Effect of the refrigerant charge on performance of transcritical CO2 refrigeration system in ice rink
In order to improve the actual operation performance of the transcritical CO2 refrigeration system in ice rinks,a transcritical CO2 ice-making system experimental setup was established.The effects of refrigerant charges on ice-making system performance under different openings of throttle valve and high-side pressures were studied.It is found that the adjustment ability of the throttle valve to the evaporator outlet refrigerant dryness and degree of superheat is limited under the fixed refrigerant charge.The appropriate charge can make the refrigerant be in a saturated gas state at the evaporator outlet without significant degree of superheat.With the increase of the refrigerant charge,the mass flow rate of the system increases significantly,and the isentropic efficiency of the compressor decreases slightly.With the increase of the charge by 0.4 kg,the mass flow rate increases by about 23 kg/h,and the compressor isentropic efficiency decreases by about 1.1%.The optimal high-side pressure and COP exist in the system under the three charges,and the optimal high-side pressure ranges from 7.9 to 8.3 MPa,and the optimal COP ranges from 1.34 to 1.75.When the charge is 4.0 kg,the system has the best performance,the cooling capacity is 6.5 kW,the system COP is 1.75,the stable ice surface temperature is-16.5℃,and the ice-making time is 135 min under the optimum high-side pressure.Compared with 3.6 kg and 4.4 kg charge,when the charge is 4.0 kg,the cooling capacity increased by 38.3%and 8.3%respectively,the system COP increased by 30.6%and 21.5%respectively,and the ice-making time is saved by 10.0%～15.6%.The research results can provide reference for the operation and maintenance of CO2 ice-making systems.
CO2ice-making systemrefrigerant chargeopening of throttle valveice-making capacity
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