The Comparison of the Performance of Combined Ejector-Vapor Compression Cycles

In this paper, the performance of four prevalent combined ejector-vapor compression cycles are compared. A non-iterative algorithm for the analysis of ejector performance in critical operational mode has been used. Moreover, using flow parameters is proposed for estimating loss coefficient in the mixing process rather than using geometrical specification and operating conditions of the ejector. The effects of the operating conditions and refrigerant type on the coefficient of performance, thermal coefficient of performance, and ejector entrainment are investigated and analyzed. Results show that, at high condenser temperatures, the difference between coefficient of performance of combined cycle and conventional vapor compression cycle significantly decreases. Combined cycles which only utilize the waste heat of the condenser in the vapor compression sub-cycle have a lower coefficient of performance than those cycles using an external heat source and can be used in smaller rang of condenser and generator temperatures.