Warm air coming from our lungs

[jgual]

Consider a hot potatoe. Will it cool faster or slower when we blow the warm air coming from our lungs or if we let it cool naturally in the cooler air room?
How do i explain this in physics terms?

 

[Chi Meson]

Consider a hot potatoe...

Who are you, Dan Quayle? :tongue2: Ha! I got it first!

Seriously. IF you just leave the potato to cool in still air, the potato will first warm the air that surrounds it to a couple of hundred degrees F.

Convection will cause this air to rise and thus will pull cooler air from the sides, but a breeze from your lungs will replace this air with cooler air faster than convection will.

Furthermore, if you blow with high pressure through a very narrow opening, the sudden expansion of you breath (going from high to low pressure) will cause it to cool to below room temperature.

Try this: blow on your fingers with the intention of cooling them. (By blowing through narrow opening in lips)

Now blow on your fingers with the intention of warming them up. (with your mouth wide open). Note the huge difference in temperature of you own breath.

 

[sir-pinski]

In physics, heat transfer occurs through three mechanisms: conduction, convection, and radiation. When we blow warm air from our lungs onto a hot potato, we are increasing the rate of heat transfer through convection. This is because the warm air carries heat energy from our lungs to the potato, causing it to cool down faster. On the other hand, if we let the hot potato cool naturally in a cooler room, heat transfer will primarily occur through conduction, which is a slower process. Therefore, the potato will cool down slower in the cooler room compared to when we blow warm air on it. This can be explained by the fact that convection is a more efficient mode of heat transfer compared to conduction. Additionally, the continuous flow of warm air from our lungs ensures a constant supply of heat energy to the potato, further accelerating its cooling rate.