White motor in a darkened, but hot space. Does it stay cooler than if it was black?

Forums › Off topic › White motor in a darkened, but hot space. Does it stay cooler than if it was black?

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geekIT

2420 posts

Uber Geek

#1973437 12-Mar-2018 17:32

The fan blade (nom. 150mm) itself is buried inside the housing. I don't know what the blade's color is in the replacement unit, because I haven't picked it up from M10 yet.

But the entire housing, motor assembly etc, according to M10, is white.

The old motor, housing etc was entirely black, including the fan blade.

As I said, I can't think of a reason the Chinese fan maker would choose to paint it white.

Black wouldn't show the dirt.

Red would be luckier.

Dark green - reminiscent of the British manufacturing industry (when they last had one)

Yellow? Could be popular in Rio.

'Those who can make you believe absurdities can make you commit atrocities.' Voltaire

'A patriot must always be ready to defend his country against his government.' Edward Abbey

colinuu

246 posts

Master Geek

#1973622 12-Mar-2018 22:33

For non-shiny metal surfaces:

Lighter colors and also whites and metallic substances absorb less illuminating light, and thus heat up less; but otherwise color makes small difference as regards heat transfer between an object at everyday temperatures and its surroundings, since the dominant emitted wavelengths are nowhere near the visible spectrum, but rather in the far infrared. Emissivities at those wavelengths have little to do with visual emissivities (visible colors); in the far infra-red, most objects have high emissivities. Thus, except in sunlight, the color of clothing makes little difference as regards warmth; likewise, paint color of houses makes little difference to warmth except when the painted part is sunlit.

See https://en.wikipedia.org/wiki/Thermal_radiation for chapter and verse on this complex topic. Cooling of the fan unit will also be affected by convection effects, ie if it''s in a draughty situation it will run a lot cooler, but again the colour will not be significant. Much more important being the surface area, so a rough surface with more area will be cooled more by the moving air.

Shoes2468

785 posts

Ultimate Geek

#1973655 12-Mar-2018 23:01

kryptonjohn:
gbwelly:

Yes, white will radiate more heat away. That is why it takes so long to get your toast to start toasting, but so little time for it to go from lightly toasted to burnt. The process accelerates as the toast darkens.

Don't think that's correct. Black is both a better radiator and absorber of heat. That's why heatsinks are often anodised black.

I agree Black is going to be better radiator, just lift the bonnet of any petrol/diesel powered car, truck, tractor etc the radiator is always black.

richms

28187 posts

Uber Geek

Trusted

Lifetime subscriber

#1973668 12-Mar-2018 23:37

Shoes2468:

I agree Black is going to be better radiator, just lift the bonnet of any petrol/diesel powered car, truck, tractor etc the radiator is always black.

Only because theyre not using aluminium cored ones in them so have to paint them.

Its a fan, any difference in radience would be far outweighed by the airflow and how thick the paint was I would have thought.

Richard rich.ms

geekIT

2420 posts

Uber Geek

#1973899 13-Mar-2018 11:48

So, is the consensus that a black motor\fan assembly, situated in a hot, dark room, would dissipate heat more effectively that its white counterpart?

'Those who can make you believe absurdities can make you commit atrocities.' Voltaire

'A patriot must always be ready to defend his country against his government.' Edward Abbey

kryptonjohn

2523 posts

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Lifetime subscriber

#1973900 13-Mar-2018 11:50

Yes, but the difference would be between negligible and unmeasurable...

geekIT

2420 posts

Uber Geek

#1973910 13-Mar-2018 12:09

OK. Maybe Mr. Mek Too Fan just ran out of black paint.

'Those who can make you believe absurdities can make you commit atrocities.' Voltaire

'A patriot must always be ready to defend his country against his government.' Edward Abbey

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geekIT

2420 posts

Uber Geek

#1977226 15-Mar-2018 15:32

Heads up: Mystery (partly) solved.

The new unit isn't painted white - it's white plastic. Housing, mounts, fan blade etc.

Still doesn't explain why white, though...

'Those who can make you believe absurdities can make you commit atrocities.' Voltaire

'A patriot must always be ready to defend his country against his government.' Edward Abbey

gbwelly

1243 posts

Uber Geek

#1977269 15-Mar-2018 16:36

Shoes2468:
kryptonjohn:

gbwelly:

Yes, white will radiate more heat away. That is why it takes so long to get your toast to start toasting, but so little time for it to go from lightly toasted to burnt. The process accelerates as the toast darkens.

Don't think that's correct. Black is both a better radiator and absorber of heat. That's why heatsinks are often anodised black.

I agree Black is going to be better radiator, just lift the bonnet of any petrol/diesel powered car, truck, tractor etc the radiator is always black.

I also agree, after I posted it I quickly realised I had said radiate away rather than absorb. Silver intercoolers out perform black ones though, which is odd given they would contain hot air like a radiator contains hot water.

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