John,
Thanks for this information in support of my "statement without proof".
Using your numbers, say a 10 degree F total temperature drop from inlet to
outlet, and if the ambient temperature were 80F and the average water temp
180F, the average temperature difference would be 100F between radiator and
air. The average temperature drop across the radiator is half of ten
degrees or five degrees out of 100, or 5%. A 5% temperature drop is small
enough to be considered "negligible" relative to the radiator versus air
temperature differential, which is what directly controls (together with
air flow) the rate of heat of heat dissipation by the radiator. In other
words, in this example, the rate of heat flow from the radiator to the air
is only 5% less than if there were zero temperature drop across the
radiator. The increase in coolant flow needed to further reduce the
temperature drop becomes impractical and unnecessary when only a 5% further
improvement in effectiveness is possible.
My apologies to the List for the occasional excursion into engineering
fundamentals.
TTFN,
Bob
At 09:07 AM 5/10/99 -0400, Carmods@aol.com wrote:
>Hi Bob,
>In a message dated 5/9/99 12:05:31 PM Eastern Daylight Time, you write:
>
><< This point is gotten backwards by many who jump
> to the intuitive assumption that the better the system is working, the
> bigger the temperature drop in the coolant across the radiator when, in
> fact, the ideal case would be approaching no temperature drop across the
> radiator. >>
>
>This is a very good point. A car or truck with a well designed cooling system
>running under load with the thermostat open should have a stabilized
>temperature drop of 8 degrees F to 10 degrees F across the radiator.
> John Logan
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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