The comparative analysis of the R290 heat pump system working with standard expansion valve and two-phase ejector

Abstract

The heat pump systems play a significant role in the global energy transition process of household heating sources towards zero-emission. One of the key technologies to improve the efficiency of heat pump systems utilizing natural working fluids is application of the two-phase ejector, which is able to recover part of the expansion losses. The comparative experimental analysis of a novel ejector-based air-source R290 heat pump was performed. The two two-phase bypass ejectors were installed in a R290 heat pump unit and a number of modifications were introduced to the baseline system. The adaptions included implementation of the internal heat exchanger, increasing the superheat at the compressor suction port, and a liquid separator for handling the two-phase flow at the ejector outlet. The performance evaluation of the system was based on COP and system heating capacity. The comparative analysis with the R290 heat pump utilizing standard expansion valve and two-phase ejector was carried out for typical operating conditions for its domestic application during heating seasons. The system working with an ejector as a throttling device allowed for up to 33% of COP improvement over the system utilizing an expansion valve. Additionally, the ejector implementation resulted in decreased pressure ratio of the compressor, which increased the system heating capacity by up to 90%.