Maker Pro
Maker Pro

Revisiting greywater in a drum

Gary said:
Looks like the (14 hour?) stratification time constant is a lot less than
the 180x0.5^2 = 45 hours I figured. Maybe the drum wall conductance... If
it's 1/16" thick and 2Pi feet around, that's like a 0.39 ft^2 vertical
steel rod conductor 1.5' long with G = 25x0.39/1.5 = 6.5 Btu/h-F between
two 225 Btu/F caps with RC = 225/2/6.5 = 17.2 hours. And with finite drum
insulation, some warm water will flow down near the walls and back up in
the middle. It might be interesting to try this again with a plastic drum
or kerfed insulation board and a plastic film liner inside the drum wall.

We might make 7 kerfs 8.26" apart in a 35"x66" piece of 1" foil-faced
foamboard, as below, and slip a 1x2 into the 0.78" gap between the drum
wall and the middle of each side of the foamboard to maintain the gap,
which adds some R-value...

20 PI=4*ATN(1)
30 RO=22.5/2'inner drum radius (inches)
40 N=8'insulation board number of sides
50 T=.5'insulation board thickness (inches)
60 THETA=2*PI/N'angle per side (radians)
70 RIMAX=RO-T*COS(THETA/2)'outer board radius (inches)
80 K=2*RIMAX*COS(PI/2-THETA/2)'distance between kerfs (inches)
90 L=N*K'foamboard length (inches)
100 LC=2.54*L'foamboard length (cm)
110 DIMIN=2*SQR(RIMAX^2-(K/2)^2)
120 BOARDGAP=RO-(DIMIN/2+T)
130 PRINT N,L,LC,DIMIN,BOARDGAP
140 D=2.54*L/N'kerf spacing (cm)
150 FOR K= 0 TO N-1
160 PRINT K,K*D
170 NEXT K

# sides foamboard length foamboard id drum-board gap

8 66.05458 (in) 167.7786 (cm) 19.93374 (in) .7831316 (in)

kerf # distance from end

0 0 (cm)
1 20.97233
2 41.94466
3 62.91698
4 83.88931
5 104.8616
6 125.834
7 146.8063

Nick
 
We might make 7 kerfs 8.26" apart in a 35"x66" piece of 1" foil-faced
foamboard, as below...
20 PI=4*ATN(1)
30 RO=22.5/2'inner drum radius (inches)
40 N=8'insulation board number of sides
50 T=.5'insulation board thickness (inches)...

Oops.

20 PI=4*ATN(1)
30 RO=22.5/2'inner drum radius (inches)
40 N=8'insulation board number of sides
50 T=1'insulation board thickness (inches)
60 THETA=2*PI/N'angle per side (radians)
70 RIMAX=RO-T*COS(THETA/2)'outer board radius (inches)
80 K=2*RIMAX*COS(PI/2-THETA/2)'distance between kerfs (inches)
90 L=N*K'foamboard length (inches)
100 LC=2.54*L'foamboard length (cm)
110 DIMIN=2*SQR(RIMAX^2-(K/2)^2)
120 BOARDGAP=RO-(DIMIN/2+T)
130 PRINT N,L,DIMIN,BOARDGAP
140 D=2.54*L/N'kerf spacing (cm)
150 FOR K= 0 TO N
160 PRINT K,K*D
170 NEXT K

# sides foamboard length foamboard id drum-board gap

8 63.22615 (in) 19.08018 (in) .7099085 (in)

kerf # distance from end

0 0 (cm)
1 20.0743
2 40.1486
3 60.2229
4 80.2972
5 100.3715
6 120.4458
7 140.5201
8 160.5944

Nick
 
N

News

Jan 1, 1970
0

Great stuff - I like the monitoring of temps at set depths. Just a few
pedantic observations, which you probably have spotted yourselves.

The coil in the drum should be more in the centre of the water mass. Better
if the coil of pipe is copper for better heat transfer.

Why a steel drum? This will corrode far easier than plastic. Or is the
steel drum for a cheap test?

A drain is required at the bottom for draining and rodding purposes.
 
N

News

Jan 1, 1970
0
News said:
Great stuff - I like the monitoring of temps at set depths. Just a few
pedantic observations, which you probably have spotted yourselves.

The coil in the drum should be more in the centre of the water mass. Better
if the coil of pipe is copper for better heat transfer.

Why a steel drum? This will corrode far easier than plastic. Or is the
steel drum for a cheap test?

A drain is required at the bottom for draining and rodding purposes.

One more observation. A flat coil near the top of the water line in the
drum would transfer more heat as hot water rises. So maybe a full length
coil connected to a flat coil at the top and then out to the water
heater/cylinder/tank.
 
http://www.builditsolar.com/Projects/GreyWaterHE/gwinbarrel.htm

You may be blessed with more ignorance than pedantry :)
Better if the coil of pipe is copper for better heat transfer.

No. Several times the price with only a slight increase in efficiency,
given a layer of crud on the outside.

Not with a plastic film liner. Steel drums are more cylindrical and have
removable bolt-ring tops, essential if the drum is under slight greywater
pressure to make it move uphill without a pump.
One more observation. A flat coil near the top of the water line in the
drum would transfer more heat as hot water rises.

Can you say "counterflow heat exchanger"?

Nick
 
We might make 7 kerfs 8.26" apart in a 35"x66" piece of 1" foil-faced
# sides foamboard length foamboard id drum-board gap

8 63.22615 (in) 19.08018 (in) .7099085 (in)

kerf # distance from end

0 0 (cm)
1 20.0743
2 40.1486
3 60.2229
4 80.2972
5 100.3715
6 120.4458
7 140.5201

Or, with 8 "internal kerfs" on 7.7" centers and less shiny foil ductape...

20 PI=4*ATN(1)
30 RO=22.5/2'inner drum radius (inches)
40 N=9'insulation board number of sides
50 T=1'insulation board thickness (inches)
60 THETA=2*PI/N'angle per side (radians)
70 K=2*RO*COS(PI/2-THETA/2)'distance between kerfs (inches)
80 RIMAX=SQR(RO^2-(K/2)^2)'outer board radius (inches)
100 L=N*K'foamboard length (inches)
110 LC=2.54*L'foamboard length (cm)
120 RIMIN=RIMAX-T
130 BOARDGAP=RO-RIMAX
140 PRINT N,L,2*RIMIN,BOARDGAP
150 D=2.54*L/N'kerf spacing (cm)
160 FOR K= 0 TO N
170 PRINT K,K*D
180 NEXT K

# sides foamboard length foamboard id drum-board gap

9 69.25906 19.14309 .6784573

kerf # distance from end

0 0
1 19.54645
2 39.09289
3 58.63934
4 78.18578
5 97.73223
6 117.2787
7 136.8251
8 156.3716
9 175.918

Nick
 
N

News

Jan 1, 1970
0
http://www.builditsolar.com/Projects/GreyWaterHE/gwinbarrel.htm


You may be blessed with more ignorance than pedantry :)

You are certainly blessed with arrogance that is certain - I wonder why many
on the ng's just merely hate you - get yourself sorted Nick. Much of my
"ignorance" you should look bit more closely at. :)
No. Several times the price with
only a slight increase in efficiency,
given a layer of crud on the outside.


Not with a plastic film liner. Steel drums are more cylindrical and have
removable bolt-ring tops, essential if the drum is under slight greywater
pressure to make it move uphill without a pump.

I would use a cylindrical plastic drum with close fitting lid, and have the
outlet on the side 10% from the top to cope with any greywater pressure -
the water just rises up into the 10% space above. Cutting a hole in plastic
is easy. Plastic tank adaptors are available.
Can you say "counterflow heat exchanger"?

I can, but I said "A flat coil near the top of the water line in the drum
would transfer more heat as hot water rises." That is:- pipes come in
coils, the spiral being fitted horizontal - have the heat exchanger (coil of
pipe) in the hottest part of the drum. A coil in the bottom section of the
drum can coiled, as in the pictures, which preheats, with it connected to a
horizontal spiral near the top water line - all common sense. Have the heat
exchanger in the mass of water which is hottest for more efficient heat
transfer - all common sense.

Sorry I never put 20 lines of numbers in this post Nick ;-)
 
http://www.builditsolar.com/Projects/GreyWaterHE/gwinbarrel.htm
I would use a cylindrical plastic drum with close fitting lid...

Where would you find one? Plastic would help preserve stratification...

The lid needs to be large enough to allow putting the pipe coils inside,
and airtight to avoid horrible odors in the house. Our steel lid has a
thermostat and a 1500 W electric immersion heater installed vertically
through it for a planned standalone water heater, which might have a
cylindrical 50' soft copper vs plastic pipe coil in the upper 6" of the
drum. We'd like to have all the holes in the lid, with none in the drum.
Bolt-ring drums are widely available and often free, if not new.
and have the outlet on the side 10% from the top to cope with any
greywater pressure - the water just rises up into the 10% space above.

That would be more difficult to fit in a basement with a drainpipe near
the ceiling, even with a strong pedestal. With 2' of head, our current
version would push up the drum lid with about 400 pounds of force.

These can be close to 100% efficient, vs 50% for parallel flow.
I can, but I said "A flat coil near the top of the water line in the drum
would transfer more heat as hot water rises." That is:- pipes come in
coils, the spiral being fitted horizontal - have the heat exchanger (coil of
pipe) in the hottest part of the drum. A coil in the bottom section of the
drum can coiled, as in the pictures, which preheats, with it connected to a
horizontal spiral near the top water line - all common sense.

Fresh water flows in through a bottom cylindrical coil like ours, then
through a flat horizontal spiral top coil? There isn't much room for that
spiral in our present design, since all the fittings go through the top. Got
any dimensions, areas, flow rates, temperature or effectiveness estimates?
Have the heat exchanger in the mass of water which is hottest for more
efficient heat transfer - all common sense.

Seems OK, if fresh water flows from bottom to top. One web description of
a greywater system in a Manitoba house contains a gloomy flat statement
that it can recover 50% of the heat at best, partly because there's a
plastic film layer between the greywater and the copper pipe coil, in
clean water, but also, they don't encourage stratification, so their
simulations show decreasing effectiveness with increasing greywater volume,
vs a system that allows a large slug of cold greywater to drop to the bottom
and slide out a dip tube without disturbing the warmer water above it.

We want this to be simple, low-cost, and efficient. We planned on external
drum insulation, but now it seems it might all be inside, with beveled kerfs
inside 1" foil-faced "R7.2" foamboard instead of flat open kerfs taped on
the outside. If the average temp in the upper part of the drum is 90 F, with
R10 insulation inside (counting the foil), it would lose 24h(90-60)15ft^2/R10
= 1080 Btu/day to a 60 F basement, small compared to a typical day's 50K Btu
hot water usage. Fiberglass insulation over the lid might be useful.

Nick
 
A

Andrew Burgess

Jan 1, 1970
0
One more observation. A flat coil
I can, but I said "A flat coil near the top of the water line in the drum
would transfer more heat as hot water rises." That is:- pipes come in
coils, the spiral being fitted horizontal - have the heat exchanger (coil of
pipe) in the hottest part of the drum. A coil in the bottom section of the
drum can coiled, as in the pictures, which preheats, with it connected to a
horizontal spiral near the top water line - all common sense. Have the heat
exchanger in the mass of water which is hottest for more efficient heat
transfer - all common sense.

A counterflow heat exchanger is more efficient. Google for it. It can
be counterintuitive at first glance...

A rude Nick is far far better than no Nick at all. Go Nick!
 
J

John P@ Bengi

Jan 1, 1970
0
Yup, It sure ain't "Saint Nick"

Andrew Burgess said:
A counterflow heat exchanger is more efficient. Google for it. It can
be counterintuitive at first glance...

A rude Nick is far far better than no Nick at all. Go Nick!
 
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