Thermal conductivity of alluminum, anodized/oxodized.

[Interlagos]

I found this forum searching for info on open headers causing burnt exhaust valves and found some very good information and what appear to be intelligent people. So I thought I would pose a question that I have wondered for sometime.

Which has higher thermal conductivity, anodized aluminum or lightly oxidized aluminum? Any solid information would be appreciated.

I ask for intercooling purposes and the choice to anodize intercoolers or not.


Thanks a lot.

 

[ivymike]

I think the more interesting question might be "which has a higher heat transfer coefficient," since generally the metal-to-air interface limits the effectiveness of the heat exchanger. I don't know the answer, but my gut tells me that they're going to be pretty darn similar.

 

[Interlagos]

Aren't the very much related?

 

[patprimmer]

No

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Interlagos]

Well then that may be what I meant to ask, what I am getting at is which will shed heat into the air faster, I guess thermal conductivity is how fast the heat will move through the material.

 

[drwebb]

'Clean' aluminum in the atmosphere is in fact completely covered with an oxide coating as soon as it is exposed. So I suspect you are practically comparing corroded aluminum to anodized, and that will depend more on the thickness of the coatings rather than the chemical properties, and will also likely be fairly sample specific. I can't really see much performance benefit realizable from anodizing unless it's for especially severe environments.

 

[Interlagos]

The anodizing is for appearances, the question is posed more to see if there is a performance loss.

 

[NickE]

I'd have to venture thast the performance loss is negligable.

One thing is that as the surface gets smoother the transfer between the aluminium and the air goes down.

One benefit of the Anodizing process is that the coating thickness and surface finish are more controlled than the oxided surface film on a raw aluminium piece. However the Anodized coating is going to be thicker.

 

[ivymike]

to further support what Nick has said, it has been my experience that anti-corrosion coatings (even thick ones) applied to aftercoolers have little impact on their effectiveness. My experience has been with the coatings on the inside, however.