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Here's the simple difference between AHU and HVAC:

HVAC = Heating, Ventilation, and Air Conditioning
It’s the whole system that controls temperature, humidity, and air quality in a building.
HVAC includes everything — chillers, boilers, air conditioners, ducts, fans, thermostats, controls, and more.
AHU = Air Handling Unit
It’s one part of the HVAC system.
The AHU's job is mainly to move and condition air — meaning it takes in outside air, filters it, heats or cools it (often with the help of a coil heat exchanger), and then distributes it through the building.

Simple way to remember:

HVAC = the entire system (like a full orchestra).
AHU = one important player (like the violin section).

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.

Category industry

What is the difference between AHU and HVAC?

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