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re: solar hot water heater for home: give me a push...
24 oct 2002
daestrom  wrote:

>"none"  wrote in message

>> what i described could be built in an afternoon with probably less
>> than $50 worth of parts from the local hardware store. the most
>> expensive piece would be the length of 1 " or 2" of hard copper
>> pipe or maybe 20' of " soft copper...

plus a $20k machine to wrap the small pipe around the big one so tightly
that it flattens the small pipe and makes a spiral groove in the big one?
that and the vertical orientation are important to make drain water flow
down in a sheet that coats the entire inside of the big one. the tight wrap
and pipe distortions also increase the heat transfer between the two pipes. 

>my experience is the thing had 1.8 gpm flow (supplying both cold to the
>shower and cold to the hw heater).  55 degree inlet and 83 degree outlet of
>the heat exchanger.  on the waste side, 107 inlet and 80 on the outlet.

>my incoming water from the public works department is ~38 degrees in
>the winter, and was still only 55 last may (this is in central ny). 

sounds like you recovered 1.8g/mx8btu/g-f(83f-55f) = 403 btu/min, or
maybe 1.8x8(107-80) = 389, ie about 7918 btu in 20 mins. should work
better with 38 f water. why 1.8 vs 1.25 gpm, like my shower?

>i figured this recovered ~1000 btu's in one 20 minute shower.  considering
>that 36 gallons of water that was used was heated from 55 to 110 degrees for
>a total heat load of 1980 btu's...

or maybe 36x8(110-55) = 15,840 btu... 100x7900/15840 = 50%

btw, this seems to have nothing to do with


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