CA2069509A1 - Azeotrope-like compositions of 1,1,1,2-tetrafluroethane and 1,1-difluoroethane - Google Patents

Abstract

Novel azeotrope-like compositions of 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane which are useful in heating and cooling applications.

Description

Is ':`2~
AZEOTROPE-LIKE COMPOSITIONS OF
1,1,1,2-TETRAFLUOROETHANE ~ND l~l-DIFLVOROETH~NE

FIELD OF THE INVENTION `

This invention ~elate6 to azeotrope-like compo~ition6 of 1,1,1,2-tetrafluocoethane and l,l-difluocoethane. The~e mixture~ a~e u~eful a6 10 cefrigerant~ for heatinq and cooling applications.

.
BACKGROUND OF THE ~NVENTION

Fluorocarbon ba6ed fluids have found widespread u6e 15 in indu6try for ce~rigeration, air conditioning and heat pump application6.

Vapoc compres6ion is one focm o refrigecation. In its simple6t ocm, vapoc compce6sion involve6 changing the 20 cefrigecant rom the liquid to the vapoc phase through heat ab60rption at a low pre6suce and then from the vapoe to the liquid pha~e theough heat removal at an elevated pre6~uce. Fie6t, the refrigerant is vaporized in the evaporator whlch i6 ln contact with the body to be 25 cooled. The pre66ure in the evapocatoc i6 6uch that the boiling point o the cefrigerant i6 below the te~pecatuce o the body to be cooled. Thu6, heat flow6 com the body to the rerigerant and cau~e6 the refrigerant to vaporize. The vapoc ormed i6 then removed by means Of a 30 compressoe in order to maintain the low pre~sure in the evaporator. The temperature and pressure of the vapoc ace then cai6ed thcough the addition of mechanical energy by the compeessoc. The high ece6sure vapor then pas6es to the condenser whereupon heat exchange6 with a "

: .
:, :
, . ,. , . .

' ' ' : :, W O 91~09089 PC~r/US90/06996 ~ 0~95~9 -2- " ~
cooler medium. The 6en5ible and latent heats are removed with subsequent conden~ation. The hot liquid ref~igerant then pas6e6 to the expansion valve and i6 ready to cycle again.

~ hile the prlmary purpo6e of refrigeration i~ to remove energy at low temperature, the primary purpose of a heat pump i5 to add energy at higher temperature.
Heat pumps are considered reverse cycle 6ystem~ becau~e for heating, the operation of the conden6er is interchanged with that of the refrigeration evaporator.

Certain chloro~luorocarbons have gained widespread use in refrigeration applications including air conditioning and heat pump applications owing to their unique combination of chemical and phy~ical propertie~. The ~ajocity oS ce~rigecants utilized in vapoc compces~ion ~ystem~ are eithec single component fluid~ or azeotcopic mixtuce~. Single component ~luids and azeotropic mixtures are chacacterized a~
con6tant-boiling because they exhibit isothermal and isobaric evaporation and conden6ation. The u~e of azeotropic mixtures as ref rigerantB ifl ~nown in the art. See, ~or example, R.C. Downing, "Fluorocacbon 2 Refrigerants Handbook", pp. 139-15~, Prentice-HalI, 198B, and U.S. Patents 2,101,993 and 2,641,579.

Azootropic or azeotcope-like compo~ition~ are desired because they qo not ~ractionate upon boiling or 30 evaQoration. This behavior iB desirable becau~e in the pre~iou~ly desccibed vapor compre~sion equipment with ~hich the~e refrigerants are e~ployed, condensed material is generated in preparation for cooling or for heating purpoae~, and unless the refrigerant 35 compo~ition i~ constant boiling, i.e. i6 azeotrope-like, fractionation and ~egregation will occur upo~
evaporation and condensation and undesirable . :
: ' ' ` , , ` ~:
.~ ,.
:

W O 91t09089 PC~/US90/06996 _3_ 2 ~ 9 refrigerant distribution may act to upser the cooling or heatinq.

Non-azeotropic mixture~ have been di6clo6ed a6 refrigerants, se2, e.g., U.S. Patent 4,303,536, but have not ~ound widespcead u6e in comme~cial application6 even though the ability of non-azeotropic refeigerant blends to exhibit improved thermodynamic performance ha6 often been di6cu66ed in the literature.
See, e.g., T. Atwood, "NARBS - The Promise and the Proble~", American Society o ~echanical Engineers, Winter Annual Meetin~, paper 86-WA/HT-61, 19a6 and ~.O.
Mc~inden et al., 'l~ethods for Comparing the Performance of Pure and Mixed Refrigerants in the Vapo~ Comp~e~sion Cycle", Int. J. Refri~. 10, 31B (19~7). Becau6e non-azeotropic miKtures may fcactionate dueing the refcigeration cycle, they ~equire ceetain hardwa~e change~. The added difficulty in changing and 6ervicing refrigeeation equipment i8 the pcimary ceason that non-azeotropic mixtures have been avoided. The situation i~ further complicated if an inadvertent leak in the ~yste~ occurs during such use or service. The composition of the mix~ure could change, affecting system peessures and system performance. Thu~, if one component of the non-azeotropic mixture i8 ~lammable, fractionation could shift the composition into the fla~able region with potentially adver~e con~equence6.

Tho art is continually seeking new fluorocarbon based azeotrope-like mixtuces which offer alternatives for refrigeration and heat pump applications.
~urrently, envieonmentally acceptable Sluorocarbon-base~ refrigerants ace of particular interest becau~e the fully halogenated chlorofluorocarbons have been implicated in cau~ing environmental peoblems associated with the depletion of the earth~s protective ozone ~' , ' "' ' . .

W O 9~/09089 PC~r/US90/06996 2 ~ ~ 9 ~

làyer. Mathematical model~ have sub6tantiated that hydrofluorocarbons like 1,1,1,2-tet~afluoroethane ~HFC-134a) and l.L-difluoroethane ~HFC-152a), will not adver~ely affect atmo~pheric chemistry becau~e their contribution to 6tratospheric ozone depletion and global warming in compari~on to the fully halogenated specie~ is negligible.

The substitute materials must alBo po6~e88 those propertie6 unique to the CFC's including chemical ~tability, low toxicity, non-fla~mability, and efficiency in-u~a. The latter characteri6tic i8 important, for example, in refrigeration applications like air conditioning where a 10BB in refrigerant thermodynamic performance or energy efficiency ~ay produce secondary environmental effects due to incceaBed fos8il fuel u~age arising from an increased de~and for electrical energy, Furthecmore, the ideal CFC cefrigerant substitutQ would not require major engineering changes to conrentional vapor compres~ion technology current}y used with CFC cefrigerants.

It i~ accordingly an object of this invention to provide novel azeotrope-like compositions based on l,l,l,Z-tetrafluoroethane and l,l-difluoroethane whic~
25 are useful in cooling and heating applications.

Another object of the invention iB to provide novel environmentally acceptable ce~rigerants for use 30 in the a~or-mentloned application~.

Other ob3ects and advantages of the invention will become apparent trom the following description.

SUMMAaY OP THE INVPNTION

The invention relates to novel environmentally acceptable azeotrope-like compositions of ~ ' ' ` ' .

1,1,1,2-tetrafluoroethane and L,l-difluoroethane which are u~eful in heating and cefrige~ation application6.

DESCRIPTION OF THE INVENTION

In accordance with the invention, novel azaotrope-like compo~ition6 have been discovered compri~ing 1.1,1,2-tetrafluocoethane and l,l-difluocoethane. The azeot~ope-like compo~ition~
comprise from about 5 to about 90 weight percent 1,1,1,2-tetrafluoroethane and from about 10 to about 95 weight percent l,l-difluoroethane and have a vapor pre~sure of about 76 p6ia ~ 5 p6ia at 20C. These compo6itions a~e azeotrope-like because they exhibit e66entially con~ta~t vapor pre66ure ver~u6 compo6ition and e66entially identical liquid and vapor compositions ove~ the aforementioned ~ange6.

In a pceferred embodiment of the invention, 6uch azeotrope-like compo6ition6 compei6e from about 40 to about 85 weight percent l,l,L,Z-tetrafluoroethane and from about 15 to about 60 veight peccent 1,1-difluoroethane and have a vapor pre66uce of 76 p6ia , 3 p6ia at ZOC.

Vapor pha~e co~po~ition6 containing in exces~ of about 80 weight peecent 1,1,1,2-tetrafluoroethane were detormined to be nonflammable in aic at ambient cond~tions uring the Bureau of Mine~ - ~tyle eudiomete~
apparatus. ~ ", The azeotcope-like compo6ition6 of thi~
invention, co~pri6ed of HFC-152a ant HFC 134a, do not ~egregate. In addition, they exhibit a number of advantage~ over dichlorodifluoromet~àne (CFC-12), HFC-134, and HFC-152a. Foc example, the azeotrope-like mixture6 are non-flammable above 80 veight percent HFC-134a the~eby teducing the hazard of explo~ion .
:

PCT/US9~/06996 ; 2~695Q9 6 which mi~ht occur if flammable HFC-152a vapor6 were u6ed, stored, or handled in pu~e ~orm.

The~e azeotrope-like mixtures al50 exhibit zero ozone depletion potential and low atmo6pheric lifetime hence they contribute negligibly to the greenhou6e warming effect. This i6 contra6ted with the hiqh ~zone depletion potential and corre6pondinqly high greenhouse warming potential of CFC-L2.

The energy efficiency and co~liny capacity of the azeotrope-like compo6ition6 of the invention are superior to tho6e of pure HFC-134a and, in addition, the 134a~152a compo6ition6 provide 6ignificantly reduced direct and indirect gceenhou6e warming potential ove~ puce HFC-134a, The azeotroeic compo6ition6 of thi6 invention uniquely pos6es6 all o~ the desireable featuces of an ideal eef rigerant i,e,, safe eo use, non-flammable, zero ozone depletion potential, negligible greenhouse warming effect, and attractive energy/cooling perfocmance compared to the mo6t relevant pure eluoromethane or fluocoethane ~luid6; i.e., fluococarbon refcigerants boiling between -19 C and -30 C (this range repre~ents the boiling point range for the majority of currently u~ed air conditioning and refrigecant working Sluids), In summary, when HFC-15Za/HPC-134a are combined in ef~ective amounts, a non-flammable, non-segregating, envi~onmentally acceptable azeotrope-like refrigerant having impcoved thecmodynamic performance re6ult6.

The ter~ ~azeotrope-likel~ i6 u6ed herein for mixtures of the invention because in the claimed Proeortion6~ the comeo6ition~ of 1,1,1,2-tetrafluoethane and 1,1-difluoroethane are con6tant boiling oc es6entially con6tant boilinq. All .
.
, ~ WOgl/09089 P~T/~S~0/06996 . _7~ ' 2~ 9 compo6ition~ within the indicated range~, a~ well as certain compo6itionE outside the indicated ~anges, are azeotrope-like, as de~ined moce pa~ticularly below.

From fundamental pcinciple~, the thermodynamic state of a fluid i~ defined by four variables:
pre66ure, temperature, liquid compo~ition, and vapor compo6ition, or P-T-~-Y, respectively. An azeotrope is a unique chaeacteri6tic of a sy6tem of two Qr more component6 where X and Y a~e equal at a 6tated P and T. In p~actice thi6 mean6 that the CompQnent6 cannot be 6eparated during a phase change, and therefore are u6e~ul in the cooling and heating application~
de6ccibed above.

For the purpo~e6 of thi~ di6cus6ion, by azeotrope-like compo6ition i~ intended to mean that the compo6ition behave~ like a true azeot~ope in tecms of thi6 con6tant boiling chacacteri6tics or tendency not to ~ractionate upon boiling o~ evaporation. Thu6, in such 6y6tems, the co~po6ition o~ the vapor formed during the evaporation is identical or sub6tantially identical to the oriqinal liquid composition. Hence, during boiling or evaporation, the li~uid compo6ition, 25 if it changes at all, change~ only slightly. Thi~ i~
contrasted ~ith non-azeotrope-like composition~ in - ~hich the liquid and vapor compositions change sub~tantially during evaporation or condensation.

I~ the vapor and 11quid phases have identical compositions, then it can be ~hown, on a rigocous thecmodynamic ba~is, that the boiling point ver~us composition curve pas6es through an absolute maximum or an absoluto minimum at thi~ compo~ition. If one of the 35 t~o conditions, identical liquid and vapor compo~ition6 or a minimum or ma%imum boiling point, are shown to eXi6t, then the sy~tem i5 an azeotrope, and the other condition mu6t ~ollow.

..

~ . . " , 2~599 -8- ~
One way to determine whether a candidate mixtuce i8 aze`otrope-like within the meaning o~ thi6 invention, is to d}still a 6ample thereo~ undec conditions ~i.e., resolution - numbec of plate6) which would be expected to separate the mixture into it6 sepa~ate components.
If the mixture i~ non-azeotrope or non-azeotrope-like, the mixture will fractionate, i.e., ~eparate into it~
va~ious components with the lowest boiling component distilling of~ first, and 60 on. If the mixture is azeotrope-like, 60me finite amount of the ~irst distillation cut will be obtained which contains all of the mixture component6 and which i~ con6tant boiling or behaves as a single sub6tance. This phenomenon cannot occur if the mixture i6 not azeotrope-like, i.e., it i5 l not part of an azeotrope 6ystem.

It follows from the above that another characteri6tic o~ azeotrope-liko compo6ition6 i6 that thece i6 a range of compo~itions containing the sa~e component6 in vacying proportions which are azeotrope-like. All such compo6itions ace intended to be covered by the term azeotrope-like as u6ed herein. A6 an example, it i3 well known that at different pres6ure6 tha composition of a given azeotrope will vary at least slightly as does the boiling point of the compo6ition.
Thus, an azeotrope of A and B repre~ents a unique type of relationship but with a variable compo~ition depending on the temperature and/or pressure. A~ i~
readily under~tood by persons skilled in the art, the boiling point of an azeotrope will vary with the pre6~ure.

In one proces~ embodiment of the invention, the azeotrope-like co~po~ition~ of the invention may be 35 uset in a method for producing cooling which compri6e~
condensinq a cefrigerant compci~ing the azeotrope-like compo6ition~ and thecea~ter evaporating the re~rigerant in the vicinity of the body to be cooled.

,~

' ` ' .~

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

~ ~ PCT/US90/069g6 ,, ,;,~. . 9 9 ~ ~ 9 In anothe~ proce~6 embodiment of the invention, the azeotrope-like compo6ition~ of the invention may be used in a method ~o~ producing heating which utilize6 conden~ing a refcige~ant in the vicinity of the body to be heated and thereafte~ evaporarlng the cef~igecant.

Fo~ pucpo6e~ of thi6 application, the proce66 embodiments for producing cooling or heatin~, discu66ed above, will gene~ally be referred to a~ heat exchange applications.
1~ .
The L,1,1,2-tetcafluoroethane and l,l-difluoroethane component6 of the novel azeotrope-like compo6ition6 of the invention are known matecial~. prefecably they 6hould be u~ed in sufficiently high purity ~o as to avoid the intcoduction of advec6e influences upon the constant boiling propeetie~ of the 6ystem.

It 6hould be unter~tood that the pce6ent 20 compo6ition6 may include additional components 60 as to form new azeot~ope-like composition6. Any such compo6itions a~e considered to be within the 6cope of the pcesent invention as long a6 the compo6itions ace es6entially constant boiling and contain all the 25 e~sential components de~ceibed herein.

In attition, the azeotrope-like compo6itions of tho invention may include components which may not form new azeotrope-like composition~. In paeticular, lubcicants like those discussed in U.S. Patent 4,755,316 may be adaed without depatting f~om the 6cope of the invention..

35The pce~ent invention i5 mo~e fully illustrated by the following non-limiting Examples.

..... .. . .. . . .
. ~ ' ' .

.

.

PCT/~S90/06996 2 0 ~ O-E~AMPLE 1 This example show6 that certain compositi~ns of 1,L,1,2-tetra~luo~oeehane and l,l-difluoroethane a~e a~eotrope-li~e, i.e., exhibit es6entially identical liquid and vapo~ composition6, and are con6tant boiling, i.e., exhibit e6sentially constant vapo~
p~e66ure ver~us compo6ition within thi~ canqe.

Vapoe liquid equilib~ium expeeiments were pe~formed by p~eparing mixture6 o~ ~FC-134a and HFC-152a in an appeoximately 150 cubic centimeter ve6sel. The ve~sel, equipped with a magnetically driven stirrer and a 0-300 psia pres6ure transducer accurate to + 0.2%, was submerged in a constant temperature bath controlled to within + 0.02C. Once thermal equilibrium was attained, as deteemined by con~tant vapoe peessure ceadings, vapor and liquid 6amples weee withdra~n ~com th~ ve6sel and analyzed by standaed gas chromatographic technique6. Thi~
procedure wa6 repeated at three nominal composition6 o~
approximately 25, 50 and 70 mole peccent HFC-134a in HFC-152a, and at threo tempecaturea, -20, 20 and 60C.
Table I sum~ari2e~ tho results of these expeeiments.

T~e data ~hown in Table I inticate that the vapor and liquid compo~itions aro essentially identical within tho eYpoci~ental uncectainty of + 2.0 weight percent unit a~ociated with the chromatographic analy~is. The ~apor pce66uce data measured at -20C
show a minimum vorsus composition wbich is evidence o~
azeotropic behavior. Tho vapor pees~ures of the blends are essentially con6tant to within + 5 psia ove~ the composition range from aboue 5 to about 90 weight percent HFC-134a and ~ro~ about ~0 to about 95 weight percent HFC-152a~ that i6, these blends are constant boiling oe az-oteope-like.

. . - , .
, , . .:

.
. .. . .

.,. ~ ,, This example show6 that azeotrope-like HFC-134a/HFC-L52a blends have certain pec~ocmance advantage6 when compared to FC-134a alone.
,. S
The perfo~mance of a ref~igerant at specific operating condition6 can be mea6ured by the coefficient of performance and the capacity of the refriqerant.
The coefficient of perfocmance, COP, i~ a unive~sally accepted measure, e~pecially u6eful in repce6enting the relative thermodynamic efficiency of a refrigerant in a 6pecific heating or cooling cycle involving evaporaeion 1 5 'S~

HFC-13~-/H~C-lS2- V~por Llquid tqulllbrl~ D-t~

T~np~r~tur~ ~quid Co~po~tion~ V-po~ Compo~ition* V~por Prossuro 20(~C)~t. S H~C-13~) (~t. ~ HFC-13~) (p8i~
-20.0 0.0 0.0 17~8 -20.0 36.0 35.9 17.1 -20.0 6~.1 63.~ 17.2 -20.2 77.~ ~9.5 17.7 -20.0 100.0 100.0 19.3 2520.0 o.o o,o 74.7 20.0 3~.~ 36.~ 75.0 20.1 60.8 63.~ 76.t 20.0 78.~ 80.1 ?9.0 20.0 100.0 100.0 82.9 60.0 0.0 0.0 218.9 3060.0 3~.7 36.7 219.5 60.~ 60.8 63.2 225.7 60.3 78.0 79.~ 233.5 60.0 100.0 100.0 2~3.9 ~ Weight percent HFC-134-a in HFC-152a or condensation of the re~cigerant. In refcigeration engineecing this ter~ expce~se~ the ratio of usoful cefcigecation to the energy appliet by the compcessor ..
, , :

i 2 0 $ ~ ~ ~ 9 -12- PCTiUS9~/06996 in compres6ing the vapor. The capacity of a refrigerant repre6ents the volumetric efficiency o~ the refriqerant. To a compre660r engineer this value expresses the capability of a co~pres60r to pump quantitiefi of heat for a given volumetric ~low rate of re~rigerant. In other word~, given a 6pecific compre660r, a refrigerant with a higher capacity will ; deliver more cooling or heating power.

The performance of a 78/22 HPC-134aiHFC-152a by weight azeotrope-like blend wa6 evaluated in a typical automotive air conditioning unit operated under controlled labocatory calorimeter condition~. The compre660c and conden6er sections o~ the aic conditioning cycle were maintained in a contcol~ed environ~ent of 100F. Thermocouplec wece u6ed to measure the tempecature of the air flowing to and from the conden~ec ant tho temperatuee o~ the re~riqerant at the discharge and suction ports o~ the compre66er as well a~ at the cond~en~er outlet. The compressor wa~
operaeed at a constant speed of 1188 revolutiona pec minute with an electric motor. A Watt-hour meter wa~
used to determine~the m-chanical wor~ input to the compressor. Heat remo~al trom the conden~er environment was ac~hieved using chilled water flowing at a measured flow rate to a cooling coil in the conden6er room. The capacity o~ the air conditioning 6ystem is determined by performing an energy balance over the condense~ coom.

The evaporatoc and expansion valve section of the air conditioning cycle were maintained at 100P and 40%
relative humidity.~ Thermocou~les were used to measure the temperatures o~ the refrigerant leavi~ng the evaporatoc and leaving the accumulator. Pour pre~ure :ransducers, located in the comp~essor suction and discharge lines and ju~t after the condenser and accumulator, were u~ed to mea~ure the refrigecant , - . . . ~ , - . .. . ..

, ,~
' ".: : .' ~ . ' . "

.. ' '' ~

WO9l/09089 PCT/US90/06996 -13- ~ ~ j9~3~9 pre~sure throughout the cycle. Two set~ of electrical heate~6 in the evaporator ~oo~ wece continuously adjusted to balance the heat ~emoved by the evapo~atoc.

Tests were pecfocmed at the above specified conditions for three cefrigerant6, CFC-12 (dichlorodifluo~omethane3. HFC-134a and the 78/22 HFC-134a/HFC-152a azeotcope-like blend. CPC-12 is a fully halogenated chlo~ofluoroca~bon which has been u6ed widely in air conditioning and reeriqeration application6. CPC-12 ha6 been determined to be a contributor to the~depletion of the Earth~6 strato6phecic ozone layer. Each test con6i6ted of at least two consecutive experiments whece the measured COP's agreed to within 1%. The data for these te6ts i6 reported in Table II.

The data listed in thi~ table eor Te6t6 1-3 ~how that the 78/22 HFC-134a/HFC-152a azeoteope-like blend pcovites a 6.6% increase in COP over HFC-134a and a capacity similar to that o~ HFC-134a. The blend al60 provide6 a COP and capacity comparable to, thaC attained with CFC-12. The co~p~essor discha~ge p~es6u~e foc the blend i8 lo~er than~that exhibited by HPC-}34a, ~hicb aliminates the need to design air conditioning equipment to withstand higher operating pre-6uces.
: :
Te6t~ ~-6 cepresents a ~oce extceme condition wher- the aiC ~low ovee the condenser has been ceduced 30 which ce~ult~ in gr-atec di~charge pre~Ure~ and temperatures. The HPC-134a/HFC-152a blend pco~ides a 4% impcove~ent in COP and a ~light (Z~) drop ~ .
~ 35 `

.
, ' .
- ::

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

2 ~ a ~ -14-T~blo II
. ~ .
Parform~nc- Of A 78~22 HrC-124~/HPC-152~ Bl~nd Pres~ure ~emperature Coolin~ Compressor Dischar~e Accumulator Disch~rge Acccumulato~ Capacity Work COP
~psia) (pgi8) ~-F) (-F) (W~tt) (Watt) T~t 1: CFC-12 255.2 60.8 174.0 53.2 5194.7 2153.4 2.41 Te~t 2: H~C-134a 284.0 59.5 163.6 S1.3 4948.8 2224.2 2.23 Test 3: HFC-13~ FC-152a(78/22) 270.9 57.1 171.2 52.3 5069.7 2128.6 2.38 T~t ~: CFC-12 313.7 60.7 187.8 53.1 3957.~ 2332.8 1.70 T~t 5: HPC-134~
352.7 59.6 180.~ 51.3 3538.9 2B81.0 1.49 T-st 6: HPC-13~-/HPC~lSZ~78/22) 339.1 57.2 19~.~ 51.6 3603.1 2321.7 1.55 in capacity compared to HPC-134a as well a~ a reduction in discharge pressure.

Having de~cribed the invention in detail ant by reference to pce~erred embodiment~ thereo~, it will be apparent that modi~ication~ and variation~ are po~sible without departinq ~rom the ~cope o~ the in~ention de~ined in the appended clai~.

.

.. . . .

. ~
' ' ~ . ' ' :

Claims (9)

1. Azeotrope-like compositions comprising 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane which have a vapor pressure of about 76 psia ? 5 psia at 20°C.

2. Azeotrope-like compositions comprising 1,1,1,2-tetrafluoroethane and 1,1-dichloroethane, which have a vapor pressure of about 76 psia ? 5 psia at 20°C, in effective amounts for heat exchange applications.

3. Azeotrope-like compositions consisting essentially of 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane which have a vapor pressure of about 76 psia ? 5 psia at 20°C.

4. Azeotrope-like compositions comprising from about 5 to about 90 weight percent 1,1,1,2-tetra-fluoroethane and from about 10 to about 95 weight percent 1,1-difluoroethane which have a vapor pressure of about 76 psia at 20°C.

5. The azeotrope-like compositions of claim 4 wherein said compositions contain from about 40 to about 85 weight percent 1,1,1,2-tetrafluoroethane and from about 15 to about 60 weight percent 1,1-difluoroethane and have a vapor pressure of about 76 psia at 20°C.

6. Azeotroge-like compositions consisting essentially of from about 5 to about 90 weight percent 1,1,1,2-tetrafluoroethane and from about 10 to about 95 weight percent 1,1-difluoroethane which have a vapor pressure of about 76 psia at 20°C.

7. The azeotrope-like compositions of claim 6 wherein said compositions contain from about 40 to about 85 weight percent 1,1,1,2-tetrafluoroethane and from about 15 to about 60 weight percent 1,1-difluoroethane which have a vapor pressure of about 76 psia at 20°C.

8. A method of producing cooling comprising condensing a composition of claim 1 and thereafter evaporating said composition in the vicinity of a body to be cooled.

9. A method of producing heating comprising condensing a composition of claim 1 in the vicinity of a body to be heated and thereafter evaporating said composition.