Painting Intercooler?
11-23-2006, 02:28 PM
#21
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That is the key though, thin layer. I would not do anymore than one layer if I was going to do it. When it is layered on there, air pockets form which become super insulators, if you paint it, take your time and make sure you are not just layering it on there. Good luck.
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11-26-2006, 11:22 AM
#25
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I'm tellin you... the amount of paint/AlO2/whatever on your intercooler is so small it doesn't really matter! I'll break out the theory and equations for you.
There you go. I did forget the second layer of AlO2 on the inside but honestly it's so meaningless in terms of heat transfer because it's like 800 angstroms thick.
Painting your intercooler will reduce the effective heat transfer by roughly 0.65% in this case. Just keep the paint thin or use conductive paint. Or you could shell out for anodizing in black. That would increase the Alo2 layer to roughly 0.00003m or so which would contribute less to the degradation in thermal transfer but cost you a brazillion dollars.
Matt
Equations and data from engineering toolbox.
Code:
overall heat transfer coefficient: U = 1 / (1/h + dx1/k1 + dx2/k2 + dx3/k3 + 1/h) where: h = convection heat transfer coeff of air dx = thickness of the material (aluminum or paint or whatever) k = thermal conductivity of material U = overall heat transfer coefficient of the layers h = 50 W/m^2-K for air dx1 = lets say 1mm or .001m aluminum thickness dx2 = lets say .0001 mm or .0000001m of alo2 dx3 = lets say .1 mm or .0001m of paint (light coat) k1 = 250 W/m-K from below k2 = 30 W/m-K from below k3 = .40 W/m-K from below U = 1 / (1/[50] + [.001]/[250] + [.0000001]/[30] + [.0001]/[.40] + 1/[50]) simplified: U = 1 / (.02 + .000004 + 3.3x10^-9 + .00025 + .02) U = 24.84 W/m^2-K with all the layers. With no paint, subtract out that ".00025" term: U = 25.00 W/m^2-K with just aluminum and AlO2.
Painting your intercooler will reduce the effective heat transfer by roughly 0.65% in this case. Just keep the paint thin or use conductive paint. Or you could shell out for anodizing in black. That would increase the Alo2 layer to roughly 0.00003m or so which would contribute less to the degradation in thermal transfer but cost you a brazillion dollars.
Matt
Equations and data from engineering toolbox.
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11-26-2006, 11:37 AM
#26
well that is the heat transfer coefficient (i don't have my book with me so ill take your word and link), it does not accurately represent the rate heat transfer from a material because it doesn't take into account radiation.
Man i wish it was that easy to really calculate the heat transfer coefficient, but thats assuming perfect materials.
Man i wish it was that easy to really calculate the heat transfer coefficient, but thats assuming perfect materials.
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11-26-2006, 03:12 PM
#28
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We are also considering that these are light coats, that is all that I was saying, do not just dump the **** on there, and you will be ok. Paint becomes an excellent insulator when put in a thicker application, and the thicker the layers, the more air bubbles get trapped in there, so now you also have an extra insulation blanket around the intercooler. Of course, when you have enough air flowing across the surface, the paint becomes less and less of a factor.
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11-26-2006, 03:42 PM
#29
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well that is the heat transfer coefficient (i don't have my book with me so ill take your word and link), it does not accurately represent the rate heat transfer from a material because it doesn't take into account radiation.
Man i wish it was that easy to really calculate the heat transfer coefficient, but thats assuming perfect materials.
Man i wish it was that easy to really calculate the heat transfer coefficient, but thats assuming perfect materials.
As for radiation, it's probably insignificant since the ambient temp is so close to the surface temp of the intercooler but painting it black would improve radiation heat transfer anyway.
fun fact sidenote: the term "radiator" for the thing in the front of your car is a misnomer. it does most of its work through convection.
Matt
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11-26-2006, 04:44 PM
#30
But whatever, Ive taken heat transfer and did all those god forsaken derivations, I think everyone has enough information to make thier own decisions.
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11-26-2006, 09:42 PM
#32
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Not from what Ive read, or from the heat transfer equations theres quite a bit of lose through radiation (the greater the delta t the greater the radiation loss).
But whatever, Ive taken heat transfer and did all those god forsaken derivations, I think everyone has enough information to make thier own decisions.
But whatever, Ive taken heat transfer and did all those god forsaken derivations, I think everyone has enough information to make thier own decisions.
Anyway... if it is heavily radiation heat transfer, then you should absolutely paint the thing. emissivity of paint: .9something. of ALO2: .2something. Curiously, emissivity of skin is really high too, near blackbody. I guess that's how we can feel an object's temperature so well without touching it.
But...even without the math, I'm paintin mine for stealth and so it matches my black 01
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11-27-2006, 10:01 AM
#35
sr design engineer here: http://www.nvisinc.com
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11-27-2006, 11:27 AM
#36
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