Black intercooler

[R33S2]

I was reading a thread in here about black intercoolers but cant find it now.

It went on about how radiators were black in all cars so does this mean they run cooler than other colors.

And thinking upon this it makes sense because white reflects energy and black absorbs it so the black layer of paint is absorbing all the energy and at the same time being cooled by air while moving of course.(makes a better transfer point) and the rougher the paint the more surface area to cool.

I liked an opion on this b4 I try it

[WazR32GTSt]

aren't stock r32/r33 GTR intercoolers black?

[raz0r$harP.UK]

i dont think overall it would make much of a difference at all due to them beind air cooled so fast anyway but i thought in theory that the black ones would get hotter initially due to them absorbing the heat energy as opposed to being reflected by the white....

[Skyrine-Dave]

I had this thread which some people posted some good information and comments

http://www.skylinesaustralia.com/forums/sh...tercooler+black

[treo]

Silver intercooler is better in direct light, however wont absorb the cold aswell in darkness.

Vice versa

Dark intercooler will absorb more heat in direct sunlight, however in complete darkness a better choice.

thats just my opinion!

[R33S2]

Thanks skyline-dave that was the thread i was looking for.

people seem 50-50 on merits but painting the back might be the way i go

[browny]

I think people are trying to read way too much into this. A radiator/intercooler is primarily a convective device. Convection is driven by airflow, surface area and temperature difference. The heat transfer by radiation is going to be relatively small.

Any gain that you get from painting it black is probably going to be lost due to the insulating properties of the paint.

[xRHETTx]

In Julian Edgars book 21st centuary performance, i think he found when he stripped the black paint from his r32 gtr intercooler the outlet temp from the intercooler increased by 2 degrees. Therefore leave it black or paint it.

[hrd-hr30]

I think people are trying to read way too much into this. A radiator/intercooler is primarily a convective device. Convection is driven by airflow, surface area and temperature difference. The heat transfer by radiation is going to be relatively small.

its about heat emissivity of the surface, ie how quickly heat can be emitted. a thin coating of matt black will increase the heat emissivity of an alloy surface.

polished alloy is on the other end of the scale and has terrible heat emmission properties, so never polish something unless you want it to retain heat (or lack thereof).

[predator]

why is the factory R34 cooler silver then?

and the earlier ones are black?

[browny]

its about heat emissivity of the surface, ie how quickly heat can be emitted. a thin coating of matt black will increase the heat emissivity of an alloy surface.  

polished alloy is on the other end of the scale and has terrible heat emmission properties, so never polish something unless you want it to retain heat (or lack thereof).

Your right, but thats not what I am arguing.

What I am saying is that I think radiative heat transfer in devices such as intercoolers and radiators is so small in comparison to the convective heat transfer, that it's insignificant and therefore there's no real advantage in painting it black, blue, pink, red or any other colour. If anything I'd tend to think the insulating properties of the paint would be undesirable.

IMO the factory coatings are designed for aesthetics and corrosion protection.

[hrd-hr30]

Your right, but thats not what I am arguing.  

What I am saying is that I think radiative heat transfer in devices such as intercoolers and radiators is so small in comparison to the convective heat transfer, that it's insignificant and therefore there's no real advantage in painting it black, blue, pink, red or any other colour. If anything I'd tend to think the insulating properties of the paint would be undesirable.

IMO the factory coatings are designed for aesthetics and corrosion protection.

ah, interesting. you're saying that emissivty properties of the material/surface are only relevant to radiation, and not to conduction or convection? The latter two are obviously the primary methods of heat transfer in an air to air intercooler - convection on either side of the tubes, and conduction through the material. But it is convection I agree that we are talking about here on the outside of the 'cooler. I'm going to have to think about this one on the train ride home.

I disagree about the insulating property of paint argument, given that high emissivity black paints (and other forms of coatings) are regularly used in industrial heat exchangers. A thin coating of paint is the only thing I'd ever recommend.

[browny]

you're saying that emissivty properties of the material/surface are only relevant to radiation, and not to conduction or convection?

Yes. Although the emmisivity may play some part in the convective heat transfer coefficient if you drilled down into the theory far enough. I can see how this is relevant to conduction tho.

It's a bit risky trying to extrapolate industrial situations to auto applications. We might be talking orders of magnitude higher temperatures. I'd also be careful to make sure that I understood exactly what a 'high emmisivity' coating actually means (I don't btw but i'm interested to learn). If it's a coating thats designed primarily for protection (or appearance) and minimal reduction in heat transfer, it does not neccesarily mean that it's better than nothing.

[Oosh]

This is taken from Dans Data, in specific relation to computer heatsinks but it amounts to the same thing, linkage

Is black better?

Recently, as part of our electronics course, we learned about the properties of heat sinks. The course notes (and exam mark schemes) claim that to make a heat sink more efficient it should be painted matte black.

I understand that this would make it more efficient, but my friend and I wondered why CPU heat sinks are not painted matte black? Most other heat sinks (attached to amplifiers etc) seem to be painted in this fashion, so why not CPU heat sinks?

Peter

Answer: Your course notes are right, and they're wrong.

A black object will, all things being equal, radiate heat better than one of any other colour. However, painting a shiny heat sink black may do nothing, or less than nothing, for its thermal performance, because the layer of paint acts as an insulator. The black colour must be an integral quality of the heat sink material, or a very thin, thermally conductive layer on the outside; black-anodised aluminium is a perfect example of a good black heat sink material. It's possible to put a useful thermal black patina on copper by putting it in a hot sodium hydroxide and sodium chloride solution bath (also useful for disposing of corpses), but that's neither a quick nor an easy process, so people usually only bother doing that for copper that's being used as a thermal absorber, as in solar water heaters, not on heat sinks.

This is because the colour of the heat sink matters less and less the more air you move over it. If the sink's hanging in vacuum (like the heat radiators on spacecraft that stop their own waste heat from boiling them) then it must be matte black; if it's sitting on earth being cooled by convection then it should be matte black; if it's got a bunch of forced air cooling from an attached fan then it doesn't matter a great deal what colour it is.

Again, all things being equal, a shiny aluminium heat sink with a fan on it won't work quite as well as a black one - but the difference will be small enough that the extra marketability of the shiny heat sink is likely to be the deciding factor.

A shiny fan-cooled copper heat sink, which can't easily be made black without pointless insulative paint, will work better than an aluminium one with the same dimensions, thanks to copper's rather higher thermal conductivity.  

For those who scim, the important line in there is: "if it's got a bunch of forced air cooling from an attached fan then it doesn't matter a great deal what colour it is." ... and while the fan doesn't really apply here your intercooler should have a fair bit of air going over it when you're on boost.

By painting it you're likely to make things worse. The oft used GTR example only holds out because I'm sure Nissan were very careful with what paint they use and how they apply it, a backyard job is gonna have a MUCH harder time replicatiing those results.

[inissane]

well said oosh i agree completely, most are looking for a cheap easy improvement in cooling with no extra hardware that simply isnt worth the effort

[Wazz]

well i plan on painting the half of the intercooler facing fowards black for the fact.. car is black and i want that sleeper look after reading that.. it shouldnt make much difference as i was only goin to do a quick spray over with matt black.. not go the full shitloads of layers.. was goin to do maybe 2 light layers if that.. shouldnt make much difference

[Abo Bob]

Wazz, check the thread I wrote which is linked to in the thread that is linked to above. Ordinary paint might not stick.

[Oosh]

I must admit i considered painting my cooler for sleeper reasons, but i was going to mask up the fins and just paint the flat bars black (bar & plate cooler), I figured that'd make it pretty dark but have minimal chance of affecting the cooling.

Now i just plain can't be bothered, there's more important things the car needs doing first.