Most users normally associate refrigeration with cold and cooling, yet the practice of refrigeration engineering deals almost entirely with the transfer of heat. This seeming paradox is one of the most fundamental concepts that must be grasped to understand the workings of a refrigeration system.
Cold is really only the absence of heat, just as darkness is the absence of light, and dryness is the absence of moisture.
After a liquid has changed to a vapor, any further heat added to the vapor raises its temperature so long as the pressure to which it is exposed remains constant. Since a temperature rise results, this is sensible heat. The term superheated vapor is used to describe a gas whose temperature is above its boiling or saturation point. The air around us is composed of superheated vapor.