Ed,

   It looks like you and I were coming to similar conclusions.

   My present plan for my, as yet, unstarted Cozy (unless
one counts completion of the shop facilities) is to mount
two cores - e.g. the Frigidaire EV6709 - in tandem, with
the water flow going first through the rear core and then
through the front one.  The delta-T won't be *ideal* in
either core, but it will be substantial.  I just have to
work out a plenum that allows no air leakage between the
cores.

Still trying to keep the expenses down, without being
"cheap".

Dale R.

> In essence, they make the statement that thicker radiators with closer fin
> spacing provides for more heat dissapation into an airstream.  The
> refer to the thickness as "L" length of the cooling block (heat exchanger)
> and the "D" the hydraulic wetted area spacing (basically related to the fin
> area/spacing) .  Re is the Reyonlds number which is smaller with lower
> velocity.
>
> So a low velocity airflow through a thick radiator (L) with close fin
> spacing (D) is the way I interpret their words and equation for the heat
> transfer coefficient "k".  This would mean you need good pressure recovery
> from a diffuser (low velocity out of your diffuser).   So long as you have
> the dynamic pressure (read that as having adequate airspeed through your
> inlet) for the thickness you are using, it appears that you are ahead of the
> game using a thicker radiator.
>
> This makes sense (to me)  in that a thicker
> radiator continues to dump heat into the airstream as long as the air is
> passing through it - even thought it becomes less efficient at this transfer
> as the air through it heats up (thereby reducing the "Delta T"), it is still
> transfering heat to the air.