Newton's Law of Cooling used for Heating 1

[WARose]

This is (hopefully) a easy question: can Newton's Law of Cooling be used for hot air flowing across (and heating) a object cooler than the air? Most examples I have seen of this is the opposite: cool air flowing across a hot surface.

Pardon the question, but it's been about 30 years since I took thermo....and this rings a vague bell with me (as far as) the turbulence of the flow (in one vs. the other).

Thanks in advance.

 

[SwinnyGG]

Yes. If the signs are inverted, it still works out. You'll just get a negative answer.

 

[WARose]

Thanks SwinnyGG.

 

[IRstuff]

The only caveat is that some cases of convection, gravity and buoyancy also matter, so while you would get heat transfer, the transfer coefficient might not be as good as the opposite scenario.

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[SuperSalad]

Yes, this is how a heat pump works. Cooling the heat transfer area (coils) before exposure to the extractable heat source (ambient air or ambient ground heat). It uses a compressor to force the initial temperature differential in the refrigerant and then goes from there.

Andrew H.

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