can be at higher temueratures to n,inimize the flow of livin~ space air.
Theoretical analysis for this moae and example establishes that, for every unit of heat supplied by the combustion proaucts, 0.96 units of heat can be supplieà from the ambient air~ When adjusted for its stack loses, the coefficient of performance is equal to or greater than 1.7.
Cold Ambient Heat_Pump Operation At outside ambient air temperatures lower than about 45F, it is not acceptable to use the higher temperature evaporator 36 to extract heat from the outside air without freezing up the higher temperature refrigerant flow with a H~O/LiBr higher temperature system. To protect the higher temperature evaporator 36 from freezing (ana the higher temperature absorber from crystalization) this heat pumping cycle is carried out by imposing re]ection heat from the lower temperature subsystem upon the higher temperature evaporator 3~.
Referring to Figure 2, the system is configurea schematically the same as in Figure 1 except that the evaporator 36 is in hea~ exchanse relationship with the conaenser 51 . This is accomplishea by causing the air flow to pass across these components as shown in Figure 6. In oraer to accomplish this, the ducting configuration is modified as shown in Figure 6~
- ~'2~ 4 1 Camper valve 106 is located so that it can isolate the condenser inlet 113 and evapvrator inlet 125 wnen closec, but lS shown open in Figure 6, allowing recircula~ion fan 130 to force a separate flow of air from the high evaporator 36 to the low concenser 51. Dampers 124 and 127 and a damper 104 must ~e in the "B" position an~ a duct 108 must be added for this recirculation air flow to occur. As in Figure 5, dampers 102, 109, 122, and 128 remain in the "B"
position.
In adaition, a punlp 65 is connected from the conaenser 33 to the desorber 30 by a conduit means 66, as shown in Figure 2~
In operation, liquia conaensate is pumpeo from the condenser 33 to the aesorber 30 by the pump 65 as necessary to balance the system when the heat rejection from the conaenser 51 is made equal to the heat aàdition to the evaporator 36 . Additional heat is supplied by the source 31 to vaporize the additional liquid condensate that is pumped from the condenser 33 to the desorber 30. This supplies extra heat to the condenser 33 which matches the requirements of desorber 50 in this mode of operation~
Referring to Figures 2 and 9, in a preferred example, the condenser 33 operates at a saturation temperature of 285F (establishing the chamber I pressure at 53.2 psia) as it gives off heat the desorber 50 operating at a peak solution temperature of 277F. The desorber 30 receives weak absorbent solution at 49.2~ Li~r from the recuperator 40 where it is heated by the strong solution leaving the desorber 30 at 375F and 55.3~ LiBr.
The absorber 38 receives refrigerant vapor at 0.32 psia from evaporator 36 and strong absorbent solution at 1~5F
and 55~3% LiBr from the recuperator 40. ~s the solution is coolea by rejecting heat to the air in the livins space (the load) the leaving solution is at 106F and 49.2% LiBr.
1 The conaenser 51 is assumea to operate at 140F
establishing a pressure of 355 psia in the cham~er II1 The weak absorbent solution enters the desor~er 50 at 24~F
ana ~1 2~ N~3 after being recuperatively heated by the S strong absorbent solution leaving the aesorbec 50 at 277F
and 33 3% NH3 The air flow heat exchange between tne condenser Sl and the evaporator 36 establishes the pressure of chamber II at 0~32 psia. The su~systems are aajustea so that the heat leavins the condenser 51 is equal to that acceptea by the evaporator 36 In the typical example system, the evaporator 54 is assumea to operate at -2.5QF establishing 29 psia as the pressure in chamber IV. The evaporator 54 extracts heat from the colà outside air and the surface will need to be defrosted perioaically. The low absorber 59 operates at ~
psia as it rejects heat to air in the heated living space (the load). Strong solution enters the absorber 59 at 103F
- ana 33.3~ N~3 and leaves at 77F and 41.2~ NH3.
With the refrigerant flow esta~lished to match the heat flow between the condenser 51 and the evaporator 36 , the desorber 50 requires more heat (about one third more in the example) than woula normally ~e rejected by the conàenser 33. This short fall of energy is suppliea by additional heat input from the source 31. The energy transfer is accomplished by additional flow of liquid refrigerant from a refrigerant well in conaenser 33 to the desorDer 30 driven by pump 65. In the desorber 30 it is mixed with the solution supplied by pump 44, accomplishing the desirea dilution of the solution flow, ana is eventually evaporatea by the increased heat flow to supply increasea vapor flow to the condenser 33.
This results in a theoretical heating COP = 1.33 which would reduce to a value near 1.20 when an aajustment is maae for stack and other loses in actual practice.
3~4 1 From a control point of view, it is aavantageous to De freea from having to maintain exact heat flow balances at both the condenser Sl and desorber S0~ The preferre~ methoa of accomplishiny this is to incluae the evaporator 36 ana the condenser 51 in the main flow of air to the heated space as shown in Figure 7~ ~hen balanced, tne evaporator 36 cools the return air ana the high absorber 3~ heats the return air the same amount so that the mixed temperature entering absorber S9 from duct 112 is the same as the temperature in duct 103 When unbalanced, there is a small net gain or loss in return air temperature entering absorber 59~
In Figure 7, dampers 102, lO9, 122, 124, 127, ana 128 are in the "B" position and damper valve 106 is open just as in Figure 6. Fan 130 is eliminated and the air flow losses are reduced.
In the example about 20~ of the heat addea to the first higher temperature subsystem passes directly to the heated space without causing any heat pump augmentation through the ~ absorber 38~ Therefore the only true heat pumping process occurs in the lower temperature secona subsystem in this combined mode Consequently, it is advantageous to increase the relative amount of condensate returned to the ~esorber 30 from the condenser 33. Various compromises are possible in the adjustment of conaensate flow producea by the pump 6~
between these components~ Those skilled in the art will find it a matter of rou~ine adjustment to determine the appropriate amount under certain operating conaitions~
Referring to Figure 3, an alternative embodiment of the cold ambient heat pump operation is schematically shown in which the heat input to evaporator 36 is virtually eliminated by closing valve 34 an~ diverting all the refrigerant flow through a dilution reservoir ~9, and directing the refrigerant from there through valve 90 to the inlet to solution pump 44~ This further reduces the LiBr concentration, increasing the vapor release from the lZZ~ 4 1 solution pumF flow wlthout excessively broaaenlng tne concentratlon aifferences across aesorber 30, anu reoucing the temperature in desor~er 3~ ~s shown in ~lgure 3, some neat flow passes directly from the heat source 31 to the conditionea air ~y heat transrer from aDsorDer 3~.
The net coefficient of performance for heating (C ~ P h) is therefore increasea to about 1.31 This woula be the preferred emboaiment since it has the potential ~or the nishest (C~O.P.h).
From the foregoins, it is seen that tne conDlnation of the various components and their heat exchange relationshi~s is variable in various com~inations to acnieve an overall refrigeration/heat pump system havins an unusually hign C ~P.C for cooling of .o8 ana an unusuaily high C.G.P.h for heating of at least 1.31, in the cola am~ient heat pum~
moae. These performances are acco~,~lisheà by staging the first subsystem relative to the second subsystem in alternative comDinations througn rearrangenlent of the heat flow in the systenl relative to heat exchange between the he~t loaa and the heat sink Figures 4, 5, 6, and 7 show various direct heat exchange relationships between the components of the absorption system and the air of the conditione~ space (the load) and/or the ambient air (the sink or source).
Alternatively, other means may ~e usea to proviae tne heat exchange in the relationsnips between tnese co~ponents ana the loaa or sink. For instance, hydronic flow loops ~i.e., the use of liquia heat exchange materials such as ethylene ylycol conveyed in pi~ing between the components ana heat exchangers in contact witn the loaa or sink) couia replace any or all of the direct heat exchangers that are ~etween the elements in the four charl;~ers and the load or the ambient. In adaition, the pressure flow relationship o~
high eva~orator ana high a~sorber shown in Figure 7 coula alternatively De a series flow relationship, either airectly with the conaitioneG space air flow or with tne hyaronic ~zz~
l&
1 flow loops, which delivers heat to the conaitioned space~
It lS herein understooa that although the present inventior. has been specifically disclosed wlth the preferreà
embodiment and examples, moaification and variations of ~he concepts herein disclosed may be resorted to by those skilled in the art Such moaifications and variations are considered to be within the scope of the invention and the appenaed claims
S~IARY 0~ T~E INVE~TION-This invention relates to an absorption refrigeration/heat pump system which comprises a higner temperature subsystem ana a lower temperature su~system with various components of the subsystems in heat exchange relationship with one another to provide greater performance than usually obtainable in such systems and/or ~o permit the use of fluids that have been unsatisfactory in conventional systems~ ~ore particularly, it relates to an absorption refrigeration or heat pump system comprising a higher temperature subsystem and a lower temperature SuDSyStem in which the higher temperature condenser is in a heat exchange relationsnip with the lower temperature desorber an~ the heating and/or cooling loads are arrangea to exchange heat with various combinations of the other components of the system Briefly and in summary, the invention comprises an absorption refrigeration and heat pump system constructed to provi~e heat to or remove heat from a load when the ambient heat sink or source of heat is aDove about 45F comprising at least one first subsystem for operation at higher temperature and at least one second subsystem for operation at lower temperature relative to the first subsystem, each subsystem having components of absorber means, desorber means, con~enser means, ana evaporator means operatively connectea together, with a conaenser means of the higher temperature subsystem in heat exchange relatlonsnip witn the desorber means of the lower temperature subsystem; with the evaporator of the higher temperature subsystem ana the evaporator of the lower temperature subsystem in series heat excnange relationship with the load in the cooling moae or with the ambient in the heating moae; ana with the absor~er . r4~
~;~2~
l of the higher temperature subsystem, the condenser of the lower ~emperature subsystem, and the absorGer of the lower temperature subsystem in series heat exchange relationshi~
with the sink in the cooling mode and the loaa in the heating mode When operated with the heat sink or source of heat below 45F, the evaporator of the higher temperature su~system is placed in heat excnange relationship with the conaenser of the lower temperature subsystem and n,eans is providea to balance the system.
An aaditional feature of the invention includes means to pump li~uid refrigerant from the conaenser of the higner temperature subsystem to the desorDer of the higher temperature subsystem to balance the evaporator of the higher temperature subsystem heatins requirement with tne heating requirement of the condenser of the lower temperature subsystem.
Absorption refrigeration and heat pump systems are well known and their basic operating characteristics need little further aescription except to establish the definitions and context in which this invention will be later aescribed In a typical system water is a refrigerant dissolved in a lithium bromide/water solution, often called the "solution pair"~ Water is absorbea in the lithium bromide solution to varying degrees throughout the sytem and the heat of absorption is added or extractea to produce heating ana cooling effects The solution pair enters a generator where it is subjected to heat~ The appliea heat aesorbs the refrigerant water in the form of vapor which is conveyed to the condenser. There, external ambient cooling condenses the water vapor to liquid, which is conveyea through an expansion valve, into an evaporator where neat is absorbed.
In the refrigeration system the heat absor~ed in the evaporator is from the cooling loaa~
~z~
1 The lo~- pressure vapor then Qasses to an absorber where ambient cooling allows the lithium bromide solution to absorb the water vapor The solution pair is then conveyea to a recuperator by a pu~,p The recuperator is a counter flow heat exchanger where heat from the absorbent, li~hiurr, bromiae~water solution, flowing from the generator to the absorber, heats the returnins solution pair flowing from the absorber to the generator In the heating cycle, the cooling appliea at the absorber and/or the condenser is the heat delivery to the heating loaa As a matter of convenience and terminology, each ~art of the aborption system, which operates at the same pressure, is termed a chamber Conventional absorption refrigeration anà heat systems are two-chamber systems~ ~hen operated as a heat pump they give respectable heating performance but give extremely poor cooling performance Using ammonia (N~3) as the refrigerant and water (H20) as the sorbent, heat pumping can occur from an ambient air source which is at temperatures below freezing. In a theoretical assessment where the air is treated as if it were dry so that no aefrosting is necessary, t~e typical two chamber NH3/~2O heat pump would represent a significant improvement over what would be expected of a simple furnace However, since heat pumps are more expensive than a furnace, cooling season performance benefits are needea to justify the aaaed 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 conaitioner with the furnace For cooling, an NH3~2u system is predicted to have a performance factor, PF (PF =
cooling effect/combustion heat input) equal to aDout 0~46.
This low performance index causes unreasonable fuel (or ener~y) costs from excessive fuel (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 3 ~Zl~
1 supplied to the absorption system at higher ~emperatures Three-cham~er systems of various types have been suggested which would improve the performance Dy staging the desorption process into effects. T~lis woulQ allow for increasing the actual tempeeature in which the ariving heat is aaded to the system (cycle)~ The reference Carnot cyc'e efficiency would be increased and the real cycle would follow suit~ However again this increase in temperature would represent an unreasonably high pressure foc ammonia/water systems anà woula force the system to operate in regions for which aata is not readily available.
Extrapolations estimate a peak cycle temperature of about 400F for an air conditioning case with a 35F evaporator and much higher for a heat pump case with a lower evaporator temperature.
In aadition the pressure ano toxicity tena to rule out ammonia/water in a three-chamber system. The search for organic material such as halogenatea hyarocarbons ana other refrigerants as a replacement for the ammonia has been limitea by fluid stability at these higher temperatures.
Normal organic refrigerant stability tests anticipate that it is necessary for oil to be present for opera~ion in vapor compression refrigeration systems. These high operating temperatures rule out most of the common refrigerants, particularly when being heated directly by combustion products which often cause local hot spots, which result in working fluid degradation and/or corrosion of components~
The subsystem of this invention employes four char,bers Two chambers are operatively connectea in one two-chamcer subsystem ana two other chambers are operatively connectea in another subsystem.
One subsystem employes a higher temperature solution pair having good higher temperature performance properties, preferably lithium bromide/water with water as the refrigerant ana lithium bromide as the absorbent. The other subsystem employes a aifferent solution pair, preferably 12Z~
1 ammonia/water, with ammonia as the refri~erant ana water as the a~sorbent, The first mentionea su~system is operatea at higher temperatures and the system configuratiGn allows the pair to be selectea to avoi~ freezing ana cr~stalization proble~s, The other, secona, s~bsystem employes a lower temperature solution pair having yood low te,nperat~re perfomance properties and is operated at lower temperatures in the ranse wnere an oryanic shouia be expectea to operate successfully without toxicity corrosion or stability problems and where t~mperatures below freezing are acceptable, The first subsystem ana the secona subsystem; i,e,, higher ten~perature and the lower temperature subsystem respectively, are operatively combinea anà connected by placing the higher temperature condenser in heat exchange relationship with the lower temperature aesor~er with other conlponents of the total system also combinea in a new and novel way as will be later described, In the prior art, others have associated various components of absorption refrigeration/heat pump systems in various ways with the purpose of improving the performance or otherwise enhancing the operation of these systems, These other prior art systems have met with varying aegrees of success but have apparently not obtained all objectives and are capable of further improvement as proviaed by this invention, In the prior art, U, S, Patent 2,350,115 - Katzaw describes what may be termed a four-chamber system that employes some of the characteristics o~ the applicant's 3G invention but which fails to recognize the advantages of proviains an arrangement that recombines and reairects the heating and cooling effects of the uncontrolled amDient atmosphere, as well as the controlled/ conditioned atmospheres or loaas, 3~4 1 ~ S Patent 3,4~3,710 - ~earint, is another exa~.ple oi a prior art version of a four-cnamber system that combines a higher temperature subsystem with a lower temperature subsystem As aisclosed in the previous patent to ~atzaw, although the advantage of placing the higher temperature conaenser in heat exchange relationship with lower temperature aesorber is revealed, tne interrelationships between other components are not the same or arranged to the same advantage as the applicant's invention This is especially to be noted in connection with the arrangement of various elements with regara to ambien~ atmosphere conditions ana the conditioned atmosphere/or loa~
It is a purpose of this invention to comoine the co~ponents of the separate subsystems of the four-chamber 1~ system to provide an absorption refrigeration and/or heat pump total system that is capable of either a higher coefficient of performance or of being manufacturea with efficiencies without reàucing performance, and without resorting to continued search for an ideal fluid pair.
Other objectives ana features of the invention will be apparent and unaerstood from the detailed description anà
the accompanying drawings wnich follow l.~Z'~
1 DESC~IPTIO~ OF THE DRA~INGS
Figure 1 is a schematic representation of the arrangements of the various components of the system of this invention in the air conditioning and warm ambient neat pump mode of operation Figure 2 is a schematic representation of the various components of the system of this invention in the cold am~lent heat pump moae of operation~
Fig~re 3 is a schematic representation of the various components of the system of this invention in another embodiment of the cold ambient heat pump mode of operation.
Fiyure 4 is an air flow diagram of the various - components of the system of this invention when operated in the air conditioning mode shown in Figure 1.
15Figure 5 is an air flow diagram of the various components of the system of this invention when operated in the warm heat pump mode shown in Figure l Figure 6 is an air flow diagram of the various components of the system of this invention when operated in the moae shown in Figure 2.
Figure 7 is an air flow aiagram of the various components of the system of this invention when opera~ed in the moae shown in Figure 3 Figure 8 is a P-T-x diagram illustrating the thermodynamic operation of the system when operated in the moaes shown in Figure 1~
Figure 9 is a F-T-x aia~ra~. illustratin~ the thermoaynamic performance of the system when operated in the modes shown in Figures ~ ana 3~
DETAILED DESCRIPTION OF THE INVENTION
In a aescription of this invention, it is important that clear distinction be made between solutions entering ana leaving various components. Therefore, adopted herein is the notation of the standard setting body on absorption systems in the U~ S~, the ASHRAE Technical Committee (8.3) on Absorption ~achines~ Their notation is given in the ~Z211~
d 1 following quote from the ASHRAE 1979 Equipment ~andDook, Cha~ter 14:
"To avoid confusion of terminology in the absorption field, AS~RAE Technical Committee (~.3) recommenas the following standaraizea terms for the absorDent-refriseran~ solution.
Weak absorbent is that solution which has picked up refrigerant in the absorber and is then weak in its affinity for refrigerant Strong a~sorbent is that solution which has had refrigerant driven from it in the generator and, therefore, has a strong affinity for refrigerant "
In the schematic representation o~ Figure 1~ the hexagonal blocks represent the components of the first subsystem of the invention and the circles represent the components of the second subsystem~ The first subsystem may ~e interchangeably termed the "high" subsystem and the second, the "low" subsystem. Components of each may be termed in the same manner, respectively In the preferred embodiment of the invention, in the first (high) subsystem the water is the refrigerant and lithium bromide (LiBr) is the absorbent.
The higher temperature desorber 30 of the first su~system is heatea by a flame 31 or other means such as electricity. The desorber 30 is connected by a suitable conduit 32 to a higher temperature condenser 33 The conduit 32 carries superheated refrigerant vapor to the condenser 33. Heat extracted from the con~enser causes the refrigerant to conaense to a liquid.
The condenser 33 is connected to an expansion valve 34 Dy a conauit 35 which carries the conaensea liquid refrigerant~
Expansion valve 34 is connectea to a high evaporator 36 where the low pressure refrigerant vaporizes ~s it extracts heat from the ambient surroundings The vaporized l refrigerant is conveyed by conauit means 37 to a high abso~ber 38 where it wea~ens the strong solution suppliea to the aosorber 38 from conduit 43 through expansion valve 42 In the nigh subsyste~" the desorber 30 is connected to 5 a recuperator 40 by conduit means 41 The recuperator 40 is connected to an expansion valve 42 ana to the absor~er 3~ by a conàuit ~eans 43 The absorber 38 is connectea through a pump 44 to the recuperator 40 by a conduit means 45 ana ~he recuperator 40 is connectea back to the aesorber 3C by a conduit ~eans 46 In this part of the subsystem strons absorbent solution is carried from the desorber 30 through the recuperator 40 to the absorber 38 where it absorbs refrigerant ana the resulting weak solution is pumpea through the recuperator 40 to the desorDer 30. Heat is exchanged between the strong absorbent and the weak absorbent solutions in the recuperator 40.
In the above described manner the two-chamDer I,II, higher temperature, first subsystem operates in a typical generally conventional manner.
The solution pair used in chambers III and IV of the second (lower temperature) subsystem is prefecably ammonia ana water, with ammonia as the refrigerant and water as the sorbent.
Combined with the conaenser 33 in heat exchange relationship is a desorber 50 which is connected to a conaenser 51 by conduit means 52. Conduit 52 may include rectifier sections as typically needea when a volatile sorbent, such as water, is usea in a lower tem~erature solution system, comprising chambers III and IV.
Condenser 51 is connected through an expanslon valve 53 to an evaporator 54 by a conauit means 55. Evaporator 54 is connecteà to an absorber 59 by a conduit means 56 ana the exit from the aesorber 50 is connected to recuperator 56 by a conauit 57 whicn continues through an expansion valve 58 to the absorber 59. Through a pump 60 r the exit from the absor~er 59 is connectea through the recuperator 56 to the ~2~ 4 1 desorber 50 tnrough conduit means 61~
In operation, ammonia refrigerant vapor is driven from the desorber 5~ by heat from the conàenser 33 ana passes through the cona~it means 52 to the condenser 51. In condenser 51 heat is given up to a cooling medium, and the liquic refrigerant is carried to the expansion valve 53 where it expands into the evaporator and becomes vapor as it receives heat from an external source. The re~rigerant vapor is carried to the absorDer 59 where heat is given up to a sink and refrigerant is absorbea in a strong absorDent solution supplied to the absorber S9 from expansion valve 5~ The weakened absorbent solution is pumpea Dac~ to the desorber 50, being warmed by heat exchange in the recuperator 56~
Throughout the continuea aetailea description, the invention is described in the context of refrigeration and heat pumping for the purpose of heating ana cooling the environmental atmosphere of living space in a building or other shelter~ This "heating and air conditioning"
application of the invention is an essential and impor~ant use but it should be understood that in the broader sense the invention may be applicable in any circumstance where cooling or heating is desired and it may be aavantageous to use an a~sorption multi-purpose system.
Air Conditionin Mode of Operation In the air conditioning moae high evaporator 36 and the low evaporator 54 are connected in series heat excnange relationship with the flow of air from the conditioned livins space environment (the load) As shown in Figure 1, components operating at higher temperatures are snown to tne right and components operating at lower temperatures are shown to the left, relative to eacn other. The loaa is progressively cooled as it passes across the evaporators 36 and 54 respectively~ As shown in Figure 4, a fan 120 draws air from a living space return auct 121, and with dampers 122 and 124 in the "A" position, i~Z~
1 forces Lhat air throu~h a duct 123 to the high evaporator 36 hith aampers 127 ~na 128 in the "~" position, house air leaves evaporator 36 and passes through a duct 126, low evaporator 54, ana a àuct 12~ from which it is returnea to the conaitioned living space.
Outside air is drawn into the system through a duct 101 t and with a damper 102 in the "A" position, throuyh duct 103 to high absorber 3~. Damper 106 isolates the outsiae air inlet duct 103 from the interior plenum 125 to nigh 10 evaporator 36. Flow continues through duct 112 to the low absorDer 59, duct 113, ana low conaenser 51 to duct 11~
Damper 109 placed in the "A" position connects auct 114 with the discharge duct 110 which contains the fan 111, that induces the flow of outsiae air.
As seen in Figures 1 and 4, heat from the absorber 38, condenser 51, and absorber 59 is re~ected to the outside air (the heat sink) by means of the air flow pattern establishea across these ~omponents.
Referring to Figures 1 and 8, in the air conditioning mode of the preferred emboadiment, a saturation temperature of 254F establishes the pressure at 32 psia for operations in chamber I. The desorber 30 receives weak absorbent solution (57 % LiBr.) after being heatea in the recuperater 40 by the strong absorbent solution leaving the desorber 30 25 at 60~ Li~r ana 363F. In the total system in this moae~
only the desorber 30 receives heat from the external source 31.
Saturation conaitions at the evaporator 36 esta~lish the pressure of 0.18 Psia and a temperature 50F In the absorber 38, the strong absrobent solution enters at a temperature of 121F and 60% LiBr equilibrium condition.
Heat is rejected to the heat sink which in an air conditioning system, may be the outside ambient atmospnere.
Because the solution pair has been selected for its performance under these conditions, operations are below tne crystalization limit and especially aàvantageous for the 1 heat exchange relationship between the conàenser 33 ano the desorber 50.
A saturation tempera~ure of 140F in condenser 51 esta~lisnes the pressure at 350 Psia for operations in chamber III with NH3/H2O as the lower temperature fluid pair The desorber 50 receives weak absorbent solution (42 8% NH3) at a temperature of 237F ana the desorber 50 receives heat from the condenser 33 Saturation conaitions at the evaporator 54 establishes the pressure at 71 psia at temperature 40F. The absorber 59 receives strong solution at 39 ~% ~H3 ana a temperature of 131F, discharges weak solutiorl at approximately 121F, ana gives up heat to the heat sink in heat exchange relationship The theoretical performance of this cycle is preaictea to be: COP = 0.96. Taking loses into the account, the actual coefficient of performance is estimated to be 0 8~ with a high performance combustor 31 Warm Ambient Heat Pump Operation When the outside ambient air conaitions are about 45F
and above, heat pump operations are carried out in the same system except that the roles of the ambient and load are reversed as shown in Figure 5 for a system which is heating or air conaitioning.
With dampers 122 ana 109 in the "B" position, return air from the living space supplied by fan 120 is aiverted to duct 103, high absorber 38, low absorber 59, ana low condenser 51 and then returned to the conditionea air exit duct 129~ With dampers 102 and 128 also in the "B"
position, outside air passes from inlet 101 through high evaporator 36 ana low evaporator 54 before being arawn to exit duct 110 by fan 111. Dampers 124 ana 127 remain in the "A" position ana da~,per 106 remains closea.
In this circumstance, the ambient outside air as a source of heat is causea to flow across the evapora~ors 36 ana 54 which are arrangea in series heat exchange 211~
1 relations~i,? with the air passing across the evaporator 36 of the hisner temperature su~system first. Retaining the series nature of the flow of air across the two evapo~ators allows the outside air to oe cooled to temperatures Delow freezing without freezin~ the higher temperature evaporator At the same time, imposing the return air from the livins space atmosphere on the high absor~er first allows it to be operated away from crystalization region. Subsequent hea~ins of the living space atmosphere by the aDsorber 59 and the con~enser 51 can be at higher temueratures to n,inimize the flow of livin~ space air.
Theoretical analysis for this moae and example establishes that, for every unit of heat supplied by the combustion proaucts, 0.96 units of heat can be supplieà from the ambient air~ When adjusted for its stack loses, the coefficient of performance is equal to or greater than 1.7.
Cold Ambient Heat_Pump Operation At outside ambient air temperatures lower than about 45F, it is not acceptable to use the higher temperature evaporator 36 to extract heat from the outside air without freezing up the higher temperature refrigerant flow with a H~O/LiBr higher temperature system. To protect the higher temperature evaporator 36 from freezing (ana the higher temperature absorber from crystalization) this heat pumping cycle is carried out by imposing re]ection heat from the lower temperature subsystem upon the higher temperature evaporator 3~.
Referring to Figure 2, the system is configurea schematically the same as in Figure 1 except that the evaporator 36 is in hea~ exchanse relationship with the conaenser 51 . This is accomplishea by causing the air flow to pass across these components as shown in Figure 6. In oraer to accomplish this, the ducting configuration is modified as shown in Figure 6~
- ~'2~ 4 1 Camper valve 106 is located so that it can isolate the condenser inlet 113 and evapvrator inlet 125 wnen closec, but lS shown open in Figure 6, allowing recircula~ion fan 130 to force a separate flow of air from the high evaporator 36 to the low concenser 51. Dampers 124 and 127 and a damper 104 must ~e in the "B" position an~ a duct 108 must be added for this recirculation air flow to occur. As in Figure 5, dampers 102, 109, 122, and 128 remain in the "B"
position.
In adaition, a punlp 65 is connected from the conaenser 33 to the desorber 30 by a conduit means 66, as shown in Figure 2~
In operation, liquia conaensate is pumpeo from the condenser 33 to the aesorber 30 by the pump 65 as necessary to balance the system when the heat rejection from the conaenser 51 is made equal to the heat aàdition to the evaporator 36 . Additional heat is supplied by the source 31 to vaporize the additional liquid condensate that is pumped from the condenser 33 to the desorber 30. This supplies extra heat to the condenser 33 which matches the requirements of desorber 50 in this mode of operation~
Referring to Figures 2 and 9, in a preferred example, the condenser 33 operates at a saturation temperature of 285F (establishing the chamber I pressure at 53.2 psia) as it gives off heat the desorber 50 operating at a peak solution temperature of 277F. The desorber 30 receives weak absorbent solution at 49.2~ Li~r from the recuperator 40 where it is heated by the strong solution leaving the desorber 30 at 375F and 55.3~ LiBr.
The absorber 38 receives refrigerant vapor at 0.32 psia from evaporator 36 and strong absorbent solution at 1~5F
and 55~3% LiBr from the recuperator 40. ~s the solution is coolea by rejecting heat to the air in the livins space (the load) the leaving solution is at 106F and 49.2% LiBr.
1 The conaenser 51 is assumea to operate at 140F
establishing a pressure of 355 psia in the cham~er II1 The weak absorbent solution enters the desor~er 50 at 24~F
ana ~1 2~ N~3 after being recuperatively heated by the S strong absorbent solution leaving the aesorbec 50 at 277F
and 33 3% NH3 The air flow heat exchange between tne condenser Sl and the evaporator 36 establishes the pressure of chamber II at 0~32 psia. The su~systems are aajustea so that the heat leavins the condenser 51 is equal to that acceptea by the evaporator 36 In the typical example system, the evaporator 54 is assumea to operate at -2.5QF establishing 29 psia as the pressure in chamber IV. The evaporator 54 extracts heat from the colà outside air and the surface will need to be defrosted perioaically. The low absorber 59 operates at ~
psia as it rejects heat to air in the heated living space (the load). Strong solution enters the absorber 59 at 103F
- ana 33.3~ N~3 and leaves at 77F and 41.2~ NH3.
With the refrigerant flow esta~lished to match the heat flow between the condenser 51 and the evaporator 36 , the desorber 50 requires more heat (about one third more in the example) than woula normally ~e rejected by the conàenser 33. This short fall of energy is suppliea by additional heat input from the source 31. The energy transfer is accomplished by additional flow of liquid refrigerant from a refrigerant well in conaenser 33 to the desorDer 30 driven by pump 65. In the desorber 30 it is mixed with the solution supplied by pump 44, accomplishing the desirea dilution of the solution flow, ana is eventually evaporatea by the increased heat flow to supply increasea vapor flow to the condenser 33.
This results in a theoretical heating COP = 1.33 which would reduce to a value near 1.20 when an aajustment is maae for stack and other loses in actual practice.
3~4 1 From a control point of view, it is aavantageous to De freea from having to maintain exact heat flow balances at both the condenser Sl and desorber S0~ The preferre~ methoa of accomplishiny this is to incluae the evaporator 36 ana the condenser 51 in the main flow of air to the heated space as shown in Figure 7~ ~hen balanced, tne evaporator 36 cools the return air ana the high absorber 3~ heats the return air the same amount so that the mixed temperature entering absorber S9 from duct 112 is the same as the temperature in duct 103 When unbalanced, there is a small net gain or loss in return air temperature entering absorber 59~
In Figure 7, dampers 102, lO9, 122, 124, 127, ana 128 are in the "B" position and damper valve 106 is open just as in Figure 6. Fan 130 is eliminated and the air flow losses are reduced.
In the example about 20~ of the heat addea to the first higher temperature subsystem passes directly to the heated space without causing any heat pump augmentation through the ~ absorber 38~ Therefore the only true heat pumping process occurs in the lower temperature secona subsystem in this combined mode Consequently, it is advantageous to increase the relative amount of condensate returned to the ~esorber 30 from the condenser 33. Various compromises are possible in the adjustment of conaensate flow producea by the pump 6~
between these components~ Those skilled in the art will find it a matter of rou~ine adjustment to determine the appropriate amount under certain operating conaitions~
Referring to Figure 3, an alternative embodiment of the cold ambient heat pump operation is schematically shown in which the heat input to evaporator 36 is virtually eliminated by closing valve 34 an~ diverting all the refrigerant flow through a dilution reservoir ~9, and directing the refrigerant from there through valve 90 to the inlet to solution pump 44~ This further reduces the LiBr concentration, increasing the vapor release from the lZZ~ 4 1 solution pumF flow wlthout excessively broaaenlng tne concentratlon aifferences across aesorber 30, anu reoucing the temperature in desor~er 3~ ~s shown in ~lgure 3, some neat flow passes directly from the heat source 31 to the conditionea air ~y heat transrer from aDsorDer 3~.
The net coefficient of performance for heating (C ~ P h) is therefore increasea to about 1.31 This woula be the preferred emboaiment since it has the potential ~or the nishest (C~O.P.h).
From the foregoins, it is seen that tne conDlnation of the various components and their heat exchange relationshi~s is variable in various com~inations to acnieve an overall refrigeration/heat pump system havins an unusually hign C ~P.C for cooling of .o8 ana an unusuaily high C.G.P.h for heating of at least 1.31, in the cola am~ient heat pum~
moae. These performances are acco~,~lisheà by staging the first subsystem relative to the second subsystem in alternative comDinations througn rearrangenlent of the heat flow in the systenl relative to heat exchange between the he~t loaa and the heat sink Figures 4, 5, 6, and 7 show various direct heat exchange relationships between the components of the absorption system and the air of the conditione~ space (the load) and/or the ambient air (the sink or source).
Alternatively, other means may ~e usea to proviae tne heat exchange in the relationsnips between tnese co~ponents ana the loaa or sink. For instance, hydronic flow loops ~i.e., the use of liquia heat exchange materials such as ethylene ylycol conveyed in pi~ing between the components ana heat exchangers in contact witn the loaa or sink) couia replace any or all of the direct heat exchangers that are ~etween the elements in the four charl;~ers and the load or the ambient. In adaition, the pressure flow relationship o~
high eva~orator ana high a~sorber shown in Figure 7 coula alternatively De a series flow relationship, either airectly with the conaitioneG space air flow or with tne hyaronic ~zz~
l&
1 flow loops, which delivers heat to the conaitioned space~
It lS herein understooa that although the present inventior. has been specifically disclosed wlth the preferreà
embodiment and examples, moaification and variations of ~he concepts herein disclosed may be resorted to by those skilled in the art Such moaifications and variations are considered to be within the scope of the invention and the appenaed claims
Claims (14)
1. An absorption refrigeration and heating system in connection with a cooling or heating load and a heat sink or source to selectively provide heat to or remove heat from the load, comprising:
(a) at least one first subsystem for operation at nigher temperature and at least one second subsystem for operation at lower temperature relative to the first subsystem;
(b) each subsystem having components of absorber means, desorber means, condenser means, and evaporator means operatively connected together;
(c) with the condenser means of the higher temperature subsystem in heat exchange relationship with the desorber means of the lower temperature subsystem; and (d) means to selectively arrange heat exchange relationships between the load and at least two of the component means including the higher temperature absorber, higher temperature evaporator, lower temperature condenser, lower temperature evaporator, and lower temperature absorber, while arranging heat exchange relationships between at least one of the other component means and the heat sink or source.
(a) at least one first subsystem for operation at nigher temperature and at least one second subsystem for operation at lower temperature relative to the first subsystem;
(b) each subsystem having components of absorber means, desorber means, condenser means, and evaporator means operatively connected together;
(c) with the condenser means of the higher temperature subsystem in heat exchange relationship with the desorber means of the lower temperature subsystem; and (d) means to selectively arrange heat exchange relationships between the load and at least two of the component means including the higher temperature absorber, higher temperature evaporator, lower temperature condenser, lower temperature evaporator, and lower temperature absorber, while arranging heat exchange relationships between at least one of the other component means and the heat sink or source.
2. A system according to Claim 1 in connection with a cooling load, wherein the evaporator of the higher temperature subsystem and the evaporator of the lower temperature subystem are in series heat exchange relationship with the cooling load.
3. A system according to Claim 1 to selectively provide heat to, or remove heat from, a load when an ambient heat sink or source of heat is above about 45°F, wherein:
the evaporator of the higher temperature subsystem and the evaporator of the lower temperature subsystem are in series heat exchange relationship with the load in the cooling mode, or with the ambient in the heating mode; and the absorber of the higher temperature subsystem and the absorber and the condenser of the lower temperature subsystem are in series heat exchange relationship with the sink in the cooling mode or the load in the heating mode.
the evaporator of the higher temperature subsystem and the evaporator of the lower temperature subsystem are in series heat exchange relationship with the load in the cooling mode, or with the ambient in the heating mode; and the absorber of the higher temperature subsystem and the absorber and the condenser of the lower temperature subsystem are in series heat exchange relationship with the sink in the cooling mode or the load in the heating mode.
4. A system according to Claim 1 in connection with a load to pump heat from ambient heat sources at a temperature less than about 45°F, wherein:
the absorber of the higher temperature subsystem and the absorber of the lower temperature subsystem are in series heat exchange relationship with the load;
the evaporator of the higher temperature subsystem is in heat exchange relationship with the condenser of the lower temperature subsystem; and means are provided to pump liquid refrigerant from the condenser of the higher temperature subsystem to the desorber of the higher temperature subsystem to balance the heating requirement of the evaporator of the higher temperature subsystem with the heating requirement of the condenser of the lower temperature subsystem.
the absorber of the higher temperature subsystem and the absorber of the lower temperature subsystem are in series heat exchange relationship with the load;
the evaporator of the higher temperature subsystem is in heat exchange relationship with the condenser of the lower temperature subsystem; and means are provided to pump liquid refrigerant from the condenser of the higher temperature subsystem to the desorber of the higher temperature subsystem to balance the heating requirement of the evaporator of the higher temperature subsystem with the heating requirement of the condenser of the lower temperature subsystem.
5. A system according to Claim 1 to pump heat from ambient heat sources at a temperature less than about 45°F, wherein:
the absorber of the higher temperature subsystem, the absorber of the lower temperature subsystem, and the condenser of the lower temperature subsystem are in series heat exchange relationship with the load, and the evaporator of the higher temperature subsystem also is in heat exchange relationship with the load; and means are provided to convey liquid refrigerant from the condenser of the higher temperature subsystem to the desorber of the higher temperature subsystem to reduce the direct flow of heat from the heat source to the conditioned space
the absorber of the higher temperature subsystem, the absorber of the lower temperature subsystem, and the condenser of the lower temperature subsystem are in series heat exchange relationship with the load, and the evaporator of the higher temperature subsystem also is in heat exchange relationship with the load; and means are provided to convey liquid refrigerant from the condenser of the higher temperature subsystem to the desorber of the higher temperature subsystem to reduce the direct flow of heat from the heat source to the conditioned space
6 A system according to Claim 1 to pump heat from ambient heat sources at a temperature less than about 45°F, wherein:
the absorber of the lower temperature subsystem and the condenser of the lower temperature subsystem are in series heat exchange relationship with the load;
the evaporator of the higher temperature subsystem is substantially eliminated from cooling the load by reducing the flow of liquid refrigerant to said evaporator;
the absorber of the higher temperature subsystem is in minimal heat transfer relation with the load; and reservoir means are provided to store excess liquid refrigerant from the condenser of the higher temperature subsystem and to control the release of liquid refrigerant to a solution pump in the higher temperature subsystem, to reduce the direct flow of heat from the heat source to the load.
the absorber of the lower temperature subsystem and the condenser of the lower temperature subsystem are in series heat exchange relationship with the load;
the evaporator of the higher temperature subsystem is substantially eliminated from cooling the load by reducing the flow of liquid refrigerant to said evaporator;
the absorber of the higher temperature subsystem is in minimal heat transfer relation with the load; and reservoir means are provided to store excess liquid refrigerant from the condenser of the higher temperature subsystem and to control the release of liquid refrigerant to a solution pump in the higher temperature subsystem, to reduce the direct flow of heat from the heat source to the load.
7. A system according to any one of Claims 1 through 3 w h e r e i n t h e f i r s t s u b s y s te m e m p l o y s a refrigerant-absorbent solution selected for high temperature performance properties and the refrigerant-absorbent solution in the second subsystem is selected for its low temperature performance properties.
8. A system according to any one of Claims 1 through 3 wherein the higher temperature subsystem employs an aqueous solution of lithium bromide and water, in which the aqueous solution of lithium bromide is the absorbent and the water is the refrigerant.
9. A system according to any one of Claims 1 through 3 wherein the lower temperature subsystem employs a solution of water and ammonia in which the ammonia is the refrigerant and the ammonia water solution is the absorbent
10. A system according to any one of Claims 1 through 3 wherein the lower temperature subsystem employs a solution of water and ammonia in which the ammonia is the refrigerant and the ammonia water solution is the absorbent, and the higher temperature subsystem employs an aqueous solution of lithium bromide and water, in which the aqueous solution of lithium bromide is the absorbent and the water is the refrigerant.
11. A system according to any one of Claims 4 through 6 w h e r e i n t h e f i r s t s u b s y s t e m e m p l o y s a refrigerant-absorbent solution selected for high temperature performance properties and the refrigerant-absorbent solution in the second subsystem is selected for its low temperature performance properties.
12. A system according to any one of Claims 4 through 6 wherein the higher temperature subsystem employs an aqueous solution of lithium bromide and water, in which the aqueous solution of lithium bromide is the absorbent and the water is the refrigerant.
13. A system according to any one of Claims 4 through 6 wherein the lower temperature subsystem employs a solution of water and ammonia in which the ammonia is the refrigerant and the ammonia water solution is the absorbent.
14. A system according to any one of Claims 4 through 6 wherein the lower temperature subsystem employs a solution of water and ammonia in which the ammonia is the refrigerant and the ammonia water solution is the absorbent, and the higher temperature subsystem employs an aqueous solution of lithium bromide and water, in which the aqueous solution of lithium bromide is the absorbent and the water is the refrigerant.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000449951A CA1221844A (en) | 1984-03-20 | 1984-03-20 | Absorption refrigeration and heat pump system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000449951A CA1221844A (en) | 1984-03-20 | 1984-03-20 | Absorption refrigeration and heat pump system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1221844A true CA1221844A (en) | 1987-05-19 |
Family
ID=4127445
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000449951A Expired CA1221844A (en) | 1984-03-20 | 1984-03-20 | Absorption refrigeration and heat pump system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1221844A (en) |
-
1984
- 1984-03-20 CA CA000449951A patent/CA1221844A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4441332A (en) | Absorption refrigeration and heat pump system | |
| US4722193A (en) | Absorption refrigeration and heat pump system | |
| US4542628A (en) | Coupled dual loop absorption heat pump | |
| EP1244890B1 (en) | Integrated aqua-ammonia chiller/heater | |
| CN108759142A (en) | A kind of special overlapping air source high-temperature heat pump cooling/warming system | |
| CN104567090A (en) | Trans-critical cycle double-stage heat absorption providing composite refrigeration system | |
| CN113701376A (en) | Air conditioner circulation system and control method of air conditioner | |
| US5456086A (en) | Valving arrangement and solution flow control for generator absorber heat exchanger (GAX) heat pump | |
| CN105466075B (en) | Freeze in heat pump and hot water heating combined system and domestic hot-water's flow processed | |
| CN206478771U (en) | A kind of multiple computer-room air conditioning system | |
| CN209147487U (en) | A kind of low circumstance temperature frequency conversion Air Resource Heat Pump Unit | |
| CA1221844A (en) | Absorption refrigeration and heat pump system | |
| CN204513843U (en) | A kind of trans critical cycle provides two-stage absorption cycle that the composite refrigeration system of heat occurs | |
| KR100634842B1 (en) | Refrigerating mechine | |
| CN219640385U (en) | Air conditioning system | |
| CN215809422U (en) | Air conditioner circulation system and air conditioner | |
| CA1288605C (en) | Absorption refrigeration and heat pump system | |
| Kaushik et al. | Computer modelling and thermodynamic assessment of an aqua-ammonia absorption cycle solar heat pump | |
| JPH0413620B2 (en) | ||
| CA1281192C (en) | Absorption refrigeration and heat pump system | |
| KR100419479B1 (en) | Auxiliary refrigerator mounted heat pump system | |
| CA1313766C (en) | Absorption refrigeration and heat pump system | |
| JPS58108372A (en) | Air-conditioning hot-water supply device | |
| CN115111802A (en) | Coupling compression and absorption type high-temperature heat pump system and method thereof | |
| CN116576515A (en) | Solar enhanced jet type double-temperature heat source heat pump air conditioning system and refrigeration equipment |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |