Numerical investigation of the effect of microchannel evaporator design and operation on the improvement potential of ejector refrigeration cycles

Recent ejector studies have focused on the design and performance of the two-phase ejector and its effect on the performance of the ejector cycle. However, recent experimental work has shown that the effect of evaporator design on ejector cycle performance can also be quite significant. In this paper, a numerical model of a microchannel air-to-refrigerant evaporator, capable of accounting for heat transfer and pressure drop effects, is used to investigate the effect that different evaporator dimensions have on the performance of ejector cycles. Two ejector cycles are compared: The standard ejector cycle, in which the ejector is used to directly lift compressor suction pressure, and the ejector recirculation cycle, in which the ejector overfeeds the evaporator but does not directly lift compressor suction pressure. The effects of microchannel port hydraulic diameter, number of evaporator passes, and liquid feed rate are investigated. The analysis is performed with refrigerants R410A and CO2.