Maximum exergy input rate from a hot stream in solar driven refrigerants

The authors believe that reducing the size of solar-driven refrigerators and air conditioning systems will make them more attractive to potential users. This paper presents a contribution to understanding the behaviour of such systems with a view to determining the manner in which refrigeration rate, mass flows and heat transfer areas are related. The intention is to make possible the identification of preliminary design rules. The basic thermodynamic problem of how to obtain maximum exergy input rate in a solar-driven refrigerator is considered. The existence of an optimal refrigerant flow rate for maximum refrigeration is investigated. The analysis proceeds by relating the entropy generation rate, the physical and operating parameters, and the constraints of the system, through well-established heat transfer relationships. Finally, a thermodynamic analysis determines the optimal characteristics that lead to minimum entropy generation. The second law efficiency is identified as the appropriate figure of merit for the thermodynamic optimum.