CA1079511A - Composition for absorption heating - Google Patents

Abstract

INVENTION: COMPOSITION FOR ABSORPTION HEATING
INVENTOR: CHIEN C. LI
ABSTRACT OF THE INVENTION

The invention comprises absorption pair compositions consisting essentially of selected two carbon fluorocarbon solutes dissolved in selected furan ring absorbents. These absorption pair compositions are useful in methods of absorption refrigera-tion, cooling and heating and particularly in an absorption heat pump.

Description

5J~
This invention relates to novel absorption pairs for absorption heating and cooling.
In view of diminishing fossil fuel supplies, and hence, increasing fuel costs, there is a need to minimize the amount of fuel society consumes to heat habitable space.
The heat pump concept, wherein available energy is taken from an ambient source such as outside air, and combined with fuel energy to heat space, is not new. Existing concepts include elec-trically driven-vapor compression heat pumps and absorption heat pumps. The latter require an absorption pair which comprises a solvent and a solute wherein the solvent remains a liquid, which may be a solution, throughout the operation of the apparatus, and the solute having a liquid and vapor phase in the cycles of the operation. The solute must be soluble in the solvent and must be readily separable as a vapor from the solvent by means of evapora-tion. In addition, the solute must be suitable for condensation from the vapor back to a liquid form. In general, all absorptlon heating apparatus require essentially the same parts and function in essentially the same way regardless of the particular solute and solvent used. Nevertheless, heat pumps as disclosed in U.S. patents 4,106,309, 4,127,009, 4,127,010 and 4,127,993 of B.A. Phillips are preferred. The major components of the apparatus are a generator, condenser, evaporator, absorber and absorption pair (also called absorber pair). The solute passes "
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.. ~

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through all units and the solvent, sometimes also known as the absorbent, is confined to movement through the generator and absorber, In operation, a mixture of absorbent and solute is heated in the generator to boil of~ most of all of the solute which rises as a vapor through a connecting conduit to the condenser.
The mixture may be heated in the generator by any suitable means such as a gas flame, geothermal heat, solar heat or warm water.
The generator and condenser operate at relatively high pressure, so the condensing temperature of the solute is suffi-ciently high to permit rejecting ~he latent heat emitted by the condensing solute to outside air or cooling water passing through or around the condenser.
The liquid solute leaving the condenser passes through a conduit to a throttling valve (or its equivalent), through the throttling valve and through another conduit to the evaporator.
- The throttling valve throttles the liquid solute to a lower pressure so it will boil at a relatively low temperature in the , .
evaporator and thus absorb heat from air or water passing through `
20 or around the evaporator. ;
The vaporized solute passes from the evaporator through a conduit to the absorber where heat of mixing is emitted (pre ferably to cooling water passing therethrough) as it is dissolved i' n cool absorbent which has been carried to the absorber by means of a conduit connecting the absorber with a generator outlet. The mixture of absorbent and solute resulting in the absorber then passes through a conduit to the generator where it is reheated to ;~ ~ contln~ue the process.
Any suitable material of construction for the apparatus may be used which can withstand the encountered temperature, ; pressure and corrosive properties, if any, of the solvent and

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solute. Such a heat ahsorption apparatus is particularly desir-able since moving parts, if any, are minimal when compared with the moving parts found in electrically driven-vapor compression heat pumps.
Unfortunately, the known solute/solvent systems for heat pumps have serious disadvantages. The most common solute/solvent pair (absorber or absorption pair) is ammonia/water. The ammonia/
water pair has a disadvantage since the heating efficiency of appa-ratus utilizing the ammonia/water absorber pair is not as high as desired; i.e. the coefficient of performance (COP) practically attainable is generally less than about 1.30 and at low generator temperature, i.e., below 180F., and at high generator temperatures, i~e. 220F., is generally below about 1.40. COP is a measure of the efficiency of the absorption cycle and is the ratio of the heat output to the energy input. The ammonia/water combination has additional disadvantages. Water is highly volatile, thus pre-venting complete separation of the ammonia from the water in the generator at high generator tempeatures. The condensing pressure required to condense the ammonia is undesirably high, thus requir-ing equipment capable of withstanding such pressure.
The only other presently commercial absorber pair iswater/lithium bromide wherein water is used as the solute and lithium bromide is used as the absorbent. The water/lithium bro-mide absorber pair (and the related water/lithium chloride absorb-er pair) has undesirable characteristics. For example, water as a ;
solute is limited to an evaporation temperature of above about 32F., which is its freeæing point. Lithium bromide is not suffi-ciently soluble in water to permit the absorber to be air cooled. `~
The extremely low pressures in the system require large vapor con-~duits~ Unless the system is preclsely controlled, lithium bromide can crystallize and cause fouling of the system and the generator

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temperature cannot efficiently operate below 180F. nor above 215F. Additionally, aqueous lithium bromide solutions are corro-sive, thus requiring special inhibitors and alloys for suitable apparatus.
Other absorber pairs which have been suggested have not been commercially accepted due to one or more disadvantages. Such disadvantages include a lack of sufficient affinity of the absor-bent for the solute vapor, thus preventing sufficient absorption of the solute vapor to draw in and compress the so!ute. The absorber pairs have frequently not been mutually soluble over the whole range of operating conditions, thus permitting crystalliza-; tion and the formation of solid articles which make it difficult ; or impossible for proper fluid circulation. The absorbent has frequently been too volatile, thus preventing the refrigerant vapor leaving the generator to be adequately purified. When absorbent evaporates from the generator, the efficiency of the system is fre-quently substantially reduced since energy input is wasted in evap-oration. Additionall~, the absorbent pairs previously suggested are frequently unstable, cause corrosion of the apparatus, are toxic or are highly flammable, Absorption pairs suggested in the prior art frequently have unacceptably high or unacceptably low working pressures. The working pressures should be as near to atmospheric pressure as possible to minimize equipment weight and minimize leaking into or out of the system. In addition, pressure difference between the high side and low side is frequently too high to facilitate circulation of the solution. The solutes sug gested in the prior art frequently have a latent heat o~ evapora-tion which is unacceptably low~ thus requiring large quantities of fluids to be circulated and the coefficient of performance of other absorber pairs suggested in ~he prior art is usually too low for serious consideration in commercial apparatus.

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Some ab~orber pairs including a halogenated hydrocarbon solute (refrigerant) and an organic absorbent have been explored over the years for absorption refrigeration. Al~hough certain specific absorber pairs wherein the absorbent included a furan-type ring had been proposed in U.S. Patent No. 2,0A0~902 as a part of a program exploring numerous potential absorber pairs, no further discussion of furan-type absorbents has app~ared in the art. Instead~ subsequent exploratory work with organic absorbents has concentrated on acyclic glycol ethers and particularly on DMETEG (dimethoxytetraethylene glycol) and the ethyl ether of di-ethylene glycol acetate. More recently, and until the present invention, exploratory work on organic absorbents for halogenated hydrocarbon refrigerants has apparently lain dormant.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with this invention, there is provided novel absorber pairs for absorption heating and reErigeration which have high coefficients of performance, have good stability, ~ -cause little corrosionl have relatively high flash points, operate at approximately atmospheric pressure and have relatively low toxicity. The high coefficient of performance is due to a strong affinity between the solute and solvent, good mutual solubility at absorber conditions and ease of separation at generator condi-tions, good absorbent vola~ility and a solute having a high latent heat of vaporization~
The new and useful compositions of matter of the inven-tion comprises from about 4 to about 60 weight percent of a lower alkyl fluorocarbon selected from the group consisting of dichloro-trifluoroethane, monochlorotrifluoroethane, Monochlorotetrafluoro-ethane and mixtures thereof dissolved in about 40 to about 96 weight percent of a furan ring containing compound having a boil-ing point between about 140C and 250C and being of the formula:

.

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~o ( R~ ( Rl ) 2 1 ~(Rl )a wherein Rl is independently at each occurrence H; lower alkyl;
lower alkoxy; phenyl; lower alkylene phenyl; hydroxy containing lower alkyl; lower al~.yl carboxy; alkoxy alkyl of from 2 through ; 6 carbon atoms; lower alkylene carboxylate of from 2 through 6 carbon atoms; fluorine or chlorine; a is independently at each occurrence an integer of 1 or 2; and Z is a single or double bond;
provided that, when Z is a single bond, a is 2, when Z is a double bond, a is 1, and provided that the compound contains at least one Rl group having an oxygen atom which has a single bond to a carbon atom. Three of the above compositions contain double bonded oxygen atoms, and, while being acceptable compositions for use in the invention under the generic disclosure, are not preferred due to increased instability resulting from the double bonded oxygen atom. It has now been found that these compositions are unex-pectedly highly efficient in a method and apparatus for absorption heating.
Some preferred compositions comprise from about 4 to about 60 weight percent of a lower alkyl fluorocarbon selected from the group consisting of dichlorotrifluoroethanet monochloro-trifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in a furan ring containing solvent selected from methyl-tetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether, propyl-tetrahydrofurfuryl ether~ n-butyl tetrahydrofurfuryl ether and methyl-2,5-dihydro,2,5-dimethoxy-2-furan carboxylate based on the total weight of solution.
i ~ ~ DETAILED DESCRIPTION OF THE IN~ENTION
In general, in accordance with this invention, the sol-vent used in the absorption pair is an assymetrical furan ring . .
' - - . . - .: . . .:............... : . :

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containing c~mpound having a boiling point between about 140 and 250C. The compound has the general formula ( 1)2~ 1 ( 1)2 (Rl)a¦ æ _ I (Rl)a wherein Rl, a and Z are as previously deined and the compound contains at least one Rl group having an oxygen atom which has a single bond to a carbon atom.
Lower alkyl, lower alkoxy, lower alkyl carboxy, or lower alkylene as used herein means alkyl, alkoxy or alkylene of from 1 through 5 carbon atoms. Examples of lower alkyl groups are -CH2CH3;
-CH3; ICH3 ; and -CH2CH2C~3--f -CH3 Example~ of lower alkoxy groups are -OCH3; -OCH2CH3 and -OCH

Phenyl groups are those groups containing a phenyl ring which is unsubstituted or substituted with methyl, ethyl, hydroxy, methoxy, ethoxy, methyl methoxy, fluorine or chlorine. Examples of phenyl groups are ; ~ - Od;

CH CH
~ 2 3 - ~ CH3 ; ~ and ~ Cl ^

Lower alkylene phenyl groups are phenyl groups connected '-to the furan ring by a lower alkylene groupO Examples of such .
30 groups are ... . "

. ~ . , . .. . - ,, ., : .

5~

-CH2 ~ and -CN2CH2_ ~ _CH3 Examples of hydroxy containing lower alkyl groups are -CH2OH; -CH2CH2OH and -C-CH2.
O O
H H
Examples of lower alkyl carboxy groups are -COOH;
-CH2COOH and -CH2CH2COOH.
Examples of alkoxy alkyl groups, i.e., those containing 2 to 6 carbon atoms, are -CH2OCH3; -CH2OCH2CH3; -CH2OCH2CH2CH3;
-CH2OCH2C~2CH2CH3 and CH2CH2OCH3. Preferred alkoxy alkyl groups are those containing either 5 or 6 carbon atoms due to higher effi-ciency at high generator temprature and due to increased stability, those alkoxy alkyl groups wherein the intermediate alkyl portion, i.e. that portion attached to the furan ring contains 2 or 3 car-; bon atoms. When the intermediate alkyl group is ethyl the furan ring compound unexpectedly exhibits improved solutility for the fluorocarbon.
Examples of lower alkylene carboxylate groups, i.e., those containing 2 to 6 carbon atoms, are -CH2-COOCH3; CH3 -CH2-cH2-C~3.

It is theorized that the boiling point of the simple furan ring is increased by adding an alkyl or an alkoxy gro~p to the furan ring to form an assymetrical mclecule. The added group should preferably permit an lncrease in the negative charge on the furan ring oxygen atom.
The furan ring containing compounds employed in the present invention are usually characterized by high flash points which reduce the flame hazard when they are used.
Assymetrical as used in relation to the furan ring con-.
:

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taining compound means either that at least one of the Rl groupsat the 2 position on the fural ring is different from both of the Rl groups at the 5 position or at least one of the Rl groups at the 3 position is different from both of the Rl groups at the 4 position. In the preferred furan ring compounds, at least one of the Rl groups at the 2 position is different from both of the R
groups at the 5 position.
Alkyl as used above means an aliphatic hydrocarbon radical in which the hydrogens may be wholly or partially substi-tuted by fluorine or chlorine.
The compound should preferably contain at least one Rl group having an oxygen atom which is bonded on one side to a carbon atom or a hydrogen atom. At high generator temperatures, carboxy groups, particularly free rather than esterified carboxy groups, should be avoided since such groups tend to increase the corrosive-ness of the compound and tend to decompose more rapidly than other groups. Carboxy groups arer however, suitable for compounds which will he used at low generator temperatures, i.e., below 225F.
The more preferred Rl groups are those containing an alcohol or ether oxygen atom.
The Eoregoing furan ring containing compounds may be . j, .,." . .
prepared by known procedures. Detailed discussions of the chemis-try of furan and its derivatives are found in Chapter 4 of Heterocyclic Compounds Volume I, edited by Robert C. Elderfield, WiIey and Sons, INc., 1950 and at pages 377 through 490 of Advances in Heterocyclic Chemistry Volume 7, edited by A. R.
Katritzky and A. J. Boulton, Academic Press 1966.
A general method for preparation of furan ring contain-ing~compounds which are suitable for use in accordance with this -invention is as follows:
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aldose + H2CRl ZnC12 O=CRl H2,Rhodium-~ Platinum RlJ Oxide Rl R2 ~ (cooH)3cH2oH EthanolR2 ~ (CHOH)3CH2oH

Where Rl is independently at each occurrence any group as pre-viously deEined. Rl may be carhonyl or carboxy; however, these groups will he reduced to alcohol groups upon hydrogenation. Such reduced groups may, however, be subsequently oxidized to a carbonyl or carboxyl group with a strong oxidizing agent such as KMnO4, lead acetate or HIO4.
Another general method for the preparat.ion of furan ring containing compounds which are suitable for use in accordance with this invention is ~y ring formation from the enol form of a 1-4 ~
carbonyl compound. .:
Rl ~ - ~ Rl 1 ll ~ 1 :

Rl C - C Rl H2S4 Rl ~ 1 Rhodium ~ 1 ;.
: Rl Ç Rl ZnC12~ l l Pt oxid~
O O Rl \~ ~ Rl ethanol R
enol Again, Rl may be.any group as previously defined; however, since carbonyl and carboxyl groups may be reduced during hydrogenation such groups are generally preferably obtained by utilizing a suit-able~hydroxy alkyl (alkanol) group and oxidizing the hydroxy alkyl , :
:~ group to~the desired carbonyl or ~arboxyl group subsequent to ; 30 hydrogenation.

: Some specific suitable furan ring containing compounds :.

'' 95~1 and their methods of preparation are as follows: A suitable cata-lyst for reduction of the furan ring to the tetrahydrofuran ring is a platinum oxide-rhodium catalyst.
II I

__ ~
~_~ ~ ¦ furfural 2H ~ CHO

w2ate ~ :
1. -tetrahydrofurfuryl alcohol Pentose III IV ;

H2, catalyst r-~~~~~~
~ 1 ` ethanol ~ ~ -furfural 2. -tetrahydrofurfuryl ~ ~ ,.
a lcohol . dimethyl formamide :~

VI V ::
! I Li ~ ~ ~ I
''~'' lithium ~ :;~

. Butadiene ~ ' H2O 2 ai ~
.~ / Manganous VII~ VIII ~! Molybdate .
r _ HgC1 HgC12 . _ O ~ < Na~c ..

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IX

.. _ _ ~ OH
II + ClH2CCH2CH2CH3 ~ 2CH2cH2cH2cH3 n-butyl chloride 3. l-n-butyl tetrahydrofurfuryl ether This compound, which is especially preferred, exhibits properties, when used in absorption pairs, which are unexpected over the prior art ethyl homolog. Prior to this invention, there 10 existed no reason to expect the butyl compound to be so much more :~
efficient in an absorption pair than the ethyl compound of the prior art.
~V XIV
~ ¦ dilute NOH2C ~ < 2 HH2C ~ CN2~

4~ 2-chloromethyl-5- -hydroxymethyl tetra- H
hydrofuran catalyst ethanol XII XIII

,_____~ dilute : HCl ~ ~

KOOC ~ COOK HOOC V COOH

, cdI2 . .

XI dilute ~ Ag2O
n ROH l l I

30~ COOK V COOH

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XVI I I XVI I XVI
r~ dilute r~ ~ dilute ¦ ¦ ~ HCl ~ NaOH
HOOC ~ ~ CH2H NaOO V CH2H HOOC V CH2Cl 5. 2-hydroxymethyl-5-carboxy ~ RMnO4 tetrahydrofuran XV
XX XIX
r~
3 ~ ~ CH2OH EtOH H3C ~ ~ CHO

10 6. 5-methyl-2-methylol \ water tetrahydrofuran methyl pentose ~:
XXII XXI
H3CO _~ M uil C3 coocH

COOCH
7. 2~5-dihydro-2,5-dimethoxy 2~furan methyl carboxylate CH3COCl . ..
VIII ~ ~ r :
~ ¦ HgCl \
XXIV XXIII

CH2CH2CH2OH ethanol ~ f H=CHCOOH

~ CH3COONa . (CH3CO)2O .
9, 2-n-propylol tetrahydrofuran ~:

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XXV
BrH2CCH3 ¦ ¦ < -- - XXIV

9. 2-n-propyl ethoxy tetrahydrofuran H / CH3 H ~ CH3 /~ . XXVI / XXVII

st 3 H2 ethanol 1¦ l C COH ~ _----~H2CH
H 2 ~
10. 2 e~hylol-4-isopropyl tetrahydrofuran ~ ~ ;
I AlCl : CH3NO2 H

\ ~ ;' XXXI XXX XXIX XXVIII
Zn,CH3COOH (CH3CO')20 H20 _ 1 -H o : ~ ~ 2 ~ 1CH=CHNO2 ~ ~ ~ CH2CH=NOH ~ CH2CN ~ H2COOH

.
Examples of other suitable furan ring containing com-pounds whlch can be prepared in accordance with known methods are: .
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~_____~ 3 2-methoxymethyl 3~methyl tetrahydrofuran \ O / 2 3 F - ~:
2-methoxy-3-fluoro tetrahydrofuran , OCH3 ~ :.
1 0 ,; .
Cl 2-methoxy n-butyl-3-chloro tetrahydrofuran ~b/ CH2CH2CH2CH20CH3 .

_ . :.r. ,., . ~ .
~ ~ OCH2CH2CH2CE 2CH3 2-methylol-3-n-pentoxy tetrahydrofuran ~ ~ CH20H
~'0~ :

' ' ; ~ . ' '~ : ~
. . - H H
O O 2-~3,5-hydroxy n-pentyl]
tetrahydrofuran ~ ' ' : :
. : .
., , : . ., 30 :
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COOH
tetrahydro-3-carboxy-2-furan methyl acetate , ~f CH2COOCH3 HOOC
CH3 2 [3,3-dimethyl propyll-4-carboxytetrahydrofuran \ / C~2CH2CH
10 ~ CH3 H3C ~ COOH
2,3-dicarboxy-4-methyl ~ tetrahydrofuran -. ~ COOH
.. ' .
, .
. .
¦ 3 1 tetrahydro-3-trifluoro-: I methyl-2-n-pentanoic acid ~ CH2 2 2 2 :
.

:
. _. l ' ',''.' 2-methylol-4-phenyl ¦ ; tetrahydrofuran : .
~ 30 . .~ , . .
~ -16~
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,~
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H
HOH2C CH C~ CH C~
¦ 2 2 2H \;==/ 3-[4-phenyl butylene]-4-¦ methyloltetrahydrofuran : , / CH2CH2COCH2CH3 tetrahydro~2-furan ethyl propionate The solute used in the absorption pair is a fluori-nated ethyl group. The group preferably con~ains at least one hydrogen atom (and more preferably one only) and at least one chlorine atom and is assymetrical. It is believed that when fluo-rine and chlorine share the same carbon with hydrogen, the fluorine makes the chlorine less negative. Therefore the hydrogen atom be-comes easily stretched once it "sees" to electron donor oxygen of ~` the solvent. This hydrogen bonding force makes the primary contri-bution to the high solubility of the halogenated methane or ethane in the solvent.
For the halogenated ethanes, either or any isomer of the named compounds can be used, but the preferred isomers are C~C12CF3, CHClFCF2Cl, CH2ClCF3, CHClFCHF2 and CHClFCF3. Among the mixtures, CE~ClFCF3 together with CH2ClCF3 (or with CHClFCHF2) is preferred.
The preferred absorption pairs of the invention comprise a fluorocarbon selected from the group consisting of dichlorotri- -~ fluoroethane, monochlorotrifluoroethane, monochlorotetrafluoro-!
ethane and mixtures thereof, dissolved in a furan ring containing ~ solvent selected from 2-methyl-tetrahydrofurfuryl ether, 2-ethyl `~ tetrahydrofurfuryl ether,~2-propyl tetrahydrofurfuryl ether, 2-butyl tetrahydrofurfuryl ether and methyl 2,5-dihydro-2,5-di- -~
methoxy-2-furan carboxylate.

Many of these absorption pairs unexpectedly have very . .
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~C17~S~Ll high efficiency at high generator temperatures, such as when the solvent is n-butyl tetrahydrofurfuryl ether.
In many preferred forms the fluorocarbon is selected from dichlorotrifluoroethane, monochlorotetrafluoroethane, mono-chlorotetrafluoroethane and mixtures thereof. For such halogenated ethanes, it is preferred that the furan compound be Ll CH20R
with R being alkyl having 1-4 carbons, preferably ethyl, n-propyl, i-propyl, n-butyl or i-butyl and most preferably ethyl or n-butyl.
Other preferred compositions have as absorbent ~--7 H3CO ~ ~ OCH3 and as refrigerant dichlorotrifluoroethane, monochlorotrifluoro-ethane, monochlorotetrafluoroethane or mixtures thereof, with dichlorotrifluoroethane, monochlorotrifluoroethane or mixtures thereof being more preferred.
Similarly, the system employing ammonia as the solute and water as the solvent cannot be operated at either high gener-ator temperatures or at low generator temperatures and the maximum COP practically obtainable with the ammonia and water system at any generator tempeature is about 1.5.
Those absorption pairs wherein the solvent is methyl 2,5-dihydro-2,5-dimethoxy-2-furan carboxylate can be used at high generator temperatures but only at low COP values; however, those ~-pairs wherein the solvent is the carboxylate, unexpectedly have hlgher COP values at low generator temperatures than any other known absorption pair.
The preferred absorption pair composition when the 2,5-.

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dihydro 2,5-dimethoxy-2-furan carboxylate absorbent is used is from about 10 to about 60 weight percent fluorocarbon.
When methyl 2,5-dihydro-2,5-dimethoxy-2-furan carboxy-late is used, the preferred temperature to which the solution is heated in the generator is preferably between about 150 and 300F.
and most preferably between about 160 and about 210F. SuCh low generator temperatures are particularly suitable for low tempera-ture heat sources such as solar energy.
In general, all of the fore~oing fluorocarbon solutes have been found to be suitable solutes over a broad range of generator temperatures for the release of solute. Acceptable generator temperatures for use with these fluorocarbons range from about 150F to about 425F.
The higher generator temperatures, i.e., from about 250 to about 425F. result in higher COP's. Highest temperatures generally result in undesirable decomposition. The most preferred generator temperature to retain high COP's and low decomposition is from about 30Q to about 350F. The lower generator tempera-tures are used when low temperature heat sources such as solar heat are to be used to heat the generator.
The temperature at which the absorption of the solute into the solvent occurs is preferably from about 90 to about 130F. A large percentage of the heat released in absorption heating occurs when heat of mixing is released during absorption of the solute by the solvent and the heat of mixing released is higher at a lower absorption temperature. The temperature of the ` absorption is; however, limited by the temperature of the area to be heated since the absorber provides heat to, and is cooled at the temperature of, such area.
The absorption heating apparatus o the invention, as previously discussed, comprises known absorption heating apparatus components in conjunction with the absorption pairs disclosed for use in the novel absorption heating method.

Calculations were made for absorption cycles of 40F
evaporator temperature, 120F. condensing temperature and 110F
absorber temperature. The latter temperature is the minimum absorber temperature which corresponds to a maximum reErigerant concentration in the rich solution. These values are representa-tive of most air conditioning conditions and moderate heating conditions. The thermodynamic advantages to be gained by heat exchange between different pathways as described in U.S. Patent 4,127,010, referenced above, have been disregarded, except for liquid hea~ exchange between the rich and weak solutions passing between the absorber and generator. Pure refrigerant refrigerant has been assumed in the condenser and evaporator.
The COP values were obtained by assuming a 40F evap-orator, a 120F condenser temperature and a 110F absorber temperature. Saturated amounts of refrigerant in absorbent at the absorber temperature (110F) and the generator temperature (250, 300, 350 or 400F) were determined experimentally. From the known heats of vaporization of the pure refrigerant, a reErigerant flow rate was determined necessary to produce 12,000 BTU/hour of cooling (1 ton of refrigeration) in the evaporator. Solution flow rates necessary to conduct that quantity of refrigerant to the higher pressure were then calculated. The mass flow rate from the ; generator to the absorber was calculated from the other flow rates.
A temperature differential of 10F was assumed for a heat exchanger such that the heat loss of the weak liquid from the ~enerator tem-perature down to 120 (10F above the absorber temperature) was assumed to have been used to heat the rich liquid from the ::

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absorber temperature of 110Fo The remaining heat required to raise the rich liquid to the generator temperature and to vaporize the required amount of refrigerant was therefore calculated as the generator heat imput.
In the above calculations, for heating of solutions, it was assumed that the heat quantities for solutions would be the sum of the heat quantities for refrigerant and for absorbent. Thus if a first quan~ity of pure refrigerant released 344 BTU by cool-ing from the generator temperature to 120F and a second quantity of pure absorbent released 23,555 BTU by cooling from the generator temperature to 120F, then it was assumed that a weak liquid having the first quan~ity of refrigerant and the second quantity of absor-bent would release 23,89~ BTU in the heat exchanger. That 23,899 BTU was apportioned between the refrigerant and absorbent of the rich liquid to determine how hot the rich liquid would be after being preheated in the heat exchanger.
The COP cooling values were calculated as 12,000 BTU
divided by the sum of the three heat input components at the generator; the amount required to heat the absorbent from the heat exchanger temperature to the generator temperature, the amount required to heat the refrigerant from the heat exchanger tempera-ture to the generator temperature and the amount required to vaporize the refrigerant~ The relatively small amount of work re-~ quired to pump the rich solution from the low absorber pressure to ; the high generator pressure was disregarded.
Since the above COP value represents a ratio betweenheat inputs at the generator and evaporator, a COP heating value can be calculated as 1 ~ COP cooling. This calculation assumes ,.
that all of the heat inputs at the generator and evaporator trans- ;

lates into heat output at the absorber and condenser whlch can be put to use. The COP value representing the ratio of heat input to ,; . .

. .

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the evaporator/heat input to the generator is also called COP .
This number plus one would be the COPH or total heat output of the system/heat input to the generator. It will be appreciated that the total heat output includes condenser and absorber heat output.
Energy consumption by solution and coolant pumps have been ignored.
Table 1 Flow Rates~ Solution Concentrations and COP Values For One Ton of Refrigeration At 40 Evaporator Pressure, 120F. Condenser Temperature, 110Absorber _ Tem~erature Using ETFE As Absorbent Concen- Concen-Mass Mass tration tration Flow Flow Rich Weak Rich Refri- Liquor Liquor Generator Liquor gerant (Wt. % (Wt. %
ExampleTemp. (lb/hr~ (lb/hr) R124 ? R124) COP

1 400 549 250.7 50 8.0 0.499*
2 350 614 250.7 50 15.5 0.573*
3 300 713 250.7 50 22.9 0.436 4 250 104g 250.7 50 34.3 0.412 Wt. % R123 Wt.% R123 400 383 183.8 48 0 0.480

6 350 39~ 183.8 48 2.5 0.527

7 300 449 183.8 48 12.0 0.562

8 250 650 183O8 48 27.5 0.558 Wt. % R21 Wt.% R21

9 400 348 1~4 43 3.0 00546 350 386 144 43 9.0 ~.571 11 300 473 144 43 18.0 0.596 12 250 731 144 43 2g.0 0.566 *These calculated values are uncertain because the pure refrig-erant would be superheated rather than liquid at the hot end o - the heat exchanger.
With proper design, CPC values over .65 have been achieved for ~21/ETFE at a 300F generator temperature. Similar results may be obtainable with R124 at a 350F generator tempera-ture and with R123 at a 300F generator temperature. Similar results may be obtainable for the following absorption pairs at the following generator temperatures:
:

- - . . . , : ~ ~

1C~795~3L
Generator Temperatures 13*R124/nBTFE 350F
14* " 400E' 16* " 350F

18* " 300F
19* " 350F
20* R21/nBTFE 350F

10 21* " 400F

23* " 300F
24* " 35dF
25 R133a/ETFE 250F
26 " 300F
27* " 350F

29 1l . 300F
30R123 ~50 Wt.%~
R124 (50 wt. %)/ETFE 300F
20 31R133 (50 wt. %), R133a ~50 Wt. %)/ETFE 300F
; 32R123 (50 Wt. %), R133 or 133a (50 Wt. %)/ETFE 300F
33R21 (S0 Wt. %), R124 (S0 Wt. %)/ETFE 300F
R133 = CF2HCHClF, R133a - CF3CH2Cl, R124 =3CF CHClF, R123 = CF3CHC12 (R123a = CF2ClCHClE' may also be used), R21 = CHC12F, ETFE = ethyltetrahydrofurfuryl ether, nBTFE =
n-butyl tetrahydrofurfuryl ether. The starred examples represent compositions that may be unstable at the indicated generator tem-peratures. For long-term operation, such compositions particularly should be stabilized as provided in U.S. Patent 4,072,027 of Berenbaum et. al..

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Claims (10)

I claim:

1. A composition of matter comprising from about 4 to about 60 weight percent of a lower alkyl fluorocarbon selected from the group consisting of dichlorotrifluoroethane, monochloro-trifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in about 40 to 96 weight percent of an assymetrical furan ring containing compound, said compound having a boiling point between about 140°C and 250°C and the generic formula:

wherein R1 is independently at each occurrence H; lower alkyl;
lower alkoxy; phenyl; lower alkylene phenyl; hydroxy containing lower alkyl; lower alkyl carboxy; alkoxy alkyl of from 2 through 6 carbon atoms; lower alkylene carboxylate of from 2 through 6 carbon atoms; fluorine or chlorine; a is independently at each occurrence an integer of 1 or 2; and Z is a single or double bond;
provided that, when Z is a single bond, a is 2, when Z is a double bond, a is 1, and provided that the compound contains at least one R1 group having an oxygen atom which has a single bond to a carbon atom.

2. A composition of matter in accordance with claim 1 which comprises from about 4 to about 60 percent of a lower alkyl fluorocarbon selected from the group consisting of monochlorotri-fluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in about 40 to 96 weight percent of a furan ring con-taining solvent compound selected from the group consisting of methyltetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether, propyl tetrahydrofurfuryl ether, n-butyl tetrahydrofurfuryl ether and methyl-2,5-dimethoxy-2-furan carboxylate.

3. A composition of matter in accordance with claim 1 wherein said assymetrical furan ring containing compound is of the formula where R is alkyl having 1-4 carbons.

4. A composition of matter in accordance with claim 3 wherein R is ethyl.

5. A composition of matter in accordance with claim 3 wherein R is n-butyl.

6. A composition of matter in accordance with claim 1 wherein said assymetrical furan ring containing compound is of the formula

7. A composition of matter in accordance with claim 1 wherein said fluorocarbon is selected from the group consisting of CHC12CF3, CHC1FCF2C1, CH2C1CF3, CHC1FCHF2, CHC1FCF3 and mixtures thereof.

8. A composition of matter in accordance with claim 1 wherein said fluorocarbon is monochlorotrifluoroethane.

9. A composition of matter in accordance with claim 4 wherein said fluorocarbon is monochlorotrifluoroethane.
10. A method of absorption heating which comprises an area to be heated by absorbing a fluorocarbon in an asymmetrical furan derivative to form the composition of claim 1, heating the

Claim 10 continued resultant solution to release said fluorocarbon in the vicinity of the area to be heated to form liquid fluorocarbon, evaporating the liquid fluorocarbon at a location removed from the vicinity of the area to be heated and returning the evaporated fluorocarbon to the vicinity of the area to be heated for reabsorption into said solvent furan derivative.