Separation of oil from refrigerant is important to reduce the oil circulation rate in a refrigeration cycle. Since the oil separation depends on the droplet size of oil mist in a compressor and the condition of the oil film on the inner surface of the compressor shell, this study examined the wettability of a metal surface with the oil/refrigerant mixture and surface tension. The wettability of metal surfaces with PAG/CO₂ mixture was evaluated by measuring the contact angle of droplets on the metal surface. The surface tension of the mixture was measured using a pendant drop method. It was found that the wetting of the metal surface with the oil/refrigerant mixture showed a complete wetting, and the contact angle decreased with the refrigerant concentration. Taking the Ohnesorge number into account, the initial spreading of oil mist on the metal surface under discharge conditions should immediately become a viscus-dominant condition.

将油与制冷剂分离对于降低制冷循环中的油循环速率很重要。由于油的分离取决于压缩机中油雾的液滴大小以及压缩机壳体内表面上油膜的状况，因此本研究检查了油/制冷剂混合物对金属表面的润湿性和表面张力。PAG / CO ₂对金属表面的润湿性通过测量液滴在金属表面的接触角来评估混合物。使用悬滴法测量混合物的表面张力。已经发现，油/制冷剂混合物对金属表面的润湿显示出完全的润湿，并且接触角随着制冷剂浓度而减小。考虑到Ohnesorge数，在排放条件下油雾在金属表面的初始扩散应立即成为以粘度为主导的条件。