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Date:         Tue, 18 Jul 95 11:23:17 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Al Knoll <alf@hpptc38.rose.hp.com>
Subject:      fizzix ?

Scott the busman said

> Ok It works like this. What happens to the cooling fin when it is cooler than the air around it? It absorbs heat right. If it's absorbing heat back from the air it isn't radiating heat into the air right. Thermo dynamics are wonderfull things but kinda tricky. You want to keep the flow of heat in one direction and cooling the fins externaly just slows down their heat radiating ability from the internal heat source. As I said if you can just pump very humid air around the fins then you would get the efficiency you want. Putting a water jacket around an air cooled engine makes it a water cooled engine! >

Lemme see, you're worrying about the air to fin temp? That's the wrong end of the dog. The operative thermo interface is the coolant to radiator material boundary. The higher the delta T at this interface the more heat will cross the boundary. Don't give a hoot in a rainbarrel about the fin to air trick it's mousenuts compared to the other transfers going on. Yeppo, the heat will go from the air to the cool fin but bunkie that is a tiny transient condition if your coolant is at 80C 'cause the fin will absorb one hell of a lot more Q from the coolant than it will from the ambient. Now back to keeping that delta T high by cooling the radiator down to as cold as you can get it. Frinstance if the fin is at 20C the ambient is at 35C (damn hot day) and the coolant is at 90C which way do you think the heat will go referencing the coolant? Gotta see the grand scale or the micro features will confuse even the most diligent. Transients are basically meaningless in the overall Q transfer in steady state. The coolant doesn't know how hot the air is it only knows how cold the radiator material is. Insofar as dumping Q that's all that matters.

-- ___ / __ __/ ____/ Al Knoll HP Performance Technology / / / / / Center Roseville, CA, USA 95747 / _____/ / / 916.785.5317 (Telnet 785-5317) / / / / email: alf@hpptc38.rose.hp.com / __/ __/ ______/ ___________________________________/


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