Comprehensive experimental performance analyses of an ejector expansion transcritical CO2 system

Abstract

An experimental study is carried out to examine the simultaneous cooling and heating performances of an ejector expansion CO2 transcritical system with an adjustable ejector and a variable speed compressor under different operating conditions in detail. Experimental results show that the total capacity and the total COP of an ejector CO2 system reach their maxima at the ejector throat diameter of 2.0 mm under extreme operating conditions. As compressor frequency decreases from 60 Hz to 35 Hz, the total COP of an ejector cycle can be increased by up to 71.4%, although the total capacity can be decreased by 21.3%. Low outdoor air temperature benefits COPs while high indoor air temperature benefit cooling and heating capacity. The empirical correlations of COPs with ejector internal geometries, compressor efficiency and operating conditions are developed, which can be used for optimization of ejector CO2 vapor compression systems.