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> push rod tube, to paint or not
jacksun
post Jul 1 2014, 11:43 AM
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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
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stugray
post Jul 2 2014, 01:19 PM
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QUOTE
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
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jacksun   push rod tube   Jul 1 2014, 11:43 AM
914Sixer   Paint holds heat. They were plated gold or clear ...   Jul 1 2014, 02:13 PM
jacksun   hmm ..... now I have four painted.............. f...   Jul 1 2014, 04:59 PM
Mike Bellis   Has anyone really done a study to find out how muc...   Jul 1 2014, 05:24 PM
Mike Bellis   BTW, Kirchoff's Law of Thermodynamics basicall...   Jul 1 2014, 05:34 PM
jacksun   just kidding about the purple....... they are blac...   Jul 1 2014, 05:37 PM
Mike Bellis   just kidding about the purple....... they are bla...   Jul 1 2014, 06:07 PM
swooshdave   Some of you are worried that a little paint on the...   Jul 1 2014, 06:08 PM
Mike Bellis   Some of you are worried that a little paint on th...   Jul 1 2014, 06:12 PM
r_towle   Some of you are worried that a little paint on th...   Jul 1 2014, 07:20 PM
swooshdave   What happens if I paint my jackstands? (oops, I h...   Jul 1 2014, 07:25 PM
PlantMan   What happens if I paint my jackstands? (oops, I ...   Jul 1 2014, 07:59 PM
malcolm2   I painted mine..... But masked off the o-ring sea...   Jul 1 2014, 08:04 PM
PanelBilly   It it looks good then do it. Are you going to race...   Jul 1 2014, 08:18 PM
malcolm2   It it looks good then do it. Are you going to rac...   Jul 1 2014, 08:21 PM
Keyser Sose   All the oil that goes to the rocker assemblies, wh...   Jul 1 2014, 08:49 PM
jacksun   http://www.vw-resource.com/cooling_qa.html ...   Jul 2 2014, 04:56 AM
Keyser Sose   Oil 'dribbles' back? Sure, at idle. Fift...   Jul 2 2014, 12:23 PM
stugray   The old wive's tale of "Black gets hott...   Jul 2 2014, 01:19 PM
Java2570   And we all know what happened to Dr. Malcolm in Ju...   Jul 2 2014, 01:47 PM
WLD419   I went ahead and painted mine :) , I ended up us...   Jul 3 2014, 04:01 AM
stugray   What's with the plug wires? Must be dual plug...   Jul 3 2014, 08:03 AM
WLD419   What's with the plug wires? Must be dual plu...   Jul 3 2014, 08:23 PM
barefoot   Sorry, slight thread hijack, but an order of magni...   Jul 3 2014, 08:36 AM
barefoot   xx   Jul 3 2014, 04:06 PM
stugray   Funny that I stumbled across this after this discu...   Jul 6 2014, 10:49 PM
jacksun   thanks for the link   Jul 7 2014, 06:08 AM
Keyser Sose   Sorry, can't believe that, no way. Bare metal...   Jul 7 2014, 06:53 AM
stugray   I think that the point was: "Black painted ...   Jul 7 2014, 07:14 AM
Keyser Sose   You're talking about the point in that video, ...   Jul 7 2014, 12:32 PM
stugray   Yes, and it also applies to this discussion. 1 ...   Jul 7 2014, 01:06 PM
Keyser Sose   In the video you posted the black paint really imp...   Jul 7 2014, 04:16 PM
stugray   That's exactly what I have been saying as wel...   Jul 7 2014, 06:07 PM
Keyser Sose   OK, reality check. Stu, we're talking about p...   Jul 7 2014, 07:54 PM
stugray   OK, reality check. Keyser - First I said it doesnt...   Jul 7 2014, 10:09 PM
Highland   I just watched both u-tube videos and it seems lik...   Jul 8 2014, 05:39 PM
Mike Bellis   I knew this would turn into a good debate... :evil...   Jul 8 2014, 06:04 PM


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