Any truth to the practice of BLACK painted parts dissipating heat better?

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Just throwing this out there. I had a '65 Sprt Fury with an RB and black headers. Radiated so much heat from the headers that the edges of the suspension cover would smoke. Solution? Painted the headers white and problem solved.
 
I remember white headers turning cherry red from holding heat in them. Black headers not as much. The next engine on the run stand I'll paint one header white and one black . Then take the temp with a digital thermometer. Just curious
 
Right! Not disagreeing or trying to dissuade anyone of their theories, but can anyone explain this; Try painting your foam core front door on your house facing south white or black.... the white will reflect the light and stay cool, the black with absorb heat and literally melt the foam and the glue will run right out of it, especially if you are in a warmer climate!! So, black can only dissipate heat in the dark???
/confoosed in Ohio lol

Easy to explain. Heat from the sun arrives in radiant form - with little convection, the heat cannot be rejected. Black will absorb and radiate away more radiative heat than white will.
 
Just throwing this out there. I had a '65 Sprt Fury with an RB and black headers. Radiated so much heat from the headers that the edges of the suspension cover would smoke. Solution? Painted the headers white and problem solved.

Makes sense - radiant heat again. The direct exposure of the headers to the suspension cover would heat the cover due to the high temperature differential and the amount of radiant heat dissipated.

Radiant heat is all about a high temperature emitter directly heating a surface within line-of-sight. The amount of heat radiated can be moderated by the color or coating of the emitter or receiver.
 
As mentioned the key to understand is colors that absorb heat faster also dissipate it faster. This is a reason why wood furnaces are painted or coated (or surface-treated) black. We feel black is "hotter" because standing in sunlight with a black shirt you get much hotter than wearing a white one but our bodies are at far too low of a temperature to notice the increased heat dissipation from the black shirt. We have only been able to prove that with objects that get up far hotter than our bodies so it's a much less "intuitive" concept to understand. I studied heat transfer as a mech engineering student (in both bachelor's and master's) and while I did pick up new concepts better than many of my classmates did a lot of it still throws me for a loop and confuses the hell out of me lmao. It's an incredibly complicated subject, so many different variables affect how heat moves from one thing to another.
 
It is true. There can be multiple factors that effect the efficiency but black has a higher emissivity rate. My company has done a lot of experiments on this for various servo drives and servo motors. The power components run up to 10% cooler if internal and external surfaces are black. Very cost effective way to increase product performance ratings or reliability.
 
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Ho!
Ho!
Holy Schiatsue!
 
I don't think black paint "per se" necessarily helps. I know rad shops used to hose down radiators with a huge think film of cheap black paint. Makes you wonder if it doesn't form an insulating layer and INHIBIT radiation
 
I don't think black paint "per se" necessarily helps. I know rad shops used to hose down radiators with a huge think film of cheap black paint. Makes you wonder if it doesn't form an insulating layer and INHIBIT radiation

Radiant barriers tend to be reflective. But you're right, a thick paint could act as a convective insulator and result in a net loss of cooling ability.
 
Think of it like this...
Aluminum heats up easier AND cools off faster than, say, cast iron. This is getting into the specific heat of a material, but think it of it as the specific rate of heat transfer, in either direction. Any thing that is slow to heat up is slow to cool off, all other factors being equal. Anything that heats up quick is quick to cool off. This also assumes things like phase change (evaporation, freezing,etc) aren't happening.

Now, instead of calling it heat, call it energy. Heat is a symptom of how much energy is in a thing. The black surface transfers energy faster than other surfaces. In, or out. In this case, radiant energy. It radiates heat/energy faster, and absorbs radiant heat/energy faster. We feel the black patterns on our shirt heat up faster in the sunlight, but they also expel more of our body heat out to the environment.

Close the hood and the engine is absorbing less radiant energy from the sun, because there's less available, but still radiates heat/energy to anything around it.

But again, all other factors need to be equal. Glossy vs. Matte has an effect, because glossy surfaces reflect more light which is its own form of energy. You can look up the specific heat for any material, and I'm sure something similar exists for colors/surfaces, but I don't know what it is.

That's my rudimentary understanding of the thermodynamics of the thing.
 
Think of it like this...
Aluminum heats up easier AND cools off faster than, say, cast iron. This is getting into the specific heat of a material, but think it of it as the specific rate of heat transfer, in either direction. Any thing that is slow to heat up is slow to cool off, all other factors being equal. Anything that heats up quick is quick to cool off. This also assumes things like phase change (evaporation, freezing,etc) aren't happening.

Now, instead of calling it heat, call it energy. Heat is a symptom of how much energy is in a thing. The black surface transfers energy faster than other surfaces. In, or out. In this case, radiant energy. It radiates heat/energy faster, and absorbs radiant heat/energy faster. We feel the black patterns on our shirt heat up faster in the sunlight, but they also expel more of our body heat out to the environment.

Close the hood and the engine is absorbing less radiant energy from the sun, because there's less available, but still radiates heat/energy to anything around it.

But again, all other factors need to be equal. Glossy vs. Matte has an effect, because glossy surfaces reflect more light which is its own form of energy. You can look up the specific heat for any material, and I'm sure something similar exists for colors/surfaces, but I don't know what it is.

That's my rudimentary understanding of the thermodynamics of the thing.

You are incorrect on one point. Thermal conductivity and specific heat are not related. While true that a material with low specific heat just can't hold much and therefore as a whole will heat and cool more quickly than something with a higher specific heat index, that does not mean the material will CONDUCT heat more or less rapidly I'm not sure, if this relates to the materials heat radiation capability, in other words one or the other characteristics may "fight" the other--overall
 
I'm pretty sure that's different. The melanin blocks UV light, which causes injuries. It also blocks the light needed to synthesize vitamin D, and with much less light in the higher latitudes in winter and consequently less vitamin D deficiency, prior to mechanized travel and vitamins people DIED or became more susceptible to disease because of vitamin D deficiency. Evolutionary pressures killed those with more inherent resistance to skin damage from sunlight, as well as selecting for REDHEADS!
So, Merry Christmas!

View attachment 1715841096
2varieties of redheads, drop dead gorgeous or drop dead ugly.
 
I have been painting blocks black for years. Long ago I was teen and a racer told us about heat dissipation and using black paint.
He also said that flat is better than shinny, as it releases heat faster.
On the same hand he stated hood/hood scoops should be light color to reflect heat and white is the best.
The guy was Warren Johnson. I know a GM guy, but he did well in NHRA.
Physics doesn't discriminate based on color or brand! The fact is engines are usually painted for rust protection regardless of color. As was said earlier, black is impossible to detect oil leaks, I built a Ford 7.3 L for a guy not long ago and he wanted to paint it Ford Oval Blue, I said that would look ugly as sin in his burnt orange truck and said it would be better to paint it black, I had already done it in black and he brought up the oil trace issue. We both agreed it would look much better painted Cat Yellow so I went to the local Cat Dealer and purchased the correct paint, he and I agreed it did look cooler in yellow. Those old 7.3l did look a bit like the old 11xx and 32xx series Cat V8 if you didn't look long at them. As for the black engines, engine masters did a show that was published in some mags some time back. Results as far as I can remember were somewhat insignificant on account of the engines temps depending more on the thermostats, and the cooling system as a whole. For what little difference it really makes is this, iron heads have been found to actually make more power but run hotter which is an issue in itself due to combustion control. Engines running aluminum heads seem to tolerate slightly more ignition advance because they keep the charge and combustion temps cooler, aluminum as well all know absords heat better and since the fluid system is tasked with removing that heat, aluminum also releases it faster and better than iron. It is know that iron blocks are more stable and stability is a key factor in engine function so painting the iron block tends to keep block temps a bit higher internally, this is a slight benefit to helping the pistons and rings to fit and seal a tiny bit better. Then to either use real aluminum heads or paint the heads aluminum. Since the heat in an engine is dissipated from the surface either inside or outside and you would have a pretty hard time coating the inside of the cooling areas unless you dipped the parts in paint, color of any engine block becomes more an issue of preference. Black guns look cool or scary based on the persons attitude towards them just the same as engines. The difference is only measured on a dyno and is very miniscule.
 
I've read through this thread and while I don't claim to be able to follow the science, I'm guessing that if black is a cooler color I should be able to hang meat in the engine bay on this spray-bombed beauty. :eek:

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