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When my face is full of sweat, I go near the A.C. and when the cool air touches my sweat it feels colder than dry parts? Why does the sweat feel colder than dry parts?

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    $\begingroup$ Because it evaporates and removes heat from your body. $\endgroup$ – orthocresol Sep 8 '17 at 15:04
  • $\begingroup$ Sweat is supposed to cool you down and has been evolutionarily ‘designed’ and kept that way. $\endgroup$ – Jan Sep 9 '17 at 7:28
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The heat of evaporation of the water is $\pu{2260J/g}$. That means for every one gram of water, it takes $\pu{2260J}$ of energy to vaporize it. The water (evaporating) takes the needed heat energy from your $\pu{37 ^\circ C}$ body.

Source

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    $\begingroup$ And OP would feel the same effect if they used plain tap water instead of sweat. $\endgroup$ – Jan Sep 9 '17 at 7:28
  • $\begingroup$ @Jan Sorry but what does OP mean? $\endgroup$ – Ram Keswani Sep 9 '17 at 8:47
  • $\begingroup$ But then I should feel the same when near a fan, but A.C. seems to be much cooler. Why? $\endgroup$ – Ram Keswani Sep 9 '17 at 8:49
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    $\begingroup$ @RamKeswani OP is original poster; in this case the person who asked the question (you). And you do feel the same effect near a fan. The aircon is colder because it is blowing cool air at you rather than ambient air. $\endgroup$ – Jan Sep 9 '17 at 9:13

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