2022 Volume 39 Issue 4 Pages 311-
In order to explore alternatives to R23 refrigerant for ultra-low temperature applications, information on the liquidus point temperature, which serves as a guideline for the lowest operating temperature limit, is required. Accordingly, the liquidus point temperature of R469A (R744/R125/R32:35.0/32.5/32.5 mass%), which is recently being considered for commercial use, was experimentally determined to be 184.3 K ± 0.7 K. In comparison with the prediction equation, the activity coefficient representing the deviation from the ideal mixing was adjusted to be 0.887 for R744 for better agreement between prediction and measurement. The composition dependence of the liquidus point temperature was predicted by using the activity coefficient of 0.887 for R744/R125/R32 ternary system. It was confirmed that the liquidus point temperature depends dominantly on the mass composition of R744 and that the R744 mass composition must be less than 15 mass% to keep the liquidus pointe temperature below -100 °C. On the other hand, a volumetric capacity is maintained as that of R23 at R744 mass compositions more than approximately 81 mass%, which is a trade-off with the liquidus point temperature.
