<VV> fanz - SPAL #30102113

[JVHRoberts at aol.com]

One thing also needs to be considered. Pressure drop goes up as the square  
of flow rate. In other words, to double the flow rate, you need to generate 4  
times as much pressure. So, getting adequate flow at idle isn't all that 
tough.  Getting enough flow at full power is a VERY different matter. 
The only way I know to do it is to use a high pressure and VERY efficient  
fan. Note, this means NOT electric!!
 
 
In a message dated 8/3/2005 11:56:05 P.M. Eastern Standard Time,  
r.gault at sbcglobal.net writes:

Under no  circumstances will higher pressure across the fins result in  lower
flow.
Even if a transition between laminar and turbulent flow was  taking place as
the pressure goes up, the slope of the mass flow vs  pressure curve will
never go negative.  In our case, with less than  1/8" fin spacing, I
seriously doubt the flow between the fins is anything  but essentially
laminar.  The air can't get far enough from the  surface for the flow to
break up.  I'll admit I could be wrong here, I  haven't calculated Reynolds
Number since 1968.  AERONED!  WHERE  ARE YOU?

An interesting paper can be found  at:
http://naca.larc.nasa.gov/reports/1937/naca-tn-621/
It takes some  study to understand the graphs and nomenclature, but the
general info is  easy to see.

One of the things that interests me most about it is the  strong relationship
of pressure drop to fin spacing at a fixed mass flow  rate.  It really
reinforces the need to adequately deflash our  heads.  And, it argues for the
1/8" drill method since that opens up  the spacing considerably.

I'd wager that the guys who have these  electric fan cooled engines have done
everything they could think of to  help them cool, including fanatically
deflashing the heads.  I'm also  really curious how well deflashed the heads
were in the GM tests.

By  the way.  If you guys haven't looked at these reports, you've missed  a
valuable resource.  Yes, they're old.  But air is still air,  even if it does
have more junk in it these  days.

Roger