How do the temperature lines run within the SAT region of an Enthalpy diagram?

In an Enthalpy diagram, the temperature lines in the Saturation (SAT) region are represented as horizontal lines at a constant pressure. This horizontal orientation indicates that as heat is added or removed from the refrigerant, the temperature remains constant during the phase change – whether it is from liquid to vapor or vice versa. This phenomenon is essential in understanding how refrigerants behave during the cooling cycle, particularly during the phase changes that occur in the evaporator and condenser.

In this region, the refrigerant is in equilibrium between its liquid and vapor phases, so any addition or removal of heat does not result in a temperature change, aligning perfectly with the characteristics of a constant-pressure system. This aspect of the enthalpy diagram is crucial for operators to analyze and calculate the efficiency and performance of refrigeration and air conditioning systems effectively.