When an expansion valve is operating correctly, what state will the refrigerant at the end of the evaporator be in?

When an expansion valve is functioning correctly, the refrigerant exiting the evaporator will be in a specific state that maximizes efficiency and cooling capacity. The correct state at the end of the evaporator is that it should ideally be a mix of liquid and vapor.

In the evaporator, the refrigerant absorbs heat from the surroundings, which causes it to change phase from liquid to vapor. If the refrigerant exits the evaporator as only superheated vapor, it indicates that it has absorbed more heat than necessary, which means it has been heated significantly beyond its saturation temperature and could hinder the refrigerant's efficiency in the cycle.

In contrast, having only liquid at the end of the evaporator would mean that the refrigerant has not properly absorbed enough heat to facilitate the cooling process, while only subcooled liquid would suggest that the refrigerant is too cold and lacks the necessary energy absorption.

Therefore, the correct answer involves understanding that at the end of the evaporation process, a proper functioning evaporator allows the refrigerant to exit in a state where it can effectively continue through the cycle, creating a mix of liquid and vapor.