An experimental study of evaporation pressure drop in single circular small tubes was conducted for flow of C_3H_8, NH_3 and CO_2 under some various flow conditions. The test matrix encompasses the entire quality range from 0.0 to 1.0, mass fluxes from 50 to 600 kg m~(-2) s~(-1), heat fluxes from 5 to 70 kW m~(-2) and saturation temperatures from 0 to 10°C. The test section was made of circular stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm, and a length of 2000 mm in horizontal orientation. The test section was heated uniformly by applying an electric power to the tubes directly. The effects of mass flux, heat flux, saturation temperature and inner tube diameter are presented in this study. The pressure drop of CO_2 is the lowest among the working refrigerants. The experimental pressure drop was compared with some existing pressure drop correlations. Existing void fraction prediction methods were evaluated for the present experimental pressure drop. A modified pressure drop correlation using homogenous void fraction model is developed.
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机译：在一些各种流动条件下，对单圆形小管中的蒸发压降进行蒸发压降的实验研究，对C_3H_8，NH_3和CO_2的流动进行。测试矩阵包括0.0至1.0，质量势态的整个质量范围，从50至600 kg m〜（-2）s〜（-1），从5到70 kW m〜（-2）和饱和气温的热量0到10°C。试验部分由圆形不锈钢管制，内径为1.5mm和3.0mm，水平取向的长度为2000毫米。通过直接向管施加电力来均匀地加热试验部分。本研究介绍了质量磁通，热通量，饱和温度和内管直径的影响。 Co_2的压降是工作制冷剂中最低的。将实验压降与一些现有的压降相关性进行了比较。对本实验压降评估了现有的空隙部分预测方法。开发了使用均匀空隙率模型的改进的压降相关性。
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