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Re: Al and H2O vs Al and O2



In a message dated 97-11-19 06:30:49 EST, you write:

<< It is a fact, as stated by his highness Corky Bell that
 >the heat transfer coeeficient of water to aluminum
 >is fourteen times that of water and air.  Mounting an air 
> to water intercooler still leaves you with a water/AL/air
> interface at the water cooler, with that shitty C_ht.  
> Now if you add a spray bar (I'll take mine as nitrious powered, 
> port flavoured cheese sprayer please) What have you got for your
> heat coefficient?  My experience says it is pretty dammed good!

 >.....

> I know it is difficult to fit a race sized intercooler into many of 
> our cars, especially if it is a simple air to air intercooler.
 >the remote mounting of a seperate cooling radiator allows both
 >the requirements of low intake tract length and optimum IC placement
 >to be met simultaneously.  It also decouples the core design
 >issues for the two ends, adding even more flexibility.
  >>
Paul,
Let me help Bell here, he should have taken one of our listers quotes and put
the statement as, "Air to water IC CAN BE up to 14 times more efficient than
Air to Air".  A real Temp study of this idea needs to be done before we can
claim we even got close in practice, for an audi "can't be" might prove a
better hypothesis.  Audis with high underhood temps aren't really optimum for
water to air conversions, since the heat soaking of the cooling components
really affects the T heat transfer of the radiators.  Optimally, Air to Water
is closer to 14 times more ICE if you mount it in a turbo boat where the
water is open loop and doesn't heat soak the exchanger components.  For a
closed loop system, life isn't so pretty, and heat soak gets really ugly in
an audi.  It takes longer for the water heat exchangers to lower the water
temp once soaked vs A2A.  

So, if you read between some of those lines in the book you reference, there
are several reasons to use A2A IC, and few to use W2A. Specifically to audis,
a good IC air flow location is available in most of the turbo cars with
minimal piping, so heat exchange with A2A is darn good and fast,  ICE high
for a given construction, and certainly faster exchange than W2A.   Bell even
references this on page 53 and 73, basically indicating that IC location
really dictates the use of W2A, no room, go water.  Good airflow position, go
A2A.  

I'm not aware of anyone running W2A IC on an audi turbo car, tho one
certainly "hints" of it right here on the list.  Love to hear from anyone
that did it, "numbers" not just claims of course:).  Given some of the sizes
that sit behind some 44 chassis cars, I'm not convinced at all that the "W2A
Can be" would outperform the "A2A what is".  Some of the wildest machines out
there now, including Ned and Scotty Davis and others, just got very
aggressive sizing and placing a large A2A.  I argue that there is good reason
for this.

Your and Jeff Goggin's spray mods are good for 5-10% according to Bell.
 Given you both drive in low humidity environs, I would venture to the 10%
side with you easily.  The gains for the normal sinus folks is probably at
most 5%.  Given the simplicity of the installs shared, a good mod.


HTH

Scott Justusson
'87 5ktqwRS2
'87 5ktq2GO
'86 5ktqw
'84 Urq