Working fluids for mechanical refrigeration - Invited paper presented at the 19th International Congress of Refrigeration, The Hague, August 1995

The phasing out of fully halogenated halocarbons becomes effective at the end of 1995 by international agreement. Under the same ozone depletion issue, the companion fluids HCFCs are suffering a similar fate, as they are considered controlled substances with a virtual phase-out by 2020, and more drastic reductions may be proposed in the near future. Some international action might also be agreed upon on refrigerants with regard to the threatened environmental emergency of anthropogenic global warming. Therefore, in choosing replacement fluids primary concern must be given to minimising the total warming impact, which, for most applications, calls for improved energy efficiency. During recent years, industry has scrutinised and proposed a number of new synthesised products as immediate drop-in or long-term replacements for fluids harmful to the environment. Together with some single-component new generation refrigerants, quite a few two-component, three-component or even four-component mixtures, both with zeotropic and azeotropic behaviour, are being considered. The main issues associated with the use of the new generation refrigerants are discussed, such as behaviour with oil; flammability; efficient use of temperature glides, fractionation and heat-transfer degradation with zeotropic mixtures. The full environmentally friendly option of resorting to natural fluids is also considered by examining some recent innovative applications as refrigerants of some hydrocarbons, ammonia, carbon dioxide, water and air. Copyright (C) 1996 Published by Elsevier Science Ltd and IIR