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re: greywater heat exchange
3 feb 2003
none wrote:
>> >one major problem i see with this is that if you do not drain the drum
>> >between showers the water will be cold when you start.
>>
>> got any numbers?
>
>for what? for the fact that if a tank of warm water sits for hours it
>becomes cold?
you might predict the average drumwater temp (68.7 f?) and yearly savings if
the drum's in a 55 f basement helping heat 12.5 gallons of 55 f wellwater to
110 f for 10 min 6 times a day. this might involve numbers vs handwaving :-)
>> with no insulation, the drumwater might cool with a 12 hour time constant,
>> but it could be warmer than the cold water supply, esp the top layer, with
>> a combination of bouyancy and a 0.00554 ft^2/h thermal diffusivity... 60 f
>> water with a 100 f surface might cool to 80 f 1' below in 180x1^2 hours...
that's d^2/0.00554, for a distance d below the surface. warm water bouyancy
helps too. how would you calculate that effect?
>your numbers are based on grey water right from the tap, so to speak.
wrong. the water comes out of the shower head at 110 f.
>what after you have drawn heat from it for your shower?
an enclosed shower might "draw little heat."
>if the heat exchanger is good then the temp of the water in the tank
>should be much cooler then before.
care to explain? how much cooler?
>it will work but i'd think a simpler desgin would work better.
what's your simpler desgin?
>big bucks were spend an exchanger that is almost 100% could be built but
>i'm thinking of the bigest bang for the buck.
i figure 98% for this exchanger were spend little bucks that is almost 100%.
improving it might save another 2 cents/day...
further suggestions welcome.
nick
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