An evaporator is the portion of an HVAC system or plant that absorbs heat from the air and transfers it to the refrigerant, making the refrigerant evaporate (similar to boiling). In the evaporator, the refrigerant evaporates at a lower temperature because the pressure is lower than in the condenser.

This process cools the surface of the evaporator and is the cold side of the refrigeration process, it is typically indoor (except in the case of a heat pump)

In a conventional refrigeration system, an evaporator is a component of an air conditioning or refrigeration system that is responsible for absorbing heat from the air inside a building or space. It consists of a coil or series of tubes through which a refrigerant is circulated at lower pressure than the condenser. As the refrigerant absorbs heat from the air, it evaporates (or boils) into a gas.

The evaporator is typically located inside the building or space that is being cooled, and it is often located in the air handler or indoor unit of a split-system air conditioner. The evaporator is an important part of the air conditioning system because it is responsible for removing heat and humidity from the air inside the building, which helps to keep the space comfortable.