I keep wondering about the efficacy of a home brew system that is

1. Not patented
2. Not sponsored by the DOE
3. is not reliant on the RAPID fall of water thru a vertical METAL tube.

Robert Gammon wrote:

I keep wondering about the efficacy of a home brew system that is
1. Not patented
2. Not sponsored by the DOE
3. is not reliant on the RAPID fall of water thru a vertical METAL tube.

That's because you are ignorant :-) Ignorance can be cured...

Nick

wrote:
Robert Gammon wrote:


I keep wondering about the efficacy of a home brew system that is
1. Not patented
2. Not sponsored by the DOE
3. is not reliant on the RAPID fall of water thru a vertical METAL tube.


That's because you are ignorant :-) Ignorance can be cured...

Nick


So a student is smarter, wiser than a PHD with a patent???

Sometimes yes, as the creative mind is at its peak in the early 20s.

However, physics clearly tells us that

1. Metal conducts heat FAR more efficiently than plastics
2. Water falls in a thin vertical film FAR faster than water that is
flowing horizontally in a pipe.

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

Robert Gammon wrote:
wrote:
Robert Gammon wrote:


I keep wondering about the efficacy of a home brew system that is
1. Not patented
2. Not sponsored by the DOE
3. is not reliant on the RAPID fall of water thru a vertical METAL tube.


That's because you are ignorant :-) Ignorance can be cured...

Nick


So a student is smarter, wiser than a PHD with a patent???

Sometimes yes, as the creative mind is at its peak in the early 20s.

However, physics clearly tells us that

1. Metal conducts heat FAR more efficiently than plastics
2. Water falls in a thin vertical film FAR faster than water that is
flowing horizontally in a pipe.

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.


Nick-

Your heat exchanger concept may or may not be better than the GFX but
****ing folks off in a relevant ng is no way to "market" your device.

The GFX has some installation (retrofit) issues but after 30 years as
an ME when I think of heat exchangers I rarely think of "plastic".

cheers
Bob

Robert Gammon wrote:

... physics clearly tells us that

1. Metal conducts heat FAR more efficiently than plastics

But plastic is FAR cheaper, and metal doesn't help much with
a layer of crud and slow-moving water on both sides.

2. Water falls in a thin vertical film FAR faster than water that is
flowing horizontally in a pipe.

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

....60% is not "great," IMO.

Here's what physics tells us on page 3.4 of the 1993 ASHRAE HOF:

1. E = (Thi-Tho)/(Thi-Tci) when Ch = Cmin and
= (Tco-Tci)/(Thi-Tci) when Ch = Cmin, where

Ch = hot fluid capacity rate, Btu/h-F
Cc = cold fluid capacity rate, Btu/h-F
Cmin = smaller of the two rates
Th = terminal temp of hot fluid (F). Subscript i indicates
entering condition; o indicates leaving condition.
Tc = terminal temp of cold fluid (F)...

2. Number of Exchanger Heat Transfer Units NTU = AUavg/Cmin.

3. Capacity rate ratio Z = Cmin/Cmax.

Generally, the heat transfer effectiveness can be expressed for a given
exchanger as a function of NTU and Z: E = f(NTU,Z,flow arrangement).
The effectiveness is independent of the temps in the exchanger.

For any exchanger with Z = 0 (where one fluid undergoes a phase change,
eg in a condenser or evaporator), E = 1-e^(-NTU).

For parallel flow exchangers, E = [1-e^(-NTU(1+Z))]/(1+Z).

For counterflow exchangers, E = [1-e^(-NTU(1-Z))]/[(1-Z(e^(-NTU(1-Z))],
= NTU/(NTU+1), when Z = 1.

For instance, if we use 50 gallons per day of hot water in short bursts
and Cmin = Cmax = 50x8.33/24h = 17.4 Btu/h-F and A = 78.5 ft^2 (a $60
300' piece of 1" polyethylene pipe with a 50 year guarantee) and U = 10
Btu/h-F-ft^2 (with slow-moving greywater and crud outside and slow-moving
fresh water inside), NTU = 78.5x10/17.4 = 45.2, and E = 0.98.

BobK207 wrote:

The GFX has some installation (retrofit) issues but after 30 years as
an ME when I think of heat exchangers I rarely think of "plastic".

Think harder :-)

Cheers,

Nick

BAAMMMMM! Kick it up a notch.

Robert Gammon wrote:

Nick uses a LONG, SLOW moving body of water to extract heat. So in many
ways, it resembles a air conditioning condenser coil.

It also resembles a chair, if you wrap enough cotton gauze around both :-)

... His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

Not a good idea. It wouldn't make a good wheelchair either.

He argues that his will extract more heat than the GFX, and that may be true

Physics clearly tells me so. She seems to lie to you. How fickle.

... he will have a much larger unit (300 feet of 1 inch tubing is more than
6 feet in length when stacked as a single layer around a larger pipe that
holds the greywater)

You seem confused. In this condition, many people read more carefully.
Some even stop talking and listen :-)

The 1" pipe would be in 3 100' pieces inside a 100' x 4" black plastic
corrugated drainpipe which can be in 1) a 2' diameter x 6' tall coil or
2) a 7' OD x 2' ID x 4" tall flat spiral under a basement ceiling, which
uses less floorspace.

Nick

wrote in message
...
Robert Gammon wrote:

... physics clearly tells us that

1. Metal conducts heat FAR more efficiently than plastics

But the conductivity of the pipe wall is only a minor factor in fluid heat
transfer. In almost all situations, the conductivity of the film layer
*next* to the wall is the dominant factor. Just look at the R values for
two conventional water films versus that of 1/16" of Cu or 3/16" of plastic.
When conducting heat through a wall, the two films and wall material are in
series so it is appropriate to just sum the R values. (we'll neglect the
calculation accounting for the wall being cylindrical and just *assume* flat
plates)

Forced convection water films R values range from 0.02 m^2-K/W to as low as
0.0001 m^2-K/W. For a flow of about 2 m/s through a 3 cm pipe, we get a
Reynolds number of about 6.4e4. For water around 20C, that gives us a
Nusselt number of about 350, and a heat transfer coefficient of about 7000
W/m^2-K (or an R value of 1.44e-4). Cu has an R value of about 0.0025
m-K/W, or about 5.0e-6 m^2-K/W for a 2mm thick layer.

So the total R value for heat transfer across a water-water heat exchanger
tube might run about 1.44e-4 + 5.0e-6 + 1.44 e-4 = 2.93e-4 m^2-K/W

If the PEX has a conductivity of only 1/10th that of copper, and is three
times thicker, we would have about 1.44e-4 + 1.5e-4 + 1.44e-4 = 4.38e-4
m^2-K/W. Worse, true. But still about 67% that of the Cu.

And that is with rather optimal surface conditions and relatively high flow
(~2.1 m/s is a common 'rule of thumb' design flow rate, it balances between
poor film coefficients and excessive erosion).


2. Water falls in a thin vertical film FAR faster than water that is
flowing horizontally in a pipe.


But the flow through a flooded horizontal pipe means a much thicker film
layer. The novelty of the GFX design is that the water film formed by
having a small flow rate of say 2 gpm flowing over the inside surface of a
3" diameter pipe. This means the total thickness layer in the GFX flow is
about the same or *less* than the boundary layer thickness in conventional
pipe flow. So the average thickness between the bulk of the water and the
pipe wall is about 1/2 that of the flow layer. This reduces one of those
two film coefficients by an order of 2. This could be...

1.44e-4 + 1.0e-5 + 7.2e-5 = 2.26e-4 m^2-K/W (assuming twice the thickness
of Cu since it is double wall design).

With the high velocity of the water film on the drain side, overall heat
transfer could even be a bit better than this.

Flow in a horizontal pipe could be done in two ways. Flood the pipe
completely. But then you have issues of venting both sides of the drain
line, and the bore of the pipe would result in very low velocities and
correspondingly poor film coefficients. Or leave the pipe only partially
filed (like most current drain lines) and then you only have a tiny surface
area coming in contact with the drain water.

While not the *best* possible performance, like many designs it compromises
between getting better heat transfer coefficient, material costs, ease of
maintenance and installation.

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.


For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2, 60% is
pretty 'great'. How much surface area does your setup require?

Here's what physics tells us on page 3.4 of the 1993 ASHRAE HOF:

1. E = (Thi-Tho)/(Thi-Tci) when Ch = Cmin and
= (Tco-Tci)/(Thi-Tci) when Ch = Cmin, where

Ch = hot fluid capacity rate, Btu/h-F
Cc = cold fluid capacity rate, Btu/h-F
Cmin = smaller of the two rates
Th = terminal temp of hot fluid (F). Subscript i indicates
entering condition; o indicates leaving condition.
Tc = terminal temp of cold fluid (F)...

2. Number of Exchanger Heat Transfer Units NTU = AUavg/Cmin.

3. Capacity rate ratio Z = Cmin/Cmax.

Generally, the heat transfer effectiveness can be expressed for a given
exchanger as a function of NTU and Z: E = f(NTU,Z,flow arrangement).
The effectiveness is independent of the temps in the exchanger.

For any exchanger with Z = 0 (where one fluid undergoes a phase change,
eg in a condenser or evaporator), E = 1-e^(-NTU).

For parallel flow exchangers, E = [1-e^(-NTU(1+Z))]/(1+Z).

For counterflow exchangers, E = [1-e^(-NTU(1-Z))]/[(1-Z(e^(-NTU(1-Z))],
= NTU/(NTU+1), when Z = 1.

For instance, if we use 50 gallons per day of hot water in short bursts
and Cmin = Cmax = 50x8.33/24h = 17.4 Btu/h-F and A = 78.5 ft^2 (a $60
300' piece of 1" polyethylene pipe with a 50 year guarantee) and U = 10
Btu/h-F-ft^2 (with slow-moving greywater and crud outside and slow-moving
fresh water inside), NTU = 78.5x10/17.4 = 45.2, and E = 0.98.


We've been through this before Nick. You can't calculate Cmin or Cmax using
a 24 hour 'average' flow rate. When water is flowing, (say 16 lbm/minute or
960 lbm/hr), your Cmin=Cmax = 960 Btu/h-F.

So *while* the water is flowing, you might see NTU=78.5*10/960 = 0.818. And
*that* would give you about E = 0.45.

By using an average flow rate that includes long periods when there is no
flow at all, you make it seem as though the heat exchanger is much longer
than just 300'. If you want to get your kind of performance with the
existing surface area and U, you would need to reduce the flow to 0.034 gpm
and keep it there all day/night. To get your kind of performance at 2 gpm,
you would need about 55 times longer tubing (~3 miles).

When you look at it that way, GFX's 0.60 performance in a 60" tall package
starts to look pretty good.

daestrom

wrote in message
...
Robert Gammon wrote:

Nick uses a LONG, SLOW moving body of water to extract heat. So in many
ways, it resembles a air conditioning condenser coil.

It also resembles a chair, if you wrap enough cotton gauze around both :-)

... His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

Not a good idea. It wouldn't make a good wheelchair either.

He argues that his will extract more heat than the GFX, and that may be
true

Physics clearly tells me so. She seems to lie to you. How fickle.


Actually, mis-applied formulae from a text book seems to be what is talking
to you again Nick ;-)

If you run your same calculations with a simple flow rate of 2 gpm (a
typical shower flow), what do your 'physics' tell you?

The fact that the answer is much different than when you run your 50 gpd
flow rate numbers should prompt you to pause and 'thick harder'.

While I agree that 'batch' flows that do not fully purge your apparatus will
give you some improvements, we haven't seenn any of your 'numbers' for that.
Quoting ASHRAE formulae that are intended for continuous flow when you
*know* you won't have that sort of flow rate is a waste of everybody's time.

daestrom

In alt.solar.thermal Robert Gammon wrote:
Nick's heat exchanger can be installed in almost any orientation, but
horizontal seems to be his desire.

Horizontal is how all of my waste plumbing is arranged. I don't have any
place to put a vertical drop without adding a pump.

His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

I have never cleaned out the drains in this house.

The beauty of the GFX, is that it is metal, it can be stacked or daisy
chained with pumps to extract even more heat in a smaller space.

"stacked" implies a lot of vertical drop. Pumping requires energy.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2, 60% is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design choice.

Here's what physics tells us on page 3.4 of the 1993 ASHRAE HOF:

1. E = (Thi-Tho)/(Thi-Tci) when Ch = Cmin and
= (Tco-Tci)/(Thi-Tci) when Cc = Cmin, where

Ch = hot fluid capacity rate, Btu/h-F
Cc = cold fluid capacity rate, Btu/h-F
Cmin = smaller of the two rates
Th = terminal temp of hot fluid (F). Subscript i indicates
entering condition; o indicates leaving condition.
Tc = terminal temp of cold fluid (F)...

2. Number of Exchanger Heat Transfer Units NTU = AUavg/Cmin.

3. Capacity rate ratio Z = Cmin/Cmax.

Generally, the heat transfer effectiveness can be expressed for a given
exchanger as a function of NTU and Z: E = f(NTU,Z,flow arrangement).
The effectiveness is independent of the temps in the exchanger.

For any exchanger with Z = 0 (where one fluid undergoes a phase change,
eg in a condenser or evaporator), E = 1-e^(-NTU).

For parallel flow exchangers, E = [1-e^(-NTU(1+Z))]/(1+Z).

For counterflow exchangers, E = [1-e^(-NTU(1-Z))]/[(1-Z(e^(-NTU(1-Z))],
= NTU/(NTU+1), when Z = 1.

For instance, if we use 50 gallons per day of hot water in short bursts
and Cmin = Cmax = 50x8.33/24h = 17.4 Btu/h-F and A = 78.5 ft^2 (a $60
300' piece of 1" polyethylene pipe with a 50 year guarantee) and U = 10
Btu/h-F-ft^2 (with slow-moving greywater and crud outside and slow-moving
fresh water inside), NTU = 78.5x10/17.4 = 45.2, and E = 0.98.

We've been through this before Nick. You can't calculate Cmin or Cmax using
a 24 hour 'average' flow rate.

Sure I can :-) You might enjoy calculating E if 50 gpd of hot water flows
in 1 second 1.25 gpm bursts, then 2 second bursts, and so on.

My shower is 1.25 gpm, so a 10 minute shower fills the 1" pipe.

So *while* the water is flowing, you might see NTU=78.5*10/960 = 0.818.
And *that* would give you about E = 0.45.

How long between showers?

By using an average flow rate that includes long periods when there is no
flow at all, you make it seem as though the heat exchanger is much longer
than just 300'. If you want to get your kind of performance with the
existing surface area and U, you would need to reduce the flow to 0.034 gpm
and keep it there all day/night.

I disagree, altho that might happen with continuous hot tub water exchange.

Nick

But you also claim you don't need to breathe oxygen for the full 10
minute shower so that you can seal your shower stall.

wrote in message
...
daestrom wrote:
My shower is 1.25 gpm, so a 10 minute shower fills the 1" pipe.
Nick

wrote:

Robert Gammon wrote:

Nick uses a LONG, SLOW moving body of water to extract heat. So in many
ways, it resembles a air conditioning condenser coil.

It also resembles a chair, if you wrap enough cotton gauze around both :-)

... His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

Not a good idea. It wouldn't make a good wheelchair either.

No kidding. Somebody seems to need a definition of "greywater".
--
derek

Derek Broughton wrote:
wrote:


Robert Gammon wrote:


Nick uses a LONG, SLOW moving body of water to extract heat. So in many
ways, it resembles a air conditioning condenser coil.

It also resembles a chair, if you wrap enough cotton gauze around both :-)


... His heat exchanger will need to be cleaned out periodically of gunk,
especially if toilets drain thru the same heat exchanger.

Not a good idea. It wouldn't make a good wheelchair either.


No kidding. Somebody seems to need a definition of "greywater".

greywater == all water going down a drain EXCEPT water from Toilets

blackwater == all water from toilets

daestrom wrote:

While I agree that 'batch' flows that do not fully purge your apparatus will
give you some improvements, we haven't seenn any of your 'numbers' for that.

Here are some numbers for that. If 100' of 3 1" pipes (polyethylene, with
a 0.07" wall thickness) has 78.5 ft^2 of surface with U = 10 Btu/h-F-ft^2,
10' has 78.5 Btu/h-F...

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater (Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M10 GOTO 170'rest vs shower
90 TF(0)=TF(1)'move fresh water up from below
100 TG(0)=(100*CFRESH+TG(0)*CGREY)/(CFRESH+CGREY)'move greywater in at the top
110 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
120 TF(S)=TF(S+1)'move fresh water up
130 TG(S)=(TG(S-1)*CFRESH+TG(S)*CGREY)/(CFRESH+CGREY)'move greywater down
140 NEXT S
150 TF(9)=55'move cold water in at the bottom
160 TG(9)=(TG(8)*CFRESH+TG(9)*CGREY)/(CFRESH+CGREY)'move greywater down
170 FOR S=0 TO 9'rest
180 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
190 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
200 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
210 NEXT S
220 NEXT M
230 NEXT SHOWER
240 FOR S=0 TO 9'results
250 PRINT S,TF(S),TG(S)
260 NEXT S
270 E=(TF(0)-55)/(100-55)'effectiveness
280 PRINT E

pipe fresh water greywater
section temp (F) temp (F)

0 93.32178 93.3218
1 90.556 90.55602
2 87.60851 87.60853
3 84.60492 84.60494
4 81.62819 81.62821
5 78.71178 78.71181
6 75.86447 75.8645
7 73.08838 73.0884
8 70.3852 70.38522
9 67.75679 67.75681

effectiveness

..8515951

The fresh and greywater temps are very close, about 6 hours after
a shower, since the pipe time constant is much shorter (less than
8 minutes.) These results wouldn't change much with only a half-hour
between showers. The effectiveness would be higher for shorter bursts.

Maybe it's worth adding 2 more $20 100' pieces of 1" pipe (altho that
would be a tight squeeze), or a handheld showerhead that only runs
when a button is pushed. Who sells them?

Nick

daestrom wrote:

While I agree that 'batch' flows that do not fully purge your apparatus will
give you some improvements, we haven't seenn any of your 'numbers' for that.

Here are some numbers for that...

Oops. Fixing lines 100, 130, and 160 improves the effectiveness to 88%.

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater (Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M10 GOTO 170'rest vs shower
90 TF(0)=TF(1)'move fresh water up
100 TG(0)=(100*CFRESH+TG(0)*(CGREY-CFRESH))/CGREY'move greywater in at the top
110 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
120 TF(S)=TF(S+1)'move fresh water up
130 TG(S)=(TG(S-1)*CFRESH+TG(S)*(CGREY-CFRESH))/CGREY'move greywater down
140 NEXT S
150 TF(9)=55'move cold water in at the bottom
160 TG(9)=(TG(8)*CFRESH+TG(9)*(CGREY-CFRESH))/CGREY'move greywater down
170 FOR S=0 TO 9'rest
180 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
190 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
200 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
210 NEXT S
220 NEXT M
230 NEXT SHOWER
240 FOR S=3 TO 9'results
250 PRINT 300+S;"'";S;TF(S),TG(S)
260 NEXT S
270 E=(TF(0)-55)/(100-55)
280 PRINT 410;"'";E

pipe fresh water greywater
section temp (F) temp (F)

0 94.53323 94.53326
1 92.54844 92.54847
2 90.32916 90.32919
3 87.93309 87.93311
4 85.42671 85.42674
5 82.85161 82.85163
6 80.22588 80.2259
7 77.55527 77.55529
8 74.8424 74.84241
9 72.08957 72.0896

effectiveness

..8785163

Nick

wrote:
daestrom wrote:


While I agree that 'batch' flows that do not fully purge your apparatus will
give you some improvements, we haven't seenn any of your 'numbers' for that.


Here are some numbers for that. If 100' of 3 1" pipes (polyethylene, with
a 0.07" wall thickness) has 78.5 ft^2 of surface with U = 10 Btu/h-F-ft^2,
10' has 78.5 Btu/h-F...


[snip]

Question, How large a space does your heat exchanger occupy?

3 PE pipes inside a larger PE pipe is NOT very flexible. Bend radius
for this configuration is measured in feet.

It not very thick, to be sure, but to collapse this into a practical
shape, (100 linear feet of tubing in the rafters of a basement will NOT
fit in most houses), you'll need to bend this into a coil of say about 5
or 6 feet in diameter, several feet high. You quoted some figures for
the dimensions of the assembled unit, but now those dimensions as I
recall them don't make sense.

wrote:
daestrom wrote:


While I agree that 'batch' flows that do not fully purge your apparatus will
give you some improvements, we haven't seenn any of your 'numbers' for that.


Here are some numbers for that. If 100' of 3 1" pipes (polyethylene, with
a 0.07" wall thickness) has 78.5 ft^2 of surface with U = 10 Btu/h-F-ft^2,
10' has 78.5 Btu/h-F...


[snip]

Question, How large a space does your heat exchanger occupy?

3 PE pipes inside a larger PE pipe is NOT very flexible. Bend radius
for this configuration is measured in feet.

It not very thick, to be sure, but to collapse this into a practical
shape, (100 linear feet of tubing in the rafters of a basement will NOT
fit in most houses), you'll need to bend this into a coil of say about 5
or 6 feet in diameter, several feet high. You quoted some figures for
the dimensions of the assembled unit, but now those dimensions as I
recall them don't make sense.

Stacked or daisy chained does NOT mean increased height. It merely
means we hook up two shorter GFX lengths in series, pumping effluent
from the outlet of the first one to the inlet of the second one.
Overall efficiency rises. For instance we could get two S4-40s and set
them on the wall parallet to each other. Inlet for the first one is
from house sewer. Outlet of first is pumped (100W power used) to inlet
of second, outlet of second is piped to city sewer/septic tank. One
BIG advantage of this system in a septic tank is that you can put
BOILING water down the kitchen drain, something you cannot do with a
plain ole septic tank.

One issue with this configuration is water pressure drop GFX Tech will
argue for manifolding, that is, connect potable water supply to coil
inlet on BOTH GFX units and tie the coil outlets from BOTH units to a
common pipe to hot water heater and cold side of showers, That
produces a pressure drop of about 2-3 psi A full series connection
with potable water to the coil inlet on the one connected to city
sewer/septic tank, its output then connected to coil input of the GFX
attached to the house sewer, and the coil outlet then connected to
house hot water and shower cold side. This produces a pressure drop of
5-6 psi.

In my configuration, the inlet water pressure will be a constant 65psi
So dropping to about 60psi is no big deal, and the water temp to the
house rises. Effluent temp in both series and parallel configs drops
by at least 20F, maybe much more

In 40 inches of vertical height, we get 80 inches of heat recovery.

wrote in message
...
daestrom wrote:

While I agree that 'batch' flows that do not fully purge your apparatus
will
give you some improvements, we haven't seenn any of your 'numbers' for
that.

Here are some numbers for that...

Oops. Fixing lines 100, 130, and 160 improves the effectiveness to 88%.

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater
(Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M10 GOTO 170'rest vs shower
90 TF(0)=TF(1)'move fresh water up
100 TG(0)=(100*CFRESH+TG(0)*(CGREY-CFRESH))/CGREY'move greywater in at the
top
110 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
120 TF(S)=TF(S+1)'move fresh water up
130 TG(S)=(TG(S-1)*CFRESH+TG(S)*(CGREY-CFRESH))/CGREY'move greywater down
140 NEXT S
150 TF(9)=55'move cold water in at the bottom
160 TG(9)=(TG(8)*CFRESH+TG(9)*(CGREY-CFRESH))/CGREY'move greywater down
170 FOR S=0 TO 9'rest
180 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
190 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
200 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
210 NEXT S
220 NEXT M
230 NEXT SHOWER
240 FOR S=3 TO 9'results
250 PRINT 300+S;"'";S;TF(S),TG(S)
260 NEXT S
270 E=(TF(0)-55)/(100-55)
280 PRINT 410;"'";E


Not bad, apparantly you've chosen a flow rate and section length so the time
step corresponds to exactly one section length.

Because the greywater drain cross-section is so much larger than the
freshwater, your Cmin/Cmax ratio ends up being about 0.24 (IIRC a 4-inch
pipe with three 1-inch pipes inside). So a high efficiency of 87% doesn't
really tell us how much energy we're saving. While your efficiency is 87%,
it looks like you're still putting (72-55)*1.25*8.33=177 BTU/minute down the
drain. Out of a total of 468.6 BTU/minute needed to heat 1.25 gpm from 55
to 100, that's nearly 38% of the heating.. Print out the data *during* the
last shower, not 350 minutes later. I'd like to see what the greywater
outlet temperature is while it's flowing. I think it's going to be a lot
cooler than 72, but not sure. Better yet, print out the freshwater and
greywater outlet temperatures *during* the ten time steps of the last
shower.

After all, it is the temperatures out *during* flow that matter. The
temperatures at the end of the stagnation period only tell us the initial
startup point for the next shower. How quickly they change *during* the
shower, and in what direction would be more telling.

After all, if the freshwater outlet during the shower really is at 94F, and
the greywater really leaves at 72F, then you don't have conservation of
energy (freshwater side picks up (94-55)*1.25*8.33 = 406 btu/min, while the
greywater side gives off (100-72)*1.25*8.33=291 btu/min). That's a clue
that something is wrong with these results.

daestrom

wrote in message
...
daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2, 60% is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design choice.


Guess again. If your setup was restricted to just 5 feet long, would its
performance be anywhere near as good as the GFX??? And that's the point.
To get performance on par with GFX, you have to resort to something several
tens of feet long.

Heck, If I had someone build a GFX that was 100 feet tall, I'm sure it's
performance would put your setup to shame. But who has space for 100' of 4"
pipe (vertical, coiled or otherwise).

snip ASHRAE calculations for steady-state problem

We've been through this before Nick. You can't calculate Cmin or Cmax
using
a 24 hour 'average' flow rate.

Sure I can :-) You might enjoy calculating E if 50 gpd of hot water flows
in 1 second 1.25 gpm bursts, then 2 second bursts, and so on.


Well, *you* can calculate using average flow, but the results are *NOT*
meaningful. Just because you found a formula in a book, doesn't mean you
can apply it to different situations, like intermittent and 'average' flow
and still get meaningful results. Those ASHRAE formula are for calculating
the steady-state performance of a heat-exchanger. Trying to apply them to
'burst' mode is a waste of time. The results do *not* mean anything. And
they don't prove anything except that you don't know when to apply them.

But just to humor you, if the 'bursts' are 1.25 gpm, then the steady-state
answer would be Cmin-Cmax=1.25*60*8.33 = 624.75 Btu/h-F. With an area of
78.4 ft^2 and U=10 Btu/h-f-ft^2, NTU=78.5*10/624.75 = 1.26 and E=55.7%.

Notice how the answer depends on the flow rate *when water is flowing*??
Not the average amount of water that flows during some arbitrary time
period.

The fact that the two different flow rates give such drasticly different
answers should be a clue that you're missing something.

My shower is 1.25 gpm, so a 10 minute shower fills the 1" pipe.

So *while* the water is flowing, you might see NTU=78.5*10/960 = 0.818.
And *that* would give you about E = 0.45.

How long between showers?


The formulae you are using from ASHRAE are for steady-state, *flowing*
heat-exchangers. The NTU and effectiveness assume *steady-state* conditions
(i.e. a constant flow rate). So the efficiency of your system when water
flows and has reached steady-state is only 0.45. But since your showers are
less than the time needed to reach steady-state, even that number is
useless.

By using an average flow rate that includes long periods when there is no
flow at all, you make it seem as though the heat exchanger is much longer
than just 300'. If you want to get your kind of performance with the
existing surface area and U, you would need to reduce the flow to 0.034
gpm
and keep it there all day/night.

I disagree, altho that might happen with continuous hot tub water
exchange.

Your other post with a step-wise simulation is probably much closer for this
sort of transient behavior, but it too has some flaws. You posted the
outlet temperature for the greywater as 72F while the outlet for freshwater
as 94F. This is with constant 55F inlet freshwater and 100F inlet
greywater. The fact that your freshwater is picking up more energy
[(94-55)*flowrate] than your greywater is losing [(100-72)*flowrate] is a
clue that something is wrong in your calculation.

Your simulation printed out the numbers after 350 minute stagnation period,
not when there is flowing water. You should print out the temperatures
*during* the last shower, when there is actual flow. *That* is when there
is energy flowing down the drain. Print out the numbers for fresh and grey
water outlet temperatures *during* the last ten minute shower.

Calculate the energy removed from the greywater during those ten minutes and
the energy being picked up by the fresh-water during those same ten minutes.
Since the inlet temperatures are both assumed fixed (100F and 55F), if the
energy picked up by fresh-water does not equal the energy given off by the
greywater during those ten minutes of flow, then something is wrong with
your calculations because energy must be conserved. (we're neglecting any
ambient losses)

To find the true effectiveness for this non-steady-state operation, just
calculate the amount of energy picked by the freshwater during the shower
and divide by the total energy to heat that same water to the greywater
inlet temperature.

*hint*, if the water outlet temperatures change a lot while the shower is
running, you might reduce the time step to less than one minute intervals so
as to get better resolution. This would make for better integration of the
temperature versus time to get total energy. Too course a time step could
lead to mismatch between greywater and freshwater energy calculations.

daestrom

daestrom wrote:

wrote in message
...
daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2,
60% is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design choice.


Guess again. If your setup was restricted to just 5 feet long, would
its performance be anywhere near as good as the GFX??? And that's the
point. To get performance on par with GFX, you have to resort to
something several tens of feet long.

Heck, If I had someone build a GFX that was 100 feet tall, I'm sure
it's performance would put your setup to shame. But who has space for
100' of 4" pipe (vertical, coiled or otherwise).

The issue with a 100 foot tall GFX is the required size of the potable
water tubing and the pressure required to get a reasonable flow rate
thru the 100ft stack.

As it is on a 60 inch GFX, manifolding is performed to limit pressure
loss (coil height is about 27 inches each) with the base of each coil
tied to the inlet water, and the top of each coil tied to the outlet.

The engineering drawings on gfxtech's web site clearing indicate an
asymptotic behavior. Adding additional length brings lower and lower
incremental benefit. Still with two S4-40s in series, pressure loss is
about 2.5psi on a 2 gal/hr flow rate. and 80 inches of gfx recovery
will get efficiency up another 5-10% over a 60 inch model and a 40inch
height is easier, in many cases, to find a spot for.

daestrom is doing us a great service by pointing out the issues with the
home brew system. I too do not believe that the home brew system
proposed will work as well as a 60 inch GFX to recover waste heat from
grey/black water and pump that heat to DHW and cold side showers.

"Robert Gammon" wrote in message
. net...
daestrom wrote:

wrote in message
...
daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24 ft^2, 60%
is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design choice.


Guess again. If your setup was restricted to just 5 feet long, would its
performance be anywhere near as good as the GFX??? And that's the point.
To get performance on par with GFX, you have to resort to something
several tens of feet long.

Heck, If I had someone build a GFX that was 100 feet tall, I'm sure it's
performance would put your setup to shame. But who has space for 100' of
4" pipe (vertical, coiled or otherwise).

The issue with a 100 foot tall GFX is the required size of the potable
water tubing and the pressure required to get a reasonable flow rate thru
the 100ft stack.

I wasn't seriously recommending a 100' GFX. Just pointing out that 100' of
any sort of piping takes considerably more space than a 5' GFX.


As it is on a 60 inch GFX, manifolding is performed to limit pressure loss
(coil height is about 27 inches each) with the base of each coil tied to
the inlet water, and the top of each coil tied to the outlet.


Yes, that is exactly how mine is constructed. The problem with piping the
freshwater side in parallel is that the two coils form a sort of
series-parallel flow heat exchanger. One heat exchanger cannot heat its
outlet as much because it only receives already-cooled greywater from the
other heat-exchanger. So when it's cooler freshwater outlet water mixes
with the warmer water from the upper one, there is a reduction in overall
efficiency. I can detect this when someone is in the shower by touch alone
on the two coil outlets.

This is the same sort of thing that multiple-pass conventional
heat-exchangers suffer from. Less than ideal, but a compromise of
heat-transfer performance versus hydraulic performance (pressure drop).

I've toyed with the idea of restricting the flow through the lower coil to
improve on this. Would increase the pressure drop some, but not as bad as
the full series model. Some weekend project I may put a throttle valve in
series with the lower coil and play around with different settings.

The engineering drawings on gfxtech's web site clearing indicate an
asymptotic behavior. Adding additional length brings lower and lower
incremental benefit. Still with two S4-40s in series, pressure loss is
about 2.5psi on a 2 gal/hr flow rate. and 80 inches of gfx recovery will
get efficiency up another 5-10% over a 60 inch model and a 40inch height
is easier, in many cases, to find a spot for.

True, but you would need two 40inch heights, or a pumping arrangement.
Since mine is installed in the main waste line for the entire house, pumping
blackwater did not seem very attractive.


daestrom is doing us a great service by pointing out the issues with the
home brew system. I too do not believe that the home brew system proposed
will work as well as a 60 inch GFX to recover waste heat from grey/black
water and pump that heat to DHW and cold side showers.


It could perform rather well. And if I know Nick at all from his postings
over the years, it will cost less than my GFX did, even though I installed
in myself. I'm just trying to keep Nick 'honest' by not letting him apply
steady-state calculations to a transient system. But it does require more
space to install, and may have some maintenance issues.

Hopefully when Nick is done building it, he'll post his performance numbers
(good or bad). Direct measurements and experimentation are always better
than theory.

daestrom
"In theory, theory and practice are the same. In practice, they're
different"

Robert Gammon wrote:

... If 100' of 3 1" pipes (polyethylene, with a 0.07" wall thickness)
has 78.5 ft^2 of surface with U = 10 Btu/h-F-ft^2, 10' has 78.5 Btu/h-F...

Question, How large a space does your heat exchanger occupy?

Either 1) 2' diam x 6' tall, or 2) 7' OD x 2' ID x 4" tall.

3 PE pipes inside a larger PE pipe is NOT very flexible. Bend radius
for this configuration is measured in feet.

About 1'.

It not very thick, to be sure, but to collapse this into a practical
shape, (100 linear feet of tubing in the rafters of a basement will NOT
fit in most houses)...

Nobody said it would, nitwit :-)

... you'll need to bend this into a coil of say about 5 or 6 feet
in diameter, several feet high.

Wrong again. The drainpipe is about 4.25" OD.

Nick

daestrom wrote:

I'd like to see what the greywater outlet temperature is while it's flowing.

How about the fresh water outlet temp? Line 100 below accumulates
the heat energy that needs to be added during the last shower...

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater (Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M9 GOTO 200'rest vs shower
90 IF SHOWER 1000 GOTO 120
100 RHEAT=RHEAT+1.25*8.33*(100-TF(0))'reheat energy required
110 PRINT 300+M;"'";M,TF(0),RHEAT
120 TF(0)=TF(1)'move fresh water up
130 TG(0)=(100*CFRESH+TG(0)*(CGREY-CFRESH))/CGREY'move greywater in at the top
140 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
150 TF(S)=TF(S+1)'move fresh water up
160 TG(S)=(TG(S-1)*CFRESH+TG(S)*(CGREY-CFRESH))/CGREY'move greywater down
170 NEXT S
180 TF(9)=55'move cold water in at the bottom
190 TG(9)=(TG(8)*CFRESH+TG(9)*(CGREY-CFRESH))/CGREY'move greywater down
200 FOR S=0 TO 9'rest
210 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
220 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
230 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
240 NEXT S
250 NEXT M
260 NEXT SHOWER
280 SHOWERGY=1.25*10*8.33*(100-55)'total heat energy with no gwhx
290 PRINT RHEAT,SHOWERGY,1-RHEAT/SHOWERGY

time fresh cum reheat
(min) temp (F) (Btu)

0 94.56091 56.6345
1 92.93514 130.1973
2 91.38136 219.9389
3 89.96538 324.4244
4 88.72086 441.8685
5 87.6472 570.492
6 86.72784 708.6885
7 85.94302 855.0568
8 85.27464 1008.385
9 84.70704 1167.623

cum reheat shower effectiveness
(Btu) heat (Btu) (fraction)

1167.623 4685.625 .7508075

Nick

GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11


"daestrom" wrote in message
...

"Robert Gammon" wrote in message
. net...
daestrom wrote:

wrote in message
...
daestrom wrote:

The GFX does well with its small surface...

OK, GFX doesn't help with heat recovery for a bath, but great
for hot
showers, dishwashing, clothes washing.

...60% is not "great," IMO.

For a total surface area of just (4 in)*pi *60 in /144 = 5.24
ft^2, 60%
is
pretty 'great'.

It might be 3 vs 4", but it's still poor overall performance.

How much surface area does your setup require?

There's no requirement... 300' of 1" pipe is a convenient design
choice.


Guess again. If your setup was restricted to just 5 feet long,
would its
performance be anywhere near as good as the GFX??? And that's
the point.
To get performance on par with GFX, you have to resort to
something
several tens of feet long.

Heck, If I had someone build a GFX that was 100 feet tall, I'm
sure it's
performance would put your setup to shame. But who has space for
100' of
4" pipe (vertical, coiled or otherwise).

The issue with a 100 foot tall GFX is the required size of the
potable
water tubing and the pressure required to get a reasonable flow
rate thru
the 100ft stack.

I wasn't seriously recommending a 100' GFX. Just pointing out that
100' of
any sort of piping takes considerably more space than a 5' GFX.


As it is on a 60 inch GFX, manifolding is performed to limit
pressure loss
(coil height is about 27 inches each) with the base of each coil
tied to
the inlet water, and the top of each coil tied to the outlet.


Yes, that is exactly how mine is constructed. The problem with
piping the
freshwater side in parallel is that the two coils form a sort of
series-parallel flow heat exchanger. One heat exchanger cannot heat
its
outlet as much because it only receives already-cooled greywater
from the
other heat-exchanger. So when it's cooler freshwater outlet water
mixes
with the warmer water from the upper one, there is a reduction in
overall
efficiency. I can detect this when someone is in the shower by
touch alone
on the two coil outlets.

This is the same sort of thing that multiple-pass conventional
heat-exchangers suffer from. Less than ideal, but a compromise of
heat-transfer performance versus hydraulic performance (pressure
drop).

I've toyed with the idea of restricting the flow through the lower
coil to
improve on this. Would increase the pressure drop some, but not as
bad as
the full series model. Some weekend project I may put a throttle
valve in
series with the lower coil and play around with different settings.

The engineering drawings on gfxtech's web site clearing indicate
an
asymptotic behavior. Adding additional length brings lower and
lower
incremental benefit. Still with two S4-40s in series, pressure
loss is
about 2.5psi on a 2 gal/hr flow rate. and 80 inches of gfx
recovery will
get efficiency up another 5-10% over a 60 inch model and a 40inch
height
is easier, in many cases, to find a spot for.

True, but you would need two 40inch heights, or a pumping
arrangement.
Since mine is installed in the main waste line for the entire house,
pumping
blackwater did not seem very attractive.


daestrom is doing us a great service by pointing out the issues
with the
home brew system. I too do not believe that the home brew system
proposed
will work as well as a 60 inch GFX to recover waste heat from
grey/black
water and pump that heat to DHW and cold side showers.


It could perform rather well. And if I know Nick at all from his
postings
over the years, it will cost less than my GFX did, even though I
installed
in myself. I'm just trying to keep Nick 'honest' by not letting him
apply
steady-state calculations to a transient system. But it does
require more
space to install, and may have some maintenance issues.

Hopefully when Nick is done building it, he'll post his performance
numbers
(good or bad). Direct measurements and experimentation are always
better
than theory.

daestrom
"In theory, theory and practice are the same. In practice, they're
different"

daestrom wrote:

... who has space for 100' of 4" pipe (vertical, coiled or otherwise).[?]

The 4" tall spiral hung under a basement ceiling would be about 7'
in diameter. The 6' tall coil would occupy a 2.7' floor circle.
It seems simpler to install and might have better stratification.

10 PI=4*ATN(1)
20 D=4.25'pipe OD (inches)
30 L=100'pipe length (feet)
40 DI=2'coil ID (feet)
50 DO=DI+2*D/12'coil OD (feet)
60 CI=PI*DI'inner circumference (feet)
70 NT=L/CI'number of turns
80 H=NT*D/12'coil height (feet)
90 PRINT D,DI,DO,NT,H

4.25 2 2.708333 15.91549 5.636738

10 PI=4*ATN(1)
20 D=4.25'pipe OD (inches)
30 L=100'pipe length (feet)
40 A=D*L/12'pipe area (ft^2)
50 DI=2'flat spiral ID (feet)
60 DO=2*SQR(A/PI+(DI/2)^2)'spiral OD (feet)
70 NT=12*(DO-DI)/2/D'number of turns
80 PRINT D,DI,DO,NT

4.25 2 7.006704 7.068288

Nick

Solar Flare wrote:
GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11



GREAT scoring system.

Particularly since GFX is non clogging and works with ALL sewer waters
(grey and black).

Efficiency is NOT the only criteria here. If we recover 40% to 60% of
the waste heat, we have made MAJOR strides in overall DHW production
efficiency. Convenience, non-clogging, wife friendly are all MAJOR
concerns.

Price is NOT the only factor either, but price and efficiency are Nick's
main concerns.

Nick's will have to be connected ONLY to non-toilet drains. Nick's will
have to be periodically cleaned of matter that goes down kitchen sinks
and out the clothes washer drain.

None of these are concerns with GFX.

If we can afford one of these, either of these, these other factors,
besides price and efficiency may well be MORE of a concern to the rest
of us.

Well the efficiency of heat exchange factor is not the only
efficiency. A purchased and installed product at 5% efficiency is much
more economical than a well designed, thought out, project that will
be implemented sometime after getting a 'Round Tuit

Efficiency of installation ease.
Efficiency of installation time.
Efficiency of product parts and pieces aquisition
Efficiency of marriage after the home space displacement.
Efficiency of trial and error costs.
Efficiency of maintenance.
Efficiency of computer time arguing about imaginary issues.
Efficiency of home resale after the newfangled frankenstein
paraphenalia is seen.


"Robert Gammon" wrote in message
. com...
Solar Flare wrote:
GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11



GREAT scoring system.

Particularly since GFX is non clogging and works with ALL sewer
waters
(grey and black).

Efficiency is NOT the only criteria here. If we recover 40% to 60%
of
the waste heat, we have made MAJOR strides in overall DHW production
efficiency. Convenience, non-clogging, wife friendly are all MAJOR
concerns.

Price is NOT the only factor either, but price and efficiency are
Nick's
main concerns.

Nick's will have to be connected ONLY to non-toilet drains. Nick's
will
have to be periodically cleaned of matter that goes down kitchen
sinks
and out the clothes washer drain.

None of these are concerns with GFX.

If we can afford one of these, either of these, these other factors,
besides price and efficiency may well be MORE of a concern to the
rest
of us.

Solar Flare wrote:

Well the efficiency of heat exchange factor is not the only
efficiency. A purchased and installed product at 5% efficiency is much
more economical than a well designed, thought out, project that will
be implemented sometime after getting a 'Round Tuit

Le mieux est l'ennemi du bien. I'm better at thinking up things
than getting round tuits.

Efficiency of installation ease.
Efficiency of installation time.
Efficiency of product parts and pieces aquisition

I can relate to that, having spent about 40 hours in the last 2 weeks
visiting various plumbing supply stores. It's been fun learning names
of fittings, like "bullnose T" and "Dismukes crampon lifter."

Efficiency of marriage after the home space displacement.

Spouses care a lot more about what's on the lawn
or in the living room than what's in the basement.

Efficiency of trial and error costs.

It might be nice to build more than one, with careful directions at
http://BuildItSolar.com

Efficiency of maintenance.

And only empty the crud once a year, using a hose instead of a toothbrush.

Efficiency of computer time arguing about imaginary issues.

Some issues are more important than others, eg daestrom's.

Efficiency of home resale after the newfangled frankenstein
paraphenalia is seen.

This leads me to make things easy to remove.

"Robert Gammon" wrote:

Solar Flare wrote:
GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11

GREAT scoring system.

Nah. Efficiency should be 8 vs 7, a lower price should give me more
vs fewer points, convenience is TBD, and wives may like saving more
money, or having more to spend in other directions.

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater (Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M9 GOTO 200'rest vs shower
90 IF SHOWER 1000 GOTO 120
100 RHEAT=RHEAT+1.25*8.33*(100-TF(0))'reheat energy
105 GLOSS=GLOSS+1.25*8.33*(TG(9)-55)'greywater heat loss
110 PRINT 300+M;"'";M,TF(0),RHEAT,TG(9),GLOSS
120 TF(0)=TF(1)'move fresh water up
130 TG(0)=(100*CFRESH+TG(0)*(CGREY-CFRESH))/CGREY'move greywater in at the top
140 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
150 TF(S)=TF(S+1)'move fresh water up
160 TG(S)=(TG(S-1)*CFRESH+TG(S)*(CGREY-CFRESH))/CGREY'move greywater down
170 NEXT S
180 TF(9)=55'move cold water in at the bottom
190 TG(9)=(TG(8)*CFRESH+TG(9)*(CGREY-CFRESH))/CGREY'move greywater down
200 FOR S=0 TO 9'rest
210 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
220 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
230 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
240 NEXT S
250 NEXT M
260 NEXT SHOWER
280 SHOWERGY=1.25*10*8.33*(100-55)
290 PRINT RHEAT,SHOWERGY,1-RHEAT/SHOWERGY

0 94.56091 56.6345 71.68895 173.7736
1 92.93514 130.1973 72.0242 351.0381
2 91.38136 219.9389 72.44145 532.6472
3 89.96538 324.4244 72.83433 718.3472
4 88.72086 441.8685 73.20448 907.9012
5 87.6472 570.492 73.55341 1101.089
6 86.72784 708.6885 73.88255 1297.703
7 85.94302 855.0568 74.19321 1497.553
8 85.27464 1008.385 74.4866 1700.457
9 84.70704 1167.623 74.76389 1906.248

1167.623 4685.625 .7508075

This is confusing. The greywater output seems to warm during the course of
a shower, but I wouldn't expect that in a real system with 100' of 4" pipe.

Nick

In article ,
Robert Gammon wrote:

Nick's will have to be connected ONLY to non-toilet drains. Nick's will
have to be periodically cleaned of matter that goes down kitchen sinks
and out the clothes washer drain.

Connecting a GFX to a toilet drain is not going to be very sensible,
however, unless you heat your toilet water - makes the most sense when
connected to drains that might have hot water - putting it in the
blackwater stack just adds one more way to have a toilet flush make your
shower uncomfortable, and reduces the potential efficiency by reducing
the temperature differential across the heat exchanger.

--
Cats, coffee, chocolate...vices to live by

wrote:
Solar Flare wrote:


Well the efficiency of heat exchange factor is not the only
efficiency. A purchased and installed product at 5% efficiency is much
more economical than a well designed, thought out, project that will
be implemented sometime after getting a 'Round Tuit


Le mieux est l'ennemi du bien. I'm better at thinking up things
than getting round tuits.


Efficiency of installation ease.
Efficiency of installation time.
Efficiency of product parts and pieces aquisition


I can relate to that, having spent about 40 hours in the last 2 weeks
visiting various plumbing supply stores. It's been fun learning names
of fittings, like "bullnose T" and "Dismukes crampon lifter."


Efficiency of marriage after the home space displacement.


Spouses care a lot more about what's on the lawn
or in the living room than what's in the basement.


Your spouse maybe, lots of others may diagree.
Efficiency of trial and error costs.


It might be nice to build more than one, with careful directions at
http://BuildItSolar.com


Efficiency of maintenance.


And only empty the crud once a year, using a hose instead of a toothbrush.


GFX need NO cleaning EVER, even when hooked to WHOLE house SEWER.

If you wanted to clean a GFX, its simple to remove and HOSE it down
also, but there is no need to do so.

Yours WILL need interior cleaning
Efficiency of computer time arguing about imaginary issues.


Some issues are more important than others, eg daestrom's.


Efficiency of home resale after the newfangled frankenstein
paraphenalia is seen.


This leads me to make things easy to remove.


"Robert Gammon" wrote:


Solar Flare wrote:

GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11


GREAT scoring system.


Nah. Efficiency should be 8 vs 7, a lower price should give me more
vs fewer points, convenience is TBD, and wives may like saving more
money, or having more to spend in other directions.

20 UPIPE=78.5'U-value of 10' section of pipe (Btu/h-F)
30 CFRESH=1.25*8.33'thermal capacitance of 10' of fresh water (Btu/F)
40 VGREY=10*3.14159*(2/12)^2'volume of 10' of greywater (ft^3)
50 CGREY=VGREY*62.33-CFRESH'thermal capacitance of 10' of greywater (Btu/F)
60 FOR SHOWER = 1 TO 1000'simulate showers
70 FOR M=0 TO 359'simulate 10 min shower + 350 min rest
80 IF M9 GOTO 200'rest vs shower
90 IF SHOWER 1000 GOTO 120
100 RHEAT=RHEAT+1.25*8.33*(100-TF(0))'reheat energy
105 GLOSS=GLOSS+1.25*8.33*(TG(9)-55)'greywater heat loss
110 PRINT 300+M;"'";M,TF(0),RHEAT,TG(9),GLOSS
120 TF(0)=TF(1)'move fresh water up
130 TG(0)=(100*CFRESH+TG(0)*(CGREY-CFRESH))/CGREY'move greywater in at the top
140 FOR S=1 TO 8'pipe section (9-fresh water in and greywater out)
150 TF(S)=TF(S+1)'move fresh water up
160 TG(S)=(TG(S-1)*CFRESH+TG(S)*(CGREY-CFRESH))/CGREY'move greywater down
170 NEXT S
180 TF(9)=55'move cold water in at the bottom
190 TG(9)=(TG(8)*CFRESH+TG(9)*(CGREY-CFRESH))/CGREY'move greywater down
200 FOR S=0 TO 9'rest
210 HEATFLOW=(TG(S)-TF(S))*UPIPE/60'heatflow into fresh water (Btu)
220 TF(S)=TF(S)+HEATFLOW/CFRESH'new fresh temp (F)
230 TG(S)=TG(S)-HEATFLOW/CGREY'new grey temp (F)
240 NEXT S
250 NEXT M
260 NEXT SHOWER
280 SHOWERGY=1.25*10*8.33*(100-55)
290 PRINT RHEAT,SHOWERGY,1-RHEAT/SHOWERGY

0 94.56091 56.6345 71.68895 173.7736
1 92.93514 130.1973 72.0242 351.0381
2 91.38136 219.9389 72.44145 532.6472
3 89.96538 324.4244 72.83433 718.3472
4 88.72086 441.8685 73.20448 907.9012
5 87.6472 570.492 73.55341 1101.089
6 86.72784 708.6885 73.88255 1297.703
7 85.94302 855.0568 74.19321 1497.553
8 85.27464 1008.385 74.4866 1700.457
9 84.70704 1167.623 74.76389 1906.248

1167.623 4685.625 .7508075

This is confusing. The greywater output seems to warm during the course of
a shower, but I wouldn't expect that in a real system with 100' of 4" pipe.



This stands to reason that greywater output will rise in temp inyour
heat exchanger as the time required to recapture the heat exceeds the
amount of time that the greywater remains in the heat exchanger. Need
higher surface area (i.e. longer, or larger diameter tubes).

Ecnerwal wrote:
In article ,
Robert Gammon wrote:


Nick's will have to be connected ONLY to non-toilet drains. Nick's will
have to be periodically cleaned of matter that goes down kitchen sinks
and out the clothes washer drain.


Connecting a GFX to a toilet drain is not going to be very sensible,
however, unless you heat your toilet water - makes the most sense when
connected to drains that might have hot water - putting it in the
blackwater stack just adds one more way to have a toilet flush make your
shower uncomfortable, and reduces the potential efficiency by reducing
the temperature differential across the heat exchanger.


Yes, there is no heat to recapture, UNLESS toliet supply is also hooked
to GFX heat exchanger.

The point to adding in the toilets is to make installation simple.
Locate the SINGLE sewer pipe in the basement that collects ALL waste
water, and insert the GFX into the pipe.

Running toilet water to the mix of effluents processed by the system
adds NOTHING to efficiency, but makes installation a BREEZE.

(in )
said:

| Solar Flare wrote:

much snippage throughout

|| Efficiency of installation ease.
|| Efficiency of installation time.
|| Efficiency of product parts and pieces aquisition
|
| I can relate to that, having spent about 40 hours in the last 2
| weeks visiting various plumbing supply stores. It's been fun
| learning names
| of fittings, like "bullnose T" and "Dismukes crampon lifter."

This may be some of the best and most encouraging news I've seen
posted to alt.solar.thermal!

I've admired Nick's tenacity in dealing with the math of solar issues;
but deplored his seeming inability to "get his wheels on the ground."

Nick, bless you! Get out even more. Take some of those fittings home
with you and play with 'em! Build at least rough prototypes of your
ideas and take pictures to share...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto

Robert Gammon wrote:
Solar Flare wrote:
GFX nick
efficiency 6 7
price 5 3
convenience 9 1
wife likes 6 0
----------------------
total score 26 11



GREAT scoring system.

Particularly since GFX is non clogging and works with ALL sewer waters
(grey and black).

Efficiency is NOT the only criteria here. If we recover 40% to 60% of
the waste heat, we have made MAJOR strides in overall DHW production
efficiency. Convenience, non-clogging, wife friendly are all MAJOR
concerns.
Price is NOT the only factor either, but price and efficiency are
Nick's main concerns.

Nick's will have to be connected ONLY to non-toilet drains. Nick's
will have to be periodically cleaned of matter that goes down kitchen
sinks and out the clothes washer drain.
None of these are concerns with GFX.
If we can afford one of these, either of these, these other factors,
besides price and efficiency may well be MORE of a concern to the rest
of us.



Nick would like us to rebalance somewhat.

GFX Nick
efficiency 6 8 give Nick the benefit of the
doubt on higher efficiency
price 5 8 lower price gets higher points
convenience 8 2 Nick must separate toilets from
processing, GFX takes ALL
wife friendly 5 1 GFX almost invisible, Nick's is
a largish stack of 4.5 inch pipe
Maintenance 10 1 GFX never needs maintenance,
Nick's will need at
least annual cleaning
------ -------
34 20

So use Nick's system if you are on a TIGHT, TIGHT budget and don't mind
the large coil of 4.5 inch black PE pipe in the basement, AND you can
isolate the toilet drains from all other drains.

Nick says GFX needs a toothbrush for cleaning. WHAT???? Its a straight
piece of 3 inch or 4 inch diameter copper pipe from 30 to 60 inches
long that the wastewater flows thru. If it ever needed to be cleaned,
its VERY simple to uncouple the clamps that hold it to the sewer,
disconnect the water (if proper disconnect fittings are installed,
usually not) , take it outside and flush the 3 inch or 4 inch copper
tube with a hose, perhaps running a soapy rag down the inside to rub
anuy residue off. However, the VERY VERY strong flow on the inside
wall of the pipe should keep the inside nearly spotless, subject to ONLY
the normal oxidation of copper in air

I can't as I have a slab foundation and NO basement (plumbing is buried
beneath the slab). The ONLY choice for me is a sewage ejector in the
corner of the garage, near where the main sewer line exits under the
slab with a GFX stack in the corner above the sewage ejector.

Robert Gammon wrote:

Running toilet water to the mix of effluents processed by the system
adds NOTHING to efficiency...

Wrong again, if the room temp is higher than the cold water temp.

Nick

Robert Gammon wrote:

Nick says GFX needs a toothbrush for cleaning.

Wrong again. Read much? :-)

... I have a slab foundation and NO basement (plumbing is buried
beneath the slab). The ONLY choice for me is a sewage ejector in the
corner of the garage, near where the main sewer line exits under the
slab with a GFX stack in the corner above the sewage ejector.

Au contraire. That way, you could easily use either heat exchanger,
and you might use the flat spiral version with no pump.

Nick

wrote:
Robert Gammon wrote:


Running toilet water to the mix of effluents processed by the system
adds NOTHING to efficiency...


Wrong again, if the room temp is higher than the cold water temp.

Nick


I just realized my error, corrected myself and said yes, heat inlet
water to toilets anyway to get a closer to a balanced flow, increasing
the efficiency of the heat exchanger

wrote:
Robert Gammon wrote:


Nick says GFX needs a toothbrush for cleaning.


Wrong again. Read much? :-)


... I have a slab foundation and NO basement (plumbing is buried
beneath the slab). The ONLY choice for me is a sewage ejector in the
corner of the garage, near where the main sewer line exits under the
slab with a GFX stack in the corner above the sewage ejector.


Au contraire. That way, you could easily use either heat exchanger,
and you might use the flat spiral version with no pump.

Nick


You are unaware of the terrain I live in. Ruler flat!!!!

Sewage ejector == PUMP

Yes I could use either one WITH A PUMP as there is NO WAY to intercept
the sewer ABOVE ground. No basements here except in high rise
buildings, certainly not in ANY homes.

In the 1200sq ft living space I have now, the ONLY unit that will work
is the GFX. There is no room for yours UNLESS it goes in the ATTIC!!!

Robert Gammon acts dumb as a post again:

Nick says GFX needs a toothbrush for cleaning.

Wrong again. Read much? :-)

... I have a slab foundation and NO basement (plumbing is buried
beneath the slab). The ONLY choice for me is a sewage ejector in the
corner of the garage, near where the main sewer line exits under the
slab with a GFX stack in the corner above the sewage ejector.

Au contraire. That way, you could easily use either heat exchanger,
and you might use the flat spiral version with no pump.

In the 1200sq ft living space I have now, the ONLY unit that will work
is the GFX. There is no room for yours UNLESS it goes in the ATTIC!!!

OK. I give up. You don't even understand "flat spiral."

Nick