Here is something from Hoerner proving that the Germans
were on to this in WW II.

You also wrote:

 > the pressure recovery is better with the bell shape so less
 > radiator area is required to generate the same cooling.

when I was asking about the picture

         Kuchemann-Weber-duct-coord-plot1.gif

you had attached.

 From the Hoerner picture it seems that by "bell shaped" you
are referring to the shape called "a: streamline diffuser" in the
K-W diagram. Is that right? I'm only unsure because I would
have called shape "b: conventional diffuser" bell shaped.

Shape "a" is the one with the higher wall pressure at the face
of the radiator.

David

Yes and by implication a: is the one with higher pressure over the face of the
"cooling block" or radiator. The use of the term "streamline" is also a bit
confusing. The book Compact Heat Exchangers Kays & London (frequently quoted 
by Fred Moreno) uses the term "header" in place of "diffuser". Apparently 
there is no nomenclature standardization on this subject. 
Here is a pertinent page from Kays & London.

Paul Lamar
 
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