Cooling through evaporation is a natural phenomenon that occurs everywhere around us. We sweat and cool the body by the evaporation of the sweat, and dogs pant and cool their body by evaporating the saliva. All these and many more such examples of evaporative cooling touch every part of our lives on a daily basis.
The same phenomenon is used in air evaporative cooling system. The principle used in this system is quite simple, where the water uses the latent heat of the surrounding atmosphere to turn into vapours. As a result, the temperature of the surrounding atmosphere drops down a few degrees. When this technology is used in air conditioning, it helps to cool your home and offices.
How Evaporative Cooling Works: Air evaporative cooling system uses the same principle of perspiration. Here is a step by step process flow of how it works:
• The sunlight heats up the air inside the buildings.
• The temperature rise in gauged by heat exchangers that pass the hot air through the refrigerant plant.
• The hot air while passing through the plant will convert the refrigerant liquid into vapours by the process of boiling. In the process the latent heat of the air is passed on to the vapours and the air cools down.
• The colder air is circulated back to the room. This air flow process continues and the temperature of the room gets maintained.
• Water from a cooling tower passes over the refrigeration plant and the water cools down the refrigerant vapours to convert back into liquid. The refrigerant is now ready to cool down more air by converting into vapours.
• In the process the heat gets transferred from the refrigerant to the water.
• The hot water will go back to the cooling tower where it will cool down. This cool water is now ready to absorb more heat from the refrigerant vapours.
• This is a cycle that keeps going on and on. Each component loops back to the original point to absorb more heat and the cooling process continues.
The cooling towers can be of two types – open and closed. In the open cooling tower the hot water is sprayed over the fills. This increases the surface areas of the water, and thus transfer of heat from water to air is faster.
In the closed cooling tower, water is not exposed to the atmosphere, and instead cold water or a solution of ethylene is used to reduce the temperature of water. The solution used for cooling in this method is enclosed in a coil, and hot water flows over the coil to cool down.
When used in air conditioning, evaporative cooling gives cool fresh air. The air cooled in this method is not dry and is also allergen free.