Back in August of last year I contacted Ron Davis for a custom
rad that looked like this. At the time he claimed he had the same idea
and was in the process of patenting it. When I was in Phoenix earlier
this week I visited Ron and asked him where my rad was. He told me
he received a patent and had built and supplied several to Nascar
racers and they worked great. I confirmed my order so hopefully
I will have my custom rad in a month or so.

This is what is called a cross counter flow rad. The rule of
thumb with rads of finite thickness is the first half of
the rad does 3/4's of the work as the difference in the air 
temp and the water temp becomes nearly equal as the air flows
through the rad from front to back  and absorbs heat. It takes
a considerable difference in air temp and water temp or there
is no heat transfer. 

This design addresses that issue. The hot water is first passed through
the back half of the rad and then through the front half in a two
pass configuration. This maximizes the temperature difference thorough
out the rad. The trick here is the front and back half's of the
rad are thermally isolated from each other by minimizing the
metal conduction paths. To not do this defeats the intent of
the cross counter flow design.

There is no weight penalty or pressure drop penalty in either the air 
flow or the water flow with this design. The cost is only slightly more 
as the same number of fins and tubes are used. In theory a slighly
smaller rad (less cooling drag) could do the same cooling job.

Paul Lamar
 
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