A Cascade refrigeration system using mixture of carbon dioxide and hydrocarbons for low temperature applications

Various binary mixtures of carbon dioxide and hydrocarbons, especially propane or ethane as alternative natural refrigerants to Chlorofluorocarbons (CFCs) or Hydrofluorocarbons (HFCs) are presented in this study. Their environmental performance is friendly with an Ozone Depletion Potential (ODP) of zero and Global Warming Potential (GWP) <20. Experimental studies for some binary mixtures of carbon dioxide and propane or ethane were performed at low temperature circuit in a cascade refrigeration system. The mixture of carbon dioxide and propane at the optimal composition 70:30 in the mass fraction was reached at an evaporating temperature of -68°C. For temperatures <-70°C then a mixture of carbon dioxide and ethane was used. The optimal composition of carbon dioxide and ethane equaling 66:34 in the mass fraction was reached at an evaporating temperature of-75°C.