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Re: Fwd: Radiator theory (with sample calc, stay with it)

To: Clayton La Baw <clabaw@jpl.nasa.gov>, spridgets@autox.team.net
Subject: Re: Fwd: Radiator theory (with sample calc, stay with it)
Date: Sat, 24 Aug 2002 10:37:19 -0700 (PDT)
--- Clayton La Baw <clabaw@jpl.nasa.gov> wrote:
> Ron -
> 
> This all looks very good; however, it doesn't take
> into account the 
> (claimed by some) loss of flow efficiency resulting
> from high rpm 
> 'cavitation' in the water pump.

Clayton,
You are taking the little-used system approach to
cooling system troubleshooting (a very good thing!). 
We were talking radiator theory - but, as you say, if
you unload the pump (or any pump, fan, turbine, etc)
by lessening backpressure, the RPM will increase, with
the possibility of cavitation or stalling.  Too much
backpressure and you will operate in surge.  Either
condition causes aerodynamic anomalies (in the case of
cavitation, there are "cavities" of extremely low
pressure around blade tip), and the load on bearings
and blades is tremendous.  For math-oriented types, a
pump curve is a parabola, and surging, for instance,
is like the pump is hunting for 2 intercepts on the
same curvee, and the hunting for 2 different pressures
is the beat you hear at surge.  Most pieces of
turbomachinery will beat themselves to death in no
time, but often the peripheral effect (like in our
case, overheating) will be what stops you.  


=====
Ron Soave
1960 Bugeye
1958-ish Bugeye  Racecar
1970 Midget
1996 Labrador Retriever
2002 F-150 tow vehicle


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