On Jul 27, 1:01*pm, Ned Simmons wrote:
On Mon, 27 Jul 2009 11:25:38 -0700 (PDT), KD7HB
wrote:

On Jul 27, 10:14*am, Ned Simmons wrote:
On Mon, 27 Jul 2009 10:03:46 -0700 (PDT), KD7HB
wrote:

One interesting thing I discovered long
ago is that the faster the water flows through a system, the less heat
transfer that occurs.

So maximum cooling occurs at zero flow? g

--
Ned Simmons

No, maximum heat transfer occurs.

I can imagine there may be specific regimes where increasing flow
reduces heat transfer, but I don't believe that it's true in general.

You then have to get that hot water
out to cool it and recycle it back to the engine. Look at the top/
bottom of a radiator. Many small, restricted openings to the cooling
tubes.

Been too long since the college physics class.

It's been 35+ years for me since I dealt with Messrs. Reynolds,
Prandtl and Nusselt, and 34 years since I forgot it all.

--
Ned Simmons

I was really hit with this a few years ago when we installed a 7 stage
convection oven at my plant for soldering surface mount printed
circuit boards. The last stage of the oven is a cooling stage cooled
by chilled water. I bought a 1 ton chiller and hooked it to the oven
using 1 inch rubber hoses that match the connections on the chiller.
The oven had 1 inch connections, but had reducers to about 1/4 inch.
It was a used oven.

Being one for more efficiency, I pulled the reducers and connected the
1 inch hoses. Guess what? No cooling, but the water really ran fast
through the unit. When I put the reducing fittings back on the oven
connection, a very slow flow of water came out, but lots of cooling
air now came out of the unit.

Paul