On Tue, 14 Feb 2006 00:09:30 +0000, Pooh Bear wrote:
Ed Huntress wrote:
Even electricity generation is no better than 37% efficient apparently (
recent
UK figure ).

Well, even that is somewhat higher than I recall, because the steam-turbine
example above is for one engaged in generating electricity.

However, my memory isn't that precise, and is getting less so, and
technology no doubt has improved. A turbine's practical efficiency isn't a
factor of theoretical heat cycles as much as it is a matter of how much heat
and erosion it can tolerate.

I came across that figure in a thread in another ng recently. Apparently up from
35% only a few years ago. There's been quite a lot of new generation built
recently in the UK using natural gas which may explain the improvement. It also
entertainly shows how short term thinking ( natural gas is cheap - so lets burn
it ) can blow up in your face !


In regard to gas turbines, I visited Pratt & Whitney's engine division
decades ago on a press junket, to hear them tell us how they'd raised the
operating temperature of a jet engine by roughly 100 degrees F, from 2,200
to 2,300 degrees. I remarked that didn't really sound very impressive. An
old P&W engineer sitting next to me said, "Son [I was much younger then
g]," there are men here who would sell their grandmothers for another
hundred degrees."

A friend of mine works in aeropsace design. I'm awed by the tricks they use to
cool those turbine blades. They would melt otherwise !


I was on a document coding project where somebody was suing somebody else
about inferior turbine blades. They're like, a single crystal of titanium
that's grown in a mold, and if you drop one on the floor, you have to
scrap it. I think maybe even if you touch it with bare fingers, you have
to scrap it. It seems a new jet engine is about $2,000,000.00, but an
overhaul, where they basically replace all of the turbine blades and
bearings, is only about $250,000.00. Or, was in the 1990's. :-)

Cheers!
Rich