What is AHU, FAHU, TFA and Heat wheel recovery system?

AHU: IS A MECHANICAL ASSEMBLY OF FANS,COILS,FILTERS AND HUMIDIFIER OR DEHUMIDIFIER INSTRUMENTS INCLUDED IN A CABINET HAS AN INLETS & OUTLETS ,

USED AS A BIG AIR CONDITIONER TO TREAT AIR  BEFORE DISTRIBUTE IT TO THE CONDITIONED AREAS.

FAHU : IS AIR AHU DEAL WITH FRESH AIR ONLY.

TFA : TREATED FRESH AIR.

HRW : IS AN INSTRUMENT TO SAVE ENERGY BY MAKING CONTACT BETWEEN EXHAUSTED AIR AND FRESH AIR ACROSS CONTACT SURFACE WITHOUT. 

AHU- Air Handling Unit. In AHU's mixing of fresh air and return air takes place.

FAHU- Fresh Air Handling Unit

TFA- Treated Fresh Air

HRW system- Heat Recovery Wheel- Using HRW, Heat is exchanged between exhaust air and fresh air, which will help to save energy.