WHY THE HELL DOES CHROME GET SO HOT IN THE SUN

"aberson Bresident of the FullyAssed Committe" (emaxxbl) 08/17/2015 at 13:52 • Filed to: None

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LIKE JESUS I NEED OVEN GLOVES JUST TO OPEN THE DOORS ON MY CAR.

Also oil is overrated

AM > aberson Bresident of the FullyAssed Committe 08/17/2015 at 13:55

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I'm assuming you have metal door handles and not plastic ones like I do. Mine aren't chrome though.

aberson Bresident of the FullyAssed Committe > AM 08/17/2015 at 13:57

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your lucky your car doesn’t give 4th degree burns

(don’t google that)

S2Konstantin > aberson Bresident of the FullyAssed Committe 08/17/2015 at 14:00

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How ironic, you’d think Firefox would be the one that gets hot.

aberson Bresident of the FullyAssed Committe > S2Konstantin 08/17/2015 at 14:02

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its funny because i’m using firefox right now.

RamblinRover Luxury-Yacht > aberson Bresident of the FullyAssed Committe 08/17/2015 at 14:08

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I *think* chrome transfers heat conductively better than most paints, so you get more heat transfer when you touch it at a given temperature. I’m not sure of everything involved there in terms of radiative heating from the sun - most chrome coatings actually reflect slightly less IR than they do visible light proportionally, and I think they suck at re-radiating, so brief exposure to sunlight = stays cool, long exposure = gets hot. Or something like that.

Satoshi "Zipang" Katsura > aberson Bresident of the FullyAssed Committe 08/17/2015 at 14:08

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Get a billet shift knob, they said.

It looks and feels cool, they said.

I think I lost a good chunk of skin on my hand.

Hermann > aberson Bresident of the FullyAssed Committe 08/17/2015 at 14:12

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I just felt the sudden urge to check my oil. BRB.

aberson Bresident of the FullyAssed Committe > RamblinRover Luxury-Yacht 08/17/2015 at 14:13

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Laurence > aberson Bresident of the FullyAssed Committe 08/17/2015 at 14:33

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It’s amazing how hot shiny and metal objects get in the sun; I’ll always remember this time I was washing a car on a really warm day, and the water started to turn into steam as it hit the car. I still don't understand how that worked tbh

WesBarton89 - The Way to Santa Fe > aberson Bresident of the FullyAssed Committe 08/17/2015 at 15:00

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Both my Infinitis have had chrome door handles. They are annoying in the heat. Even worse, with my previous Infiniti, it was black on black, and I mistakenly left the windows up on a 100 degree day. The chrome was bad enough. The blister on my arm from the black seat leather was even worse.

AM > aberson Bresident of the FullyAssed Committe 08/17/2015 at 15:08

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You know I'm gonna have to now.

someassemblyrequired > RamblinRover Luxury-Yacht 08/17/2015 at 15:08

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This is really close to the explanation, but has more to do with radiative heat transfer than conductive heat transfer, except at the point where your hand touches the chrome (which is all conduction, and you’re right metals conduct very well). The temperature of an object exposed to solar radiation is driven by the absorbtivity and emissivity of the surface. The absorbtivity is the amount of thermal radiation incident on the surface that will be accepted by the surface. Emissivity is a measure of how well the surface emits thermal radiation to its surroundings. A lot of surfaces are called gray (e.g. their absorbtivity ~ emissivity) - a black car would be a good example of a gray surface, strangely enough. Chrome isn’t like that - its absorbtivity is very high, and its emissivity is low. So the steady state temperature of an object exposed to solar radiation (or high temperatures surroundings) is higher than a black object where absorbivity is usually equal to emissivity. The steady state temperature of the surface (if conduction and convection are negligible) occurs when the emissivity of the surface times the Stefan-Boltzman constant times the surface temperature in Kelvin to the 4th power equals the absorbtivity of the surface times the thermal radiation incident on the surface. AKA WAY TOO DAMN HOT ON A SUMMER DAY!

Sam > Laurence 08/17/2015 at 15:19

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Wouldn’t you think that reflectivity would correlate to reduced heat? Damned thermodynamics.

RamblinRover Luxury-Yacht > someassemblyrequired 08/17/2015 at 16:24

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Yep, I’ve studied all that, I just wasn’t operating at my sharpest re: non-gray surfaces, so I didn’t look up absorbtivity vs. emissivity. I suspected it was about the furthest from a black body imaginable (and the shineyness is a big hint it’s not a diffuse surface at any rate). I knew the emissivity was going to be crap, but without the refresher I didn’t think about the absorbtivity being different. Thanks.

someassemblyrequired > RamblinRover Luxury-Yacht 08/17/2015 at 17:21

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No worries - it’s definitely an interesting phenomenon. This would totally have ended up as an assignment question if I still taught heat transfer.