"Before Turning on the Car AC, Try This"...An Unexpected Way to Cool a Hot Vehicle

[Sportschosun Reporter Jang Jong-ho] When you get into a car that has been parked under the blazing summer sun, hot air can hit your face at once, making it feel as if you have stepped into a sauna. Even after turning on the air conditioner, you may still have to endure the heat for a while. That is why a simple trick of quickly opening and closing the car door several times is drawing attention as a way to help expel the hot air trapped inside the vehicle.

Hannah Fry, a British mathematician and science communicator, introduced a quick way to ventilate a heated car interior through her social networking service (SNS). The method is simple. Open one rear window on the side opposite the driver's seat, then stand outside the car and quickly open and close the driver's door several times.

Fry said that the method might make people around you think you look strange.

But there is a scientific principle behind it. When the car door moves quickly, it pushes the surrounding air away and creates airflow inside the vehicle. As a result, relatively cooler outside air enters through the open window on the opposite side, helping the hot air trapped inside escape.

Fry explained the process from the perspective of Fluid Mechanics, saying that the rapid opening and closing of the door pushes hot air out of the car and draws fresh air in through the opposite window. Repeating the motion several times can help remove some of the heat trapped inside the vehicle.

As the method spread, online users began sharing that they had actually tried it. In particular, it has gained attention as a simple summer car-cooling trick because it can first release the hot air trapped inside the vehicle before the air conditioner is turned on.

However, it should not be taken to mean that simply opening and closing the door can cool a car faster than the air conditioner.

In an experiment conducted by the Japan Automobile Federation (JAF), air-conditioning methods proved far more effective than other ways of lowering the temperature inside a heated car.

Using five identical vehicles, JAF tested different methods to reduce the interior temperature after it reached 55 degrees Celsius.

In one test, the interior temperature fell from 55 degrees Celsius to 47.5 degrees Celsius when only the passenger-side window was opened and the driver's door was opened and closed five times without using the air conditioner. It was effective at pushing the trapped hot air outside, but the temperature remained very high.

By contrast, driving with the air conditioner on produced a much stronger cooling effect. With all windows open and the air conditioner set to outside-air intake mode, the temperature dropped to 28 degrees Celsius within five minutes after driving for two minutes with the windows open, then closing them and switching to recirculation mode.

When the windows were closed and the air conditioner was set to recirculation mode, the temperature fell to 27.5 degrees Celsius after 10 minutes. In outside-air intake mode, it dropped to 29.5 degrees Celsius after 10 minutes.

Based on these results, JAF recommended driving with the air conditioner on as the fastest way to cool down a hot car interior.

So, opening and closing the door should be used only as a supplementary step to first remove the hot air trapped inside the vehicle. After that, turning on the air conditioner and driving safely can lower the interior temperature more quickly.

One expert advised, "When it comes to cooling a car quickly in extreme heat, basic ventilation and proper use of the air conditioner matter more than any special trick. If you open the door a few times to let the hot air out and then use the air conditioner properly, you can lower the interior temperature quickly."

Jang Jong-ho, bellho@sportschosun.com

This article has been translated by GripLabs Mingo AI.