blowing hot and cold

[@Keronin]

When I was a very young kid, I often asked my dad how things worked, and at the time my dad liked to explain things in the way that Calvin's dad (from Calvin and Hobbes) does and make up something that sounds plausible to the kid, but is totally incorrect. So when I asked how air conditioning made air cold, he told me that it blows air through small holes, and he did the two types of blowing as shown in this short as "proof" that small holes causes cold air. And that made perfect sense to 5-year old me.

[@johnnydollard8632]

For some air conditioners and refrigerators, the drop in temperature happens due to a gas expanding from a small passageway into a larger volume, dropping in pressure and temperature as it does so. Your dad actually wasn’t too far off!

[@mikesteffen3378]

There is a commercial product called the Nemo Vortex Pump Sack that uses this concept to quickly fill a camping sleeping pad. It’s a big sack that you blow sharply into from 6 or so inches back and it will inflate the bag with much more air than you exhaled. You then seal off the sack and push the air into a sleeping pad through a valve. Pretty slick.

[@nathantjohnson1000]

It works SO well. Other brands like Thermarest have a version too.

[@sloupy1486]

I always thought higher velocity -> lower pressure -> adiabatic expansion -> lower temperature

[@nathantjohnson1000]

This may be true but has less influence than Steve’s explanation.

[@narutokunn]

That's what I was taught in Physics class!

[@cee8mee]

The Man and the Satyr- Aesop's Fable. The satyr wants nothing to do with man after witnessing his breath both warming his hands and cooling his tea. He finds this very disturbing and can't trust man after seeing this paradox.

[@gouransh3752]

Hey Steve Would you mind to please increase the volume on the short a bit . I just watched you unilluminable room video and its sound was good , but this short is just very low in volume .

[@SteveMouldShorts]

Noted! Thanks for the feedback

[@maxsilbert]

Didn't sound quiet to me

[@shivangkeshari436]

Thnx, i was searching for the rson behind this experiment since i started learning thermodynamic

[@EebstertheGreat]

Also, the entrained air isn't any cooler than the air around it. In fact, it is slightly warmer due to conduction from the warm air. It's just that the moving air increases convection over your skin, which allows it to lose heat faster, making your hand colder than if it were in still air.

[@mikaelkorpela]

Yep. You'll feel the opposite in hot sauna: blow air like that and suddenly the air around your hand feels much hotter than the sauna otherwise feels.

[@umchoyka]

Bernoulli's principle!

[@thanksfernuthin]

Yeah. Normally your body temperature is warmer than the ambient air. Just not in Tucson when it's 115 degrees. (Fahrenheit... you do the math.) (smile)

[@iCODeRUS]

also brearh with wife open mouth cause more mouth surface contact with air. if mouth almost closed air contacts less with mouth. because of that it have less chance to warm up.