Posted by nicksanspam on August 30, 2007, 12:17 pm
>The simplest solution seems to be installing a sump in the gray water
>system that is about 0.5 meters deeper than than the existing waste lines.
Maybe a 55 gallon plastic drum or a steel drum with a plastic liner and
a lid with a locking ring, with a way to backwash it to remove crud once
in a while, eg a garden hose connection.
>... Then drop in in a standard float activated sump pump to deliver
>gay water to your heat exchange(s). This configuration should be
>easy to service and uses standard hardware.
Can we recover 90% of the heat from one shower?
We could estimate efficiency with section 7.3 of the SRCC OG300 standard,
which specifies measuring solar water heater performance with 6 hourly
3 gpm 10.7 gallon hot water draws totaling 64.3 gallons per day.
If a well-enclosed shower drain is 105 F and the cold supply is 50 F,
heating 64.3 gallons (536 pounds) takes 536(105-50) = 29.5K Btu.
A counterflow exchanger with equal heat capacity flow rates Cmin = Cmax
= 536/6h = 89 Btu/h-F and effectiveness E = 0.9 = NTU/(NTU+1) needs NTU
= 9 = AU/Cmin. With wall conductivity U = 30 Btu/h-F-ft^2, heat exchange
area A = 27 ft^2, eg 100' of 1" black PE plastic water pipe inside 100'
of 1.5" pipe, coiled around the the drum, surrounded by insulation.
We could pump fresh and graywater at 64.3/6/60 = 0.18 gpm with a dual
metering pump and store the preheated cold water in the lower half of
an electric water heater, with the lower heating element disconnected.
Nick
Posted by nicksanspam on August 30, 2007, 1:17 pm
>Can we recover 90% of the heat from one shower?
>We could estimate efficiency with section 7.3 of the SRCC OG300 standard,
>which specifies measuring solar water heater performance with 6 hourly
>3 gpm 10.7 gallon hot water draws totaling 64.3 gallons per day.
>If a well-enclosed shower drain is 105 F and the cold supply is 50 F,
>heating 64.3 gallons (536 pounds) takes 536(105-50) = 29.5K Btu.
>A counterflow exchanger with equal heat capacity flow rates Cmin = Cmax
>= 536/6h = 89 Btu/h-F and effectiveness E = 0.9 = NTU/(NTU+1) needs NTU
>= 9 = AU/Cmin. With wall conductivity U = 30 Btu/h-F-ft^2, heat exchange
>area A = 27 ft^2, eg 100' of 1" black PE plastic water pipe inside 100'
>of 1.5" pipe, coiled around the the drum, surrounded by insulation.
>We could pump fresh and graywater at 64.3/6/60 = 0.18 gpm with a dual
>metering pump and store the preheated cold water in the lower half of
>an electric water heater, with the lower heating element disconnected.
Better yet, use a float switch and a single metering pump like Grainger's
$204 2P305 to move 64.3 gpd at C = 22 Btu/h-F with NTU = 30x27/22 = 36
and E = 0.97. Preheated water might thermosyphon into the lower part
of a water heater from the fresh water heat exchanger outlet 3' above
the floor into a T 3' above the floor, connecting the upper and lower
parts of the tank, with a common cold water connection at floor level.
Nick
Posted by marson on August 30, 2007, 9:01 pm
On Aug 30, 12:17 pm, nicksans...@ece.villanova.edu wrote:
> >Can we recover 90% of the heat from one shower?
> >We could estimate efficiency with section 7.3 of the SRCC OG300 standard,
> >which specifies measuring solar water heater performance with 6 hourly
> >3 gpm 10.7 gallon hot water draws totaling 64.3 gallons per day.
> >If a well-enclosed shower drain is 105 F and the cold supply is 50 F,
> >heating 64.3 gallons (536 pounds) takes 536(105-50) = 29.5K Btu.
> >A counterflow exchanger with equal heat capacity flow rates Cmin = Cmax
> >= 536/6h = 89 Btu/h-F and effectiveness E = 0.9 = NTU/(NTU+1) needs NTU
> >= 9 = AU/Cmin. With wall conductivity U = 30 Btu/h-F-ft^2, heat exchange
> >area A = 27 ft^2, eg 100' of 1" black PE plastic water pipe inside 100'
> >of 1.5" pipe, coiled around the the drum, surrounded by insulation.
> >We could pump fresh and graywater at 64.3/6/60 = 0.18 gpm with a dual
> >metering pump and store the preheated cold water in the lower half of
> >an electric water heater, with the lower heating element disconnected.
> Better yet, use a float switch and a single metering pump like Grainger's
> $204 2P305 to move 64.3 gpd at C = 22 Btu/h-F with NTU = 30x27/22 = 36
> and E = 0.97. Preheated water might thermosyphon into the lower part
> of a water heater from the fresh water heat exchanger outlet 3' above
> the floor into a T 3' above the floor, connecting the upper and lower
> parts of the tank, with a common cold water connection at floor level.
> Nick
This existing technology would be much simpler: http://gfxtechnology.com/
Posted by nicksanspam on August 31, 2007, 2:14 am
>This existing technology would be much simpler: http://gfxtechnology.com/
About the same cost, with 60 vs 97% efficiency. With no graywater storage,
it won't work with a bathtub. With no pump, it needs a few feet of drop
between the shower drain and the sewer connection.
Nick
Posted by daestrom on August 31, 2007, 10:08 am
>>This existing technology would be much simpler: http://gfxtechnology.com/
> About the same cost, with 60 vs 97% efficiency.
Well, that's 60% measured, actual performance versus 97% theoretical,
never-been-done performance.
> With no graywater storage,
> it won't work with a bathtub.
True
> With no pump, it needs a few feet of drop
> between the shower drain and the sewer connection.
Also true. But then, how much would the pump use moving 64.3 gpd ?
daestrom
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>system that is about 0.5 meters deeper than than the existing waste lines.