It’s so hot this summer! Several times when I walked from indoors to outdoors, it was like being punched in the face by a heat wave. At this time, if you can use some tips to prevent heatstroke, it can be said to be life-saving.
Recently, a cooling trick has become popular on the Internet. It is said that can quickly cool down by blowing the fan outdoors, which is much more effective than blowing the fan indoors. . Some people even said: " is as cool as an air conditioner! "
Is there such a good thing? Then I don’t need to buy an air conditioner.
In order to verify whether it is true, we did a small experiment and found that: the fan blows towards the outside, which makes some sense! It’s just that the effect and usage may be different from what everyone thinks.
1. Can it cool down? It depends on the conditions
According to the introduction in these videos, this method uses " Bernoulli's principle ". To put it simply, the fan blows toward the outdoors, which can effectively exchange indoor and outdoor air.
(Our usual fan usage is more about indoor air circulation rather than indoor and outdoor air exchange)
The fan blows outdoors, and you can obviously see that the indoor and outdoor air exchange speeds up
At this time, some friends should have seen it. The fan itself can only accelerate the flow of air, but cannot cool or heat. If the outdoor temperature is lower than the indoor temperature, the fan blowing outdoors can indeed cool down. But if the outdoor temperature is higher than the indoor temperature, this will not achieve the cooling effect.
So here comes the question, When the outdoor temperature is lower than the indoor temperature, how much cooler can it be by letting the fan blow towards the window?
2. Can it cool down quickly? How fast?
Judging from the principle of this method, when the outdoor temperature is lower than the indoor temperature, how low the indoor temperature can be depends on how low the outdoor temperature is. and the fan blows outside, it just speeds up the cooling.
Therefore, we simulated the situation of "the outdoor temperature is lower than the indoor temperature" in our self-built experimental cabin to see how fast this method can cool down.
Experimental conditions
Temperature control: Turn on the heater to heat the temperature inside the experimental cabin to 32.5°C, while running refrigeration and air conditioning outside the experimental cabin to maintain the temperature at around 27°C.
experimental settings: Use "open the hatch but not the fan" to simulate natural ventilation, and "open the hatch and fan at the same time" to simulate the fan blowing out the window.
experimental process: Measure the time required for the temperature in the middle area of the experimental cabin to drop to 30°C under two conditions.
The results show that when does not use a fan, it takes 17 minutes to lower the temperature by 2.5°C. When using a fan to blow outdoors: It takes 13 minutes to lower the temperature by 2.5°C.
Note: The actual cooling effect will vary due to the fan wind force and the difference between indoor and outdoor temperatures.
It can be seen that the fan blowing towards the outdoors does accelerate the cooling effect, but the effect is not that obvious.
In addition, the actual indoor and outdoor temperature difference in summer is not large, and the lowest temperature of the day in some places is still very high (for example, the lowest temperature of the day in Hangzhou was 27℃). It is obviously not possible for to use this method to achieve "as cool as an air conditioner". Realistic.
If there is no air conditioner, you can use this method temporarily. However, if possible, it is still recommended to turn on the air conditioner as much as possible. After all, heat stroke is no joke on hot days.
However, despite its less prominent cooling effect, ’s ability to remove formaldehyde is still very powerful!
3. The fan blows toward the window, doubling the formaldehyde removal effect!
Before, we did popular science. One of the most cost-effective ways to remove formaldehyde in is ventilation. Fans can enhance ventilation.
In order to understand "which direction of the fan is better at blowing out formaldehyde", we used a formaldehyde mattress as the release source (after being sealed for one night, the nearby formaldehyde concentration directly reached about 0.7 mg/m³) and tested several different fans. Blowing method, finally found:
"Blow towards the window without shaking your head" has the best effect of removing formaldehyde , the indoor formaldehyde concentration directly dropped by 93% !
Note: Formaldehyde concentration ≤ 0.1 mg/m³ is qualified
This is actually the same as the principle of "fan blowing toward the outdoors to cool down": expels formaldehyde indoors and removes indoor formaldehyde outdoors by accelerating the exchange of indoor and outdoor air. Fresh air is brought in, thereby reducing indoor formaldehyde concentration.
(The outdoor formaldehyde concentration is generally very low, and the difference between the indoor formaldehyde concentration and the indoor formaldehyde concentration is huge. In this case, blowing the fan against the window can achieve obvious formaldehyde removal effect.)
4. How far away from the window is the fan to achieve the best effect? good?
Since the formaldehyde removal effect of "blowing the fan toward the window" is so good, I will put an electric fan in the window and blow it!
Wait! Do you know how far away the fan should be from the window?
We tested the formaldehyde concentration when the fan was placed less than 0.5 meters, 2 meters, and 4 meters away from the "window" .
found that in the experiment, the further away is from the "window", the better the formaldehyde removal effect!
This is because when "the fan blows formaldehyde against the window", in addition to indoor and outdoor air exchange, also involves air exchange in different locations indoors.
Under the condition of ensuring sufficient wind power, placing the fan relatively far away from the window can better promote the exchange of air indoors and outdoors and in different locations indoors .
If we usually use this method to remove formaldehyde at home, we can place the fan inside the room, turn the air volume to the maximum possible, and blow it towards the window. As long as the wind flow can be clearly felt where the window is open, it will be fine.
Finally, let’s summarize:
Finally, I still want to remind everyone: Opening windows for natural ventilation is sufficient for daily ventilation and air purification, but if it has just been renovated or low-quality materials are used, opening windows alone is not enough. There is really not enough ventilation!
Therefore, if serious formaldehyde release sources are found in mattresses and furniture, they must be removed in time.
