Table 16-10 is a pressure-temperature table for R-401a. Like most other new refrigerant blends, R-401a is a nonazeotropic mixture. Consequently, the several components of the refrigerant blend do not vaporize at the same temperature at a common pressure. For this reason, the mean evaporator temperature obtained with R-401a is approximately 4F below the saturation temperature listed in the table for given pressure. This also is true for R-401b.
The saturation temperature listed in Table 16-10 corresponding to a given pressure is taken as the temperature at which the last drop of liquid in the mixture is vaporized and is referred to as the “dew point” temperature. Similarly, the several components of the mixture do not condense at the same temperature at a common pressure , and for any given pressure, the condensing temperature is taken as the temperature at which the last bit of vapor is condensed and is called the “bubble point” of the mixture. The dew point and bubble point temperature for some of the refrigerant blends now in use are listed in Table 16-11, along with a pH diagram that illustrates these conditions.