Hi Gregory
On (02 Aug 97) Gregory Procter wrote to Phil Kane...
 GP>       Heating hot water isn't as silly as it initially sounds!
 GP>       There's one of those continual arguements around as to whether you
 GP> should
 GP>       fill the electric jug from the hot or the cold tap?
I worked in a Railway generating station [Ultimo] in 1947........ we would
launder our overalls, in a bucket of hot water with soft soap AND immersed a
metal flexible steam hose into it to agitate and cook the dirt out.
Unsolved problem- would the steam evaporate the water and the bucket become
empty......... or would the steam condense to water so's the bucket
overflowed?
I never did find out, there was always a queue of washer- men waiting turn!
 GP>       If in a steam loco, you try to recover the exhaust heat energy by
 GP>       directing it to the cold water supply (the tender) you end up with 
a
 GP> hot
 GP>       water supply and boiler feed problems.
Comparable problems in stationary boilers. If you use the exhaust to preheat
something, then this must impede the exhaust flow and increase the back
pressure.
Consequently the engine delivers less HP, because it is not the stop valve
pressure but the difference between SV pressure and exhaust pressure, that
defines the work done by the pistons.
Hence racing cars may have "open exhausts" ie no muffler, hence little or no
back pressure to subtract from the pistons' output. Noisy!
Cheers......ALEC
... Wunce i coodn even spll ingineer. Now i are wun!!
--- PPoint 1.92
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