That would of course explain why all the cars coming new from the factory have radiators painted black. If I run into cooling problems in the future, I will probably go ahead and do that.

Definately would want to do a thin painting of my planned intercoolers.

Thanks,
Jon

 

How about an anodized (black) aluminum radiator, I would not want to try to paint a radiator i would think that might restrict the airflow somewhat. Then what would anodizing do to the plastic end tanks?

 

That is why you use paint made for the application. I believe Eastwood has a very thin coating black paint specifically for radiators. Might work well on intercoolers too.

 

The reason to leave them bare or to use a paint specific for the application is that even though paint might be the 'right' color, it will also act to insulate the fins some from the airflow resulting in less heat transfer...

 

Not true. It has already been documented that a correct application of the proper black paint will increase the heat transfer vs. bare metal. But, as mentioned, you would be correct if a heavy or overapplied coating was used.

 

A brief study of emissivity would help alot here. Color, while important in solar radiation issues, is of little importance when talking paints... which generally have high emissivity anyways regardless of color.

I'm in a rush but maybe I can post more on this later. Let me encourage anyone intersted to do a search.... look up the terms "emissivity" and "Planck's Law". That should get you started.

Take care

 

What is it with people on this board that can’t read a whole response?

In the line right before where you cut out my response I suggest using paint “specific for the application” (obviously dissipating heat as per this discussion) so either your “Not true” part or “proper black paint” contradict the rest of your statement…

Mr. Horsepower you’ve got at least me listening, but to be honest I don’t see where you’re going. Based on what is left of some 15y/o high school chemistry in my head (in college I kept butting heads with the chemistry dean till I was told that ‘you will never be allowed to take another chemistry class here again’), Planck's Law just describes how energy is emitted/radiated in quanta of set energy and frequency, so adding in emmisivity and coatings to the idea the only thing comes to my head is that when a substance is coated that the energy released is often lower then the quantum energy predicted…

I guess if the quantum energy of the coating was lower then that of what was coated the item might have an easier time releasing energy in smaller quanta…

Let’s have all our radiators and intercoolers coated in copper/beryllium alloy…

 

Copper heatsinks are popular, or copper base with alum fins, when cheap steel heatsinks are used they are 'always' painted flat black. There are advantages and disadvantages to using aluminum but the prime one being weight I believe. I haven't seen the alum stuff painted, but that could just be because they are 'good enough' for the job and just made larger if need be.

 

Where I'm going and why I suggested a read-up on emissivity or should I say emittances per the NIST's recommendation.

1) The best radiation effect will depend more on the surface finish than the color. A matte finish is generally the best due to the fact the IR emissions become more diffuse the rougher the surface.... eg, oxidized aluminum is a better emitter than polished.

Subject: emittances

2) This is independent of color. On the subject of "paints"... most white paints are as emissive as black paints.

Subject: emittances

3) Paint thickness in the .001-.010 thickness range have very little influence on insulation (conduction). In an example relative to this forum..... GM engineers would have gained greater thermal efficiency by painting the LS1 block if the reverse were true. [q=kA*(DeltaT/DeltaX)], the proof is in the pudding.

4) Car radiator design: radiation takes a back seat, with convection governing. Paint was only used for aesthetic reasons and like any other material has a coefficient of heat transfer less than 100% and absorbs some amount of heat. Again, the coefficient is related to the material makeup of the paint i.e. laquer, acrylic, etc., not the color.
One should conclude that the ideal paint for maximum heat transfer is none at all.
Anodize is only feasible with aluminum alloys and magnesium. Again, the surface is generally smooth and shiny. Again to the subject of emmitances.

5) (1.714E-9)(A)(e)(T**4) where T is the surface temperature in degrees Rankin, A is the area of the body, e is the emittance of the body, and 1.714E-9 is the Stefan-Boltzmann constant.

Again, to the subject of heat transfer and emmitances.

Further reading for those of you who are not already experts in the area... Siegel and Howell's Thermal Radiation Heat Transfer, 3rd Edition

Not aware of a beryllium alloy "coating". But why, when you can use iridium oxide?

Take care

 

Ir02 over Ti maybe?

 

WS6 TA-Misunderstood your intent with the way it was worded. No flame intended.

Chuck-I'm afraid to ask how much iridium oxide coating costs!