Should radiator core be painted black?

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:[color=blue]
> 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[/color]

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.earthlink.net...[color=blue]
> 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
>[/color]

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

On Thu, 19 Oct 2006 19:44:32 GMT, "Mike Harris"
<harrisremovethiswest@sbcglobal.net> wrote:
[color=blue]
>
>"Doc" <docsavage20@xhotmail.xom> wrote in message
>news:9lQZg.11607$Y24.9191@newsread4.news.pas.earthlink.net...[color=green]
>> 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
>>[/color]
>
>No. It makes little difference. Old brass radiators were painted for
>corrosion protection.[/color]

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" <docsavage20@xhotmail.xom> wrote in message
news:9lQZg.11607$Y24.9191@newsread4.news.pas.earthlink.net...[color=blue]
> 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[/color]

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:[color=blue]
> 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
>
>[/color]


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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Doc wrote:
[color=blue]
> 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
>
>[/color]

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:[color=blue]
>
> 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[/color]

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.

Add: In the shade in space.

hls wrote:[color=blue]
>
> "Doc" <docsavage20@xhotmail.xom> wrote in message
> news:9lQZg.11607$Y24.9191@newsread4.news.pas.earthlink.net...[color=green]
> > 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[/color]
>
> 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.[/color]

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
------------------------------------------------------------------
Error: Keyboard not attached. Press F1 to continue.

Doc wrote:
Should spray paint it matte black before installing?[color=blue]
>[/color]

My 2005 Tacoma has a silver radiator.

I think I'll trust Toyota on that... <G>

In article <45383138.F313903C@houston.rr.com>
HoustonTexasUSA
"=?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?=" writes:
[color=blue]
> Add: In the shade in space.[/color]

Actually <g> -- the radiator would radiate the same, whether in
shade or full light, in space or not. But, if there was gas (ie
liquid, in the general case) around it, convection would become
another way to lose heat. And if it was not in darkness (at all
wavelengths) then (depending on wavelength and such factors) it
could gain energy by incoming radiation. This kind of exchange
is going on all the time but isn't always obvious. (And let's
not be forgetting plain old conduction as an energy conduit.)

Isn't pedantry way more fun than bigotry?
--
Andrew Stephenson

Doc wrote:[color=blue]
> 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
>
>[/color]
The paint will act as more of an insulator than any aid to radiation.
Actually, oxidized aluminum is a fairly good radiator in the infrared,
the waveband of most interest at the temperature a radiator runs at. I
am not so sure about the infrared emissivity of copper, I don't think it
is too bad. I suspect painting was done more for appearance than heat
transfer.

Most of the cooling will be by convection, which is why there is a fan.
A paint coating definitely adds a thermal impedance to getting the
heat into the air.

Andrew Stephenson wrote:[color=blue]
>
> In article <45383138.F313903C@houston.rr.com>
> HoustonTexasUSA
> "=?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?=" writes:
>[color=green]
> > Add: In the shade in space.[/color]
>
> Actually <g> -- the radiator would radiate the same, whether in
> shade or full light, in space or not. But, if there was gas (ie
> liquid, in the general case) around it, convection would become
> another way to lose heat. And if it was not in darkness (at all
> wavelengths) then (depending on wavelength and such factors) it
> could gain energy by incoming radiation. This kind of exchange
> is going on all the time but isn't always obvious. (And let's
> not be forgetting plain old conduction as an energy conduit.)
>
> Isn't pedantry way more fun than bigotry?
> --
> Andrew Stephenson[/color]

Yes! After thinking about it for a while, I have to agree.