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re: greywater heat exchange
4 feb 2003
none wrote:
>> >> what's your simpler design?
>> >take a length of soft copper pipe and loosely wrap it around something to
>> >form a coil. place this coil inside a length of pvc pipe then run your
>> >shower drain into the system...
>> sounds fine in principle, like micro-hydro using rainwater from a roof.
>you're saying it won't work? what flaws do you see?
it's perfect in principle.
>> >if you made it long enough i'd think, guess, you could get output water
>> >almost as warm as the gray water input water.
>> how warm is almost, and how long is enough?
>again guessing i'd say within 2f and less than 50 feet.
>are you saying that you want to seen the thermo and fuild dynamics
>calculations?
yes. let's seen your fuild dynamics. here's a start...
>e = 0.9 = ntu/(ntu+1) for a counterflow heat exchanger with equal heat
>capacity rates. this makes ntu = 9 = au/c = 30a/600 at 1.25 gpm with
>a 60 btu/h-f-ft^2 water film on each side of the tubing (measured with
>a pot in a pot in my kitchen.) this makes a = 180 ft^2, eg 917 feet of
>3/4" copper tubing...
e = 0.9 makes the cold output temp 55+0.9(100-55) = 95.5 f.
nick
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