What is the term for a vapor in contact with a liquid?

The term for a vapor in contact with a liquid is "Saturated Vapor." This occurs when the vapor and the liquid coexist in a state of equilibrium at a specific temperature and pressure. In this condition, any additional heat added to the system will not increase the temperature of the liquid; instead, it will change some of the liquid into vapor. This equilibrium condition is critical in refrigeration and air conditioning systems, as it dictates how effectively heat can be transferred during the phase change between liquid and vapor.

Saturated vapor represents the maximum amount of vapor that can exist in contact with a given amount of liquid at a specific temperature and pressure. Recognizing this concept is essential for understanding the principles of thermodynamics and fluid mechanics as they apply to HVAC applications.