Motorists told ‘do not blast air con in cars' – the fluid dynamics trick you should try to cool it down instead

The Irish Sun

11-07-2025

BLASTING you car's AC to battle the summer heat can be a costly venture.
Thankfully, there's a simple trick you can use instead, and it won't cost you a thing.
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A simple trick can help cool down your car's interior in the scorching summer heat (stock image)
Credit: Getty
An Instagram user Hannah Fry, who has a PhD in fluid dynamics,
And with yet another stint of soaring temperatures across the UK, now is the time to try it out.
According to Hannah, you can cool down the inside of your car in seconds using a simple scientific method.
With temperatures set to spike as high as 33 degrees Celsius in certain areas, now is the time to beat the summer heat.
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But don't waste time and money running your car's air con on the highest setting.
Free hack
Instead, make use of fluid dynamics to cool your car's interior by strategically opening certain doors and windows.
"Don't bother putting on the air con, that would take about five minutes, it's not worth it," Hannah explained.
She stepped out of the driver's seat to demonstrate the quick car cooling technique.
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Hannah recommended opening the window on the opposite side of the driver's seat.
After rolling down the back window, she "very quickly" hopped out of her car.
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"I mean you do look a bit like an idiot if you do this - but you just very quickly open and close the driver's doors," she said as she carried out the step.
Hannah rapidly opened and closed the car door three times before re-entering the vehicle.
She told her followers that the car's interior already felt significantly cooler than before.
Scientific method
The Instagrammer detailed the scientific method behind her approach.
She explained how swinging the door outward pushes away all the air in its path.
How to keep cool in a heatwave
Most of us welcome hot weather, but when it's too hot, there are health risks. Here are three ways to keep cool according to the NHS...
Keep out of the heat if you can.
If you have to go outside, stay in the shade especially between 11am and 3pm, wear sunscreen, a hat and light clothes, and avoid exercise or activity that makes you hotter.
Cool yourself down.
Have cold food and drinks, avoid alcohol, caffeine and hot drinks, and have a cool shower or put cool water on your skin or clothes.
Keep your living space cool.
Close windows during the day and open them at night when the temperature outside has gone down. Electric fans can help if the temperature is below 35 degrees. Check the temperature of rooms, especially where people at higher risk live and sleep.
This then creates a low-pressure zone between the driver's seat and the door.
According to the scientist, this sets up something called bulk flow, drawing the "hot sweaty horrible air" inside outwards.
This is then replaced with "nice fresh easy air" ensuring your space is "suddenly beautifully temperate".
Hannah recommended swinging your door open and closed three to four times to see the best results.
More heatwave hacks
Or if you still prefer to use your car's AC, use this
And
Another
Plus, how to look out for symptoms of your body overheating this summer.
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Instead of blasting your car's AC, you can use fluid dynamics to cool down the interior (stock image)
Credit: Getty