On Sun, 02 Nov 2003 11:05:12 -0800, "Lloyd Sumpter" wrote:

On Sun, 02 Nov 2003 00:31:47 +0000, James Johnson wrote:

Hydrogen is even better yet (better heat transfer coefficient). It is what is
used to cool the 1000 megawatt generators at power plants as air can't carry the
heat from resistance in the windings away fast enough. Just watch out for
flames or sparks. Also hydrogen tends to diffuse through the tire so you have
to replenish it more often.



I've worked at Perry, OH; Enrico Fermi, MI; Calvert Cliffs, MD; Oyster Creek,
NJ; Salem, NJ; Peach Bottom, PA as a contractor for maintenance outages and as
part of the operating staff for 2 of them. They ranged from 600 MW to 1300 MW.

In all of these the internal cooling for the generator was recirculating gaseous
hydrogen. The H2 is recirced through the windings picking up heat and then pass
through water cooled heat exchangers to give up the heat. The systems are
built into the generator casings so unless you were part of the disassembly you
would not know of the specifics.

To use air the generators would have to be much larger to provide sufficient
surface area to remove the heat generated by resistance in the windings (i.e. it
is cheaper to build it this way). They have elaborate bearing seals, and no
oxygen inside (nitrogen purged for maintenance or prior to filling for
operation) to prevent combustion. So doggie-donuts yourself.

JJ

Having worked in a 1000 MW generating station, I can safely say this is
doggie-donuts. I wouldn't have hydrogen (or any explosive gas) within
100ft of a high-power generator!

Lloyd Sumpter

James Johnson
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