Simulation and optimization of CO2/HCs transcritical heat pump system
In order to study the performance of a transcritical CO2/HCs mixed refrigerant single stage heat pump system with throttle valve,a system model was established for the CO2/R1270 and CO2/R290 mixed refrigerants,and it was verified through experiments.The effects of evaporator inlet temperature,gas cooler outlet temperature,high-pressure pressure,cooling water temperature and flow rate on system performance were analyzed.And the system optimization is carried out by analyzing the effects of inner pipe diameter,outer pipe diameter,and pipe length of the gas cooler on heat transfer coefficient and heat transfer capacity.The results show that when the inlet temperature of the evaporator increases,the outlet temperature of the air cooler and the inlet temperature of the cooling water decrease,and the cooling water flow rate increases,COPc increases.The optimal refrigeration high-side pressure for CO2/R1270 and CO2/R290 system is around 9 MPa and 8.5 MPa,which is 3%and 8%lower than that of pure CO2,respectively.Properly increasing the inner pipe diameter or reducing the outer pipe diameter of gas cooler can effectively improve its heat transfer capacity.The research results can provide reference for the optimization and design of a transcritical CO2/HCs mixed refrigerant systems.
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