please explain about A.H.U (air handle uni), the process making the air cool, types of ahu, etc.....?

Answer 1

When gases (especially ideal gases) get compressed, they heat up. In a heat exchanger (radiator) they give this heat to the atmosphere, or a handy water supply.

If the gas is piped somewhere else, and allowed to expand, it *cools*, and absorbs heat in a similar heat exchanger.

*MOST* HVAC units (AHUs, etc.) use a refrigerant rather than a simple gas, which has the effect of absorbing or rejecting more heat over a narrower temperature range, making them more efficient. Ammonia used to be popular for this, but leaks were toxic and dangerous. The CFCs damaged ozone and were powerful greenhouse gases. The newer CFCs are less so.

Answer 2

An air handling unit consists of a fan or blower and a set of coils to exchange heat through. In a freon based system, this unit might also be referred to as the evaporator. The compressed freon would go through an expansion valve and then into the coils where air would be blown through the coils and cool the air.
If the system was a chilled water system, the cold water is run through the coils to cool the air.