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-   -   Painting Intercooler? (https://www.miataturbo.net/prefabbed-turbo-kits-3/painting-intercooler-5750/)

boostinsteve 11-23-2006 02:28 PM

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.

lukydvll 11-26-2006 12:51 AM

FWIW, on my old turbo setup I datalogged before and after when I spray painted my intercooler. intake temps were the same.

boostinsteve 11-26-2006 01:33 AM

That is what we needed, some evidence of someone that had done it, did you just put a real thin layer on there.

Loki047 11-26-2006 03:15 AM


Originally Posted by boostinsteve (Post 59363)
That is what we needed, some evidence of someone that had done it, did you just put a real thin layer on there.


Not necessiarly he could have done this at -30 and it wouldnt have made a difference if he had an intercooler or not. But yes i would say it settles the argument, but i still wouldnt do it.

y8s 11-26-2006 11:22 AM

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.
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.

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.

Loki047 11-26-2006 11:37 AM

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.

lukydvll 11-26-2006 11:49 AM


Originally Posted by boostinsteve (Post 59363)
That is what we needed, some evidence of someone that had done it, did you just put a real thin layer on there.

Yeah, I just put a few really light coats on it. Just enough make the IC a little less obvious.
FWIW, I used radiator paint. Got it at a ma&pa auto parts store. Ambient temps were around 95 when I tested it.

boostinsteve 11-26-2006 03:12 PM

We are also considering that these are light coats, that is all that I was saying, do not just dump the shit 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.

y8s 11-26-2006 03:42 PM


Originally Posted by Loki047 (Post 59417)
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.

I bet even knowing exactly the h and k of the materials, you'd still find it was only half a percent decrease in efficiency.

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

Loki047 11-26-2006 04:44 PM


Originally Posted by y8s (Post 59468)

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

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.

savior 11-26-2006 06:27 PM

talk to the AMS shop from the evo forums.. they always have designs on their IC

y8s 11-26-2006 09:42 PM


Originally Posted by Loki047 (Post 59492)
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.

I feel your pain... BSME Cal Poly '98.

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 :cool:

Loki047 11-27-2006 12:18 AM

y8s what are you doing? Im looking for jobs and theres just so many options its overwhelming

y8s 11-27-2006 09:57 AM

sr design engineer here: http://www.nvisinc.com

olderguy 11-27-2006 10:01 AM


Originally Posted by y8s (Post 59632)
sr design engineer here: http://www.nvisinc.com

Guess with that stuff you can see yourself coming and going at the same time.:gay:

Loki047 11-27-2006 11:27 AM


Originally Posted by y8s (Post 59632)
sr design engineer here: http://www.nvisinc.com

Hey ill be in DC in feb, any good places to drink?

y8s 11-27-2006 02:20 PM


Originally Posted by Loki047 (Post 59668)
Hey ill be in DC in feb, any good places to drink?

does howdy doody have wooden balls??

hells yes, there are plenty.


feb eh? you can buy me a bday beverage.

Loki047 11-27-2006 05:17 PM

buy you a drink? I'm a broke college student, so unless your a blonde with big tits..... jk

no but seriously you a hot blonde?

y8s 11-27-2006 09:01 PM

dark blonde? and the ladies think I'm hot. how bout if I FIND you some to buy drinks for. then you can buy me one.

Loki047 11-27-2006 09:35 PM

tough negotiater, but DEAL!


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