A great trick to make your fan instantly cooler

When it comes to using a fan, many people's first reaction is to just pick it up and blow it, but in fact, you may have been using it wrong all along!

Fans can never actually cool down?

Before revealing the correct way to use a fan, let's talk about the cooling principle of the fan.

I don't know if you have ever thought about a question: the air conditioner transfers the heat in the room to the outside of the room through the work of the refrigerant and the compressor, which can be said to blow out cold air. But ordinary fans seem to just send the wind in front of you, and the air temperature before and after the fan has not changed, so why does blowing an ordinary fan make people feel cool?

In fact, the principle is very simple, and it can be simply summarized with the knowledge learned in junior high school: evaporation-heat absorption-cooling.

This method of blowing a fan is actually "incorrect"

First of all, the increase in gas flow rate can accelerate the evaporation of water (sweat), and the process of water evaporation can effectively take away the heat from the body surface.

In life, the body temperature of the human body is generally higher than the ambient temperature, 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, and the temperature difference with the body is reduced, the heat convection will also be weakened, and the heat on the body surface will be more difficult to transfer. The electric fan can make the air flow, take away the relatively hot air on the skin surface, and make the heat convection between the skin and the air smoother, so we feel cool.

In other words, the fan does not really reduce the temperature, it just reduces our body temperature through air flow. In fact, by using this feature of the fan, we can reduce the electricity bill for air conditioning.

For example, the U.S. Department of Energy recommends turning on the electric fan while turning on the air conditioner, which can reduce your body temperature by about 2℃. In this way, the air conditioner temperature can be slightly increased.

"Cooling down" can also be achieved with only an ordinary fan

In fact, the fan does not have to be used with the air conditioner to cool down. As long as the fan is placed in the right position, it can have an unexpected effect-blowing the fan head out of the window.

Netizens found in the experiment that when the electric fan is 0.5~2.1 meters away from the window, the indoor ventilation effect will be significantly improved. This is because when the fan is blowing, the air flow rate around the fan is relatively fast. According to the Bernoulli effect, the higher the flow rate, the lower the pressure, 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 is not directly opposite), the cool air outside will be quickly replenished, and this method can quickly cool the entire room.

This method of renewing indoor air can not only help cool the room at night, but also provide assistance to firefighters at the fire scene. For example, the "negative pressure ventilation method" used by the Ottawa Fire Department when dealing with fire smoke is to use a similar method to blow air out of a certain opening in the room to quickly empty the smoke in the room.

If there is no fan, using water flow can also achieve a similar effect. Of course, this method of inviting cold air into the house is only applicable when the outdoor temperature is lower than the indoor temperature.

Air conditioning fan = air conditioning + fan?

Since we are talking about the combination of air conditioning + fan, let's talk about air conditioning fans here. There are many types of air conditioning fans (or cold air fans) on the market. Can these fans really achieve cooling effects?

First of all, it is certain that they can indeed cool, but the cooling method is also relatively simple and crude - the cooling method of most air-conditioning fans is to add water and "ice crystals" in front of the fan, and use the fan to blow the cool air into the room to help cool down.

Ice crystals of air-conditioning fans on an e-commerce platform

 

Ice crystals look magical. To put it bluntly, they are just ice bags. The wind blown out by the fan will pass through the ice crystals and naturally cool down. According to this principle, if you only have an ordinary fan at home, putting a bowl of ice or a mineral water bottle filled with ice in front of the fan can also achieve a similar effect.

Finally, I would like to remind everyone that this summer is extremely hot, and the air conditioner should be turned on. Don't get heatstroke in order to save air conditioning fees, otherwise it will not be worth it.