Goodbye to brutal heat in your car in summer: Scientist reveals weird way to cool your car quickly
In summer, opening your car can feel unbearable when it’s been sitting in the sun. But scientist Hannah Fry has a solution.
Opening a car that’s been parked in the heat can be brutal, especially when the air inside feels like an oven. But there’s a clever trick to quickly bring in fresh air, and it’s all thanks to fluid dynamics.
Scientist and mathematician Hannah Fry, who regularly explains cool science on social media and also works as a broadcaster, demonstrates how you can cool your car quickly and effectively.
@fryrsquared That age-old dilemma of choosing between having a non-sweltering car or baffling a passerby because you look like a fool who doesn't know how to use a door
♬ Feels Like Summer - Samuel Jack
How to cool your car quickly
The trick is to open only the rear window opposite the driver’s side door. Then, quickly open and close the driver’s door several times. As Fry admits, it might look a little strange, but if you can handle a few odd looks, you’ll feel a rush of fresh air enter the car.
When the door opens it “sweeps out all of the air that’s in its way, creating this area of low pressure,” located just inside the car behind the door. That creates a phenomenon called “bulk flow”, where all the hot air in the car is drawn towards the low pressure and then out of the car, and “the only way to refill it” is to draw in fresh air from the other side, where the window is open.
Of course, if the outside air is also hot, the car won’t feel cool right away — but it will be noticeably cooler than the superheated air that was trapped inside.
Why it gets so hot inside a car
The air inside a car can get much hotter than the air outside. That’s because sunlight passes through the windows and gets absorbed by the seats, dashboard, and other surfaces. These materials heat up and then release energy as infrared radiation, but that heat gets trapped, because it doesn’t easily escape through the glass. With the windows shut, there’s also no airflow to carry it away.
What makes it worse is that many cars have dark-colored interiors, which absorb more heat than lighter materials, intensifying the effect.
The results are brutal, even on a 75°F day, the temperature inside a parked car can reach over 110°F in just 30 minutes. And on a 95°F day, it can climb past 140°F, and the dashboard, steering wheel, and seatbelt buckles can get hot enough to cause burns.
That’s why you should never leave children or pets inside a car in summer. Temperatures can become life-threatening in a matter of minutes.
Can’t I just turn on the A/C?
Sure, but as Fry points out, “that will take five minutes.” It’s much more efficient to first flush out the trapped hot air. Once that’s done, your A/C will be cooling fresher, already cooler air, helping your vehicle reach a comfortable temperature faster and with less effort.
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