绝热毛细管的临界流动分析

制冷系统的蒸发温度、制冷量、输入功率、性能系数随毛细管的改变而变化，其工作特性对整个系统而言显得十分重要的。因此对毛细管的流动过程建立了质量、能量和动量守恒特性方程，以熵最大原则建立了临界流状态下毛细管出口临界状态的参数关联式，分析计算了进口压力和毛细管内径对出口临界参数的影响，并与标准试验毛细管曲线进行了对比，结果表明，该模型在一定参数范围内与实际状况吻合。

Analysis of the Critical Flow in Adiabatic Capillary Tube

Evaporating temperature varies with the different balance points between capillary tube and compressor, thus the refrigerating capacity, power input and the coefficient of performance are changed. The characteristic of the capillary tube is of significant importance to the system. Thereby, most of the capillary tube in refrigeration system works in critical flow condition, and in this case, the mass, momentum and energy conservation equation could be listed, then be solved based on the theory that entropy is maximal. The paper presented a numerical model for the adiabatic flow in capillary tube, a detail analysis of the critical flow were given based on the numerical model, and the influence of the inlet conditions and size of the capillary tube were discussed. The model shows that it fits close to the testing data compared to the experimental curve given by standard test.