Tom Hargrave wrote:
> -----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

Thanks for making a stab at the numbers, Tom. I had a gut feeling that
cooling the rad's fairly small volume of coolant a few more degrees
prior to a climb would not make a noticeable difference if the climb was
of any duration worth mentioning.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
Bend, OR
KG6RCR