Ultimate heatwave hack for keeping cool in sweltering car

A maths professor has revealed a genius heatwave car hack using fluid dynamics to cool down your sweltering vehicle in seconds. No air con is needed, just a smart door trick which, while certainly unusual, is scientifically backed to work

A Cambridge University maths professor has shared a brilliant and surprisingly simple hack for instantly cooling down your car during a heatwave, and it’s all backed by science.

Hannah Fry, who describes herself as a “Maths Professor @cambridgeuniversity, science writer and all round bad ass”, took to social media to reveal a trick that she swears by and it only takes seconds to do. The hack has gone viral with over 2.4million views on Hannah’s YouTube channel @fryrsquared.

In her video she said: “You know that thing when you get into your car in the summer and it’s absolutely boiling hot,” she says. “There’s actually a fluid dynamics trick you can use to quickly cool your car down. That’s what my PhD is in, fluid dynamics. And this is the trick I continue to use.”

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Yesterday, Mirror Online reported the UK could see temperatures reaching highs of a scorching 38C in the coming weeks. Following an extremely hot weekend where temperatures hit 33.2C in Charlwood, Surrey, the UK could face another wave of heat next month, according to the latest weather maps.

WXCharts maps have turned a volcanic red when looking at Wednesday, July 9 with most areas of the country experiencing highs of 35C to 37C. Astonishingly, the West Midlands is likely to see the hottest temperatures, with areas such as Birmingham, Worcester, Derby, Nottingham and Mansfield potentially reaching a scorching 38C.

So as the hot weather persists, those in cars might want to take some advice from the experts. Instead of switching on the air con and waiting forever to feel the difference, Hannah explains that you’re better off harnessing a little physics. She added: “Don’t bother putting on the air con..instead, you open one of the windows on the opposite side of the door.”

Then she gets out of the car and says: “Then what you do is you very quickly, I mean you do look like a bit of an idiot if you do this, but you very quickly just open and close the driver’s door,” she says while demonstrating the motion. “You do it a few times, then get in the car.”

The car should feel cooler now and she explains the magic or the science behind it. “The reason why it works is that when you open and close the door – especially if you do it quickly the door is moving outwards, it sweeps out all of the air that’s in its way, creating an area of low pressure that you get here,” she says from the driver’s seat.

“And then that sets up something called bulk flow, which is where all of the hot, sweaty, horrible air inside the car is drawn outwards and the only way to refill it is with nice, fresh, easy air from over that side,” she adds, pointing to the opposite window.

“It only takes about two or three goes and suddenly it’s absolutely beautifully temperate.”

The hack quickly went viral, with thousands of people thanking her for putting science behind a summer ritual many of us already do.

One person wrote: “Been doing this for 20 years with the blind belief that it’s better than just opening all the windows. Thanks for the scientific pardon.”

Another added: “I forgot this trick! Thank you for reminding me. I used it a few summers ago and then completely forgot. I didn’t slam the door, just kind of waved it as close to closed as I could without it making noise. Still worked!”

A third chimed in: “As a 20-year veteran of Florida, I’ve used this method for many years and couldn’t have told you the thermodynamic reason it works, but it just does.”

With the UK facing more scorching days ahead, it’s a clever little trick worth keeping in your back pocket.

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