-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
David Beierl
Sent: Sunday, April 25, 2010 3:01 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Water Cooler System Design Flaw Workaround?

At 01:22 PM 4/25/2010, Jake de Villiers wrote:
>When approaching the long (15 - 30 minute) second and third gear grades
>through Eastern Washington and Idaho you'd turn on the fan before the
>rad got too hot.

Ok, I see the idea.  But do the numbers make sense?

Lessee... at 75 horsepower output and 1/3 efficiency the engine's going to
be putting out something like 200 kw of waste heat, or 3.4 kWh per minute.

18 quarts of 50/50 coolant weighs around 36 lb and has a specific heat
capacity of roughly 0.85 BTU per lb per deg F at working temperature.  So
changing the entire coolant by 20F would get you
0.85 x 20 x 36 = ~600 BTU, about what a sedentary human throws off in an
hour.

600 BTU = ~0.18 kWh.  3.4 kWh x 0.18 x 60 = ~32

So a twenty-degree change in the entire coolant would absorb the waste heat
of the engine for about thirty two seconds.  I think this is conservative
since the coolant inside the engine won't be participating in this, and
because 75 hp may be conservative for climbing a steep hill.

Somebody check my numbers.  If this number is anywhere near correct I don't
think it's worth the hassle.

Yours,
David