Nature’s most efficient means of cooling is through the evaporation of water Evaporative cooling works in the principle of heat absorption by moisture evaporation. The process happens whenever dry air passes over water. Some of the water will be absorbed by the air. This happens because the temperature and the vapor pressure of the water and the air attempt to equalize. Liquid water and the air attempt to equalize. Liquid water molecules become gas in the dry air, a process that uses energy to change its physical state. Heart moves from the higher temperature of the air to the lower temperature of the water resulting in cooler air. The evaporative cooler draws exterior air into special pads soaked with water, there the air is cooled by evaporative, and then circulated.