When using a Mollier diagram, what is the starting point for determining saturation vapor temperature?

The correct approach when using a Mollier diagram, which presents the relationship between enthalpy, temperature, and other properties of refrigerants, involves understanding the concept of saturation. Saturation vapor temperature is dependent on the pressure of the refrigerant. To determine the saturation vapor temperature, one typically refers to the pressure of the refrigerant being used in the system.

The choice of 19°F as the starting point signifies a specific pressure where the refrigerant begins to change from liquid to vapor. At this temperature, the corresponding saturation vapor temperature indicates the point at which the refrigerant can begin to absorb heat and transition into vapor.

In the context of the other temperature options, such as 26°F, 30°F, and 85°F, these points may correspond to higher saturation pressures or may not align with the refrigerant’s phase change characteristics at typical operational pressures. Hence, 19°F is particularly relevant for determining saturation vapor temperature under specific commonly encountered conditions in industrial refrigeration systems.