[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]
On 31 Dec 97, Veeduber wrote:
> Jim,
>
> I'm sure you're correct.
>
> I'm equally sure that it doesn't really matter,
This may be the most important fact. I got an email that agreed
that everything I claimed was true and that it made all of 4-6 deg
difference. He said it as if he had seen actual figures, so this is
interesting. It is true that radiative cooling is pretty weak at low
temps like these, so it may be totally pointless to worry about it.
> It appears that so long as the blower is spinning the shrouding does not
> absorb an appreciable amount of heat. Or, if it does, it is immediately
> carried away by the air-flow within the shrouding.
The latter was my contention, so cool tin would be consistent with
either no heat load, or good cooling by that layer of air next to the
tin. I'm afraid this doesn't help us decide which theory is right.
> Now consider this: Let us say that you treat your shrouding with something
> that makes it transparent to radiated thermal energy, or as nearly so as you
> can get it. Where does that radiated heat go?
>
> I suggest it goes into your engine compartment, and from there, into the
> blower... and back over your engine.
That would be the case in a T! or T2 engine, and I'll have to admit
that I was thinking only of the T3 engine were the cooling air is
pulled in separately. Still, it the sheet tin absorbs a significant
amount of heat, I think most of it would be carried off by the active
airflow on the inside and a lesser amount would make it to the
outside. this is just because there will be a temp differential
between the inside and outside, caused by the flow of heat in that
direction and the finite thermal conductivity of the metal, two paint
layers, and two interfaces.
> Personally, I'm content to follow Volkswagen's lead when it comes to the color
> of the engine's tin-ware. Over the years I've seen stock VW automotive and
> industrial engines painted gray, black, yellow, green, olive drab and red.
Really? Very Interesting? Probably your best argument. Black was
probably just cheap and an easy compromise.
> And now Propane Blue, of course :-)
thanks for the mental exercise.
Jim
---------------------------------------------------------------------
Melissa Kepner Jim Adney
Laura Kepner-Adney
jadney@vwtype3.org
Madison, Wisconsin
---------------------------------------------------------------------