充注量对冰场跨临界CO_(2)制冷系统性能的影响

Effect of the refrigerant charge on performance of transcritical CO_(2) refrigeration system in ice rink

为了提高冰场跨临界CO_(2)制冷系统的实际运行性能,搭建了跨临界CO_(2)制冰系统试验台,研究了在不同节流阀开度和高压压力下,充注量对系统性能的影响。结果表明:在充注量一定时,节流阀对蒸发器出口干度与过热度的调节能力有限;合适的充注量使得蒸发器出口制冷剂状态处于饱和态附近,不会出现大幅过热现象;随着充注量的增加,系统的质量流量显著增加,压缩机等熵效率略有下降,充注量每增加0.4 kg,系统质量流量增加约23 kg/h,压缩机等熵效率下降约1.1%;3种充注量下,系统均存在最优高压压力和COP,最优高压压力范围为7.9~8.3 MPa,最优COP范围为1.34~1.75;充注量为4.0 kg时的系统性能最优,在最优高压压力下,制冷量为6.5 kW,COP为1.75,稳定冰面温度为-16.5℃,制冰时间为135 min;相对于3.6 kg和4.4 kg充注量,充注量为4.0 kg的制冷量分别提高了38.3%和8.3%,最优COP分别提高了30.6%和21.5%,制冰时间节省了10.0%~15.6%。研究结果可为CO_(2)制冰系统运行与维护提供参考。

In order to improve the actual operation performance of the transcritical CO_(2) refrigeration system in ice rinks,a transcritical CO_(2) 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 CO_(2) ice-making systems.