Why does the air blown by a fan in a warm room seem cool? Surely it will be blowing hot air?

Question

Why does the air blown by a fan in a warm room seem cool? Surely it will be blowing hot air?

Answer 1

not if you blow on it

Answer 2

It causes your sweat to evaporate quicker, causing a cooling effect.

Answer 3

You feel as if the air is cooler due to evaporation of moisture on your skin.the air removes the heat Thur convection, leaving you to feel cooler.

Answer 4

If you put a metal object in front of the fan for 10 minutes or so you will find it gets hot;but your skin does not because evaporation of the moisture in your skin takes a lot of heat from the surface;so it feels cool,A piece of soft plastic will melt in the hot air and a thermometer will show a temperature in excess of 70degC.

Answer 5

You feel cold as you lose heat when your perspiration evaporates. Your sweat evaporates faster with the presense of more wind.

Answer 6

Evaporation  of sweat (moisture) from the skin will cause cooling. the amount of this cooling effect also depend on the humidity of the air.  Dry air causes evaporation to ocurr at a faster rate resulting in a lower temperature.    As the liquid moisture is turned into a vapor the water absorbs heat.  Air can only hold a certain amount of moisture before it become saturated. Much like a spounge can only hold a certain amount of water.  Blow air onto the skin the room air is much drier and can absorbe water at a much faster rate than the saturated air that was previously in contact with the skin.

The increase in evaporation is allowed because the drier air can hold some more water. But to evaporate liquid water into vapor requires energy (heat). The heat comes from the skin which is absorbed by the water as it turns into vapor.

  

Also.... Convection also comes into play.    The body temperature of 98.6F is hotter than the comfortable room temp of 70F.   So why don't we feel cold all of the time? The answer is that there is boundary layer of air next to the surface of the skin.    Air is basically an insulator (poor conductor of heat)   so still calm air next to the skin warms up to body temp and acts like an insulator.      This boundary layer of air is easily blown away bringing the much colder room air into contact with your skin.     The rate that heat flows from a hotter to a cooler surface depends upon the difference in temperature.  

If you remove heat from an object faster than heat being added the object cools down.   Heat is being added to your skin by the blood circulating underneth it.  Heat is being removed by convective and evaporative losses .    

This is why we layer our clothing when its cold and wear wind breakers. We are trapping layers of air next to our body and preventing the wind from blowing away these warmed boundary layers of air.

Increasing blood circulation to the skin adds heat to the skin faster than its being removed.   Ever get red faced embarrassed and feel your face get hot?    Frost bite happens at extreamities first as the body reduces blood circulation to these areas thereby lowering skin temperature.