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Re: Crossflow considered

To: spridgets@autox.team.net
Subject: Re: Crossflow considered
Date: Thu, 20 Jan 2000 20:15:58 -0800 (PST)
Glen,
I'm not familiar with the crossflow, but you are
definitely on the right track - the overall heat
transfer coefficient for a radiator is its "UA", where
A is the heat transfer area.  Ideally, you'd want to
dimple that big tube in a helical pattern to turbulate
the flow (NOBODY RUN OUT AND HAMMER YOUR RADIATOR
PLEASE!!! You have to balance increased heat transfer
from the dimples with the reduced flow caused by the
dent).  You want the header big enough to have a nice
flow distribution (low velocity plenum effect), but
core design is where the heat transfer magic can
occur, particularly in fin design.  I recently looked
at a proposal for a fin .003" thick.  This allows a
tremendous fin density with less pressure drop. 
'Course fragility is an issue... 

--- Glen Byrns <grbyrns@ucdavis.edu> wrote:
> It was nice to hear from a fellow 1275 owner in the
> central valley who has
> had good luck with a set-up similar to what I am
> considering.  
> One thing crosses my mind, doesn't that cross pipe
> have a rather
> considerable surface area presented to a reasonable
> flow of air?  I know its
> not a thin little high efficiency radiator tube, but
> it is one comapratively
> large, fairly thin metal pipe full of hot water. It
> must add measureably to
> the overall efficiency of the system. The surface
> area of the two cores
> looks to be about equal.
>                                 Regards, Glen Byrns
> 
> 

=====
Ron Soave

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