Turn on the air conditioner in summer. Is it internal circulation or external circulation？

Turning on the air conditioner in summer is faster in terms of cooling effect, but if you are exposed to the sun, it is still recommended to cycle outside first.First of all, what’s the difference between internal and external circulation?

What’s the difference between internal and external circulation?

The quality of internal circulating air is good, but the oxygen content is low.

Internal circulation, it may lead to too high carbon dioxide, because the air intake is in the car. Simply put, the air outside can’t get in, and the air inside can’t get out.

After the internal circulation is turned on, the air is sucked in the car and filtered repeatedly by the filter in the air conditioner. The car with pm2.5 filtering function is equivalent to the role of an air purifier.

According to the measured data, the value of pm2.5 in open internal circulation is about 1/3 to 1/4 of that in external circulation. However, the current car sealing is relatively good, and long-term internal circulation is also problematic.

Low oxygen content will affect driving safety.

Generally, the interior space of a car is about 3 to 4 cubic meters. According to the larger one, an adult can breathe in a closed space of 4 cubic meters, and the carbon dioxide concentration can reach 1% in about 50 minutes.

The decrease of oxygen content makes people feel hot, tired and anxious. Anyway, it is uncomfortable, which actually affects driving safety.

For example, the air quality on the moon is good. Without pm2.5 and oxygen, people can’t stand your fresh air.

External circulating air has good circulation and high oxygen content.

Let’s talk about the external circulation, which is equivalent to sucking in the wind outside the car, usually under the windshield wiper, at the junction of the windshield and the hood.

To put it simply, the wind from the air outlet is sucked in from the outside of the car, which can ensure that the air inside the car is relatively circulated, so that the concentration of carbon dioxide is not too high or oxygen is not enough.

How to use internal and external circulation?

Conventional refrigeration, first open internal circulation and then external circulation.

According to the conventional refrigeration effect, it is better to open the internal circulation. When you drive out in the basement or garage in summer, the temperature of the car itself is not high. As soon as the internal circulation is opened, the hot air outside can’t enter, and the air inside is cooled by air conditioning as much as possible, the effect is the best.

You are like, staying in an air-conditioned room knows that the doors and windows should be closed tightly, or the air conditioner will run away. It is similar to turn on the air conditioner in the car. Internal circulation is equivalent to closing the doors and windows, which will make the cooling speed faster and the effect better.

As I said before, your internal circulation is on for too long, just like when your door is closed, it’s stuffy in the back, and your air has not been circulating, and the carbon dioxide is high and the oxygen is low.

Open the internal circulation for half an hour and then switch the external circulation.

Therefore, if the internal circulation is on for half an hour, the temperature is almost stable. I suggest you open the external circulation to let fresh oxygen in.

At present, more expensive cars have automatic adjustment function. In the first half hour, you pressed the inner loop, and later it will switch to the outer loop for you, which is more convenient. Then if it’s manual, you can press it yourself.

In the exposure environment, open the window first and then circulate outside.

However, the exposure environment is different. The temperature is actually very high when parked on the road. The School of Public Health of Nantong University sampled 100 cars and counted a data.

There are 60% of the air in cars, which exceeds the National Indoor Air Quality Standard. The formaldehyde concentration in each cubic meter is less than 0.1 mg, which is the standard and higher than this.

Exposure will double the formaldehyde concentration in the car.

Summer exposure, it will make the formaldehyde in the car emit at a faster speed and bake it out.

Looking for some data from other people’s experiments, you can make the original formaldehyde concentration of 0.16 mg per cubic meter rise to 0.33 mg per cubic meter, which is more than twice the air quality index.

Long-term exposure to formaldehyde, chronic respiratory diseases, induced cancer, anyway, everyone knows that formaldehyde is not good. So in this case, you should not only consider whether the temperature drops fast or not, but also consider whether the air quality inside the car is poisonous.

Open the window to allow air convection and reduce the concentration of formaldehyde.

Therefore, the formaldehyde concentration can be reduced from 0.27 mg/m to 0.09 mg/m by opening the window first and then circulating the air for five minutes.

You see, the drop is still quite a lot, from 0.27 to 0.09, which actually takes only five minutes. It is also a good choice to open the window first and then close it after five minutes.

The higher the temperature inside the car, the greater the load.

Another is that you are exposed to the sun. If the temperature is high, the load will be even greater. If you get a bad tan, the temperature inside the car may be sixty or seventy degrees Celsius, which some friends don’t know yet.

Your car will start the AC refrigeration button immediately, and the heat load it bears is still relatively large. It is possible to damage or three-way catalysis and reduce the service life of components, which is a small probability.

No matter how you say that you are cold and slow down, it will definitely have an impact. If you pour a glass of ice water into a glass of water at room temperature, the water at room temperature will get colder. If you pour a glass of ice water into a cup of hot water, it will be good to turn it into water at room temperature. That’s the truth.

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