Design optimization of refrigeration system for alternative refrigerants

Abstract

Man, from prehistoric times has been using refrigeration for a wide range of applications in his daily life. The major changes that have occurred in this field through ages mainly comprise of the changes in the trends in mode of creating refrigerating conditions. Having commenced with the use of naturally occurring ice and sailed through the use of a variety of compounds such as ammonia, hydrocarbons etc. and finally arrived at the use of CFCs and HCFCs. However, the use of CFCs and HCFCs results in the impending dangers of ozone depletion and global warming. Till date, a quantum of work has been performed to completely abolish the use of these CFCs and HCFCs at both the scientific as well as the= social fronts, but majority of these efforts have been abortive. In the recent times, the usage of mixtures of refrigerants has proved to be an excellent method of devising the substitutes for the menacing refrigerants. At the advent of the Montreal protocol, R134a has been recommended as an alternate refrigerant to R12. R134a is not miscible in mineral oil. Polyol ester (POE) based synthetic oils are recommended. On the other hand HC refrigerants do have flammable properties and safety standards that limit the usage of pure HC refrigerants for domestic appliances. Due to the above factors, safe conversion of existing R134a refrigerators with environmental friendly refrigerants would be critical for the Refrigeration and Air-conditioning sector. In India, more than 80% of the domestic refrigerators utilize R134a as refrigerant due to its excellent thermo physical properties. R134a is a high global warming potential gas and needs to be controlled as per the Kyoto protocol. It is reported that there is no singlerefrigerant or mixture available to satisfy both the Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) issues. In this scenario, the objective of the researcher is to develop an eco-friendly refrigerant mixture with negligible ODP and decreased GWP values that are nearly equivalent to R134a in its performance. In the present work endeavoured to fabricate a ternary zeotropic mixture of refrigerants (R134a/R600a/R290) which could be a drop in replacements for R134a.