Ed,

The most the rejected heat could change in this case
is 300%. You made a 300% change in thickness which
results in a 300% change in wetted surface area.

Your number will be lower for a couple reasons:

1) Decreased mass flow (5% in your case)

2) Boundary layer thickness grows as you go deeper
into the radiator. The last 1" of radiator will never
be as effective as the first 1".

I know your equations accounted for (1) but not sure
about (2). I haven't checked your reference.

The drag increase of 58% sounds way too low. You
increased surface area by 300%. Unless mass flow
decreased a lot (it didn't) or drag coefficient
dropped a lot (it shouldn't), then this can't be
right.

Ron

--- Ed Anderson <eanderson@carolina.rr.com> wrote:

> But in any case, assuming I did not screw up
> someplace, here are the results I got when I changed
> only the thickness of the radiator on drag, mass
> flow and heat removal:
> 1. The Drag (R) went from 4.28 lbf/ft2 to 6.77
> lbf/ft2 or a 58% increase presumably due to wall
> friction
>
> 2. The Mass flow (M) decreased from 12.33
> lbm/ft^2/sec to 11.705 or a 5.13 % decrease  
>
> 3. The Heat Rejected(Q) increased from 6.1707
> HP/100F to 23.66 HP/100F for a 283% increase