Auto A/C Terms - Glossary
Latent Heat of Evaporation

Every A/C system cools because the refrigerant in the evaporator is actually boiling and changing state to vapor refrigerant. In order to cause a liquid (refrigerant) to boil, it must, like water, absorb heat. The heat that is absorbed if known as latent heat, because it can not be measured with a thermometer, and that heat does not change the temperature of the substance.

The term ‘latent’ is a Latin term meaning ‘hidden’. Understand that when a liquid changes state, the vapor rising off that liquid is the same temperature as the boiling liquid. That’s because the heat that was absorbed to cause it to change state was consumed or used to cause the change of state. It can not be measured with a thermometer, therefore it is known as latent heat or latent heat of evaporation.

The amount of heat required to change a liquid into a vapor with out raising the temperature of the vapor above that of the original liquid.