With temperatures sitting in the 80’s these past few weeks, you’ve probably needed some way to stay cool. The most popular way on campus to stay cool in your room is usually to get a fan. But how does a fan actually make you cooler? Why does the pushing around of air make your body so much more comfortable? You may also have broken a sweat a few times walking to classes. How does this cool you off? Isn’t sweat usually just warm water anyways? Interestingly enough, these two processes are somewhat similar in the way they cool us off.

First of all, sweating happens when our brain recognizes that our body temperature is higher than it should be. The brain then activates our sweat glands, which are found all over our bodies except for our lips. Sweating cools us when the water droplets absorb heat from our body. The heated water molecules move more rapidly, and it is easier for the molecules to break away and become a gas, also known as water vapor, in a process called evaporation. The heat leaves the surface of our skin in the form of a gas and leaves behind cooler water droplets and less body heat.

Fans work with this process by increasing the rate of evaporation. If we are sweating a lot, and a lot of sweat is turning into water vapor, that vapor may be hanging around in the air around our bodies, causing us to be in a humid air space. Evaporation works significantly slower if the surrounding air is too humid. In order to speed up evaporation, fans push this humid air away from us and replaces that air with normal, dry air. Evaporation then speeds up so we can get more heat away from us more quickly through sweating.

But fans also work even if you’re not sweating in a very similar way. Our bodies are warm, and they are constantly giving off heat that flows into the air around us. This happens because nature is constantly trying to make everything the same temperature. Heat naturally moves and heats up cooler things to try to make it even. So when we are hot, our heat transfers to the cooler air around us. But as it was with sweating, when this heat hangs around in the air around our bodies, the process of transferring heat becomes slow. Again, the fan pushes this hot air away from us and replaces that air with normal, cooler air. This makes the transfer of heat more efficient as heat transfers faster to colder substances.

However, fans actually don’t decrease the overall temperature of the room at all. In fact, they might actually raise the temperature as a result of the electricity powering the fan. But what fans actually do is create a wind chill effect. If you pay attention to the weather at any time, you may hear the forecasters talk about wind chill. This isn’t an actual change in temperature, but it is a change in how the world feels to us. You may notice the weather people sometimes post the real temperature, and then they post a “feels like” temperature beneath it. This is because the wind works in the same way fans do at cooling you off. As mentioned before, the warm air surrounding your body is pushed away and replaced by normal air. This speeds up the transfer of heat from our bodies to the outside world.

The next time you feel a gust of fresh air from the wind or a fan, remember that it isn’t simply “giving you cold” but instead it is helping to take away the heat from your body by pushing away that uncomfortable, warm air that won’t leave you alone and replaces it with nice fresh air that you can release more of your body heat to.

Sources:

How Stuff Works

eHow

The California Aggie