GB1592939A

GB1592939A - Compositions for absorption heating

Info

Publication number: GB1592939A
Application number: GB22044/78A
Authority: GB
Original assignee: Allied Chemical Corp
Current assignee: Honeywell International Inc
Priority date: 1977-07-22
Filing date: 1978-05-24
Publication date: 1981-07-15
Also published as: NL7807590A; IT1159682B; CA1079511A; FR2398101A2; IT7868148A0; SE7806195L; DE2832237A1; JPS5423085A

Description

(54) COMPOSITION FOR ABSORPTION HEATING (71) We, ALLIED CHEMICAL CORPORATION, a Corporation organized and existing under the laws of the State of New York, United States of America, of Columbia Road and Park Avenue, Morris Township, Morris County, New Jersey 07960, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to novel absorption pairs for absorption heating and cooling. The invention is a modification of that disclosed in our co-pending Application No. 14586/76, (Serial No. 1539287) and published in United States Patent No. 4,005,584.

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 electrically 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 evaporation. In addition, the solute must be suitable for condensation from the vapor back to a liquid form.In general, all absorption 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 our U.S. Patents No's. 4,127,010, 4,106,309, 4,127,993 and 4,127,009 are preferred. The major components of the apparatus are a generator, condenser, evaporator, absorber and absorption pair (also called absorber pair).

The solute passes 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 off 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 sufficiently high to permit rejecting the 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 or around the evaporator.

The vaporized solute passes from the evaporator through a conduit to the absorber where heat of mixing is emitted (preferably to cooling water passing therethrough) as it is dissolved in 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 continue 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 solute. Such a heat absorption apparatus is particularly desirable since moving parts, if any, are minimal when compared with the moving parts found in electrically driven-vapor compression heat pumps.

Many 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 apparatus 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 1800F., and at high generator temperatures, i.e. 220"F., 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 preventing complete separation of the ammonia from the water in the generator at high generator temperatures. The condensing pressure required to condense the ammonia is undesirably high, thus requiring equipment capable of withstanding such pressure.

Another presently available absorber pair is water/lithium bromide wherein water is used as the solute and lithium bromide is used as the absorbent. The water/lithium bromide absorber pair (and the related water/lithium chloride absorber pair) has undesirable characteristics. For example, water as a solute is limited to an evaporation temperature of above about 32"F., which is its freezing point. Lithium bromide is not sufficiently soluble in water to permit the absorber to be air cooled. The extremely low pressures in the system require large vapor conduits.Unless the system is precisely controlled, lithium bromide can crystallize and cause fouling of the system and the generator temperature cannot efficiently operate below 180 0F. nor above 215 F. Additionally, aqueous lithium bromide solutions are corrosive, thus requiring special inhibitors and alloys for suitable apparatus.

Some absorber pairs including a halogenated hydrocarbon solute (refrigerant) and an organic absorbent have been explored over the years for absorption refrigeration; and certain specific absorber pairs wherein the absorbent included a furan-type ring had been proposed in U.S. Patent No. 2,040,902 as a part of a program exploring numerous potential absorber pairs.

According to our co-pending Application No. 14586/76, (Serial No. 1539287) there is provided a method of absorption heating with an absorption pair, in which the absorption pair comprises (a) as solute, at least one of four defined halomethanes and (b) as solvent, a defined furan compound. The present invention provides an absorption pair which comprises (a) as solute, at least one of three defined halo-ethanes and (b) as solvent, the same furan as in our copending application.Thus there is provided, according to the present invention, a mixture which comprises from 4 to 60 weight percent of a lower alkyl fluorocarbon selected from dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in 40 to 96 weight percent of a furan ring-containing compound having a boiling point between 140"C. and 250"C. and being of the formula set out below.

In our co-pending Application No. 2125/78 (Serial No. 1586009) and U.S. Patent 4,072,027 we claim a stabilized heat absorption composition which comprises (a) as refrigerant a fluorocarbon which may be a halomethane as disclosed in our Application 14586/76 (Serial No. 1539287) or a halo-ethane as disclosed for the present invention; (b) as solvent, a furan as disclosed in our Application 14586/76 (Serial No. 1539287) and also for the present invention; and (c) as stabilizer, a phosphite of defined formula.

The present invention does not include compositions comprising a halo-ethane as refrigerant and a furan as solvent, when the composition includes also a phosphite as stabilizer. The preferred compositions of the present invention are binary compositions consisting solely of the halo-ethane refrigerant and the furan solvent.(There may be more than one of the halo-ethanes or more than one of the furans, but a simple binary composition is preferred).

The furan present in the compositions of our co-pending Applications 14586/76 and 2125/78 (Serial No's. 1539287 and 1586009) and in the composition of the present invention has the formula:

wherein R, is independently at each occurrence, provided the furan is asymmetrical as defined below, 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 in 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. The alkyl, phenyl, and lower alkylene phenyl groups may be substituted as defined below. Some of the above furans 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 unexpectedly 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 dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in a furan ring-containing solvent which is at least one of methyltetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether, propyltetrahydrofurfuryl ether, n-butyl tetrahydrofurfuryl ether and methyl-2,5dihydro,2,5-dimethoxy-2-furan carboxylate (based on the total weight of solution).

The solvent present in the absorption pair of this invention is an asymmetrical furan ring containing compound having a boiling point between about 140 and 250"C. The compound has the general formula

wherein Rl, a and Z are as previously defined and the compound contains at least one R 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 alkoxy or alkylene of from 1 to 5 carbon atoms. Examples of lower alkyl groups are -CH2CH3;

and -CH2CH2CH3.

Examples of lower alkoxy groups are -OCH3; -OCH2CH3

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

Lower alkylene phenyl groups are phenyl groups (which may be substituted as listed above) connected to the furan ring by a lower alkylene group. Examples of such groups are

Examples of hydroxy containing lower alkyl groups are -CH2Oll; -CH2CH2Oll and

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 -CH20CH3; -CH2OCH2CH3; -CH2OCH2CH2CH,; -CH20CH2CH2CH2CH3 and CH2CH2OCH3. Preferred alkoxy alkyl groups are those containing either 5 or 6 carbon atoms due to higher efficiency at high generator temperature 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 carbon atoms. When the intermediate alkyl group is ethyl the furan ring compound unexpectedly exhibits improved solubility for the fluorocarbon.

Examples of lower alkylene carboxylate groups, i.e., those containing 2 to 6 carbon atoms,

It is thcorized that the boiling point of the simple furan ring is increased by adding an alkyl or an alkoxy group to the furan ring to form an assymetrical molecule. The added group should preferably permit an increase in the negative charge on the furan ring oxygen atom.

The furan ring-containing compounds employed in the present invention are usually characterised by high flash points which reduce the flame hazard when they are used.

Asymetrical as used in relation to the furan ring containing compound means either that at least one of the R, groups at the 2 position on the furan ring is different from both of the R, groups at the 5 position or at least one of the Rt groups at the 3 position is different from both of the R, groups at the 4 position. In the preferred furan ring compounds, at least one of the R, groups at the 2 position is different from both of the Rl groups at the 5 position.

Alkyl as used above means an aliphatic hydrocarbon radical in which the hydrogens may be wholly or partially substituted by fluorine or chlorine.

The compound must contain at least one Rl group having an oxygen atom which has a single bond to a carbon atom. At high generator temperatures, carboxy groups, particularly free rather than esterified carboxy groups, should be avoided since such groups tend to increase the corrosiveness of the compound and tend to decompose more rapidly than other groups. Carboxy groups are, however, suitable for compounds which will be used at low generator temperatures, i.e., below 225"F. The more preferred R1 groups are those containing an alcohol or ether oxygen atom.

The foregoing furan ring-containing compounds may be prepared by known procedurcs. Detailed discussions of the chemistry of furan and its derivatives are found in Chaptcr 4 of Heterocyclic Compounds Volume I, edited by Robert C. Elderfield, Wiley 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-containing compounds which are suitable for use in accordance with this invention is as follows:

aletos d ll2t J Zr0Cl 2 0 112,Rhodium platinum Oxide R1 R2 (COOIi)3cH2oH Ethanol (cnO)3cll2o}i Where R1 is independently at each occurrence any group as previously defined. Rl may be carbonyl or carboxy; however, these groups will be 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 preparation of furan ring containing compounds which are suitable for use in accordance with this invention is by ring formation from the enol form of a 1-4 carbonyl compound.

R1 C - C R 2SO4 all [| R 1R1 C 1 -tPtoxid R1 0 R1 R1 ZnC12 > l l Pt Rhodium O oRi R1 ethanol R1R1 H H e nol Again, R1 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 suitable hydroxy alkyl (alkanol) group and oxidizing the hydroxy alkyl group to the desired carbonyl or carboxyl group subsequent to hydrogenation.

Some specific suitable furan ring containing compounds are as follows:

1. 2-tctrahydrofurfuryl alcohol. 2. 3-tetrahydrofurfuryl alcohol.

3. 1-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 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.

4. 2-chloromethyl-5 hydroxymethyl tetra hydrofuran 5. 2-hydroxymethyl-5 carboxy tetrahydrofuran

6. 5-methyl-2-methylol tetrahydrofuran 7. 2,5-dihydro-2,5-dimethoxy 2-fur an methyl carboxylate

8. 2-n-propylol tetrahydrofur an # CH2CH2CH2OCH2CH3 9. 2-n-propyl ethoxy tetrahydrofuran

10. 2-ethylol-4-isopropyl tetrahydrofuran.

Examples of other suitable furan ring containing compounds which can be prepared in accordance with known methods are:

2-methoxymethyl-3-methyl tetrahydrofuran 2-methoxy-3-fluoro tetrahydrofuran 2-methoxy n-butyl-3-chloro tetrahydrofuran 2-methylol-3-n-pentoxy tetrahydrofuran 2-[3,5-hydroxy n-pentyl] tetrahydrofuran tetrahydro-3-carboxy-2- furan methyl acetate

2-[3,3-dimethyl propyl]-4 carboxytetrahydrofuran 2,3-dicarboxy-4-methyl tetrahydrofuran tetrahydro-3-trifluoro methyl-2-n-pentanoic acid 2-methylol-4-phenyl tetrahydrofuran 3-(4-phenyl butylenel-4 methyloltetrahydrofuran tetrahydro-2-furan ethyl propionate The solute used in the abosrption pair is a fluorinated ethane which preferably contains at least one hydrogen atom (and more preferably one only) and at least one chlorine atom and is assymetrical. It is believed that when fluorine and chlorine share the same carbon with hydrogen, the fluorine makes the chlorine less negative. Therefore the hydrogen atom becomes easily stretched once it "sees" to electron donor oxygen of the solvent. This hydrogen bonding force makes the primary contribution 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 CHCl2CF3, CHCIFCF2Cl, CH2C1CF3, CHCIFCHF2 and CHCIFCF3. Among the mixtures, CHCIFCF3 together with CH2CICF3 (or with CHCIFCHF2) is preferred.

The preferred absorption pairs of the invention comprise a fluorocarbon selected from the group consisting of dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane 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 2,5dihydro-2,5-dimethoxy-2-furan carboxylate and mixtures thereof.

Many of these absorption pairs unexpectedly have very high efficiency at high generator temperatures, such as when the solvent is n-butyl tetrahydrofurfuryl ether.

The fluorocarbon is selected from dichlorotrifluorethane, monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof. For such halogenated ethanes, it is preferred that the furan compound be

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

and as refrigerant dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane or mixtures thereof, with dichlorotrifluoroethane, monochlorotrifluoroethane or mixtures thereof being more preferred.

The system employing ammonia as the solute and water as the solvent cannot be operated at either high generator temperatures or at low generator temperatures and the maximum COP practically obtainable with the ammonia and water system at any generator temperature 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 this carboxylate is the solvent, unexpectedly have higher COP values at low generator temperatures than any other known absorption pair.

The preferred absorption pair composition when the methyl 2,5-dihydro-2,5dimethoxy-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 carboxylate is used, the preferred temperature to which the solution is heated in the generator is preferably between about 1500 and 300"F. and most preferably between about 1600 and about 210 F. Such low generator temperatures are particularly suitable for low temperature heat sources such as solar energy.

In general, all of the foregoing 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 1500F to about 425"F.

The higher generator temperatures, i.e., from about 250 to about 425"F.

The higher generator temperatures, i.e., from about 250 to about 425"F. 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 300 to about 350 F. The lower generator temperatures 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 1300F. 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 temperaturc of, such area.

The absorption heating apparatus of 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.

EXAMPLES 1-33 Calculations were made for absorption cycles of 40"F evaporator temperature, 1200F.

condensing temperature and llO"F absorber temperature. The latter temperature is the minimum absorber temperature which corresponds to a maximum refrigerant concentration in the rich solution. These values are representative 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 Number 4,127,010, referenced above, have been disregarded, except for liquid heat exchange between the rich and weak solutions passing between the absorber and generator. Pure refrigerant has been assumed in the condenser and evaporator.

The COP values were obtained by assuming a 40"F evaporator, a 120"F condenser temperature and a llO"F absorber temperature. Saturated amounts of refrigerant in absorbent at the absorber temperature (110 F) and the generator temperature (250, 300, 350 or 400"F) were determined experimentally. From the known heats of vaporization of the pure refrigerant, a refrigerant 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 10 F was assumed for a heat exchanger such that the heat loss of the weak liquid from the generator temperature down to 1200F (10"F above the absorber temperature) was assumed to have been used to heat the rich liquid from the absorber temperature of 110 F. 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 input.

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 quantity of pure refrigerant released 344 BTU by cooling from the generator temperature 1200F and a second quantity of pure absorbent released 23,555 BTU by cooling from the generator temperature to 120 F, then it was assumed that a weak liquid having the first quantity of refrigerant and the second quantity of absorbent would release 23,899 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 temperature to the generator temperature and the amount required to vaporize the refrigerant. The relatively small amount of work required to pump the rich solution from the low absorber pressure to the high generator pressure was disregarded.

Since the above COP valuc represents a ratio between heat inputs at the generator and evaporator, a COP heating value can be calculated as I + COP cooling. This calculation assumes that all of the heat inputs at the generator and evaporator translates into heat output at the absorber and condenser which can be put to use. The COP value representing the ratio of heat input to the evaporator/heat input to the generator is also called COPc. This number plus one would be the COPH or total heat output of the system/hcat input to the generator. It will be appreciated that the total heat output includes condenser and absorber heat output. Energy consumption by solution and cool ant pumps have been ignored.

Table 1 Flow Rates, Solution Concentrations and COP Values For One Ton of Refrigeration At 40 Evaporator Pressure, 1200F. Condenser Temperature, 110 Absorber Temperature Using ETFE As Absorbent Concen- Concen Mass Mass tration tration Flow Flow Rich Weak Rich Re fri- Liquor Liquor Generator Liquor gerant (Wt. % (Wt. % Example Temp. (Ib/hr) (Ib/hr) R124) R124) COPc 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 1049 250.7 50 34.3 0.412 Wt. %R123 Wt. %R123 5 400 383 183.8 48 0 0.480 6 350 394 183.8 48 2.5 0.527 7 300 449 183.8 48 12.0 0.562 8 250 650 183.8 48 27.5 0.558 Wt. %R21 Wt. %R21 9 400 348 144 43 3.0 0.546 10 350 386 144 43 9.0 0.571 11 300 473 144 43 18.0 0.596 12 250 731 144 43 29.0 0.566 *These calculated values are uncertain because the pure refrigerant would be superheated rather than liquid at the hot end of the heat exchanger.

With proper design, COPc values over 0.65 have been achieved for R21/ETFE (as defined below) at a 3000F generator temperature. Similar results may be obtainable with R124 at a 350"F generator temperature and with R123 at a 3000F generator temperature. Similar results may be obtainable for the following absorption pairs at the following generator temperatures: Generator Temperatures 13* R124/nBTFE 350 F 14* " 400 F 15 R124/ETFE 300 F 16* " 350 F 17 R21/ETFE 250 F 18* " 300 F 19* " 350 F 20* R21/nBTFE 350 F 21* " 400 F 22 R123/ETFE 250 F 23* " 300 F 24* " 350 F 25 R133a/ETFE 250 F 26 " 300 F 27* " 350 F 28 R133/ETFE 250 F 29 " 300 F 30 R123 (50 Wt.%), R124 (50 Wt. %)/ETFE 300 F 31 R133 (50 Wt. %), R133a (50 Wt. %)/ETFE 300 F 32 R123 (50 Wt. %), R133 or 133a (50 Wt. %)/ETFE 300 F 33 R21 (50 Wt. %).

Rl24 (50 Wt. %)/ETFE 300 f R133 = CF2HCHClF,R133a = CF,CH2CL,R124 = CF3CHClF, R123 = CF3CHCl2 (R123a = CF2CICHCIF may also be used), R21 = CHCl2F, ETFE = ethyltetrahydrofurfuryl ether, nBTFE = n-butyl tetrahydrofurfuryl ether. The starred examples represent compositions that may be unstable at the indicated generator temperatures.

It will be noted that the generic formula

where a is 1 or 2 and Z is a single bond when a is 2 and a double bond when a is 1, can be expressed as the formulae

where all the R's are chosen independently from the same set of meanings. This alternative expression is adopted in our co-penting Application No. 2125/78. (Serial No.

156009).

As stated, we make no claim to a composition containing a phosphite stabilizer.

Subject to the foregoing disclaimer, WHAT WE CLAIM IS: 1. A heat-absorption composition comprising as absorption pair (a) as refrigerant, from 4 to 60 weight percent of a lower alkyl fluorocarbon selected from dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in (b) as solvent. 40 to 96 weight percent of an asymmetrical (as

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Generator Temperatures 13* R124/nBTFE 350 F 14* " 400 F

15 R124/ETFE 300 F 16* " 350 F

17 R21/ETFE 250 F 18* " 300 F 19* " 350 F 20* R21/nBTFE 350 F 21* " 400 F

22 R123/ETFE 250 F 23* " 300 F 24* " 350 F

25 R133a/ETFE 250 F

26 " 300 F 27* " 350 F

28 R133/ETFE 250 F

29 " 300 F

30 R123 (50 Wt.%), R124 (50 Wt. %)/ETFE 300 F

31 R133 (50 Wt. %), R133a (50 Wt. %)/ETFE 300 F

32 R123 (50 Wt. %), R133 or 133a (50 Wt. %)/ETFE 300 F

33 R21 (50 Wt. %).

Rl24 (50 Wt. %)/ETFE 300 f R133 = CF2HCHClF,R133a = CF,CH2CL,R124 = CF3CHClF, R123 = CF3CHCl2 (R123a = CF2CICHCIF may also be used), R21 = CHCl2F, ETFE = ethyltetrahydrofurfuryl ether, nBTFE = n-butyl tetrahydrofurfuryl ether. The starred examples represent compositions that may be unstable at the indicated generator temperatures.

It will be noted that the generic formula

where a is 1 or 2 and Z is a single bond when a is 2 and a double bond when a is 1, can be expressed as the formulae

where all the R's are chosen independently from the same set of meanings. This alternative expression is adopted in our co-penting Application No. 2125/78. (Serial No.

156009).

As stated, we make no claim to a composition containing a phosphite stabilizer.

Subject to the foregoing disclaimer, WHAT WE CLAIM IS: 1. A heat-absorption composition comprising as absorption pair (a) as refrigerant, from 4 to 60 weight percent of a lower alkyl fluorocarbon selected from dichlorotrifluoroethane, monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in (b) as solvent. 40 to 96 weight percent of an asymmetrical (as

herein defined) furan ring containing compound, said compound having a boiling point between about 140"C. and 250"C. and the generic formula:

wherein Rl is independently at each occurrence, provided the furan is asymmetrical, H; lower alkyl including partly or wholly fluoro-substituted alkyl and hydroxy-alkyl; lower alkoxy; phenyl including methyl-, ethyl-, hydroxy-, methoxy-, ethoxy-, fluoro- or chlorosubstituted phenyl; lower alkylene phenyl as herein defined; lower alkyl carboxy; alkoxy alkyl of from 2 to 6 carbon atoms; lower alkylene carboxylate of from 2 to 6 carbon atoms; or fluorine or chlorine; a is independently at each occurrence the integer 1 or 2; and Z is a single or double bond; provided that, when Z is a single bond, a is 2, and 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.
2. A composition 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 monochlorotrifluoroethane, monochlorotetrafluoroethane and mixtures thereof dissolved in about 40 to 96 weight percent of a furan ring containing solvent compound selected from the group consisting of methyltetrahydrofurfuryl ether, ethyl tetrahydrofurfuryl ether, propyl tetrahydrofurfuryl ether, n-butyl tetrahydrofurfuryl ether and methyl-2,5dimethoxy-2-furan carboxylate.
3. A composition in accordance with claim 1 wherein said assymetrical furan ring containing compound is of the formula

where R is alkyl having 1 to 4 carbons.
4. A composition in accordance with claim 3 wherein R is ethyl.
5. A composition in accordance with claim 3 wherein R is n-butyl.
6. A composition in accordance with claim 1 wherein said assymetrical furan ring containing compound is of the formula
7. A composition in accordance with any preceding claim wherein said fluorocarbon is selected from CHCl2CF3, CHCIFCF2Cl, CH2ClCF3, CHClFCHF2, CHC1FCF3 and mixtures thereof.
8. A composition in accordance with claim 1 wherein said fluorocarbon is mono chlorotrifluoroethane.
9. A composition in accordance with claim 4 wherein said fluorocarbon is monochlorotrifluoroethane.
10. A composition according to claim 1 consisting solely of the halocarbon and the furan solvent.
11. A composition according to claim 1, wherein the furan is any one of those having the generic formula shown in claim 1 identified herein.
12. A method of absorption heating which comprises releasing heat of solution in the vicinity of an area to be heated by absorbing a fluorocarbon in an assymetrical furan derivative to form a composition according to any preceding claim, heating the 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 remote 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.
13. A heat pump of the type designed to operate with an absorption pair comprising a solvent which remains liquid in operation and a solute which is changed cyclically from the liquid to the vapor phase and back, wherein the absorption pair is as claimed in any of claims 1 to 11.