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The sweat on our body evaporate taking energy from our body in the form of heat.the temperature of our body decreases and we feel cool. Thus sweating cools down our body.

Now why does our body cool down faster?

All the sources I have come across to find the answer,as I understan , state that, the fan speeds up the eveporation process ,so sweat eveporates faster taking energy from our body faster,and we get the feeling of chill sooner. However,this does not seem to me to be the actual case.

But my understanding on the following points are,

HOW EVAPORATION SPEED INCREASES WHEN THERE IS AIR FLOWING IN AIR(CAUSED BY THE FAN IN THIS case): The air is flowing becauseof the fan.so the speed of air molecules is greater. They have more kinetic energy .they hit hit the sweat molecules with more kinetic energy. This energy helps the sweat molecules overcome the intermolecular force among themselves and evaporate faster. In a word ,my understanding is that sweat evaporates faster because they are getting the xtra energy to evaporate faster from the flowing air ,and not from the body . Which means the rate of heat energy transfer from my body does not increase in this case.

Then how does my body cool down sooner?

Is it that ,the body starts sweating more when sweat eveporates faster and despite getting some energy from the turbulent air the sweat still takes some energy from the body to evaporate and that is the process that causes the body to lose more heat in a shorter period of time and thus cool down the body faster?

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  • $\begingroup$ Is turbulence the right term here? Isn't air flow caused by fan quite well defined? $\endgroup$ – Protein Jul 16 at 6:52
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It is necessary that the swear drops evaporate, extracting the latent heat from our body in order to cool us.

The kinetics of the evaporation depends on the amount of water vapor in the air, compared to the maximum vapor allowable for that temperature.(see this answer).

If the air is saturated of water vapor, the evaporation is not possible, and we are simply wet, without getting cooler.

But if it is not saturated, the air surrounding ourselves is being richer in water vapor from our bodies, that gradually difuses to the environment.

The air current from a fan accelerates this process, avoiding that, due to a high concentration of water vapor near our skin, the evaporation be too slow.

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One explanation may be from chemical equilibrium . The air flow blows away the vapours removing the products and lowering the reaction coefficient and thus helps move the reaction in forward direction.

Higher humidity results in a lower rate of evaporation. You could see it as more vapour moleucles hitting the liquid surface and thus more molecules returning to liquid.

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  • $\begingroup$ This and seems to be more appropriate for chemistry SE😅 $\endgroup$ – Protein Jul 16 at 6:54
  • $\begingroup$ Thanks for the edit suggestion. $\endgroup$ – user459284 Jul 16 at 23:12
  • $\begingroup$ What reaction are you talking about?Do you mean the the sweat turning into gas from liquid a reaction? $\endgroup$ – user459284 Jul 16 at 23:16
  • $\begingroup$ Yup that's the reaction $\endgroup$ – Protein Jul 17 at 9:17

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