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Painting the radiator
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Author:  Mike [ Thu Feb 03, 2005 3:53 am ]
Post subject:  Painting the radiator
I took the rad off (as part of a bigger engine removal thing). Now I've flushed it in every possible direction and position, degreased it and washed the fins. Now the paint is still ok but is pealing in some places and is scratched in others so since its out I thought I'll repaint it.

Now should I use the messy and questionably effective paint stripper to remove the existing paint or should I use a wire brush? Can I wire brush the fins?

Whats the best paint to use once the old one's gone? Just black kill rust or something else? Do I paint the fins?

cheers
Author:  drmini in aust [ Thu Feb 03, 2005 7:00 am ]
Post subject: 
1. It's important to paint the fins- black fins radiate heat better. But you want a thin coat.
I would use VHT quick coat spraycan. Thin, quick dry, good finish.
Don't use killrust, it's too thick I reckon.
2. Don't wire brush the fins hard- they are real fragile. Maybe a hand brush used gently. Toothbrush is even better. :wink:
Author:  Wombat [ Thu Feb 03, 2005 10:10 am ]
Post subject: 
Use a matt finish as well - radiates better than gloss
Author:  drmini in aust [ Thu Feb 03, 2005 10:58 am ]
Post subject: 
Wombat wrote:
Use a matt finish as well - radiates better than gloss

True- VHT do a matt black.
Having said all that, I'm about to polish my top rad tank for enhanced Bling! It's brass...8)
Author:  BigGig [ Thu Feb 03, 2005 11:27 am ]
Post subject: 
Ok, this is some of the technical info that I use at work as an aircraft engineer – not blowing my own horn just giving you a background for my knowledge and experience in this matter because what I am going to tell you is against what most people think. The theory that painting a heat source (engine or radiator) black to increase the amount of radiant energy released is a bit of a fallacy.

Most heat emitted by an engine a components is in the invisible infrared portion of the spectrum. What appears to us as black, white, red or green in the visible spectrum is not what we would see in the infrared spectrum. Any colour paint that uses organic (non-metallic) pigments is BLACK in the infrared spectrum. Painting the engine or radiator increases cooling but the colour of the paint doesn’t. However seeing as white paint is about 1% less of an emitter than black but does have a much lower absorbance the ideal situation would be to paint the emitter white – i.e. engine or radiator white and the engine bay and under bonnet black. That way you get less reflected heat energy back to the source due to the absorption by the black surrounds.

Cheers

Gig
Author:  Wombat [ Thu Feb 03, 2005 11:44 am ]
Post subject: 
Makes sense :shock: Interesting the PO painted the engine silver and the engine bay black :?

I suppose the idea of black came from the original discovery of infrared radiation was called "Black Body Radiation" as the research was looking at the fact that objects absorb all the radiation falling on it except the ojects colour so a black object was supposed to absorb all light/radiation but the experiment showed it was reflecting "something" hence infrared radiation was discovered with black objects.

Gig is correct in saying all colours will radiate in the infrared. :roll: so a white radiator would ABSORB less heat radiating from the hot engine next to it (as opposed to the hot water circulating inside it.)
Author:  drmini in aust [ Thu Feb 03, 2005 11:47 am ]
Post subject: 
Gig is right- that's why solar collectors are black- better absorption.
(I used to work for Rheem..., building collectors amongst other things) :wink:
Author:  fuzzy-hair-man [ Thu Feb 03, 2005 12:01 pm ]
Post subject: 
Why does painting the engine or radiator increase cooling if colour isn't an issue? :?:
Author:  Wombat [ Thu Feb 03, 2005 12:08 pm ]
Post subject: 
And the fins in your air conditioner are silver :mrgreen:
Author:  BigGig [ Thu Feb 03, 2005 12:18 pm ]
Post subject: 
Because the paint itself regardless of colour is an energy emitter – it does appear black in the infrared spectrum which is the area of interest when dealing with heat transfer. It becomes a better emitter of heat than the bare metal of the engine etc. There are metals which are developed to transfer heat more efficiently and these would not need painting. However the most important aspect of this is the absorption properties of the paint which does differ considerably so even though colours might radiate at basically the same rate the reflectance qualities of each will still be a big factor in how much heat energy they absorb back. As an example we changed our aircraft engines from dark grey to light grey (we couldn’t use white as they would look very dirty after a while) we reduced the Cylinder head temps by 10 degrees C.

Gig
Author:  gafmo [ Fri Feb 04, 2005 4:06 pm ]
Post subject: 
The colour would make little differance to the cooling..PLease :roll:
Just paint it waht ever colour except white or Yellow as you will have to continusely clean the the Bugger.
Additional clean of the top tank and polish it...it Brass :shock:
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