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[Bill Jones <billj AT harborside.com>]

I just thought of a few changes.

Bill Jones wrote:

> A pneumatic water pump made from PVC costs so little, and for 
> such a short lift the "static" components of inefficiency are 
> negligible.
>  
To take advantage of this, you'd have to reset the pressure switch on 
your compressor, so that it never exceeds the low pressure required for 
a short lift (or modify the drive ratio, for a windmill).  Otherwise, 
the static inefficiency of piston pumping at 50 PSI would still be 
present, even if you used it for a low-pressure job.

> It will be possible to run my new pump at the usual 
> high speed, off an electric compressor, but at this rate some energy 
> will be lost through frictional heat and heat from sudden compression.  
> We could call this the "dynamic" component of inefficiency.  You can't 
> calculate this, but most of it can be evaluated from the compressor 
> specs (including the inherent "static" loss of the piston pump).
Actually, loss from "adiabatic compression" (sudden) must be estimated 
by taking the temperature of the air that leaves the compressor.  It's 
not included in the compressor specs, which ignore how hot the air 
becomes.  Hot air shrinks in volume upon cooling according to Boyle's 
Law, so you basically just get less air than you thought you would.

One nice thing about mechanics, compared to other engineering endeavors, 
is that energy loss is always palpable; either something makes noise, or 
heats up, or cools down (in sudden _expansion_ of gases), or 
accelerates.  So no "belief" is required to see that only fast pumping 
generates heat through sudden compression; you can feel it for yourself.

> Bill
> S. Oregon coast
> _______________________________________________
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