Just got a radiator for my '89 Cressida, but the core is bare aluminum.
Every radiator I've seen has been painted black. Seems I read somewhere the
reason is more than just cosmetic, that the black helps it transmit heat
better. Should spray paint it matte black before installing?

Thanks

Doc wrote:
> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks

I've seen a lot of bare AL radiators.

My guess would be that the paint (any color) would act as a small layer
of insulation. They painted brass radiators because they used to be
outside the engine compartment, and they'd get fugly in a hurry (IIRC).
AL doesn't have as much of a problem.


-phaeton

*sings* "....I see a row of rads and want them painted black.."

"Doc" <docsavage20@xhotmail.xom> wrote in message
news:9lQZg.11607$Y24.9191@newsread4.news.pas.earth link.net...
> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere
> the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks
>

No. It makes little difference. Old brass radiators were painted for
corrosion protection.
--
Mike Harris
Austin TX

"Doc" <docsavage20@xhotmail.xom> wrote in message
news:9lQZg.11607$Y24.9191@newsread4.news.pas.earth link.net...
> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere
> the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks

Your comments rang a bell with me too. This concept is true for some heat
radiating devices, but I think it is
for electronic radiating heat sinks. I wouldnt bet my life on it, but think
this might be the source. Helps in the IR
range IIRC.

Auto radiators work largely by convective heat transfer. Radiative is a
relatively minor component.

Maybe someone else can add something.

Doc wrote:
> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks
>
>


The paint is just to hide it behind the grill. It also provides some
corrosion resistance. Not really worth the bother to paint it.

--
Steve W.

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On Thu, 19 Oct 2006 19:44:32 GMT, "Mike Harris"
<harrisremovethiswest@sbcglobal.net> wrote:

>
>"Doc" <docsavage20@xhotmail.xom> wrote in message
>news:9lQZg.11607$Y24.9191@newsread4.news.pas.eart hlink.net...
>> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
>> Every radiator I've seen has been painted black. Seems I read somewhere
>> the
>> reason is more than just cosmetic, that the black helps it transmit heat
>> better. Should spray paint it matte black before installing?
>>
>> Thanks
>>
>
>No. It makes little difference. Old brass radiators were painted for
>corrosion protection.

A black surface is actually capable of radiating heat better than
other colors, including plain metal.

However, it is likely that a bare aluminum radiator will be better at
radiating heat than the same radiator with a coat of regular paint
will. The paint could act as an insulator, as someone else pointed
out.

In this particular case, the maker designed it to work properly when
bare. I'd recommend you leave it as is.

Doc wrote:

> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks
>
>

If radiation were the main process by which the radiator (interesting
misnomer in even calling it a "radiator") were cooled, then painting it
black would help. But since car "radiators" are actually cooled by
CONVECTION (moving cool air over the fins) the color doesn't matter at
all, and paint would in fact add a little bit of insulation.

Most modern vehicle radiators that I've seen are bare aluminum, UNLESS
they can easily be seen through the grille (and even then, they
frequently only "dust" the front surface with black paint and the engine
side is still silver).

Doc wrote:
>
> Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> Every radiator I've seen has been painted black. Seems I read somewhere the
> reason is more than just cosmetic, that the black helps it transmit heat
> better. Should spray paint it matte black before installing?
>
> Thanks

A asked that question about my house a/c condenser to a couple of NASA engineers
at JSC a few years ago. Their answer was: "it does not matter". However, if the
radiator was in space with no air flow, a black body would be the most efficient
heat emitter.

hls wrote:
>
> "Doc" <docsavage20@xhotmail.xom> wrote in message
> news:9lQZg.11607$Y24.9191@newsread4.news.pas.earth link.net...
> > Just got a radiator for my '89 Cressida, but the core is bare aluminum.
> > Every radiator I've seen has been painted black. Seems I read somewhere
> > the
> > reason is more than just cosmetic, that the black helps it transmit heat
> > better. Should spray paint it matte black before installing?
> >
> > Thanks
>
> Your comments rang a bell with me too. This concept is true for some heat
> radiating devices, but I think it is
> for electronic radiating heat sinks. I wouldnt bet my life on it, but think
> this might be the source. Helps in the IR
> range IIRC.
>
> Auto radiators work largely by convective heat transfer. Radiative is a
> relatively minor component.
>
> Maybe someone else can add something.

This is true. Although its a small effect compared to convection.

A black object will also gain heat via absorption faster than a lighter
colored one. So the side of the radiator facing a hot engine will gain
more heat than a lighter color.

--
Paul Hovnanian mailto:Paul@Hovnanian.com
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