This paper presents the results of an experimental study of the flow visualization of the refrigerant R600a through a capillary tube with an internal diameter of 0.8 mm made from a FEP (fluorinated ethylene propylene) polymer that was installed in a small-scale, vapor-compression refrigeration system. The main purpose of the study was to determine the flow patterns of the refrigerant flow in capillary tubes under different operating conditions and to verify whether the results obtained using a FEP tube are representative for the flow of a refrigerant in copper capillary tubes. The results of the study revealed that the two-phase refrigerant flow in the FEP capillary tubes consists predominantly of slug flow. These slugs continuously expand while traveling downstream. It was also found that different operating conditions can have a strong influence on the frequency of the vapor bubbles’ formation and their growth. In addition, an experimental study of the effect of local or global imperfections on the inner surface of the FEP tube was performed. In some cases the imperfections increased the number of vapor-bubble inception points, which caused a homogenization of the two-phase flow.

本文介绍了制冷剂R600a通过内径为0.8 mm的毛细管的流动可视化的实验研究结果，该毛细管由FEP（氟化乙烯丙烯）聚合物制成，并以小规模，蒸汽压缩方式安装制冷系统。该研究的主要目的是确定在不同工作条件下毛细管中制冷剂的流动方式，并验证使用FEP管获得的结果是否代表铜毛细管中制冷剂的流动。研究结果表明，FEP毛细管中的两相制冷剂流主要由团状流组成。这些弹头在向下游移动时不断膨胀。还发现，不同的操作条件可能会对气泡的形成频率及其增长产生重大影响。另外，进行了对FEP管内表面局部或整体缺陷影响的实验研究。在某些情况下，这些缺陷会增加汽泡起始点的数量，从而引起两相流的均质化。