GFX vs home brew

[nicksanspam]

Robert Gammon acts dumb as a post again:

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

Nick

[Robert Gammon]

Flat spiral == 7 feet diameter, 2 feet high. NO ROOM FOR THAT EXCEPT IN CEILING!!!

[nicksanspam]

... 4" high, fool.

Nick

[Robert Gammon]

Ok, 4 INCHES high actually 4.5 inches high as that is the diameter of your outer tubing.

Still 7 feet in diameter, it could only hang vertically on the garage wall, over thee plastic, steel, aluminum, paper recycling rack and the sewage ejector pump would sit under the rack. The sewage ejector pump would cost around $350. Punching a hole in the slab would cost another $350. Installing the sewage ejector in the hole, running power to it, hooking it up to the sewer, installing a vent pipe to the collection tank, piping in the potable water and back tothe hot water tank will cost another $500+ as I will NOT do this myself.

This is getting to be EXPENSIVE for a project that will save me maybe $10-$20/mo on my Natural Gas Plus Solar Hot water system.

Now in new house, not likely to install Solar, but could. DHW is likely to be a 190K BTU tankless model, and I could easily install either Nick's or GFX. MY choice, given that budget will NOT be a concern, will be GFX. May even plumb the GFX thru the geothermal heat pump as it will be in the same room, and preheat the input to he GFX - maybe overkill to do that, but anything will be possible.

[Solar Flare]

So you are saying "Better nick's wife batting him around than ours"?

[nicksanspam]

Mine objected to 300 55 gallon drums on the lawn. When I moved 200 into a greenhouse and the rest into the basement, that was OK. Go figure.

Fat plumbers in grimy jeans come in and say "Gimmie a 45 degree Thomson slidearm and a couple of 16" vertical Whittakers with the purple nibs."

Do what you do best. Lots of people can build things that don't leak. I'd like to know why the energy that flows into the gwhx is less than the energy that flows out during a shower, in that simulation.

My 4th HP digital camera stopped working. They seem fragile. Otherwise, you might see me stretching the curves out of 300' of 1" pipe with a tree and a pickup truck.

Nick

[nicksanspam]

Changing the heatflow from linear to a more accurate exponential (two caps equalizing voltage through a resistor) made little difference...

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 CSERIES=CFRESH*CGREY/(CFRESH+CGREY)'caps in series (Btu/F) 70 RC=CSERIES/UPIPE'combined time constant (hours) 80 EXPF=EXP(-1/60/RC)'exponential factor 100 FOR SHOWER = 1 TO 100'simulate showers 110 FOR M=0 TO 59'simulate 10 min shower + 50 min rest 120 IF M>9 GOTO 250'rest vs shower 130 IF SHOWER

[nicksanspam]

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 CSERIES=CFRESH*CGREY/(CFRESH+CGREY)'caps in series (Btu/F) 70 RC=CSERIES/UPIPE'combined time constant (hours) 80 EXPF=EXP(-1/60/RC)'exponential factor 90 FOR SHOWER = 1 TO 100'simulate showers 100 FOR M=0 TO 59'simulate 10 min shower + 50 min rest 110 IF M>9 GOTO 270'rest vs shower 120 IF SHOWER

[nicksanspam]

... 5 vs 3 100' pipes only raised the effectiveness from 68 to 77%. A 200' version makes 82%... 200' of 4" drainpipe would wrap around the lower 3' of an 86" diam x 48" tall STSS heat storage tank.

15 DIM TF(20),TG(20) 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 CSERIES=CFRESH*CGREY/(CFRESH+CGREY)'caps in series (Btu/F) 70 RC=CSERIES/UPIPE'combined time constant (hours) 80 EXPF=EXP(-1/60/RC)'exponential factor 90 FOR SHOWER = 1 TO 100'simulate showers 100 FOR M=0 TO 59'simulate 10 min shower + 50 min rest 110 IF M>9 GOTO 270'rest vs shower 120 IF SHOWER

[nicksanspam]

But that's pretty big. How about this?

We collect all the shower water in a tank, with an infinite cold water tank next to it, then circulate the cold water through a coil in the shower tank until it all cools to the cold water temp... Then again, infinite tanks are hard to come by.

So maybe mix hot and cold fresh water to 90 F and circulate that through the coil until the shower tank drops from 100 to 95, then pump some of the 95 F fresh water back into the hot water tank and add enough cold fresh water to make the fresh mix 85, then circulate for a while, then pump some

90 F fresh water back into the hot water tank and add enough cold water to make the fresh mix 80, and so on. How can we do this automatically, on a continuous basis? We need a 20 gallon expansion tank too. Lots of pumping, but little energy, if the hot and cold supplies stay pressurized.

Nick

[Robert Gammon]

At some point the water needs to be heated to about 140F to kill bacteria before use in showers and baths.

I fail to see the point of all this pumping and mixing between hot and cold sources. What do we gain by this??

Bronze Taco pumps are cheap and use less than 100W to move 10+Gal/Hr to

15 feet or more.

[Rod Speed]

No it doesnt.

[nicksanspam]

I've learned that further discussions with you would be pointless.

Nick

[Robert Gammon]

Do a little research and you will find that Canada HAS such a spec. Read about it today searching for the valve (Tempering Valve) that mixes hot water with cold to prevent scalding. Their spec says that hot water heaters must attain a temp of at least 60C (about 140F) in order to kill this bacteria, and that water heaters can frequently output 75C water (about 167F) Scalding occurs (and I was a victim of this at about age 4) most often in households that draw a bath using solely Hot water, then temper with cold to get the desired temp. I was impatient to get my bath that night, and due to the arrangement of water controls and my size, I could not reach the cold water control without climbing around the lip of the tub. Needless to ay, I slipped and dropped my foot into the HOT water. My ankle bone was VISIBLE thru the skin for several days after that.

[daestrom]

More like I expect. Your system's outlet temperature drops from the high of

94F the longer you run the shower. The fact that it's a 'batch' process allows you to get better performance than the steady-state parameters would allow.

But show the greywater too. As I said before, if the greywater is giving off less energy than the freshwater is picking up, then something's broke. I notice you chose to show the more optimistic of the two numbers. I'll bet the greywater shows more energy going down the drain than physics would allow if these numbers were accurate.

So then it's just a matter of adjusting gwhx versus shower time to keep performance high. Too long a shower, or too short a gwhx and performance drops.

How would two showers spaced fairly close together look? Looks like this would support four, 10-minute showers a day, spaced 6 hours apart right now.

daestrom

[daestrom]

But remember GFX can only recover heat from a 'running water' situation. So laundry (if you use hot water??), a bathtub, or a sink full of water used to wash dishes doesn't do *anything* in the GFX. It stores very little heat for recovery in these 'batch' mode processes.

It really only performs up to it's reputation with showers or if you run water continuously while doing the dishes or some such.

While Nick's is not as convenient, and it may have some long-term maintenance issues, it *does* recover/save energy from such batch processes. But with a total 'storage' of only about 12 gallons, it still wouldn't really help much in large bath-tub sort of thing (unless you bath in just 12 gallons of water).

daestrom

[Rod Speed]

Robert Gammon wrote

More fool canada. You cant ignore chlorination.

Separate matter entirely.

[daestrom]

Oh, I see you had done this in another branch. I'll go there and see "what's up"

daestrom

[daestrom]

No, I don't think this is the way to go. When using warm water to heat cool water, the smaller the temperature difference along each section, the better as far as entropy goes.

That is one of the reasons why counter-flow hx are so good. The warm water is never more than a few degrees above the 'cool' water. Where the 'warm' water is the hottest, the 'cool' water has already been heated up to almost the same temperature. And where the 'cool' water is the coldest, the 'warm' water has already been cooled to almost the same temperature.

Compared to a parallel flow, where the 'warm' and 'cool' water start out with vastly different temperatures and aproach each other over the length of piping.

With your 'infinite' tank idea, you end up with very cold greywater, but the freshwater is hardly warmed at all. Making the two tanks nearly equal, you approach the limits for a parallel flow system (e.g. grey and fresh leave at the same temperature, about (100+55)/2 = 77.5F.

I take it you've considered what the pressure drop would be with the flow rates? Check the greywater side pressure drop carefully. Although you have larger x-section, the *available* driving pressure for a shower drain is just a few feet of water.

daestrom

[daestrom]

Well, if by 'spiral' you mean some sort of serpentine.

Since the pipe is nominally 4", to get a spiral (even a 'flat spiral'), you need at least 8" where one turn crosses over the other ;-)

7' diameter coils for 100' total length means about 18 turns. Coiled in a vertical stack and then 'shoved' off to the side to spread the coils out nearly flat would take a floor space 7' wide and about 72' long (18 turns spaced about 4' apart). That's a tad much floor space for most folks ;-)

daestrom