push rod tube, to paint or not Options

[jacksun]

Hi,

got my first push rod tube cleaned up and would like to paint it with

hi-temp paint? any problems doing so?

tks

randal

[stugray]

BTW,Kirchoff's Law of Thermodynamics basically states black (black body) absorbs better AND radiates heat better due to it's infrared properties. If this is the case, we should all paint our engines flat black.

The old wive's tale of "Black gets hotter" or "Black radiates better" was made even worse by Dr. Iam Malcom in Jurrasic park.
We all know that the black interiors of our cars definitely get hotter in the sun, so why?

Just because the color "looks" black to our eyes does not mean that it is black as far as the Infrared spectrum is concerned.

Black is "Black" in the visible spectrum because it does not reflect light that we can see. It means nothing to the BIG contributor - Infrared.
The term "black body radiator" actually has nothing to do with the color of the radiator.
The term "black body" really means that the radiator has no actual color other than that which is due to the temperature and nothing else.

The real answer is that we dont know if one paint radiates better than another unless we can measure it's emissivity which requires a high tech instrument.
If a material absorbs heat good, it has a low reflectivity.
Flat Black paint might radiate heat better (high emissivity), but if it absorbs better (low reflectivity) than it will get hotter becuase it is absorbing the heat from it's surroundings better.

So to make something good at getting rid of heat you want high emissivity and high reflectivity.
Those two are often conflicting because a good radiator is a rough surface which makes it a bad reflector.

But keep in mind that heat moves away from the pushrod tubes three ways: Radiation (light), convection (moving air), and conduction (it's touching somehting else).

For this application the biggest contributor to cooling is the convection part. SO if you really want to make a difference, put some aluminum cooling fins on the tubes and orient them so air flows downward through them.

/Lecture