音速による冷媒/油混合物の混合率測定

抄録

In refrigeration cycles, mixing of refrigeration oil with refrigerant has great influence on the cycle performance, and a concentration measurement of the refrigerant/oil mixture is inevitable. The method of measuring the concentration ratio by detecting density, electric capacity, and refractive index etc. of the mixture has been examined.
In this study, a sound speed measurement is applied to measure the concentration of the refrigerant/oil mixture. The sound speed of the mixture is measured by ultrasonic wave, and the relationship between the mixing ratio and the sound speed is obtained experimentally. There is a big difference between the sound speeds of refrigerant and refrigeration oil, and the sound speed can be a suitable physical property for the measurement of the mixing ratio of refrigerant/refrigeration oil mixture. Sound speed of R 410A/PVE mixture and CO₂/PAG mixture showed different tendency from calculation values based on a volume fraction. It is found that the change in the sound speed is sufficient to measure the mixing ratio of the refrigerant in the refrigeration oil when the oil mixing ratio is high.