Regarding downflow vs. crossflow, we've had the
discussion before - personally, I have had no problems
at all with the downflow in a 1275 Bugeye that is
driven pretty hard, most of its life in Florida. Here
is something from the archives from a class in
automotive HX design I took over this past summer:
Just got back from a 2 day conference/class on
automotive heat exchangers given by the SAE, with a
fellow named Ram Shah as the instructor (if you're a
Mech E, you have probably used one of his 25 books in
school, and he works at Harrison, which does many many
of the radiators, condensers, evaps, oil coolers for
all cars). After 2 days of mind numbing equations, we
got down to some folksy questions, and the topic
of vertical vs. horizontal flow came up,as did
"sucking
vs. blowing" for cooling fans. All things being equal
(core size, and available airflow), there is no
difference. The reason a lot of manufacturers went to
horizontal was because of the reduction in vehicle
frontal height in modern cars, which require lower
profile radiators. Also, if the manufacturer wants to
increase the size of the core, a horizontal flow HX
allows for the same headers and collectors, the only
difference being longer tubes (or plates). In a
downflow radiator, it is unlikely that the height
could be increased, so more columns of tubes would be
required, increasing manufacturing cost. In the auto
industry, Shah said they start to worry if cost goes
up for something by more than 3 or 4 cents.
=====
Ron Soave
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