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Post by Dan (Upstate NY, USA) on Jan 4, 2012 13:31:15 GMT -8
Same question but for the hear riser.
I have the fire brick to built the heat riser but I could get a hold of a 1/4" (6.35mm) steel 8" (20.32cm) pipe, which do you think would last longer?
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Post by Donkey on Jan 4, 2012 21:47:45 GMT -8
I like doing it with metal, 1/8 inch or better steel is nice, thinner stainless works.
Metal can be insulated REALLY well while brick tends to have higher thermal mass. Higher mass heat risers take a little longer to get fully hot, a little longer to really kick into action.
I use black, single wall chimney pipe and insulate around it with pearlite/clay. I'll go a little extra heavy on the clay slip, single wall stovepipe WILL burn out and I want the pearlite/clay mix to hold together well. I try to hold off on plasters right away and just live with the thing for a while. When the stovepipe does burn out, I'll take off the barrel, open up the stove, give it a good cleaning, pull out the metal shards and do any last minuet fix/adjustment. After all that and things are still working fine, THEN I go ahead and plaster it and make it pretty.
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Post by Dan (Upstate NY, USA) on Jan 5, 2012 22:20:44 GMT -8
Thanks Donkey, I'll post pics as I continue...
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Post by canyon on Jan 6, 2012 11:52:26 GMT -8
I have built several with steel pipe heat risers and now have come to the conclusion that refractory brick is how I will do them now. The steel pipe will not last as long. Especially 8" will burn away quicker than I thought with the demanding heating use that we have here in Alaska. If you are in the warmer climes with not so heavy use expected, steel is much easier and as Donkey says lower mass for heat up. If you are in the great white north or equivelent and really need to heat for a serious winter I recommend refractory brick for long term.  |
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Post by Rinchen on Mar 27, 2012 23:34:06 GMT -8
I like doing it with metal, 1/8 inch or better steel is nice, thinner stainless works. Metal can be insulated REALLY well while brick tends to have higher thermal mass. Higher mass heat risers take a little longer to get fully hot, a little longer to really kick into action. I use black, single wall chimney pipe and insulate around it with pearlite/clay. I'll go a little extra heavy on the clay slip, single wall stovepipe WILL burn out and I want the pearlite/clay mix to hold together well. I try to hold off on plasters right away and just live with the thing for a while. When the stovepipe does burn out, I'll take off the barrel, open up the stove, give it a good cleaning, pull out the metal shards and do any last minuet fix/adjustment. After all that and things are still working fine, THEN I go ahead and plaster it and make it pretty. Hi Donkey, Does that mean that after the pipe has been burned out and you have cleaned out the metal shards, you run the system with a perlite/clay heatriser only, without the metal pipe inside? How does this hold up over time? Has the perlite/clay not cracked due to the metal pipe expanding under high heat? Could you then just as wel cast perlite/clay around a pipe, let it dry and then take the pipe out and use the perlite/clay heatriser in the system without a metal liner? |
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Post by Deleted on Mar 28, 2012 3:07:12 GMT -8
For my experiments I have done this several times.
Cast with a mix of paper, cat litter, kaolin and a bit cement.
I have oiled the tubes a bit to make them easier removeable.
With three tubes one can cast heat ricer, burn tunnel, and feed chamber in one pice.
After removing the horizontal tube the open end can be closed.
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Post by Donkey on Mar 28, 2012 6:58:32 GMT -8
Rinchen: Yep.. You could build the works out of paper mache or cardboard and burn it out later. You've just got to get the mix right. Also, you need to know if your local clay soils can stand up to the abuse, mine can. Gotta test, test, test. @karl, you're using portland in that mix, correct? how does it hold up? It's pretty likely that you don't (actually) need the cement. You may wish to try on without and see the difference.
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Post by Deleted on Mar 28, 2012 8:39:03 GMT -8
allmost any kind of clay soil can be improved by mixing in some alumina.
I'm using Trass cement, which is a mixture of Trass a natural pozzolanic mineral
and burnt lime.
It's bit more heat resistant than portland, but slower reacting.
As I'm using only around 10% portland would do it too.
I have testet it during my last visit of our house in the Phils.
In a few weeks I will be there again.
Patience has never been one of my strong points.
As I'm using a lot of paper in the mix it would dry very slowly, especialy in the winter.
At such low temperatures it would have taken several days, maybe a whole week, to get enough green strengs to remove the tubes.
Wit a bit cement it becomes hard in short time and schrinks a lot less.
The mix then withstands forced drying by firing very well.
Once the water has been forced out the fire in it becomes hot enough to turn the mix into lightweight ceramic.
And it's water proof even at the parts which didn't became hot enough to be turned into ceramic.
Placing the whole thing into a fire or burning it in a kiln would be even better.
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Post by kemperextremegreen on Jul 9, 2012 7:28:02 GMT -8
Hello all, This is my first post/question. I just dicovered rocket mass heaters 4 days ago. In this thread Donkey mentioned stainless as a riser. Wouldn't it last indefinately?
I was reading another thread this weekend in which Dakman was participating. I saw a lot of potential with the model shown in reply #19 dated Feb 2011. I am also of the opinion that he should focus on a continuous firing and use thermal storage.
I am building an off the grid - straw bale house and I see the beauty of the rocket mass heater for that application. And...
I have a current project that is much larger scale than anything I have seen in my short time researching rocket stoves. It is a 19,000 square foot slab inside a commercial building that was designed from the ground up to be super energy efficient. The entire slab is insulated and heated with hydronics. The ultimate plan is that Solar collectors on the roof will capture heat energy to store in a 1,200 gl. thermal bank. The back up for solar is to be wood fired heat and the secondary backup is what we are currently operating on which is a propane fired boiler "Munchkin".
So the subject here is wood fired heat. I have been expecting to use a wood gasification boiler such as Tarm. It's job is to recharge the delta T in the heat bank to aproximately 170*. The circulator system sends water to the zones at 130*.
The calculated maximum load in the building is 125,000 Btu. I need to get wood sourced heat installed before next winter.
Is there a rocket water heater in existance that is being used for an application similar to mine. Do any of you have opinions about feasibility of creating such a heater.
I am a fairly handy fabricator/builder/welder. I tend to think outside the box much like many of you. My intuition tells me that this is good stuff, and yes I know the devil is in the details. I also believe in keeping systems as simple as possible and I think the delta T of 40* in a 1,200 tank gives enough buffer to stay well clear of critical temperatures. I really don't want to play with bombs.
I am hoping to benefit from your experience with this technology and that you might speed my learning curve.
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Post by Deleted on Jul 9, 2012 8:32:36 GMT -8
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Post by satamax on Jul 9, 2012 19:57:04 GMT -8
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Post by kemperextremegreen on Jul 22, 2012 14:07:48 GMT -8
Thanks Karl,
Excellent article! It makes it very clear that steel, even stainless is not a good long term solution. So my next question is regarding clay sewer pipe. Has anyone done any experiments with using the appropriate size sewer pipe insulated for a heat riser.
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Post by Donkey on Jul 22, 2012 22:06:21 GMT -8
Clay sewer pipe heat shocks, breaks up and eventually falls in. Sorry.. I've tried it.
Maybe you'll get lucky (or I got unlucky) no harm in trying it again in an experimental setting..
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Post by Deleted on Jul 23, 2012 4:38:45 GMT -8
Clay sewer pipes are not built to withstand heat.
Even clay chimneys are only build to withstand 400°C-600°C.
I have cast all my rockets around tubes.
Plastic tubes need to be removed.
Paper or even thin metal will burn out.
Square tubes for casting can be build from plywood.
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Post by ashurbanapol on Oct 17, 2012 8:08:09 GMT -8
I'm a career blacksmith metal artist with 45 years professional experience and I build a lot of gas forges and metal melting furnaces ( Probably 20 or so). Stainless does not hold up enough at high temperatures (over say 1500 F) for any long term use. It does not oxidze as quickly at that temperature, but it's (stainless) quality tends to break down at high heats. Welders experience this and it is a skill to weld and retain anticorrosion properties. After forging the surface of the metal will rust due to cahnges from the heat. In a furnace this is constantly happening. It will last longer than mild steel up to certain temperatures. Also, at high temperatures wood ash acts to break down a lot of refractories. High aluminate cement content will help prevent this; coating Kaowool or Insulwool with Satanite is a good idea. Since I currently heat with a plumbed outside wood boiler, I am interested in heating water with one as well. I just learned of Rocket Thermal Mass heaters and have some potential ideas based on experience, but it will take some experimentation. The outside wood boiler works well, but uses a lot of wood, though I have a top of the line one (Central Boiler). Problem for me is twofold - - not wanting to feed to stove too often so when I'm away our conventional plumbing does not freeze and so simplfy life. Problem with woodboilers besides the large wood use is the demand for electricity to move the heated water and run the blower. I previously lived in a simply heated earth sheltered house, but this was my wife's house and the attached plumbed studio also needs heat. Still may build this into the house as backup heat while I experiment, but, of course $ is low and an issue.
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