compared and discussed for better performance of refrigeration system with respect to
the injection type and ratio. In vapor injection,
the COP decreased with increasing injection ratio while in the liquid injection, the COP increased up to 10% of injection ratio and decreased beyond that. Thus, the liquid injection up to 10% is recommended at high compression ratio in order to minimize the performance decrease and extend operating range of a refrigeration system. In addition, the subcooling for liquid injection could be considered as a proper parameter to control the injection for the reliable operation in the liquid injection case.