Compositions – Vaporization – or expansion – refrigeration or heat or energy...
Patent
1996-04-19
1997-11-18
Green, Anthony
Compositions
Vaporization, or expansion, refrigeration or heat or energy...
C09K 504
Patent
active
056884320
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a refrigerant composition, which contains no chlorine atoms.
BACKGROUND
Chlorofluorocarbon (CFC) gases, such as refrigerant R12 (CCl.sub.2 F.sub.2), have been used for many years as refrigerants and are especially used in domestic refrigerators and car air conditioning systems. However, such gases have been implicated in environmental damage. These gases, which are very inert, are released from refrigeration systems at ground level and diffuse into the upper atmosphere. Because of their inertness, the gases are able to survive without decomposition until they reach the stratosphere where they are broken down by ultra-violet radiation, releasing chlorine atoms which catalyse breakdown of the stratospheric ozone layer. There has recently been considerable concern about reduction in stratospheric ozone levels and this has led to proposed restrictions and prohibitions on certain CFC's.
Other refrigerants such as chlorodifluoromethane (R22) are environmentally less objectionable as they tend to be degraded naturally at lower levels of the atmosphere before reaching the ozone layer. However, R22 contains chlorine and is still considered to contribute to ozone depletion. Further, R22 has a higher index of compression than, for example, R12, such that compressor discharge temperatures become excessive at pressure ratios which would not cause excessive discharge temperatures if R12 were being used.
It is among the objects of the present invention to provide a refrigerant composition which does not contain any chlorine but which has acceptable refrigerant characteristics for use in vapour compression refrigerators as a replacement for refrigerant R22 and/or R12 in existing refrigeration equipment.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a refrigerant composition for use in a refrigeration apparatus which comprises a mixture of:
(i) pentafluoroethane;
(ii) tetrafluoroethane; and
(iii) a hydrocarbon selected from isobutane, propane and mixtures thereof.
A further aspect of the present invention provides a method of refrigeration which employs the composition as a refrigerant medium, particularly a vapour-compression refrigerator.
A still further aspect provides a refrigeration apparatus which employs the composition as a refrigerant medium, particularly a vapour-compression refrigerator.
None of the components of the mixture contribute to ozone depletion nor are any toxic to humans. Further, the mixture may be used with a variety of existing lubricants as conventionally used in vapour compression refrigeration apparatus, including mineral oil lubricants, alkylbenzene lubricants and polyolester lubricants. Specialised lubricants are not required.
It is found that by forming mixtures of these three or four components in chosen proportions, it is possible to provide refrigerant compositions which have pressure-temperature relationships which are sufficiently similar to those of the current refrigerants R22 and R12 to allow their use as replacements therefor in existing refrigeration equipment. The pressure-temperature relationship refers to the vapour pressure of the refrigerant composition at various temperatures corresponding to those used in the refrigeration apparatus. Thus, the design pressure capabilities of the apparatus are not exceeded. It is also found that the refrigeration capacities of the compositions of the invention may be arranged to be similar to those of the current refrigerants R22 and R12, so that the refrigeration capacity (i.e. the amount of cooling produced) of refrigeration apparatus intended to be used with R22 or R12 respectively is substantially unaffected.
Advantageously, the compositions of the invention tend to have lower compressor discharge temperatures than the corresponding conventional refrigerant.
The pentafluoroethane (R125) is preferably present in an amount of 0.5 to 60 wt %, particularly 1 to 50 wt %. In compositions for use as an R22 replacement, R125 is preferably pres
REFERENCES:
patent: 5108637 (1992-04-01), Pearson
Green Anthony
Star Refrigeration Limited
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