CA2006784A1 - Chilling system with vapor refrigerant and desiccant - Google Patents

Abstract

CHILLING SYSTEM WITH VAPOR REFRIGERANT
AND DESICCANT
ABSTRACT OF THE DISCLOSURE
A chiller system for satisfying a cyclical cooling load including a fuel-fired prime mover and compressor set, and a cold storage bank. The prime mover compressor set is sized for efficient, substantially continuous operation from cycle to cycle and the cold storage is sized to provide any short term deficiency of cooling rate in the prime mover compressor set. The prime mover compressor set is preferably operated during periods of cooling demand and is modulated in output capacity to extend real time matching of cooling delivery rate and consumption. A
condenser reset temperature feature takes advantage of cyclic changes in operation to improve efficiency. A
heat utilization circuit converts prime mover rejected heat to latent heat removal capacity in a desiccant storage medium.

Description

'-~` X00~`78~

1 CHILLING SYSTEM WITH VAPOR REFRIGERAN'r 3 This is a continuation-in-part of application ~' 4 Serial No. 104,353, filed October 2, 1987. ;

BACKGROUND OF THE INVENTION
6 The invention relates to apparatus and a 7 method for supplying cooling and dehumidification ;, 8 energy particularly in applications where the cooling ;;~
9 and dehumidification loads are cyclical.

PRIOR AR' 11 Air conditioning, i.e. space cooling, is a 12 common example of a cooling load which varies with ~ ;
13 time. Normally, the cooling load for air conditioning 14 cycles on a daily basis. When the air conditioning equipment is powered by utility supplied electrical 16 power, the periodically billed utility demand charge 17 assessed the user, typically, can be greatly increased.
18 'rhis often results where operation of such equipment 19 coincides with the peaking of other electrical demands at the site being air conditioned normally during ; i 21 working hours. ;;~i~
22 To reduce total peak electrical demand, it is 23 known to "time shift" the production of cooling energy 24 to periods such as nighttime when other electrical loads are at a low level. This cooling energy is ~;
26 stored typically in an ice bank and used later as 27 required. Such a solution is imperfect because the 28 production of ice can require roughly 20X more energy, ~ -29 for a given amount of air conditioning capacity, than S
is required to supply such capacity on a real time, - ;
31 i.e. as used, basis. Moreover, since operation of the ,'' -, ,.:
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,,"''",''~' '' '' .i 200~'84 1 electrical air conditioning unit incurs the maximum 2 demand charge at times of high demand of other 3 appliances, it is often an economic necessity to 4 discontinue its operation during such periods and it cannot therefore be fully downsized to a minimum for 6 greatest savings in capital investment 7 U.S. Patent No. 4,565,069 to MacCracken 8 discloses a system in which air conditioning capacity 9 is derived through an absorption cycle, heat for the absorption cycle being supplied from that rejected from 11 an internal combustion engine. Generally, the initial 12 cost of absorption cycle systems is relatively high 13 and, consequently, such systems have not been widely 14 commercially accepted.

J5 ~IJMMARY ~ T~E INV~.NTTON
16 The invention provides a fuel-fired 17 refrigeration compressor system for meeting cyclical -18 cooling loads, such as air conditioning, where the 19 production of cooling energy may be spread over a time substantially greater than the duration of the load so 21 as to reduce the size and therefore the capital costs 22 of the refrigeration components. Cooling energy 23 produced prior to the occurrence of the load is stored 24 in an ice bank or other cold storage medium.
Preferably, where the load occurs for a substantial 26 period, e.g. a significant part of a day, the system is 27 caused to operate through such period so that cooling 28 energy i9 supplied simultaneously from the 29 refrigeration compressor and from the ice bank. This mode of operation improves efficiency by avoiding 31 expenditure of the energy required to reach freezing ;
32 temperatures for that part of the cooling energy -33 produced as it is being used. Additionally, generation . :
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1 of cooling energy through the duration of the load ' ~
2 allows the system to be fully downsized for ~reater ;`
8 savings ~n capital costs.
4 The fuel-fired prime mover operating the compressor can be an internal combustion engine, a 6 steam or gas turbine, or a Stirling engine, for " . :~, 7 example. In accordance with one aspect of the 8 invention, the speed of the prime mover is controlled 9 to modulate the output of the compressor so that as much of the cooling load as possible can be met ;~
11 directly on a real time basis with the prime mover and ;~
12 refrigeration compressor fully loaded in order to 13 maximize efficiency of operation.
14 In accordance with another aspect of the `
invention, the heat rejected by the prime mover is used 16 at a site where t.here is need for hot water or low 17 pressure steam. The engine is operated at times when 18 heat is required and the shaft power of the engine is 19 stored as cold energy in the ice bank. The engine can be fitted with an electrical generator so that when the 21 requirement for cold energy storage has been met, 22 engine operation and heat generation can continue in 23 response to the heat load while electrical energy is 24 simultaneously produced. In some installations it can be beneficial to operate a generator, with cold storage 26 requirements satisfied, without utilization of heat -27 rejected by the engine. For example, the generatorjcan ; -:
28 be moved to shave peak electrical demands supplied by a 29 utility to reduce electrical charges to the user.

In accordance with still another aspect of 31 the invention, where the cooling load occurs primarily ;~
32 during the daytime, such as in air conditioning, ~ , 33 nighttime ambient temperatures are characteristically 34 substantially lower than daytime temperatures and ''' .'. ,' .~:
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1 refrigeration heat is transferred to the atmosphere, 2 the condenser operating temperature is reset to a lower 3 value at night. Since the ambient temperature is lower 4 at night, sufficient heat transfer is achieved at the condenser despite the lowered operating temperature.
6 With the lower operating temperature at the condenser, 7 less energy is required to produce a given quantity of 8 stored cooling capacity. With temperature reset of the 9 condenser, the penalty for making ice, because of the relatively low temperature of the ice as compared to 11 the temperature of brine used in real time cooling, is 12 substantially eliminated.
1.1 The d;.qclo~ed fl~el-fired refr;gerAt;on sy~tem 14 takes advantage of the relatively low cost, reliability and safety inherent in the use of an ice bank for , -;
16 energy storage. A downsized fuel-fired refrigeration 17 compressor, used with an ice bank of relatively low 18 cost, in accordance with the invention, allows such ~;
19 refrigeration equipment to be competitive on an initial cost basis with electrically operated equipment. ~he ~;
21 fuel-fired refrigeration system of the invention when 22 operating on natural gas is significantly less 23 expen~ive to operate on a cost of fuel basis, than are 24 known electrically operated systems on a cost of -electricity basis. The cooling load time spreading 26 effect afforded by the invention is applicable to other 27 processes, besides air conditioning, such as industrial 28 processes involving chemical reactions, melting or 29 ~reezing as well as cooking operations. ~ , In accordance with a further aspect of the ;
31 invention, means are provided for utilizing the 32 rejected heat of the fuel-fired prime mover to assist 33 in meeting the air conditioning load. By using the 34 rejected heat for air conditioning, a significant Z006~78~

l increase in operatina efficiency i9 achi.eved. More :: ;,'.
2 ~pecifically, the rejected heat utilizinq means is 3 applied to the latent heat portion of t.he air ,: `
4 conditioninq load while the vapor compressi,on chiller system is applied to the sensible heat portion of the 6 ~oad. It is recoqnized, accordinq to the invention, 7 that in many cases, depending on climate and other ,.. ''~
~ ~a~t,ors, t,he ener~y avai.1abl,e as re~ect.ed heat from a 9 conventional prime mover heat enqine matches the latent '-~
1.n h~t, p~rtion of an air conditi,oni.n~ 10ad, the sensihle -,', ':~
1.1 heat portion of which i 9 met by a vapor compressor '~
~l~ mechanically driven by t,he heat engine. The re,~ected ;,:~, 1.3 heat utilizinq means inc1udes storaqe capaci,ty that is '~' ~4 matched to the col.d stora~e capaci.t,y of t,he vapor 1.6 compression chi~ler system. '~
16 The reJected heat utilizinq means, according :~
17 to the invention, employs a desiccant medium that when :'~
18 re,a,enerated with rejected heat from the prime mover, , ' ,i.
l9 has the ability to absorb moi,sture from air beinq ', ~,~
. condi,tioned and, importantly, the capacity when stored 21 to indefinitely maintain its desiccatinq potential for . ',:,' 22 the absorption of moisture. Ideally, accordi.nq to the '~
23 invention, there is provided sufficient desiccant ; "~,.' 24 storaqe capacity to match the ice stora~e capacity :, '',~'' substantially in proportion to the ratio of latent heat 26 load to ~ensi.ble heat load at the site beinq air :~,`~.. ,'., 27 conditioned. , .,~,., ".,,' 2~ The i,nvent.i.on provi.des a sti],l further ,:,:'",,~,~",' 29 improvement in overall efficiency where the latent heat ' '' , load i,s met. by rejected heat reqenerated desi.ccant and "
31 the evaporator of the vapor compres.s~,on nnit, duri.nq ." ,:~,"
32 real time load satisfyina compressor operation, is ' ',:,, 33 allowed to operate at a re],ativel~y hi~h temperature. ' :,- .,.
34 With moisture removal by the desiccant, the evaporator :,,. ,.,.,'-",. . . .
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~I a.qsocjated coolina oi.l i.. s not reqllire~ to operat~ at a 2 re1at,ive1y low temperature. as i.s customary, t,o 3 condense moisture from the air. Operation of the .. -.
4 eva~orator at a relatively hiqh temperature i.mproves compressor capacity and o~eratina efficiency by 6 increasinq refri~erant densi.ty and t.hereby the ,, 7 compressor mass f]ow per revolution and it.s volumetric 8 efficiency. .:
9 BRIF,F DESCRIPTTON OF T~E DRAWINGS .,.
~ FIG. l i.s a diaqrammatic representation of an . ,:
J1 air conditioninq circuit embodving the invention; and : ' 'l2 FTG, 2 is a diaara~at,ic representation of an . ;~
13 air condition circuit utili.~i.nq the reiected heat of a .' .. ,'~, I a f1~h L -fired prime mover i.n accordance wit.h a second '' 1~ em~hdi~ent of the inventi.on.
'l~ 0~.$~RTPTIOh! ~F T~Æ PRFFFRRRD FMB~DIM~NTS '' 17 ~efhrrinq nhw t.o t.he drawinas. t,here is ,,.
18 schemat~cally ill.ustrated in FJG. ~. a chiller circuit ' 1,9 10 u~ed, for examo].e, to provide air condi.tioninq, i.e. ' ''.,,',.
~pace coo1in~. in an enc1.o.sed zone of a bni.ld1na or the :' 2~ lika at which the circlli.t i~ installad. Tn the 22 i111~strated embodi.ment, t.he chiller circuit ~0 inclllde~ ' 23 a hri.ne section l9. The chiller circui.t also includes 24 a refrigeration ~ection 20 comprising a compressor ll '.
a5 powered b~ a fuel-fired prime mover 12 as well a~ a 26 condenser 13 and an evaporator 15.
27 The refriqeration circui.t o~erates in a 28 aenerally convent;.onal manner, The compressor 11. usinq -, 29 a fluorocarbon such as Freon or ot.her su;.table refriqerant. sup~lies hiqh-pressure vapor to ~ condenser .'3'l 1:3, The refri ~Prant ~ives un heat in the chndenser and3~ jc condensed t.o a 1 i quj d .~tat.æ and pa~e~ t.hen to an :3:~ P~ an~ion va1ve 1 a where i t r)art.ially eva,r~orate~: and is .~4 cooled and t.hen f~ows int.o an evapora~.or 15. rrhe ". ~ .

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:. ~-', 1 refrigerant completes evaporation and absorbs heat in 2 the evaporator 15 (from the brine circuit 19 by means 3 of heat transfer) and then the vapor is sucked into the 4 compressor to repeat the compression and expansion cycle.
6 The prime mover 12 can be an internal 7 combustion engine, a turbine, or a Stirling engine, for 8 example. The prime mover or engine 12 is supplied with 9 a combustible fuel such as natural gas through a line 16.
11 The condenser 13, when used in an air 12 conditioning system, transfers heat to the earth's 13 atmosphere either directly by circulation and contact 14 with air, or through a cooling tower 17 in a known ;;
manner. The evaporator 15 includes heat exchanger '~;
16 means 18 through which brine, in the form of ethylene 17 glycol or other suitable liquid, circulates to give up ; ;~
18 heat to the refrigerant in the evaporator. The brine 19 i8 circulated through the heat exchanger means 18 by a pump 26 through lines 27, 28. ~ ;
21 A cold storage tank or bank 31 preferably ;;~ ~
22 containing water andJor ice is chilled by brine from ; ;
23 the evaporator 15 through a line 32. Brine which has ~
24 chilled or is chilled by the ice in the tank 31 is i:
carried in a line 33 to a mixing valve 34. Another 26 line 36 bypasses the tank 31 to carry brine from the 27 evaporator 15 to the mixing valve 34. Brine from the 28 mixing valve 34 passes through a two-position three-way 29 valve 37 either to the coils of a heat exchanger 38 in an air duct or directly to the inlet of the brine pump 31 26, depending on its position. The valve 37 is 32 illustrated in an air conditioning mode where the brine ~ :~
33 passes through the coils 38. These air duct coils 38 `
34 represent the cooling load served by the circuit 10. A :
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1 fan, not shown, f orces air across the air duct coils 38 2 thereby allowing such air to be cooled and recirculated 3 throngh th~ huildlng ~p~ce or z~nR bein~ ~ir 4 conditioned.
Typically, air conditioning of an occupied 6 building represents a cyclic cooling load with the 7 greatest demand for cooling energy occurring in the 8 afternoon period and the minimum demand occurring in 9 the nighttime period. A high air conditioning load may exist for 8 to 12 hours, for instance, and a nominal or 11 non-existent load will exist for the remainder of a 24-12 hour day. The ice-storage bank 31 is sized such that 13 it can store and supply the cooling capacity required 14 to cool the air conditioned zone serviced by the coils during the period of highest cooling load in a design 16 day, less any cooling created by operation of the 17 compressor 11 during such period. The compressor 11, 18 in conjunction with the evaporator 15 and condenser 13, 19 is sized to produce the total cooling energy required throughout the 24-hour period of a cooling design day.
21 By operating the prime mover and compressor set con-22 tinuously throughout a 24-hour period of a design day, 23 its size can be reduced substantially to a minimum 24 while still meeting the cooling requirements of the site.
26 Whenever there is a demand for cooling ~7 energy, it is preferable that the compressor produce 28 such energy contemporaneously with the demand, i.e. on 29 a real time basis, to the extent of its capacity. This simultaneous production of cooling energy is ordinarily 31 more efficient in fuel energy consumption since, in 32 this mode, the evaporator 15 can operate with 33 temperatures near chilled brine temperatures of, for 34 example 44 F. rather than below freezing temperatures, ... ' , ;.
g :

1 e.g. 260 F. Since the refrigerant temperature 2 differential between the evaporator and the condenser 3 is reduced, approximately ~0~ less fuel ener~y i5 A required to move heat from the evaporator to the condenser. , ;
6 The mixing valve 34 is normally operated to 7 supply chilled brine exclusively from the evaporator 15 8 during operation of the compressor 11 through the line 9 36 when the compressor 11 is capable of fulfilling the current demand. In accordance with an important aspect ;;
11 of the invention, the speed of the engine 12 is 12 modulated to match the output of the compressor to the ;~ ;
13 contemporaneous cooling load. In the illustrated case, ,;~ ;
14 the compressor 11 is a constant volume per revolution device and is directly driven by the shaft of the 16 engine 12. Where the prime mover 12 is an internal 17 combustion engine, for example, it can be efficiently 18 run through a speed range of approximately 2 to 1 or 19 more. When the cooling load is relatively light, the engine 12 is driven at relatively low speed. Con-21 versely, when the cooling load is moderate, the engine 22 is run at a higher speed to cause greater power through 23 the compressor 11 to deliver greater cooling capacity.
24 Below a speed at which the engine and compressor efficiency is greatly diminished, the compressor 26 operation is discontinued and the cooling load can be 27 met by full reliance on energy stored in the ice bank 28 31. In this latter circumstance, the mixing valve 34 29 allows the pump 26 to circulate sufficient brine through the ice bank and coil 38 to meet the demand.
31 When the cooling demand exceeds the rated output of the -32 compressor 11, the mixing valve supplements its output 33 energy being carried in line 36 with cooling energy in 34 the ice bank transferred through the line 33.

2006~

1 When the cooling energy stored in the ice 2 bank 31 is below a predetermined value, the diverting 3 valve 37 is moved from the illustrated position to its 4 alternative position and the compressor 11 is operated to recharge it by causing a phase-change of water to 6 ice in the storage bank. As previously indicated, when .~ .
7 making ice, the evaporator 15 operates with a brine 8 temperature in the chamber 18 of approximately 26 F.
9 When producing cooling energy directly to the air coil 38 Ibypassing the ice storage 31 through the 11 line 36) on a real time basis, the evaporator chamber 12 18 operates at a temperature of, for example, 44O F.
13 In accordance with another important aspect of the 14 i~vention, when the compressor 11 is operated at nighttime to replenish the cooling capacity stored in 16 the bank 31, the operating pressure of the condenser 13 17 can be reset to a relatively lower pressure and a 18 correspondingly lower temperature by conventional 19 control methods to take advantage of the ordinarily lower nighttime outdoor air temperature to which the 21 cooling tower 17 ~or the condenser 13 when no cooling 22 tower is used~ is exposed. Operation of the compressor 23 11 with this reduced condenser temperature (a drop of, .
24 for example, 25 F. from a daytime temperature of 90 ;
F. with a cooling tower or from a daytime temperature 26 of 125 F. with a dry air cooled condenser) improves 27 fuel efficiency of the prime mover compressor since 28 less energy is required to transfer heat between the 29 evaporator and condenser. The amount of power required :~
to operate the compressor on a per ton of refrigeration 31 capacity basis increases as the compressor discharge ~ :
32 pressure increases. Since the temperature at the :~
33 condenser 13 is decreased, the pressure is likewise .. :~
34 decreased. :
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.1 "-;,, ., ,~, , ', 1 It will be noted that since the evaporator is 2 held at a relatively cold temperature, for example 26 3 F., during ice-making, a sufficient temperature and 4 pressure differential will exist between the evaporator and condenser so that proper functioning of the ~ ~
6 refrigerant expansion valve 14 is ensured. During the ;
7 ice-making mode at nighttime, compressor suction 8 (inlet) pressure is substantially reduced due to a 9 depressed evaporator temperature relative to the evaporator temperature that exists during the chilled 11 water mode when the compressor is contributing directly 12 to the air conditioning load. Evaporator ~3 temperature/pressure can be controlled by monitoring 14 the compressor discharge pressure and regulating heat exchange from the condenser such as by the control of "
16 the fans serving the cooling tower or evaporator.
17 During daytime hours, the temperature of the ~;
18 condenser can be reset to a higher temperature when the 19 compressor 11 is operated.
Rejected heat from the fuel-fired prime mover 21 12 such as water jacket and exhaust heat of an internal 22 combustion engine can be used for a heat load 23 diagrammatically indicated at 41. A heat load, in the 24 form of a supply of hot water or low pressure steam is ~ ;
found, for example, in commercial and industrial 26 applications such as in restaurants, canneries, and 27 chemical processing plants. The prime mover 12 can be 28 operated to supply rejected heat through an appropriate 29 medium to the load 41 on a real time basis and the ; ;~

3~ shaft power of the prime mover 12 operating the 31 compressor 11 can be stored in the form of 32 refrigeration in the ice hank for subsequent use.
33 Cogeneration of heat energy and cooling capacity 34 affords dramatic savings in energy costs to the user.
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ZOO~; 78~
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1 Whenever substantial amounts of the rejected heat of 2 the prime mover 12 can be used on a real time basis, 3 the prime mover can be operated to build a store of 4 coo~ing capacity in the ice bank 31. The preference of generating cooling ener~y on a real time bas;s, if 6 heating ~nd cooling loads are not contemporaneous, can 7 be ignored since a 20% penalty in efficiency to use ice 8 storage is more than offset by the heat energy gain~
9 An electrical generator 42 can be selectively coupled to the shaft of the prime mover 12 by a 11 positive drive clutch. Normally, the prime mover 12 drives either the compressor 11 or the generator 42, 13 but not both. When the circuit 10 is used in a climate 14 where refrigeration-ba~ed air-conditioning i5 not required year round, for example, certain applications 16 may warrant the provision of the generator 42 and its 17 attendant controls for supplying on-site electrical 18 energy needs or for interconnection with an electrical 19 utility.
Besides the disclosed air-conditioning 21 application, other industrial and commercial 22 applications exist which can be benefited by a 23 refrigeration circuit which operates essentially the 24 ~ame as that described hereinabove. While the illustrated embodiment utilizes a brine circuit to 26 transfer heat between the evaporator 15 and cold 27 storage bank 31, the invention is applicable to other 28 systems without brine circuits, such as where the 29 evaporator is in direct heat transfer relation with the ~;
co]d storage medium. Examples of such systems include 31 ice-making apparatus where ice is formed directly on ~
32 the evaporator and, periodically, is mechanically ; ~;
33 removed or is thermally removed in a defrost-type 34 cycle.
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I The circuit 10 is particular].y suited for 2 application where th~ cooli.nq load exhibits cyclic 3 peak~ an~ t.he co]~ st.oraqe bank can su~pl~ a 4 ~u~st.anti,al portion of the enerqy required in a peak .~ cycle. A measure of a "peak" characteristi.c of an ~ appl,icati.on can be expressed in terms of desi~n cooli,nq -;~
7 load di.vided by installed mechanical refrigeration . , ~.
8 ca~acity of the ~rime mover compressor set. A typical .
9 rati,o, by way of examp].e, i9 1.6:1 with some situati.~ns exceeding 2:0:1. Where there is need for both cool,ing ~ ~, 11 and heating capacity, the disclosed circuit and method : ,:
1.2 are o~ particular advantaqe. ~.
13 Referrinq now to FIG. 2, there i~ ~hown a . :
14 ~econd embodiment of the invention. An air conditioning circuit or system 110 i.ncludes elements 16 that correspond e~sentially to elements in the,, 17 embodiment of FIG. 1 and are so designated with,.
18 identical reference numerals and operate in essentially 19 the same manner as that described above in connection with the circuit 10. The air conditioninq load at the .:, ,;
~1 site of the system 110 consists of a latent heat 22 portion and a sensible heat portion. The system 110 23 inc~udes a re~iected heat utilization ci,rcui.t 1.11. The ... ; .
2A heat utilization circuit 111 receives heat from the .~ .
fuel-fired prime mover 12 which, typically, i.s an ~.
26 int,ernal combustion enqine. The rejected heat, whi.ch 27 , i~ ~enerally the balance of the combustion h~at not 28 converted to shaft power, passes through the walls of ~;;
29 the en~ine and throuqh its exhaust. Thi.s wall, and ~, exhaust rejected heat is collected, for example, by a 31 conventional water coolinq circuit diaqrammatical].y 32 represented at 112. The total enerqy of this heat, can 33 approximate 2/3 of the fuel energy input to the engine 3A 12 (althou~h in practice onl,y 70 to 75% of thi~ heat is ~ ~00678~

1 recovered so that 50 to 55% of the total fllel energy is ~ recoverable a5 rejected heat) with the remaininq ener~y 3 being taken out as sheft power to the compressor 11 or 4 qenerator 42. The water coolinq circui,t 112 is coupled .~ with a first coil 1~3 of a de~siccant regener~tor 114. '~.
6 The enqi.ne coolinq coi.l 113 i.s i.n thermal heat exchanqe ,.
7 relation with dilute desi.ccant 116 in the de~iccant 8 reqenerator 114.
9 A desiccant storage unit 117 of the heat utilization circuit 111 contai.ns a desiccant medi~lm ~, 11 such as lithium chloride. The storage unit 117 is ,~
12 divided into two separate compartments or tanks 118, 13 119. The tank 118 holds weak or dilute li.quid '~.
~4 desiccant while the other tank 119 contains re,qenerated ~ .
1~ concentrated desiccant. The concentrated desiccant .6 contain~ less water and, therefore, has a greater ~ ,,.
17 potential for absorbing moisture from air than does 18 dilute desiccant.
19 Weak desiccant ~ollltion 116 is circulated by ,~
a pump 121 from the tank 118 throu,qh the desiccant "~.''"~
21 re~ener~tor 114, ~o that it is in heat exchan~e~ ".'' 22 re~ation with the coil 113 carrvi.ng enqine jacket wall 23 and exhaust coolant fluid. At the reqenerator 1.14, the ';~
24 desiccant 116 is exposed to 01~tside air passlnq over ,~
~5 i.t. Re,jected enqine heat i.n the reqenerator 1.1A drives '~:'',',:,"' 26 moisture from the incoming dilute desi.ccant 116 thereby ,: '',;,'",' 27 reqenerating it to a concentrated condition on i.ts way :'' '"',.''28 back to the stora~e unit 117. The regenerated,.:','' 29 desiccant is conveyed from the regenerator llA to the ,.:,,.,',:~.,.
concentrated desiccant storage compartment 119 by a ' ;,,:;,~
31 line 122. Conduits for recirculatinq desiccant or ,''',',. ~, 32 other means for conductinq heat away from the desiccant ,,-'::;'.,', 33 in the compartment 119 to the coolinq tower 1.7 is ~'.'~; ,' 34 represented by the line 120. The compartment 119 is ~ : ~

'''','"''" ;"' -- 2006~8~
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1 closed to prevent air circulation which would otherwise ;~
2 impart moisture to the desiccant stored in it.
3 A pump 123 circulates concentrated desiccant 4 from the storage compartment 119 through a coil 124 in the form of an air wash. The air wash coil is in a 6 duct 126 through which a fan 127 circulates return air 7 and/or make-up air for the space being conditioned.
8 Concentrated desiccant solution passing through the air 9 wash coil 124 absorbs moisture from the stream of air passing through the duct 126 and thereby becomes 11 diluted or weakened. This dilute or high water content 12 desiccant is carried to the storage compartment 118 13 through a line 128. The latent heat load in the form 14 of moisture content of air in the duct 126 is thus removed by the air dryer coil 116. The dried air in 16 the duct is directed through the cooling coil 38 where 17 sensible heat i9 removed. From the air cooling coil 38 18 air returns to the conditioned space.
19 The rejected heat utilization circuit means 111 increases operating efficiency by employing part of ~ ~
21 the engine combustion heat not converted into shaft ~ ;
22 power for the compressor 11 to reduce the latent heat 23 load portion of the air conditioning load. As 24 explained above, such rejected heat is used to remove ;;-~
moisture in the regeneration of desiccant and that 26 desiccant i9 subsequently used to satisfy the latent 27 heat load portion of the air conditioning demand.
28 Where the latent heat is a relatively high percentage 29 of the air conditioning load, for example, exceeding 30%, substantially all of the practically recoverable 31 rejected heat of the engine 12 can be used in meeting 32 the latent heat load. This is demonstrated by assuming 33 an engine thermal efficiency of 30%, a compressor 34 coefficient of performance of 3 to 4, and practical -- 200~

1 recoverable rejected heat of 50 to 55%. Calculations 2 show a maximum latent heat to sensible heat ratio of 3 about between 40:100 and 50:100. This ratio is a 4 preferred ratio of latent heat storage (in the form of concentrated desiccant) to sensible heat storage (in 6 the form of ice). At a given site, the size of the 7 compressor 11 related vapor compression refrigeration 8 circuitry and ice storage can be reduced accordingly 9 from that which would otherwise be required.
Operation of the system 110 is analogous to 11 that of the system of FIG. 1. Suitable controls are 12 provided for operating to the pumps 121 and 123 13 ordinarily the former whenever the engine 12 is 14 operating and the latter whenever there is a latent heat air conditioning demand. An important advantage 16 of latent heat moisture removal by the desiccant coil 17 116 of the heat utilization circuit means 111 is that 18 it allows the surfaces of the air cooling coil 38 to be 19 operated at a higher temperature than is ordinarily ~;~
re~uired. By operating the air cooling coil 38 at a ~ ;
21 somewhat elevated temperature, greater operating -~
22 efficiency is achieved. With the desiccant latent heat ~ ~, 23 removal coil 124 operating, the evaporator chilled air 24 cooling coil 38 can operate at a temperature above that ~ ~;
which is required to permit this coil to condense water 26 on its surfaces for latent heat removal. The 27 evaporator 18, in turn, can operate at a higher 28 temperature and such operation permits the compressor 29 11 to operate at increased capacity and operating ;~
efficiency because of increased refrigerant density and 31 therefore increased mass flow per revolution and 32 greater volumetric efficiency in the compressor 11.
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1 In applications where it is important to 2 reduce initial capital costs of an installation and 3 where the air conditioning load exhibits cyclic peaks, 4 e.g. a high load once a 24 hour day, the ice storage and desiccant storage allow the engine 12 and 6 compressor 11 to be downsized and operated throughout a 7 24 hour period essentially as explained hereinabove in 8 connection with the circuit of FIG. 1. The ice storage 9 unit 31 and desiccant storage unit 117 are arranged to store and deliver a sensible cooling rate and a latent 11 cooling rate, respectively, substantially equal to that 12 of the design day air conditioning load less the output 13 of the compressor and the desiccant regenerator that 14 can be produced by the engine on a real time basis~
The desiccant storage unit 117 is capable of 16 storing its moisture absorbing energy potential 17 indefinitely by virtue of being closed to free exchange 18 with circulating air. The principles of the invention 19 are adaptable to use with dry desiccants such as silica gel.
21 While the invention has been shown and 22 described with respect to particular embodiments 23 thereof, this is for the purpose of illustration rather 24 than limitation, and other variations and modifications of the specific embodiments herein shown and described 26 will be apparent to those skilled in the art all within 27 the intended spirit and scope of the invention.
28 Accordingly, the patent is not to be limited in scope 29 and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent -31 with the extent to which the progress in the art has 32 been advanced by the invention.

Claims (7)

1. An air conditioning system at a building site that has an air conditioning load including both sensible and latent heat portions, comprising a heat engine prime mover, a vapor compressor operatively connected to the engine, a refrigeration circuit operatively connected with the compressor and including a condenser, evaporator, and expansion valve, a cold storage bank in heat exchange relationship with the evaporator, a storage unit containing desiccant which absorbs moisture from air contacting it. and which is regenerated by releasing moisture to air contacting it when the desiccant is heated, means for conducting air being conditioned into contact with the desiccant, means for conducting rejected heat from the engine to desiccant contained in the storage unit to regenerate the desiccant.

2. An air conditioning system as set forth in claim 1, including means to expose air being conditioned to regenerated desiccant at a first location and means to expose said air being conditioned to a surface cooled by said evaporator at a location downstream of the flow path of said air being conditioned.

3. An air conditioning system at a building site that has an air conditioning load varying through short periods, the air conditioning load including both sensible and latent heat portions, comprising a heat engine prime mover, a vapor compressor operatively connected to the engine, a refrigeration circuit operatively connected with the compressor and including a condenser, evaporator, and expansion valve, a cold storage bank in heat exchange relationship with the evaporator, a storage unit containing desiccant which absorbs moisture from air contacting it and which is regenerated by releasing moisture to air contacting it when the desiccant is heated, means for conducting air being conditioned into contact with the desiccant, means for conducting rejected heat from the engine to desiccant contained in the storage unit to regenerate the desiccant, the cold storage bank being sized to store a sufficient quantity of cooling energy to satisfy the sensible heat air conditioning load portion of a design day less the output of the compressor produced on a real time basis with the sensible heat portion of the air conditioning load, the desiccant storage unit capacity being sized to satisfy the latent heat air conditioning load portion of a design day less the output of the desiccant regenerator produced on a real time basis with the latent heat load portion of the air conditioning load.

4. An air conditioning system at a building site that has an air conditioning load varying through short periods, the air conditioning load including both sensible and latent heat portions, comprising a heat engine prime mover, a vapor compressor operatively connected to the engine, a refrigeration circuit operatively connected with the compressor and including a condenser, evaporator, and expansion valve, a cold storage bank in heat exchange relationship with the evaporator, a storage unit containing desiccant which absorbs moisture from air contacting it and which is regenerated by releasing moisture to air contacting it when the desiccant is heated, means for conducting air being conditioned into contact with the desiccant, means for conducting rejected heat from the engine to desiccant contained in the storage unit to regenerate the desiccant, the latent heat absorbing capacity of the desiccant storage unit being in a ratio of about between 40:100 and 50:100 to the sensible heat absorbing capacity of the cold storage bank.

5. A method of conditioning air at a site comprising operating a heat engine to drive a vapor compressor in a refrigeration system including an evaporator and a condenser, exposing desiccant to heat rejected from the engine to regenerate the desiccant, exposing air being conditioned to the regenerated desiccant, and to a coil cooled by said evaporator.

6. A method as set forth in claim 5, wherein a cold bank is provided to store refrigeration energy made by the compressor and a desiccant storage unit is provided to store heat energy rejected by the engine during compressor operation to make refrigeration energy for storage in said cold bank.

7. A method as set forth in claim 5, wherein the desiccant is exposed to a stream of air being conditioned prior to exposure to the evaporator coil.