Working mechanism of Humidifiers.

When air blows over a wet surface it gets saturated with water vapour. Its relative humidity becomes almost 100%. This implies that some liquid water evaporated to form the vapour. For this to happen the latent heat of vaporization has to be supplied. In this case the air supplies the heat and in the process itself is cooled.

it is however not used in southern India, owing to the humid climate prevailing here, which may lead to causing pneumonia.

Not exactly. If the humidity of the air is high no evaporative cooling takes place. These units work well in Karnataka where RH is not very high. Pneumonia is not caused by high humidity. Actually our noses and the passages up to the lung humidify the air we breathe to 100% RH before the air enters the lungs. Otherwise we will have a major problem of lungs, which have a huge area of about 20 square meters drying up.

is it the cooling system being discussed here.? the chiller coil and evaporative cooling ones?

Amith Guptais it the cooling system being discussed here.? the chiller coil and evaporative cooling ones?

What is being discussed is the air coolers also known as desert coolers. The hot air that has a low enough RH gets cooled as it passes over a large surface area wet fabric because of latent heat is removed from the air by the evaporating water film. However, the air gets 100% humidified.