[s-cars] Thermal properties of anodizing Aluminum

[J. Khang]

 --- MLP <mlped at qwest.net> wrote:
> At 27 to 30 psi of boost, on a 60 ~ 80F F ambient
> temperature day,
> Depending on your turbo, I believe one can see IC
> inlet temps of 400 F+.

Actually, an isentropic (perfect) compressor will only
raise the temperature to 95C. I tried to calculate the
actual temperature rise but there are too many
variables whose value I don't know.

I think that 110-150C is more realistic, 400F (205C)
is too high unless the compressor is very inefficient.

As for the increase in heat transfer due to black
anodizing, don't plan on anything significant. I made
some approximations and calculated that you would see
a maximum of 2.5C drop, probably less in reality.

Radiation accounts for very little of the heat
transferred. A 24"x10" radiator with a surface
emmissivity of 0.9 will radiate 820 Watts at 205C.

This might sound like a lot but at 3000 rpm, I
estimate that the AAN is ingesting about 200 grams of
air per second. Air has a heat capacity of 1010 J/kgK
so the 820W = 4C, ignoring volumetric work as the air
contracts during cooling (negligible in this case).

The radiator was already rejecting heat before
anodizing and that was worth about 1.35C so the
difference is 2.65C. My slightly more rigorous
calculation gave 2.5C. This figure drops some more if
rpm increases.

Why are you anodizing?

Jonathan
'96 S6

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