John,
Thanks for amplifying your previous answer. Your "rules of thumb" sound
like the result of considerable experience and/or engineering analysis. I'm
sure you would agree, however, that the sweet spot around a delta of ten
degrees is somewhat loose; as I pointed out previously, an additional delta
of five degrees is only about 2.5 degrees average difference across the
radiator, which compared to the radiator-to-air delta of about 100 degrees
is pretty negligible. On the other hand, as it represents a 50% improvement
in heat removal, it would be welcomed by someone in Chris's predicament.
(Pssst!! Get a bigger fan Chris.)
At least we're not arguing about the virtues of putting in a restriction so
as to purposely increase the delta T across the radiator, which was the
prevailing theory a few years back.
Have a great day,
Bob
At 11:02 AM 5/10/00 -0400, Carmods@aol.com wrote:
>In a message dated 5/9/00 10:17:26 AM Eastern Daylight Time,
>
> Hi Bob,
>Ten degrees delta T across the radiator is optimum in respect to a properly
>balanced total cooling system on the road at a steady state. If you are
>having cooling problems and getting a delta T of fifteen degrees then your
>problem is low water flow rate through the radiator. This could be the pump
>or restrictions in the system. If you are getting five degrees under the same
>conditions and having cooling problems then your problem is heat transfer to
>the air. This could be caused by low cool air flow through the radiator, a
>heat transfer problem through the radiator such as loose fins, internal and
>external dirt or insufficient fin area or just not enough radiator frontal
>area which isn't easy to correct in a Tiger.
>
>These are just rules of thumb that give you a clue to where to look for the
>problem. Idle will follow the same rules but you can't optimize both
>conditions with the same hardware so you end up over designing something to
>solve both problems.
>
>If you are designing a race car then conditions are not steady state and
>different rules apply.
>
>If you are designing a car from scratch and you want to optimize the system,
>these rules of thumb help you decide if you have too much or too little
>radiator, the frontal area is too large or too small, or you are using too
>much or to little water pump HP.
>
> John Logan
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