Optimum design of ejector refrigeration systems with environmentally benign fluids

A design methodology for simple ejector refrigeration systems of fixed cooling capacity operating with fixed temperatures of the external fluids entering the generator, the condenser and the evaporator is presented and applied for a particular combination of these four parameters. The results establish the existence of optimum values for the refrigerant pressure in the generator (PG) and the temperature difference in the heat exchangers (ΔT) which minimize the total thermal conductance of the system. These optimum values of PG and ΔT are particularly interesting since they yield high values for the coefficient of performance and the exergetic efficiency of the system. They have been determined for four refrigerants (R134a, R152a, R290, and R600a). An objective function, which to a first approximation is proportional to the product of the capital and operational costs, is defined and used to compare the performance of the system with these refrigerants.