Development and validation of variable frequency transcritical CO2 heat pump systems.

In order to improve the performance of transcritical CO2 heat pump system, a variable frequency transcritical CO2 heat pump water heat system is developed. Using variable frequency compressor, the transcritical CO2 heat pump system could run in the condition of wide temperature range and achieve considerable energy savings. The experimental system can be switched to conventional transcritical CO2 heat pump system (TCHS), transcritical CO2 heat pump system with internal heat exchanger (TCHSI), transcritical CO2 heat pump system with ejector (TCHSE) and transcritical CO2 heat pump system with both internal heat exchanger and ejector (TCHSEI). Experimental investigation on the performances of TCHS and TCHSE are presented in this paper. Key systematic parameters are analyzed. The maximum heating coefficient (COPh) of TCHS is 4.04 when the evaporation pressure is 4.1MPa. In TCHSE, the entrainment ratio of the ejector is 0.723 and the the pressure lift ratio is obvious when the evaporation pressure is 3.12MPa.