Hi again Chris
On (16 Sep 96) Chris Harper wrote to Alec Cameron...
 AC> The severe conditions I remember, were with coastal generating
 CH> stations
 AC> which used ocean or river water for condenser cooling. The condenser
 AC> running at negative pressure [vacuum] there would sometimes be water
 AC> ingress due to leaks in the condenser structure. Counter measures
 CH> included
 AC> dumping truckloads of sawdust into the water canal, the sawdust
 CH> plugging
 AC> the condenser leaks then swelling so improving the temporary
 CH> "repair".
 CH> I'll have to remember that, as I will be running at much lower temps, 
nd
 CH> the condensation will thus be much faster, and create a vacume in my
 CH> condensor tubes.
This vacuum is very desirable because the quicker the steam condenses at
engine exhaust, the "harder" is the vacuum and the greater is the HP [kW] of
the engine or turbine shaft.  Very approximately the shaft power is
proportional to P1 minus P2, these being the inlet and outlet pressures
measured at the engine. So if the throttle valve pressure is 50psi and the
condenser pressure is a perfect vacuum [minus 14psi] then the effective 
ngine
pressure is 50 minus [minus14] ie a net value of 64. That is a 14psi ie 28%
power hike, in the example I gave.
I will definately have to take this into account in my
 CH> design. I had thought of using garden hose for condensor tubes once the
 CH> steam was cooler than 250 F., but with a vacume there, they would 
collapse
 CH> and expand repeatedly, and thus wear out. Now I will have to use a
 CH> pressure equalization chamber to allow for expansion and contraction, if 
I
 CH> want to keep it a "closed" system.
A dedicated "chamber" is what the condenser itself is. In a thermal power
station the condenser is a steel cylinder about 30 feet dia and 30 feet long.
It is packed with tubing. Exhaust steam is cooled by circulated water, the
latter may be sea or river or lake water, or for inland stations a large
Cooling Tower is used to chill the circulating water. The boiler feed is
"closed" but the second [circulating water] system is very open. In coastal
stations the prawns and fish are attracted by the warm conditions, great fun
for the employees!!
Cheers.....ALEC
......Wunce I coodn evan spll Ingineer but now I are one!!
... ........When I contemplate the moon, my head aches [Galileo]
--- PPoint 1.92
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