From: Wayne Alan Martin <wm1h+@andrew.cmu.edu>
Subject: Re: What do Nuclear Site's Cooling Towers do?
Organization: Senior, Electrical and Computer Engineering, Carnegie Mellon, Pittsburgh, PA
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Distribution: world
NNTP-Posting-Host: po2.andrew.cmu.edu
In-Reply-To: <79694@cup.portal.com>

Excerpts from netnews.sci.electronics: 16-Apr-93 Re: What do Nuclear
Site's .. by R_Tim_Coslet@cup.portal. 
> From: R_Tim_Coslet@cup.portal.com
> Subject: Re: What do Nuclear Site's Cooling Towers do?
> Date: Fri, 16 Apr 93 21:27:21 PDT
>  
> In article: <1qlg9o$d7q@sequoia.ccsd.uts.EDU.AU>
>         swalker@uts.EDU.AU (-s87271077-s.walker-man-50-) wrote:
> >I really don't know where to post this question so I figured that
> >this board would be most appropriate.
> >I was wondering about those massive concrete cylinders that
> >are ever present at nuclear poer sites. They look like cylinders
> >that have been pinched in the middle. Does anybody know what the
> >actual purpose of those things are?. I hear that they're called
> >'Cooling Towers' but what the heck do they cool?
>  
> Except for their size, the cooling towers on nuclear power plants
> are vertually identical in construction and operation to cooling
> towers designed and built in the 1890's (a hundred years ago) for
> coal fired power plants used for lighting and early electric railways.
>  
> Basicly, the cylindrical tower supports a rapid air draft when
> its air is heated by hot water and/or steam circulating thru a network
> of pipes that fill about the lower 1/3 of the tower. To assist cooling
> and the draft, water misters are added that spray cold water over the
> hot pipes. The cold water evaporates, removing the heat faster than
> just air flow from the draft would and the resulting water vapor is
> rapidly carried away by the draft. This produces the clouds frequently
> seen rising out of these towers.
>  
> That slight pinch (maybe 2/3 of the way up the tower) is there because
> it produces a very significant increase in the strength and rate of
> the air draft produced, compared to a straight cylinder shape.
>  
> The towers are used to recondense the steam in the sealed steam
> system of the power plant so that it can be recirculated back to the
> boiler and used again. The wider the temperature difference across
> the turbines used in the power plant the more effecient they are and
> by recondensing the steam in the cooling towers before sending it
> back to the boilers you maintain a very wide temperature difference
> (sometimes as high as 1000 degrees or more from first stage "hot"
> turbine to final stage "cold" turbine).
>  
>                                         R. Tim Coslet
>  
> Usenet: R_Tim_Coslet@cup.portal.com
>         technology, n.  domesticated natural phenomena

Great Explaination, however you left off one detail, why do you always
see them at nuclear plants, but not always at fossil fuel plants.  At
nuclear plants it is prefered to run the water closed cycle, whereas
fossil fuel plants can in some cases get away with dumping the hot
water.  As I recall the water isn't as hot (thermodynamically) in many
fossil fuel plants, and of course there is less danger of radioactive
contamination.

Wayne Martin



