Technical Will painting an AC Condenser affect cooling?

The old original 60’s and 70’s cars and trucks I had that came with factory AC had black condensers, everything I’ve had from the 80’s to present are just bare aluminum, my guess is automakers could eliminate a step in the process and save a buck or two in expense and work just the same.
I know it’s kind of a spread in years, but an ‘82 Chevy PU I have has a painted condenser, the ‘89 Camaro I gave my kid is bare.

 

Blues4u, I guess we did! Ha ha!
We all know dark colors are hotter than lighter colors. But it is a matter of perspective. I believe, with no proof, other than 70 years on this planet that the coat of paint will insulate the aluminum from the air and reduce that heat exchange more than the color change will effect the exchange of heat.I think we all know black absorbs more heat from a heat source. Just not sure if it works the other way and at the same rate. Almost all racing radiators I see today are unpainted. Is this because it transfers heat better….or just cheaper to not paint it? Not sure.
I think the darker colors have the most effect in sun light. Or at least that’s where I have experienced the difference, the most. But I have never seen a study on it, exactly.
But I bet there is one somewhere on the net….and we all know the net never lies!






Bones

 

It's to save weight bones

Want that race car as light as possible!!

.

 

The science says you're wrong. Heat is transferred from a condenser (or a radiator) via "radiation". This is a process involving light, the heat is radiated as light energy, and a dark surface is more efficient at radiating light energy than a light or shiny surface.
https://www.gcsescience.com/pen10-matt-black.htm

 

As been said only paint with condenser/radiator paint. You can actually block the tiny louvers in the fins. I was a Engineer for a condenser/ radiator manufacturer before I retired.

 

Yeah , I am aware of that, I remember the little spinning thing in a vacuum that used light and dark panels on it. But it only worked in a vacuum, any air would keep it from moving. So, that’s what I meant by “ perspective “ it does work, but at what level and what conditions.






Bones

 

Try Bar-B-Q flat black spray paint. It goes on very thin with good coverage.

 

I would like to see a real world test where the capacity of a bare radiator or condenser is measured. Then paint the radiator/condenser black and then measure it’s capacity again.
That would seem to me to be a real world test of actually what happens when it is painted.
Maybe some one here knows of such a test.






Bones

 

Keeping real simple, the heat is absorbed on the outside being black (like sunlight) and moving air takes away more of it than just a raw surface.

Well, most early sportsters, the ol K models and others? Black. The terrifying Z1R, black. Even some liquid cooled varieties are black, just like their little radiators. I didn't invent the science of it, and research can easily be done on the SAE websites. My whole race motor was Krylon black. Worked for me.

 

By the numbers it makes a difference. In the real world (the one that me and @BamaMav live in) it really does not make any difference. Automotive AC condensors are typically made from aluminum and many of them come factory black.

Your best bet is to use radiator paint. Is is made to not effect heat transfer.

 

Would be a tricky test to pull off, but certainly doable. You could heat the oil to a certain temp, then run it through a radiator and measure the delta T between inlet and outlet. You would have to control the temperature of the cooling air and the air movement as well. You also could measure the delta T of the cooling air between the unpainted and painted radiator say at a specified distance from the radiator, maybe on both sides if you have a controlled flow of air across it. I think it would be a good project for one of our HAMB members that is also a school teacher. A science class would be best for doing this, but maybe auto shop could do it.

 

Sounds good! I knew you would know how to set it up. I would definitely be interested in the outcome! I may be able to crow about the results……or eat crow!

Either way it would be interesting!






Bones

 

Bones: This GOOGLE search reveals tons of information re: painting of radiators. There are many variables.
It's good reading.
https://www.google.com/search?q=does+painting+a+car+radiator+make+it+less+efficient&sxsrf=APq-WBsnccumva60EFLCmXsSbko9zQnbhw:1645053884853&ei=vIcNYv3aM6_I_Qab7pTIDw&oq=heat+disapation+of+painted+radiators&gs_lcp=Cgdnd3Mtd2l6EAEYADIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwAzIHCAAQRxCwA0oECEEYAEoECEYYAFAAWABg8iloAXAAeACAAQCIAQCSAQCYAQDIAQjAAQE&sclient=gws-wiz
For example: https://www.jalopyjournal.com/forum/threads/painting-radiator-good-or-bad.456713/

 

NASA taught me a hell of a lot about radiation/emission, ect.
I stand by what i said: flat black is a great emitter of heat.
Here's just a quick class: (check it out)
What color radiates the most heat?
Black objects radiate more heat (and light) than white objects. White objects reflect more light (and also heat usually) than black objects. Note that black body is a technical term in physics. It's a theoretically ideal absorber (and emitter) of electromagnetic radiation.
Blues4U got it right and has posted the pure technical side of the discussion. See above.

 

The main reason for painting aluminum heat exchangers is black out as seen through the grill.

 

Very aged radiator man had me help with the painting of 4 radiators fresh out of his hot acid cleaning tank.
The radiator paint was thinned (by him) with...GASOLINE!
Read some about the process. It'll arm you. (with knowledge)

 

Addendum to my earlier post on using rad paint. If I couldn't get rad paint in any way like say, from a rad shop, my next choice would be the flat black specifically made for & used on oem wood stoves & restorations. Not hard to get, go lightly, just enough to blacken. Another thing the thin black paint does, is help protect the alum, or copper/brass, from corrosion forming on the fins. Which acts like a very good heat block, preventing heat transfer out from the rad/condenser to the air passing by. Read: causes problems in performance that cost time & $$$ to find & rectify.
Mike; that sounds about right, from what I remember, but I think the gas wasn't required as a diluting agent, just an easy quick/cheap available substance that worked ok. I didn't use that to mix when I coated a couple of my rads. Wasn't too fond of the highly "vaporized gasoline in the air" around me, concept.
Marcus...

 

my dad had mentioned carbon black. It’s much thinner than black paint.

 

Black paint, I'd say, as long as the coat is thin enough not to affect airflow through the core materially — purely for considerations of appearance.

Absorption/emission of electromagnetic radiation is frequency-specific. Remember that what we call "colour," including light/dark, is an indication of what we pick up with our eyes out of the visible light spectrum. An object with a dark-coloured surface is able to absorb radiation at visible-light frequencies, into the near infra-red, better than one with a light-coloured surface. This absorption will raise the temperature of the object, causing it to reradiate, or emit, EMR at a frequency determined by the temperature of the object. The higher the temperature and, hence, frequency gets, into the near infra-red or beyond, the greater a role the object's colour is going to play in its ability to emit EMR. The lower the frequency, the more it depends on surface finish: the rougher the finish, the higher the emissivity, and vice versa.

A temperature of car radiator or A/C condenser is likely to be such as to emit EMR in around the 40GHz range. Whatever difference the core's colour makes is splitting hairs: but we definitely want a matt finish regardless of what the colour is.