US 2641580 A
Description (OCR text may contain errors)
"particularly to flu'orine co Patented June 9, 1953 2,641,580 a I .AZEQTROPIC REFRIGERANT *GOMPQSITIQN 1 9: 3-, lil-fip F-LUQfi flANE. MQND- OHLOROPENTAFLUORQETHANE fiamilton liewigwoodbury, N. J., assignoi' to -i. do Pom dc )Nemcurs and company, Winning-'- tlm, Bush, a :corporation of Delaware NoTDraw'ing', Application Mar ch 2, 19'51,
, "Serial No. 213,673
*1 This invention relates to refrigerants and more ining "compounds and mixtures thereof-which are useful as refrigera-nts.
The mixed fiuori'ne-and'chlorine derivatives of methane and ethane have attained wide-spread use in the field of refrigeration as aresul't of their chemical inertness, their low specific volumes and the wide range "of boiling points which "is available inthe various members of the series. Di'fluorodichloromethane' (B'. 'P. 2'9.8 Ci), fiuorotrichloromethane (B. P. "23.7" C.'), fluerodichloromethane ('13. P. 859 :C.) and tetrafl-uorodichloro'ethane -(B'.'P. C.) are among the mostcommonly use-d compounds of this type. Other valuable members of the series are monochloropentafluoroethane, which boils-at -38.5 C., and chlorodifiuoromethane, which boils at -40.8 C. These compounds make it possible to attain lower temperatures than can be reached with the refrigerants mentioned above.
It is necessary that a considerable range of refrigerants having various boiling points be available in order to perm-it efficient design of apparatus for various refrigerating needs. The selection of the most isati-sfactury equipment must be made with a view to the temperature to be attained, the power cost, the cost of the refrigerating apparatus itself, and .re'duii'emj .ofsp'ace.
To the extent that a wide range or refrigerants is not available, this factor must also be taken into account and in some cases becomes controlling. Greater efliciency and flexibility of design therefore becomes possible as additional refrigerants of suitable characteristics are developed.
When apparatus designed to employ a particular refrigerant has been installed, the need sometimes arises for greater refrigerating capacity. This may be obtained by the use of a refrigerant having a lower boiling point and consequently a higher vapor pressure at the temperature attained by the gas prior to its being compressed and liquefied. The capacity of any given refrigeration compressor is roughly proportional to the pressure'of the gas at the suction side of the compressor. Since the compressor can handle a fixed volume of gas per unit of time, an increase in the suction pressure means an increase in the number of moles of gas put through the compressor in a given time. An increase in the number of moles means an increase in the total amount of heat required to vaporize the liquid in the evaporator, and an increase in the amount of heat that is removed from the 12 Claims. (Cl. 252M457 '2 refrigerated space. In general, other factors sees as variations in "the latent heat of vaporization play a relatively minor part in determining the change in capacity of a given refrigeratingapparatus which will result from the substitution of one refrigerant for another. 1 In a given apparatus, it is not possible to a refrigerant having a boiling point too much lower than that for which the apparatus Ehas been designed, as the power input becomes desirabIy high andthe compressor-motor become-s overloaded.
:In' order to provide somewhat greater refrigerating capacity :for installations designed for the use of ehlorodifluoremethane withoutssubstantial change in power input, is therefore :desirable to employ a :gas which may he liquefied slightly below the boiling point of that material. In this general boiling range, propane and propylene are the only pure compounds .known having suitable 'pr'dper'tiesfand sufficient-availability for extensive use as refrigerants. vPropane :boils at 429 0.- :and propylene :a't -48 G; :Howeverpeach xofxthes'e @compdimds' is iiamnia'bl'e, and presents an :ex-
plesionhazardrin casefof leakage I The use of aaeotropie mixtures :of pure :materials as refrigerants :is disclosed in Si vPa'tent ND.- 2 ,l'0.l, 99:3 and elsewhere :inwtheart. Such mixtures have the advantage v:over pther @gas mixtures that the rvapor"- .eomposition sofifthe azeotrope is the same as the liquid composition with which it is in equilibrium. With nonazeotropic mixtures, fractionation takes place during the refrigeration cycle, with consequent increase in condenser pressures and reduction in evaporator pressures and an overall loss of emciency. Azeotropic gas mixtures are not subject to this defect.
It is an object of this invention to provide lowboiling compositions which are useful as refrigerating agents, and more particularly to provide an azeotropic mixture which is effective in low temperature refrigerating installations. A further object is to provide a refrigerant which may be used to give somewhat greater refrigerating capacity with apparatus designed for use with chlorodifiuoromethane.
I have discovered that mixtures of 1,1-difluoroethane and monochloropentafluoroethane form an azeotrope boiling at approximately 41.3 C., in which about 69 mole percent is monochloropentafiuoroethane. The mixture is a highly useful refrigerant suitable for replacement of chlorodifluoromethane in refrigeration equipment when somewhat greater capacity is desired.
The boiling points of mixtures of 1,1-difluor ethane and monochloropentafluoroethane were determined experimentally with the following results:
Boiling Mole percent monochloropentafiuoroethane point 0 O It is apparent from these figures that a minimum-boiling azeotrope exists at approximately 69 mole percent monochloropentafluoroethane and that the change in boiling point between the limits of 60 and 80 mole percent monochloropentafluoroethane is very small. The boiling point of the mixture containing 60 mole percent monochloropentofluoroethane and also of the mixture containing 80 mole percent of this component will be seen to be approximately -41.1 C.
In preparing these mixtures, it is desirable that the components be at least 99% pure and that they contain no appreciable amount of impurities which are corrosive or which separate upon evaporation, so as to interfere with the efficiency of refrigeration. No special mixing procedure need be followed, provided the proper relative amounts of the two components are used.
The compositions disclosed herein are chemically inert, non-inflammable and are essentially non-corrosive. They combine the valuable char- '4 acteristics possessed generally by fluorochlorohydrocarbons with a low boiling point which is of particular significance when low temperatures are to be attained or when extra capacity must be obtained with existingrefrigerating equipment.
If the azeotropic mixturehere disclosed is substituted for pure monochloropentafiuoroethane,
an increase in refrigerating capacity of 20% is obtained. The capacity of apparatus designed for and containing monochloropentofluoroethane may be increased easily and effectively by removing from 20 to 40 percent of the refrigerant and replacing it with an equal number of moles of 1,1-difluoroethane.
These refrigerants may be used in domestic or commercial refrigerators and freezers, industrial cooling systems and air-conditioning systems, or in any other system in which cooling is efiected by the evaporation and expansion of liquid refrigerant. In such systems, the expanded gas is compressed and condensed to a liquid, and is recycled to the expansion device. Various specific types of refrigerating units for which the compositions here disclosed are of value are described in Refrigeration Fundamentals, 6th edition, 1949 (American Society of Refrigerating Engineers).
1. A low-boiling refrigerant composition which consists of a mixture of 1,1-difiuoroethane and monochloropentafiuoroethane in which the mole percent of monochloropentafluoroethane is 69.
2. A low-boiling refrigerant composition consisting of a mixture of 1,1-difluor0ethane and monochloropentafluoroethane, in which the mole percent of monochloropentafiuoroethane is between and 80.
References Cited in the file of this patent UNITED STATES PATENTS Name Date Reed et 'al Aug. 16, 1949 Number OTHER REFERENCES