When it comes to using a fan, many people's first instinct is to just pick it up and blow it, but in fact, you may have used it wrong all the time!
Fans never cool down?
Before revealing to you the correct way to use the fan, let's first talk about the cooling principle of the fan.
I don't know if you have ever thought about a problem: the air conditioner works through the refrigerant and compressor to transfer the heat in the room to the outside of the room, which can be said to blow out the cold air. But an ordinary fan seems to just send the wind to you, and the air temperature before and after the fan does not change, so why does blowing an ordinary fan make people feel cool?
In fact, the principle is very simple, and you can simply summarize it with the knowledge you learned in junior high school: evaporation-endothermy-refrigeration.
This method of blowing the fan is actually "incorrect". The stock copyright picture, reprinting and using may cause copyright disputes
First of all, the increased gas flow rate can accelerate the evaporation of water (sweat), and the process of water evaporation can effectively remove heat from the surface of the body.
In life, the body temperature of the human body is generally higher than the ambient temperature (it is relatively rare to exceed 35°C for many consecutive days like this year), so under normal circumstances, our body will release heat to the surroundings, and the air close to the skin will also be "heated".
If the air flow is poor, the air near the skin is "heated" by the body, the temperature difference with the body decreases, the heat convection will also weaken, and it will be more difficult for the heat on the surface of the body to be transferred. The electric fan can make the air flow, take away the relatively hot air on the surface of the skin, so that the heat convection between the skin and the air can be carried out more smoothly, so we feel cool.
That said, the fan really doesn't lower the air temperature, it just lowers the temperature we feel through the air flow. In fact, by using this feature of the fan, we can reduce the electricity bill of the air conditioner.
For example, the U.S. Department of Energy recommends turning on an electric fan while the air conditioner is on, which will reduce your perceived temperature by about 2°C. In this way, you can turn up the temperature of the air conditioner a little higher.
"Cooling" can be achieved with just a normal fan
In fact, the fan does not have to cooperate with the air conditioner to cool down, as long as the position of the fan is right, it can have an unexpected effect - blowing the fan head out of the window.
Netizen experiments have found that when the electric fan is 0.5~2.1 meters away from the window, the indoor ventilation effect will be significantly better. The image is taken from the video of netizen Matthias random stuff
This is because, when the fan is blowing, the air around the fan flows at a faster rate, and according to the Bernoulli effect, the flow rate is high and the pressure is small, and the gas in other parts of the room will move in this direction. If you can open a window on the other side (even if it's not directly opposite), the cool air from outside will quickly add in, which will quickly cool the whole room.
This method of updating the indoor air not only helps to cool the room at night, but also helps the firefighters at the scene of a fire. For example, the Ottawa Fire Department's "negative pressure ventilation method" used in response to fire smoke uses a similar method to quickly empty the room by blowing air through an opening in the room.
Without a fan, a similar effect can be achieved with a stream of water. Image source: firedynamicstraining.ca
Of course, this method of bringing cold air into the home is only suitable if the outside temperature is lower than the indoor temperature.
Air Conditioner Fan = Air Conditioner + Fan?
Since we are talking about the combination of air conditioner + fan, we will also talk about air conditioning fans here. There are many types of air conditioning fans (or air conditioning fans) on the market, but can these fans really do cooling?
First of all, it is certain that they can indeed cool, but the cooling method is also relatively simple and crude - most air conditioning fans refrigerate by adding water and "ice crystals" in front of the fan, and blowing cool air into the room through the fan to help cool down.
Ice crystals of an air conditioning fan on an e-commerce platform
Ice crystals look magical, to put it bluntly, they are ice packs, and the wind blown by the fan will pass through the ice crystals, which will naturally cool down. According to this principle, if you only have a regular fan at home, placing a bowl of ice or a mineral water bottle full of ice in front of the fan can have a similar effect.
Finally, I would like to remind everyone that this summer is unusually hot, you should turn on the air conditioner, don't suffer from heat stroke in order to save air conditioning costs, it will outweigh the losses.