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:
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Energy recovery: save heating or cooling energy by preheating or precooling incoming fresh air.
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Improve efficiency: reduce the load on the building’s heating or cooling system.
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Enhance indoor air quality: by maintaining ventilation without wasting energy.
There are different types of heat exchangers used in AHUs:
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Plate heat exchanger (fixed plate): Air flows across thin metal plates, transferring heat through the plate without mixing.
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Rotary heat exchanger (thermal wheel): A rotating wheel picks up heat from one air stream and transfers it to the other.
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Run-around coil: Uses a liquid (usually glycol water) circulating between two finned-tube coils to transfer heat between separate airstreams.
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Heat pipe: A sealed pipe with refrigerant inside moves heat from the warm side to the cool side passively.
