The heat exchanger inside an air handling unit (AHU) is a component that transfers heat between two airflows — typically between the incoming fresh air and the outgoing exhaust air — without mixing them directly.

Its main purposes are:

• Energy recovery: save heating or cooling energy by preheating or precooling incoming fresh air.

• Improve efficiency: reduce the load on the building’s heating or cooling system.

• Enhance indoor air quality: by maintaining ventilation without wasting energy.

There are different types of heat exchangers used in AHUs:

• Plate heat exchanger (fixed plate): Air flows across thin metal plates, transferring heat through the plate without mixing.

• Rotary heat exchanger (thermal wheel): A rotating wheel picks up heat from one air stream and transfers it to the other.

• Run-around coil: Uses a liquid (usually glycol water) circulating between two finned-tube coils to transfer heat between separate airstreams.

• Heat pipe: A sealed pipe with refrigerant inside moves heat from the warm side to the cool side passively.