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Posted by stu on July 23, 2008, 9:10 pm
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>
> >Subject: Re: Energy 101 [was Re: OT Hydrogen economy, not?]
> >If you'd bothered to actually READ ALL of my post you'd realize that I
was
> >talking about the added drag from raising the condenser temperature and
> >therefore pressure enough to make the temperature of condenser discharge
water
> >useful.
>
> For those who are still following this subthread: If you haven't
studied the
> thermodynamics involved in steam plants, it is impossible for you to
understand
> the importance of a condensing system to the system's efficiency. (I only
know
> because the Navy made me learn)
>
> Here are a few simple points:
>
> 1) Understand this if you understand nothing else: A condenser system is
not
> just about the convenience of returning feed water to the steam system! A
steam
> plant operating without a condenser (exhausting spent steam directly to
the
> atmosphere) is operating at a fraction of the efficiency compared to the
same
> plant operating with a condenser.
How much of "a fraction" are you talking about? I wouldn't have thought it
would make that much difference. Although they would be upset about losing
their wonderfully clean feed water.
>
> 2) You can't possibly economically "tap steam" from a condensing system
because
> at that point in the system you have a vacuum. At a guess, you would have
to
> expend more energy pumping the steam out of the condenser than you would
recover
> from the steam. This is why John tells us that you would have to tap the
steam
> from some higher pressure point.
>
> 3) It is possible to recover heat from the cooling water that passes
through the
> condenser, but the cooling water side of condensers are always designed
for a
> high flow rate and minimum temperature gain. This is because condensers
must be
> kept as cold as possible for most efficient steam plant operation. River
water
> might enter the plant at 50 degrees and leave at 55 degrees. You can't
heat a
> house with 55 degree water. Therefore, the energy gained by this cooling
water
> is nearly useless to us. Though John just suggested a use I hadn't
thought of,
> as a source for a heat pump.
I thought the low temp raise from inlet to outlet was about protecting the
fish/plants in the river. I'm not even sure all the water passing through
the plant goes over the condenser, I think there is some "post mixing" to
cool the condenser water before release. (but this would vary from place to
place)
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