Question

How does a desert cooler work?

Answer 1

Firstly, Heat transfer not only depends on temperature gradient but also on humidity content in the air. For example, in rainy season or in coastal areas though the temperature of the surrounding is less, but we still feel hot because humidity is more. Higher humidity at a given temperature leads to difficulty in heat transfer.

Secondly, for a water droplet to evaporate it absorbs energy that is Latent heat , the amount of heat that is needed to evaporate the liquid, is drawn from it's surroundings thus cooling the surroundings! A phenomenon that happens in porous earthern pots that leads to the water inside to be cooler!

Keeping the above in mind, desert coolers employ the processes of cooling+humidification( increase humidity) unlike coolers used in normal regions which apply cooling+dehumification(decrease humidity).

In deserts(dry climate), humidity is very less and temperature gradient more thus high rate of heat transfer, thus making us hot!! Apart from cooling surrounding air,water droplets are added to this air to reduce the rate of heat transfer,temperature gradient.

In normal regions, humidity is reduced in summers to aid heat transfer in the given temperature gradient, due to evaporation that is sweating in our case.