The optimal design of refrigerant mixtures for a two-evaporator refrigeration system

Abstract The use of liquid-phase mixtures is common in a number of industrial applications. Mixtures have certain advantages over individual components, and these have been exploited advantageously. For the case of refrigerants, a number of azeotropic mixtures are used in practise. The use of non-azeotropic refrigerant mixtures, however, is not as common. This paper looks at the design of refrigerant mixtures for a refrigeration cycle consisting of two evaporators operating at two different temperatures. Such a cycle has been proposed for use in, for example, a commercial refrigerator having a separate freezer section. Compared to the single evaporator cycle operating at the freezer temperature and circulating the cold air from the freezer to the rest of the refrigerator, the double-evaporator cycle can give higher efficiencies since cooling is not done at a lower temperature than what is required. Also, the use of nonazeotropic mixtures has a number of advantages over single component refrigerants and azeotropic mixtures. A mathematical programming approach developed earlier is applied to the double-evaporator cycle to obtain refrigerant mixtures that maximize cooling.