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Rocket stove heat question for an aquaponics greenhouse.  RSS feed

 
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Hello to the great gathering of wisdom and knowledge for all things massively rockety!
The question I have is this,
I just redid my rocket stove yesterday, went from a muchly burnt out steel J-tube rocket stove to a brick and cob rocket stove with a clay/pearlite riser. How I am heating my greenhouse is I am heating the water for the fish system with the stove.
I've got 50' of 1/2" stainless steel tubing coiled inside the barrel, so I am essentially heating mass, water rather than air, and this works well, however, it seems to me like I had better heating of the water with the steel rocket stove.
The brick stove is running seemingly perfectly, is very rockety, have no visible smoke or anything coming out of the chimney pipe, (It's a 6" system BTW) so it seems to me that the system is running good.
What way would I get the most heat to the barrel itself and not out the chimney? It seems like with the single wall steel pipe the barrel was hotter as well. With the brick system I've got a 6 inch inner pipe with a 10" outer pipe and I packed it with pearlite/clay.
If I were to use steel instead of the highly insulated method would I get more heat the the barrel?
Any and all input is greatly appreciated.
Thanks much!
Wendell
 
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How long and how often are you firing it?

One major difference is the mass of the masonry. Before, the steel would heat very quickly and anything it did absorb would be conducted through the wall to the barrel. Now all that mass absorbs heat,a lot more than the steel and instead of passing it on right away holds and radiates it for a long time.

If the cob is still a little wet or the masonry is cold by the time you come back to burn again you spend some energy getting the temps back up. Which would be heat not getting to your coil which explains the perceived drop in performance.
 
Wendell Keresztyen
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Mike Leo wrote:How long and how often are you firing it?

One major difference is the mass of the masonry. Before, the steel would heat very quickly and anything it did absorb would be conducted through the wall to the barrel. Now all that mass absorbs heat,a lot more than the steel and instead of passing it on right away holds and radiates it for a long time.

If the cob is still a little wet or the masonry is cold by the time you come back to burn again you spend some energy getting the temps back up. Which would be heat not getting to your coil which explains the perceived drop in performance.


I fired it yesterday for probably 3 hours, then today for probably 7 hours, it's going now as we speak.
 
Mike Leo
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Is the exhaust still very hot?

Are you using any storage mass after the coil in the barrel?
 
Wendell Keresztyen
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Mike Leo wrote:Is the exhaust still very hot?

Are you using any storage mass after the coil in the barrel?

The exhaust is hot enough to where I can't put my hand over the chimney. I can't touch the chimney pipe either right before it exits the greenhouse. I am not using any other mass. It (the exhaust)goes out of the barrel and then out of the greenhouse.
 
Mike Leo
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Adding more thermal mass to the exhaust (if you can) would help increase the temp of the system day to day as it would store more heat longer. That might help.

You might also consider getting more of the SS tubing and wrapping it around the exhaust. The coolest water should come from furthest away and as the coil approaches the barrel it will be preheated further reducing the amount of wasted heat.

Ideally I think you would want the preheating coil wrapped in thermal mass for as much of the system as you can. Either way, good luck.
 
pollinator
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Wenden K. : I do Not like, nor trust your system, and I Know it is not safe, please take the time to read this as your next several choices will affect your life, and
the lives of people you know and who love you !

A well working rocket mass heater quickly and very efficiently produces Temperatures ranging from a efficient 1000-1200 degrees F, 550-670 C, easily seeing
2000 degrees F, with excursions to 2400 degrees F 1300C-ish

Because water Can Not be heated (Except under High Pressure), to temps above 212 degrees F or 100 C without flashing to steam, expanding 1600 Xs, we have
to respect the awesome power at our finger tips ! We call that Moment when water 'flashes to steam' Boom=>Squish !

Please take the time right now to goto-> U-Tube and find and watch the Myth Busters '' Exploding hot water heater Episodes, think the Boston Marathon
Bombing only with more Full Thickness And Full Body Burns !

I expect that your original system seemed to be working better as a water heater before was your exhaust Temperatures were not running as hot, this would be
due to the rapid cooling of your burn temps by the cold water in your other system !

There is NO safe way to run enough water through 50' of 1/2 inch Inside Diameter tubing even using high volume/pressure pumps due to the high friction loss in
the system at that Inside Diameter! With the water in your piping having such long dwell times, and potentially exposed to such high temps, the likely hood of a
hot spot where your water can 'flash to steam' is near 100% !!!

While it would be much safer to build a more conventional rocket mass heater, and then wrap your much larger Diameter Tubing around a thick-walled piece of
metal that is itself buried in the cob of your Thermal Mass to which would buffer the expected initial Temperature -500 F-ish, the temperature spread is still to high
to be safe during normal operation and I could fill a book with ways a seemingly minor flaw in the system could be deadly !

And at this time you have approximately 60% of your heat energy wasted up your vertical chimney, This is the place for your greatest efficiencies to come from!

Hopefully you will be able to independently verify much of what I have shared, and you will be looking for quick easy fixes for these problems, please come back
here to Permies.com where your fellow members can discuss your plans and find BOTH problems and solutions and improvements in your systems ! BIG AL
 
Wendell Keresztyen
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allen lumley wrote:Wenden K. : I do Not like, nor trust your system, and I Know it is not safe, please take the time to read this as your next several choices will affect your life, and
the lives of people you know and who love you !

A well working Rocket Mass heater quickly and very efficiently produces Temperatures ranging from a efficient 1000-1200 degrees F, 550-670 C, easily seeing
2000 degrees F, with excursions to 2400 degrees F 1300C-ish

Because water Can Not be heated (Except under High Pressure), to temps above 212 degrees F or 100 C without flashing to steam, expanding 1600 Xs, we have
to respect the awesome power at our finger tips ! We call that Moment when water 'flashes to steam' Boom=>Squish !

Please take the time right now to goto-> U-Tube and find and watch the Myth Busters '' Exploding hot water heater Episodes, think the Boston Marathon
Bombing only with more Full Thickness And Full Body Burns !

I expect that your original system seemed to be working better as a water heater before was your exhaust Temperatures were not running as hot, this would be
due to the rapid cooling of your burn temps by the cold water in your other system !

There is NO safe way to run enough water through 50' of 1/2 inch Inside Diameter tubing even using high volume/pressure pumps due to the high friction loss in
the system at that Inside Diameter! With the water in your piping having such long dwell times, and potentially exposed to such high temps, the likely hood of a
hot spot where your water can 'flash to steam' is near 100% !!!

While it would be much safer to build a more conventional Rocket Mass Heater, and then wrap your much larger Diameter Tubing around a thick-walled piece of
metal that is itself buried in the cob of your Thermal Mass to which would buffer the expected initial Temperature -500 F-ish, the temperature spread is still to high
to be safe during normal operation and I could fill a book with ways a seemingly minor flaw in the system could be deadly !

And at this time you have approximately 60% of your heat energy wasted up your vertical chimney, This is the place for your greatest efficiencies to come from!

Hopefully you will be able to independently verify much of what I have shared, and you will be looking for quick easy fixes for these problems, please come back
here to Permies.com where your fellow members can discuss your plans and find BOTH problems and solutions and improvements in your systems ! BIG AL


I agree water heaters will explode but then again there is no outlet for pressure on a water heater until you open a valve. In an open loop system like mine is if the pump were to quit(which it has before) the water starts to boil inside and just pushes the water out. One day the pump came unattached from the line for a minute or two and I caught it and hooked it back up and the water that came out was probably 130-140 degrees, still nowhere near steam flashing after that long.
In my system I have a 600gph pump pushing through, and I have maybe 3 or 4 gpm coming out the other end.
The only travesty I see happening is if the pump I melt a stainless line and get water everywhere. the temperature differential or Delta T of my water in and out is never more than 10-15 degrees.
 
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Just going to second Allen Lumley's opinion. I think you have a potentially explosive situation on your hands. Your system may be an 'open loop', but when a given section flashes, the exansion will be far to rapid for your tubing to handle. Water will not push out the far end, instead your tubing will explode.

Please do a little more research, Allen's suggestions are very sound. I could be wrong, but it doesnt sound like you have a safe situation at all. Heating water with a high temp source is dangerous business.

Please let us know what you learn, so we can all learn together.

good luck!
 
Wendell Keresztyen
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Adam Klaus wrote:Just going to second Allen Lumley's opinion. I think you have a potentially explosive situation on your hands. Your system may be an 'open loop', but when a given section flashes, the exansion will be far to rapid for your tubing to handle. Water will not push out the far end, instead your tubing will explode.

Please do a little more research, Allen's suggestions are very sound. I could be wrong, but it doesnt sound like you have a safe situation at all. Heating water with a high temp source is dangerous business.

Please let us know what you learn, so we can all learn together.

good luck!

It ran for two years on the previous system with no ill happenings. Normal temperature of water coming out is about 90 degrees, if that. I just looked it up, the steel pipe I'm using has a burst pressure of 6000 PSI, the water heater in their experiment burst at 330ish. Im not seeing how water in a 350 degree barrel can steam flash and burst 6000 psi pipe, rather than push the water out of the end. It's not adding up to me.
 
allen lumley
pollinator
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Wendell Keresztyen : Thank you for clarifying that this is an open system, something that Mike Leo was apparently able to work out better than me! If I over-
reacted, it was both a matter of immediate safety and a necessity to protect the safety of your fellow members who could still have missed that point,
however I still have issues !

We Are all learning here, I only recently became aware of a strong bias against using any Copper, Brass, or Bronze in Aquaponic use, However- there are
problems connected to sourcing Stainless tubing, irregardless of the direct supplier, approx. 80% of Stainless Steel available for Wholesale/Retail purchase
was manufactured by Pacific Rim countries with uncertain Quality Control, while all Stainless manufactured within the U.S. is Most certainly worked in Low
humidity environments I doubt if production even slows down on Rainy days overseas with resulting wide variations in protection from Hydrogen Embrittlement,
and High Temperature Hydrogen Attack !

I must say that I am impressed that you got ~ 2 years ~ out of a mostly steel built Rocket type heater, However that units past performance can not be used
to gauge the longevity of your present set-up even though its failure does show a familiar pattern, I wonder if the steels in your old unit were acting like a
Sacrificial Anode to reduce the effects of Hydrogen on the Stainless tubing ! Were you able to re-use all of the S. S. tubing when you rebuilt your Unit ?!!

I am sure that you are aware of the affects of laminar flow on the surfaces of all vessels/and tubing subjected to a flow through of Gases or Liquids, this would
Not effect the accuracy of the Temps measured at your barrels surface, but nether would it represent the temperatures of the gas flowing through 1'' away,
especially if your S. S. Tubing is inducing turbulence ! Actually I find those temps to be low, this could be due to the heat extraction to your Aquaponic system!
Still, there are many ways for air to be introduced into the system, and a air bubble trapped due to the heat stress and flexing of your tubing creating problems
right at the Heat Riser / Barrel interface could expose the tubing to temperatures well over 1000dF

I am assuming that even it you had municipal water available for makeup water that it would have to stand and out-gas the Chlorine before it could be added
to the system! Do you have some kind of floating cover over your tanks ?!

If we go by the rough rule of thumb, that with an Average rocket mass heater RMH, you are radiating 40% off of the barrel, and 60 % should be going to a
Thermal Mass Then your system is probably running Probably about 50 - 50 , depending on the 'dwell time' for your gases. This is mostly affected by the height
of the Heat Riser, the height of the Barrel and the Barrel Gap, and the height of the external chimney, the effects of the Horizontal Chimney, Its Elbows and 'T's
and any interior roughness are all negative !

Because of a continuing bias against attempting to extract the heat energy for any form of hydronic heating sooner than the Cob Thermal Mass little research has
been done in extracting heat from the drum ! It is a little bit pre-mature to suggest a Layer of Cob on the outside of the barrel to decrease the amount of heat
radiated off of its surface, I expect that there might be a small rise in temperature in the water as it then could extract more heat energy from the gas flow.

What I suspect would happen is more heat would be shunted to the vertical chimney and exhausted out of the building- Which brings us full circle, a Fully charged
raised bench that is waist high or a little higher (your back will thank you!) both creates the cold sink and provides the heat directly to where the plants are, or
can be under or completely surrounding your aquaponic set up, failing in that a much safer Hydroponics set-up within the thermal mass still gives you what you
want !

I come from a long line of 'If it works, don't 'fix' it if it doesn't work- kick it people, but a good short term goal would be for a 12 vt - 24 volt hydronic circulating
pump with a couple of batteries an a trickle charger to carry you through 48 - 60 hours of power outage !

I look forward to pictures or sketches showing your present set-up, For the Good of the Craft ! Big AL
 
Wendell Keresztyen
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Here are videos!
Part 1

Part 2

Part 3

Part 4

Let me know what you guys think.
 
allen lumley
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Wendell K. ; Congratulations ! You have built a successful sub 6'' system with a sacrificial Lining for your Heat Riser, w/ a vertical chimney made with corrugated piping
and no horizontal chimney or thermal mass! Your build will serve to give great hope to some of our fellow members who have trouble assembling enough parts and
materials -that quite a bit of leeway is possible !

Usually we recommend that for a first rocket mass heater RMH that a slightly more conventional, or traditional RMH is planned for on a first build ! We like everyone
to have success with their 1st RMH !

I would recommend finishing burning/sanding the rest of the paint off of the outside of your Barrel, before you go much farther, it is not healthy to breath that toxic
Crud!

Only running Your RMH will show you when the sacrificial inner form of your Heat Riser will fail and need to be picked out. If you are lucky most, if not all of it will
come out through the Burn Tunnel and Feed Tube, without ever buckling and blocking the flow of your hot Exhaust gases ! There are a few reports of the inner steel
liner expanding and cracking the Perlite and Clay Slip Heat Riser. Many people are going to cardboard sonotubes that burn out on 1st firing, and Double thickness
Heat Riser Walls !

As the Heat riser is the most fragile part of the whole build, Be sure you have help removing and placing the barrel over the top ! For the good of the Crafts !

Think like Fire! Flow like a Gas! Don't be the Marshmallow! As always, All Questions and comments are welcome and solicited ! PYRO - Logically Big AL !
 
Wendell Keresztyen
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allen lumley wrote:Wendell K. ; Congratulations ! You have built a successful sub 6'' system with a sacrificial Lining for your Heat Riser, w/ a vertical chimney made with corrugated piping
and no horizontal chimney or thermal mass! Your build will serve to give great hope to some of our fellow members who have trouble assembling enough parts and
materials -that quite a bit of leeway is possible !

Usually we recommend that for a first Rocket Mass Heater RMH that a slightly more conventional, or traditional RMH is planned for on a first build ! We like everyone
to have success with their 1st RMH !

I would recommend finishing burning/sanding the rest of the paint off of the outside of your Barrel, before you go much farther, it is not healthy to breath that toxic
Crud!

Only running Your RMH will show you when the sacrificial inner form of your Heat Riser will fail and need to be picked out. If you are lucky most, if not all of it will
come out through the Burn Tunnel and Feed Tube, without ever buckling and blocking the flow of your hot Exhaust gases ! There are a few reports of the inner steel
liner expanding and cracking the Perlite and Clay Slip Heat Riser. Many people are going to cardboard sonotubes that burn out on 1st firing, and Double thickness
Heat Riser Walls !

As the Heat riser is the most fragile part of the whole build, Be sure you have help removing and placing the barrel over the top ! For the good of the Crafts !

Think like Fire! Flow like a Gas! Don't be the Marshmallow! As always, All Questions and comments are welcome and solicited ! PYRO - Logically Big AL !


Hello! Yah, It works, but is not the most efficient of systems. If you watch the older video I have posted I show the whole greenhouse, you can see there is hardly any room in there. I kindof need to shimmy when walking inbetween the main fish tank and the grow beds.
If I redid it I think it would be neat to steak out the area, run your piping from the barrel, and then pour a slab to cover it, in floor heating the rocket mass heater way. I probably would not use the corrugated dryer vent for that haha.
I'm going to redo the exhaust so it doesn't look so ghetto. Run it out properly and put it above the ridgeline with a proper chimney cap.
Tho I don't need it for draft purposes, the thing drafts so hard. If there's coals in it and you put wood on it there's no need to blow on it, it'll start itself up.
 
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