How and Why Does a Fan Cool a Room?
It seems obvious to say that moving air helps us cool. After all, what does a breeze do? And that’s why you find people waving a folder in front of their face in a hot room and find a little relief. However, since temperature is a feature or substance with molecular properties, the air itself cannot be cooled by movement- we feel cooler when the air is blown by.
On a hot day, it is the wind or moving air that helps your body to cool off; moving air carries hot air from our surrounding. We human lose heat- which is a good thing for thermoregulation- through radiation, convection, evaporation, and conduction. Fans account for the convection and evaporation.
On a hot day, your body loses heat through sweating which causes evaporation of sweat in the form of moisture. In still air, the immediate area surrounding your skin reach the same temperature and humidity as your skin temperature, which makes it quite difficult to cool down. A fan or moving air helps move this hot, humid air away from your skin surrounding and replaces it with cooler, drier air that makes way for more evaporation.
However, even if you don’t sweat, your body loses heat to the immediate air surrounding your skin simply by convection. If you have a higher internal temperature than that in your surrounding air, then heat is transferred from your body to the cooler areas through convection. However, if there is no moving air, you will find it hard to lose heat even if the surrounding area is cooler. The breeze from your fan carries hot, humid air away and facilitate the process, thereby cooling you off.
This now brings us to our topic, how does a fan cool down a room. Let’s talk about a ceiling fan. What would you do without this helpful device? Turn up your air conditioning unit a bit more? That will be a bit fair, but the air in your room would feel stuffy and stale. I can term ceiling fans as co-managers of your home air supply. The whole point of having a ceiling fan is to make sure that air is moved to where you want it to go as fast as possible.
The air conditioning unit moves air around your house, but it is the ceiling fan that optimizes air in your home. Understanding how a fan works and using it effectively will help keep the air flowing, and also help you save money since you will not be turning up your AC while it is the fan that needs to be turned on.
Here is the simple science on how a fan keeps your room cool
As you probably recall what you learned in middle school, hot air rises while cold air descends. When a fan rotates counter-clockwise, it’s spinning blades forces hot air to rise towards the fan. The hot air is sucked between the blades, and it’s simultaneously accelerated and pushed downwards as a breeze.
By creating a downdraft, whereby rising hot air is pushed back down, a ceiling fan creates a vacuum that has to be filled. Cool air rushes in to fill that vacuum.
Hot air continues attempting to rise, and fan operation keeps pushing it back down. The warm air rises, is pushed down, and tries to rise again. In short, it keeps circulating throughout the room. All that is created is a wind chill effect.
Ceiling fans don’t cool rooms. They make the people in the room feel like there is a breeze. The breeze and air circulation produced by fans all contribute to creating a wind chill effect by displacing hot air and giving the cool air a chance to descend.
All the air in the room will be the same as was before you turned your fan on, but you will have more access to cooler air when the fan is on than when the air is still. This way, you will be losing heat at a faster rate than you were.
Unlike in air conditioning, a fan doesn’t make the air in your room cooler. Instead, it cools the people in it. The breeze from a fan cools the occupants by disrupting stagnant layer of air surrounding the body thereby accelerating the heat loss process. The removal of stagnant layer of air makes your body lose more heat thus helping you feel cooler.