1997 年 14 巻 1 号 p. 75-85
Mixing of refrigerant with refrigeration oil has great influence on viscosity and foaming of the oil in refrigerant compressors. This paper dealt with transient characteristics of mixing process of refrigerant into refrigeration oil. The mixing phenomena were investigated by using an experimental apparatus which modeled process of the oil-refrigerant mixing in a casing of refrigerant compressors. Mass of refrigerant dissolved into the oil stored in a cylindrical vessel was recorded continuously under different conditions of pressure, temperature, amount of the oil, diameter of the vessel and combination of the refrigerant and the oil. On the other hand, the mixing phenomena were analyzed theoretically by two mathematical models, one is a one-dimensional diffusion model and the other is a mass transfer model. Based on the comparison of theoretical and experimental results, values of apparent diffusion coefficient and mean mass transfer coefficient were decided. The mixing process can be easily predicted by these models, but an applicable range of mass transfer model is wider than that of diffusion model. The mixing characteristics were correlated by a non-dimensional equation composed of Schmidt number, Grashof number and aspect ratio in the diffusion model and by another non-dimensional equation composed of Sherwood number, Schmidt number and Grashof number in the mass transfer model.