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Date:         Sun, 25 Apr 2010 16:00:31 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Water Cooler System Design Flaw Workaround?
Comments: To: Jake de Villiers <crescentbeachguitar@gmail.com>
In-Reply-To:  <y2k71d9cdf91004251022r2e8ed7a7lcfca98e87661bfca@mail.gmail .com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

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


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