Air Handling Equipments & Systems are a device which cools water through the evaporation of water. This process tends to differ from the traditional air conditioning systems which use vapor compression. This requires a source of water as well as water must be consumed to make it operational.
A typical example would be perspiration or sweat, evaporation of which cools the body. In this regard the amount of heat transferred depends on the rate of evaporation. The greater the difference is observed when the temperatures of two different places are compared in terms of the evaporating cooling effect. When temperatures are the same no evaporation in the air occurs and the cooling effect tends to be minimal of sorts. At a given temperature the wet bulb temperature happens to be lowest temperature which can be attained by evaporative cooling.