带膨胀机和回热器的两级压缩跨临界CO_(2)制冷循环研究

Research on transcritical CO_(2) two-stage compression refrigeration cycles with expander and internal heat exchanger

通过对比3种不同的两级压缩跨临界CO_(2)制冷循环,研究节流阀、回热器和膨胀机对制冷循环COP和效率的影响。结果显示:在3种两级压缩跨临界CO_(2)制冷循环中,带膨胀机的制冷循环的COP和效率最高,带膨胀机和回热器的循环次之,带回热器和节流阀的循环的COP和效率最低;在合理参数范围内,增大压缩机1的压比可以提高3种循环的COP和效率;在合理参数范围内增大压缩机2的压比,3种制冷循环的COP和效率均先增大后降低;增大压缩机和膨胀机的等熵效率均可以显著提高两级压缩跨临界CO_(2)制冷循环的COP和效率。

The influence of throttle valves,internal heat exchanger and expanders on COP and the exergy efficiency of refrigeration cycles are studied through comparing three transcritical CO_(2) two-stage compression refrigeration cycles.The results show that the COP and exergy efficiency of the cycle with expander is the highest in the three transcritical CO_(2) two-stage compression refrigeration cycles,the cycle with internal heat exchanger and expander takes second place,and the cycle with internal heat exchanger and throttle valve has the lowest COP and exergy efficiency.The COP and exergy efficiency of the three cycles can be improved by increasing the pressure ratio of the first compressor in a reasonable range.The COP and exergy efficiency of the three cycles first increase and then decrease with the increase in the pressure ratio of the second compressor in a reasonable range.The COP and exergy efficiency can be significantly improved by increasing the isentropic efficiency of compressors and expanders.