电动汽车的一个可逆热泵系统除霜过程的参数分析

图

显示了上述所提到3个阀门开度的冷却过程对比结果。明显，开度为85%的阀，在除霜过程中，冷却剂在外部热交换器的出口已经被冷却。由于较低的质量流量，这将降低了除霜性能。在热交换器表面上的一个可视的仿真霜厚度在图

体现。

在85%的“Kvopt”到“Kvopt”之间，每隔30秒，依次从左到右排列。然而“Kvopt”值的阀门开度对应均匀快速的除霜过程，过小的阀门开度由于冷却剂的冷却导致除霜过程耗时多，这引起不均匀的除霜过程。

4、结论

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测量结果外部热交换器在选定操作条件下的除霜比逆循环除霜耗时少2分钟。在除霜过程中，压缩机的压力值达到37 bar 后会略有涨幅。在压缩机启动后，吸管的压力值总是保持着21 bar 。在压缩机启动2分30秒后，外部热交换器的冷却剂进口温度大约达到50℃.启动后，压缩机的功率保持在270W，速度保持在1500r/min，平均冷却剂流量21Kg/h.

含有一个热交换器的制冷剂循环的模型，模拟压缩机的工作功率Wdefrost与测量结果相比较显示的相对误差为1.6%。因此，根据这些仿真结果，不同节流阀参数分析似乎是合理的，原因在于该模型的可预测性。仿真结果表明，存在一个最佳的Kvalue 值使得除霜的运行时间和效率处于最佳。大的节流阀开度使得除霜时间增加和效率低。但是过小的Kvalue 值会更加加剧时间的增加，效率降低。这是由于较低的冷却剂质量流量所引起的结果，这将会引起冷却剂在交换器的最后阶段冷却。从而导致了不平衡的除霜过程。

对逆循环除霜过程的研究，表明在亚临界系统条件下使用二氧化碳作为工作流体（恒温冷凝），得到的结果也可能被转移到其他的除霜制冷剂中，如逆循环除霜过程与R134a，除霜热量很大一部分来自于过冷制冷剂冷凝，也可能导致不均匀的低效率的除霜过程。因此，优化膨胀阀开度（大小）的类似建议值得采纳。

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