Revisiting greywater in a drum

[[email protected]]

PT Industries (1 800 44 ENDOT) sell 1/2"x400' coils of 125 psi (tested to
600 psi) NSF-certified HDPE pipe (0.752" OD and 0.622" ID, with a nominal
minimum bending radius of 20xOD = 15") for $67, list. Ferguson's price is
$48. I figure 800' in 3 vertical spirals in a 55-gallon drum with a liner
and a removable bolt-ring top would have 143 ft^2 of surface and hold 12.5
gallons, with an NTU of 6.8 and a burst efficacy of 87%. The layers could
use some separators to prevent nesting, eg some lengthwise slices of pipe.
This single-wall heat exchanger is not NSF-compliant as is, but endurance
testing and leak detection and safety devices could change that.

It has enough volume to do better over a day, with water usage in small
bursts, eg a 10 minute 1.25 gpm shower. How could we calculate that? I
tried hard to make this with 300' of 1" pipe, but it kinked too often
when two of us (looking like Laurel and Hardy tried to spiral it
carefully into a drum on a warm day...

All the holes would be in the drum lid. Cold water would enter the spirals
at the bottom via a dip tube and exit from the top. Greywater would enter
the bulk of the drum at the top via a 1.5" PVC dip tube with holes to let
it find its own thermal level and leave from the bottom via another tube,
with 1-2 psi in the drum to get it back up into a sewer pipe near the top
of a basement ceiling (The GFX requires lots of vertical drop.) We might
put a thermostat on the lid and an electric heating element through the lid
to make a standalone water heater.

Nick

10 SCREEN 9:KEY OFFI=4*ATN(1)
20 DOP=.752'pipe od (inches)
30 DIP=.622'pipe id (inches)
40 NTURNS=34.5/DOP'number of turns in layer
50 RLOOP=23.5/2'loop radius (inches)
60 CLOOP=2*PI*RLOOP/12'loop od (feet)
70 LLAYER=NTURNS*CLOOP'length per layer (feet)
80 L=LLAYER
90 PRINT 1,RLOOP/DOP,NTURNS,LLAYER
100 RLOOP=RLOOP-DOP'loop radius (inches)
110 CLOOP=2*PI*RLOOP/12'loop od (feet)
120 LLAYER=NTURNS*CLOOP'length per layer (feet)
130 L=L+LLAYER
140 PRINT 2,RLOOP/DOP,NTURNS,LLAYER
150 RLOOP=RLOOP-DOP'loop radius (inches)
160 CLOOP=2*PI*RLOOP/12'loop od (feet)
170 LLAYER=NTURNS*CLOOP'length per layer (feet)
180 L=L+LLAYER
190 PRINT 3,RLOOP/DOP,NTURNS,LLAYER
200 AP=AP+L*PI*(DOP+DIP)/2/12'pipe area (ft^2)
210 VP=VP+L*PI*(DIP/2/12)^2*7.48'pipe volume (gallons)
220 PRINT L,AP,VP
230 C=60*1.25*8.33'burst heat capacity rate (Btu/h-F)
240 NTU=30*AP/C'burst NTU for counterflow heat exchanger
250 E=NTU/(NTU+1)'burst heat exchanger efficacy
260 TCI=55'fresh water inlet temp (F)
270 TSH=110'shower head outlet temp (F)
280 THI=105'greywater inlet (shower drain) temp (F)
290 THO=TCI+E*(THI-TCI)'burst fresh water outlet temp (F)
300 ESAVINGS=100*(1-(TSH-THO)/(TSH-TCI))'burst % savings
305 VHW=120'daily hot water consumption (gallons)
310 CKWH=.1'$/kWh
320 DSAVINGS=365*ESAVINGS/100*VHW*8.33*(TSH-TCI)/3412*CKWH'$/year savings
330 PRINT NTU,E,THO,ESAVINGS,DSAVINGS
350 C=VHW*8.33/24'continuous heat capacity rate (Btu/h-F)
360 NTU=30*AP/C'continuous NTU for counterflow heat exchanger
370 E=NTU/(NTU+1)'continuous heat exchanger efficacy
380 THO=TCI+E*(THI-TCI)'continuous fresh water outlet temp (F)
390 SAVINGS=100*(1-(TSH-THO)/(TSH-TCI))'continuous % savings
400 ESAVINGS=100*(1-(TSH-THO)/(TSH-TCI))'burst % savings
410 DSAVINGS=365*ESAVINGS/100*VHW*8.33*(TSH-TCI)/3412*CKWH'$/year savings
420 PRINT NTU,E,THO,ESAVINGS,DSAVINGS

layer radius/od # turns pipe length (feet)

1 15.625 45.87767 282.2525
2 14.625 45.87767 264.1884
3 13.625 45.87767 246.1242

total length total area total volume
(feet) (ft^2) (gallons)

792.5651 142.5478 12.50964

Fresh output energy yearly
NTU Efficacy temp (F) savings (%) savings ($)

6.84503 .8725308 98.62654 79.32098 466.5099 burst
102.6754 .9903546 104.5177 90.03223 529.5059 continuous

 

[Gymn Bob]

What do you intend to do with this room temperature water product?

 

[p j m@see _my _sig _for_address.com]

Boil some ASHRAE bunnies, make a nice stew.

What do you intend to do with this room temperature water product?

 

[[email protected]]

What do you intend to do with this room temperature water product?

The greywater might flow into a drainfield at about 105-0.85(105-55) = 63 F,
after heating 55 F fresh water to about 101. The preheated fresh water might
enter a conventional water heater through the drain connection and come out
the top at 110.

A fully-enclosed shower might be more efficient, with lower temp water and
less heat loss by condensation to bathroom walls.

Nick

 

[p j m@see _my _sig _for_address.com]

The greywater might flow into a drainfield at about 105-0.85(105-55) = 63 F,
after heating 55 F fresh water to about 101. The preheated fresh water might
enter a conventional water heater through the drain connection and come out
the top at 110.

A fully-enclosed shower might be more efficient, with lower temp water and
less heat loss by condensation to bathroom walls.

Nick

GB - don't mind Nick. He's our resident loony-tune from the
planet Trafalgar. The laws of physics are very different on his home
planet than they are here, and he hasn't quite made the adjustment
yet.

Also, the creatures that infest his home planet have very
different standards of comfort than us humans do. They even think a
110 degree, 1.5 GPM shower is acceptable.

 

[Derek Broughton]

GB - don't mind Nick. He's our resident loony-tune from the
planet Trafalgar. The laws of physics are very different on his home
planet than they are here, and he hasn't quite made the adjustment
yet.

Also, the creatures that infest his home planet have very
different standards of comfort than us humans do. They even think a
110 degree, 1.5 GPM shower is acceptable.

Some of his ideas may be borderline for feasibility, but I can't handle a
shower more than 110F, and I'm happy with 1.5GPM - even your tiny little
gallons. If you can't live with this sort of shower, what on earth are you
doing crossposting to groups such as alt.energy.homepower and
misc.consumers.frugal-living?

 

[Gymn Bob]

He hasn't been an asshole here that I remember like most are.
People laughed at Einstein too.
go away control freak.

 

[Gymn Bob]

I don't undertsnad your Basic or Perl code (I don't want to spend the time)
and I do not get where your figures come from.

Consider this.
Use the pre-heated (if you will) water to feed the cold water supply to the
shower. Now the human can adjust the mix to conpensate for any deficiencies
in the ystem, timing or whatever is needed.

Better yet.
Forget the heat exchange barrel with all it's leak and plumbing problems.
Somehow (mechanics aren't stable yet) run your copper supply tube up the
drain pipe of the shower and/or tube. Try to keep it to the bottom to always
be wet. Feed the inlet of this with the cold water supply and the outlet to
the cold water valve for the shower. Noiw we have a drain to cold water heat
exchanger to recover some shower water heat. Sounds simple except the pipe
in pipe couplings. The beauty of it is if the inner pipe leaks it is inside
a drain pipe already. Leak detectors could be arranged later.

 

[p j m@see _my _sig _for_address.com]

Some of his ideas may be borderline for feasibility, but I can't handle a
shower more than 110F, and I'm happy with 1.5GPM - even your tiny little
gallons. If you can't live with this sort of shower, what on earth are you
doing crossposting to groups such as alt.energy.homepower and
misc.consumers.frugal-living?

I didn't set the cross-post list, friend, and I didn't change
it.

Whether your 'numbers of happiness' happen to match mine or
not doesn't really change that.

Of course, he ignores reality, as always - for instance, the
fact that the second you turn on the shower, cold make-up water is
coming into the tank and mixing, and you have nowhere near 110 F
coming out after the first minute.

And his assumptions about the efficiency of the heat transfer
between his grey water and supply water show a complete lack of
understanding.

His assumptions re: the grey water temperature itself are
ludicrous.

Outside of that, he has some silly little lines of code,
impressive to non-programmers, laughable to real programmers, to
'support' his fallacious assumptions.

He's only been doing this for 10 years here, probably longer
elsewhere, I'd think he'd be better at it by now.

 

[Gymn Bob]

Either put up or shut up.

Show figures, cites, reasons, fellings or what your mommy told you and stop
being an asshole. This newsgroup is full of selfproclaimed experts like you.
Always something negative to say about everything and anything but nothing
to back up their big foul mouths. They are a dime a dozen. If you disagree
with something, say so, and show why. This is called discussion and it
promotes the sport and advances people

If you just want to troll, go elsewhere. (half the friggin' group
leaves...LOL)

 

[[email protected]]

...They even think a 110 degree, 1.5 GPM shower is acceptable.

I measured 110 F at 1.15 gpm from a 1.25 gpm "Earth" brand head.
Higher flow heads can use 105 water. What do you find acceptable?

...the second you turn on the shower, cold make-up water is coming
into the tank and mixing, and you have nowhere near 110 F coming
out after the first minute.

The drum contains 3 1/2"x200' vertical pipe spirals. Cold water enters
the pipes at the bottom and stays in the pipes. It does not mix in
the drum. It seems reasonable to expect plug flow. Warm greywater enters
at a low velocity from the top via a large dip tube containing holes to
allow it to find its own thermal level in the bulk of the drum. I don't
anticipate mixing. Does that address your concern?

...his assumptions about the efficiency of the heat transfer between
his grey water and supply water show a complete lack of understanding.

I assumed 30 Btu/h-F-ft^2 through the 0.060" HDPE pipe wall because
that's what I measured for 2 still water films. This is low compared to
most liquid-liquid heat exchangers with a range of 25-150 Btu/h-F-ft^2,
and high compared to a measured value of 10 for water inside a pipe and
a warm liquid (10%) manure slurry outside. Flow in the pipe will raise it.
Fouling outside the pipe will lower it. Copper vs HDPE won't help much.
What number would you use for this thermal conductance?

...His assumptions re: the grey water temperature itself are ludicrous.

I measured 105 F at the drain. With 105 from a higher flow head, the drain
temp is about 100. A fully-enclosed shower would reduce this 5-degree drop.
What have you measured?

Nick

 

[[email protected]]

[email protected] wrote:

Sounds like an interesting idea.

Hey, why don't you build one and measure the performance?

One concern might be the pressure drop in the half inch tubing...

The Hazen-Williams equation says L' of d" smooth pipe with a G gpm flow has
a 0.0004227LG^1.852d^-4.871 psi pressure loss. Each 260' spiral has 1.25/3
= 0.42 gpm, and 0.0004227x260x0.42^1.852x0.622^-4.871 = 0.22 psi.

Nick

 

[Derek Broughton]

I didn't set the cross-post list, friend, and I didn't change
it.

Well, there were 6 groups when I responded, and my post went to all of them
since I didn't know where you were coming from.

Whether your 'numbers of happiness' happen to match mine or
not doesn't really change that.
irrelevant.

Of course, he ignores reality, as always - for instance, the
fact that the second you turn on the shower, cold make-up water is
coming into the tank and mixing, and you have nowhere near 110 F
coming out after the first minute.

So what? Who'd use greywater heat recovery as a primary heat source?
(seems to me, that's a violation of one of the laws of thermodynamics).
It's a way to preheat water for a standard water heater. I don't have a
clue if his system is workable - I'm not prepared to invest all my weekends
building something for little obvious gain - but, if his method _could_ get
110F out, that would be about 60F I wouldn't have to raise the temperature
of the water coming out of my well.

And his assumptions about the efficiency of the heat transfer
between his grey water and supply water show a complete lack of
understanding.

Possibly. And yours show a complete lack of willingness to experiment. If
he's wrong, argue on the numbers or leave him be.

 

[Gymn Bob]

The shower head temperature may indicate the "start out" temperature but by
the time it gets down the drain it may be considerably less.... no?

 

[[email protected]]

The shower head temperature may indicate the "start out" temperature but
by the time it gets down the drain it may be considerably less... no?

About 5 F degrees less. Read much?

If a fully-enclosed 3'x5'x7' shower with R10 insulation behind low-mass
walls loses (105-70)182ft^2/R10 = 637 Btu/h, 1.25 gpm of 105 F head water
would enter the drain at 105 - 637/(60x1.25x8.33) = 104 F. With less heat
loss from the enclosure, 105 vs 110 should be fine with a low-flow head.

Nick

 

[Gymn Bob]

oooops. I missed it. The gobble-dee-gook disguised it...LOL

I doubt the fully enclosed shower would lower this delta much. You have to
have some fresh air coming in or it can get hard to breathe after a while. I
have a tight shower curtain and it happens.

Witht the exchange tank you will still have sediment problems IMO. The soap
film will become a buildup eventually and be hard to maintain. Will this
barrel be used to make some homepower brandy after?...LOL

What about the temp drop at the end of the drain line where the proposed
exhange tank will be?

 

[Gymn Bob]

Exactly!
Are the people in this NG all so friggin anxious they know of nothing other
than "you're stupid"? Is their business that bad they have nothing better to
do?

Either discuss pro or con, ignore mentally or physically killfilter or shut
the **** up. All these self-proclaimed tech experts and they haven't learned
how to use their own browser yet.

 

[[email protected]]

I doubt the fully enclosed shower would lower this delta much...

Got a problem with 300-year-old physics?

You have to have some fresh air coming in or it can get hard to breathe
after a while. I have a tight shower curtain and it happens.

Perhaps you are claustrophobic... 3x5x7 = 105 ft^3 of air is enough for
21 minutes, unless you exhale With a 5 cfm air leak, you could stay
in the shower forever, with a (105-70)23.2 = 812 Btu/h heat loss and
105 - 812/(60x1.25-8.33) = 103.7 F drain water.

Witht the exchange tank you will still have sediment problems IMO. The soap
film will become a buildup eventually and be hard to maintain.

We might drain or backwash it once in a while, or send disobedient children
into the drum with a brush.

What about the temp drop at the end of the drain line where the proposed
exhange tank will be?

I'd put it close to the shower, but the end of the (greywater) line is OK.

Nick

 

[Gymn Bob]

Experience with a fairly tight shower curtain tells me all your physics are
just nonsense anyway. You won't know until you try it.

Problem is in this high speed world I shower so fast the water hasn't hit
the end of the drian before I am out of the shower...LOL

My problem is my house layout. My ensuite shower is at the opposite corner
of the house and it takes between 2-3 minutes to get hot water to flow. With
1/2 copper pipe, that is a lot of wasted hot water left in the pipe when it
is done, not to mention the cold wastage. I have drained this plumbing
before and many, many gallons come out. This could present some other
logistical problems with this idea too. A lot fo cold water going down the
drain before the action takes place. I may have to shower on yesterday's
water...LOL I have thought many times about changing the 1/2 pipe to 3/8"
tubing dedicated to the shower but it would awful tearing walls out to get
access.

 

[[email protected]]

My ensuite shower is at the opposite corner of the house... With 1/2
copper pipe, that is a lot of wasted hot water left in the pipe...
I have drained this plumbing before and many, many gallons come out.

....100' of 1/2" pipe holds a gallon. You must have a very large house.

Nick