If you are in a hot room.....?

Question

a you have a fan on high why does it blow out cooler air....how come it doesnt blow out hot air?

How can it blow out air cooler than the temp of the room?

Answer 1

It does not blow out cooler air.  Put a dry thermometer in front of the fan and another out in the room, and they should both read the exact same temperature.

The coolness you feel is from your sweat evaporating.  Even if you are not dripping with sweat, you skin is still damp.  When water (sweat) evaporates, it carries off the higher energy molecules, leaving the cool ones behind, and thus decreasing your skin temperature.  Evaporation is enhanced by a few factors, including humidity of the air around it and convection (blowing or moving air).  A wet object will have a thin film of highly humid air surrounding it from the water that has already evaporated.  This humid but invisible fog around you keeps you from cooling off as fast as you could.  When you blow a fan, it causes convection that carries away the humid air near your skin, enhancing evaporation, and making you cool off quicker.  

Remember how I said that a dry thermometer should read the same in a fan or in still air?  Try it with a wet thermometer (wrap the bulb in a wet tissue).  A wet thermometer will read a lower temperature in the fan than in the still air, at least until it dries out.

The same thing applies to blowing on a hot spoonful of soup.  Even though your breath is warmer than the surrounding air, convection caused by your breath causes the soup to evaporate quicker than it would in the cooler air around you.