中间完全冷却CO_2跨临界双级压缩节流循环

Trans-critical throttling cycle of CO_2 in two-stagecompression with complete inter-cooling

双级压缩是提高CO2跨临界制冷循环性能系数COP的有效途径,且中间完全冷却形式的性能优于中间不完全冷却形式。对于中间完全冷却CO2跨临界双级压缩节流循环,节流形式有一次节流(STDC循环)和两次节流(DTDC循环)。分析了高压压力和气体冷却器出口温度对STDC循环和DTDC循环的性能影响,并与CO2跨临界单级压缩(STSC)节流循环进行了比较。结果表明:在给定条件下,DTDC循环的COP值最大、STDC循环的最优高压压力值最高;随着气体冷却器出口温度的升高,3个循环的最大COP均减小,最优高压压力均升高,压缩机的等熵效率均降低。对于DTDC和STDC循环,最优中间压力值偏离高压压力与低压压力的几何平均值,但是对系统的性能系数影响不大。

Two-stage compression is an effective method to improve the coefficient of performance（COP）of trans-critical refrigeration cycle of CO2,and COP of a complete inter-cooling mode is higher than that of an incomplete mode.For the trans-critical throttling cycle of CO2 in a two-stage compression with complete inter-cooling,the throttling cycle can be divided into two types,single-throttling（STDC）cycle and double-throttling（DTDC）cycle.For these two cycles,the effects of outlet temperature of gas-cooler and heat rejection pressure on the COP are investigated,and compared with those in a single-stage compression（STSC）.The results indicate that under given condition,DTDC cycle presents the maximum COP,while the STDC cycle presents the highest optimum high pressure.For the three cycles,increase in gas-cooler outlet temperature decreases the COP,increases the optimum high pressure,and decreases the isentropic compression efficiency.The optimum inter-cooling pressure for STDC cycle and DTDC cycle deviates from the geometric mean of high pressure and low pressure,but this has little effect on the system performance.