What is the temperature at which the refrigerant starts to evaporate?

• A. Freezing point
• B. Boiling point
• C. Bubble point
• D. Saturation point

Answer: (C)

The temperature at which a refrigerant starts to evaporate is referred to as its saturation point. This is the temperature at which the refrigerant changes from a liquid to a gas at a given pressure. At the saturation point, the refrigerant is in equilibrium, meaning that any heat added will cause the liquid to start evaporating into vapor.

Understanding the saturation point is key, particularly in refrigeration and air conditioning systems, as it dictates the operating conditions under which the refrigerant can effectively absorb heat and operate within the cycle. Both the boiling point and bubble point refer to similar concepts, but the saturation point is more comprehensive as it encompasses the entire phase transition process. The freezing point is related to the transition from liquid to solid rather than liquid to gas, and therefore does not apply in the context of refrigerant evaporation.