Limited cooling space

[steve ravet]

Frederic Breitwieser wrote:
> 
> > The way I see it, the coolant now "sees" a radiator that is 1/3 as high and
> > 3 times longer.  Why does this cool better than normal.  The log delta T is
> > the same, no?  Is it a flow turbulence thing?  That is the only change I
> > see.
> 
> Here would be my <cough> guess...
> 
> If you increase the width of the radiator, the coolant has to move
> further to reach the other side and be sucked back into the system,
> therefore its exposed to the ambient (and hopefully cooler) air
> temperature, which reduces the temperature of the coolant going back
> in.

But, heat lost is proportional to the temperature delta.  As the water
passes through this longer radiator you dump less and less heat because
the temp delta is getting closer to zero.  Maybe Gary can weigh in here
but I think you want the radiator at the highest possible average
temperature to maximize heat transfer.  That situation is achieved by
the "parallel" radiator, not the serial radiator.


--steve

-- 
Steve Ravet
steve.ravet at arm.com
Advanced Risc Machines, Inc.
www.arm.com