Mike Wills wrote:

An 800 cu. in. radiator 20 x 20 x 2 inches thick is probably far more rad than
you need for a 180HP rotary (assuming proper ducting). On the other hand an 800
cu in rad that is 10 x 14 x 6 inches thick may not cool at all because you cant
get any air to go through that core.

Russell Kent wrote:

Minor nit.  The problem isn't that you can't get enough air through the 6 inch
thick radiator (true to a small extent), but that the 10 x 14 x 6 radiator
doesn't transfer six times as much heat as a 10 x 14 x 1 radiator.  In fact, six
10 x 14 x 1 radiators plumbed back-to-front (a la Paul) will transfer somewhat
*more* heat than a single 10 x 14 x 6 radiator.  This is because the heat
transfer function includes delta T as a factor.  The larger delta T is maintained
(step-wise) in the six radiator situation as the air moves through the radiators;
in the single radiator case, the air temperature rapidly rises in the first 1-2
inches, and the remaining 4-5 inches of radiator has a poorer transfer function
because of the smaller delta T.

In short, the higher the delta T, the better.

BTW, this is a major argument *against* oil/water heat transfer systems: the oil
radiator has a *much* higher delta T than the water radiator even with the oil's
heat added to the water.

Anyone else notice the parallel between the "cross counter flow" radiator
arrangement and the method of refilling gas cylinders from a set of tanks?  With
gas cylinders, you fill with the *lowest* pressure tank first, then work your way
up to the *highest* pressure tank.  With the "cross counter flow" arrangement,
you heat the air with the *coldest* coolant first, then work the air through
progressively hotter coolant.

Russell Kent

Well put Russell. The new Chrysler 3.3 L mini vans have rads 32 inches wide
no less!!! and 19 inches high with about a 3/4 inch thick core.
The rads go from wheel well to wheel well.

Paul Lamar

 
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