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RMH in emergency shelter

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posted 15 years ago

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Well I started raising the floor in my 10'dia. sweat lodge because of the location and water table being so near the surface on my property. I cut the top 1/3 off my experimental 55gal pocket rocket and used it to line the rock pit.
This is when my mind started to work on the what if-f's.
I put the shorted version of the pocket rocket inside the lodge and put an 8'' feed in the top like a conventional pocket rocket. I then slid some 6'' stove pipe over the 5'' pipe to create a double wall exhaust. Inside the stove I attached a pc. of metal hanging down 6'' from the top of the lid (creating a baffle of sorts) forcing the flame out and around instead of just going straight up and out.
I got to thinking of thermal mass in the floor (ground).
This could become great for homeless dwelling spaces.

Has any one else considered this.

paul wheaton

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posted 15 years ago

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I know that folks have used a floor for the mass before. Is that what you are asking?

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Jami McBride

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posted 15 years ago

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Never having built a RMH it's a bit hard to follow your description. Can you post images, links or other such visual aids

If your on to something I want to understand it - that's for sure!

Ernie Wisner

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posted 15 years ago

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yep done it to what do you need to know. i will give the fist consideration free
you need to isolate the thermal mass from the surrounding earth. in other words you will want an insulation layer around the floor you are planning to heat. so you figure your pipe is 8" and you want 4 inches over the top of the pipe and you want another five or six inches below the pipe your insulation trench needs to be 16 to 18" deep. a good thickness is 1 inch. you are gonna want this around the entire perimeter. since you are on a high water table you will want to do drainage in the isolation trench so your actually talking about 22 to 24 inches deep.

Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info

Anonymous

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posted 15 years ago

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Well lets say it is located without the water problem.
What would be a good thermal break, styrofoam is used in frost protected shallow foundations under the concrete flores.
Could a layer of straw be used ?

I have another thought of routing the exhaust of the pocket rocket out the bottom side of the barrel. Taking 2- 6'' pipes straight out and 18'' away from the barrel one going rt. and one going lft. making a circle around the barrel and then turning and exiting outside.
And have a horizontal air intake coming into the barrel just below the feed tube. The exhaust tubes exiting the structure could have the air intake between them.

What about a rocket mass heater without a heat riser.

paul wheaton

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Location: missoula, montana (zone 4)

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posted 15 years ago

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woodman wrote:

What about a rocket mass heater without a heat riser.

I don't understand this statement. Surely you don't mean to take out the combustion chamber.

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Anonymous

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posted 15 years ago

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Take out the vertical and keep it all horizontal. Could it still draw.

Ernie Wisner

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posted 15 years ago

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foam, perlite, air gap, straw in that order of effectiveness.

you need a push system pocket rockets are a pull system.

the last is a no unless you have enough draw.

you are now outside the rocket stove realm.

charles c. johnson

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posted 15 years ago

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could you set the heat riser to 30 degrees? or maybe just 3-4 inches higher than back wall of chimney?

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ronie dean

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posted 15 years ago

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woodman wrote:
Take out the vertical and keep it all horizontal. Could it still draw.

If you have a fan outside in the chimney sucking the smoke out.

Otherwise NO it wud burn and smoke straight up the load chamber into yer room.

--

The vertical chamber heats up - hot air rising causes a high pressure area - and the upward pull of the high pressure area causes a low pressure area behind it at the air intake. (Sucks air at the intake and pushes air out the exhaust.)

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

paul wheaton

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posted 15 years ago

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Somehow, I thought it was the expanding heat wanted to go up at that point. A convective heat thing.

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ronie dean

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posted 15 years ago

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Yes i forgot to mention that the hot air is expanding also... hot expanding gases rise and pull cooler air in behind it.

It is literally the same thing that causes the wind in nature. A high pressure area (usually down south in the winter) has hot air rising and expanding and that pulls cooler (northern) air in to equalize the pressure.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

Ernie Wisner

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posted 15 years ago

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laying it out flat like that is simply building a box stove. if you want a box stove there are several on the market to choose from. the rocket wont work in that configuration.

ronie dean

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Location: NW MO

posted 15 years ago

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Ernie wrote:
laying it out flat like that is simply building a box stove. if you want a box stove there are several on the market to choose from. the rocket wont work in that configuration.

Yes I thought that too... you would have an inefficient fireplace or box stove.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

Ernie Wisner

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posted 15 years ago

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uh look I am not trying to shoot down dreams or good ideas. please do keep working on a design. I would suggest however; that you go to your library and look into:
Fluid dynamics,
laminar flow,
hot stack effect,
fire behavior,
and something about how fire behaves in a small space. those are some of the basic principals the stove was designed around; and its what we teach in our fire science portion of a rocket stove work shop.

I for one would say you need to stop thinking of fire as air and start thinking of it as a fluid. it will solve allot of misconceptions about how it moves.

ronie dean

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Location: NW MO

posted 15 years ago

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Sorry I sometimes call gases - air, as it is the most common gas that everyone knows about.
-------------------------

Well i could be wrong Ernie, but i think that the fire is causing the gases in the enclosed space, to behave like a fluid. The fire would be a chemical reaction between fuel, oxygen and heat (Oxidation Reduction). The heat ,that the chemical reaction produces,(and the combustion gases) is causing a rapid expansion of gases in the enclosed space that makes a high pressure area which causes a vacuum behind the rapidly expanding gases. Atmospheric pressure then moves air into the vacuum... The same thing that happens with a water pump (note that the hot gases are lighter than air and fluid water is not).

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

Anonymous

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posted 15 years ago

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The stove might need a draft starter fire near the chimney to get it going.
This would be in the center of a 10'-12' dome shelter and would be nice to have a cook surface that wouldn't get so hot that it would run you out of there before the ground mass has a chance to heat up.
The air inlet is on the left of the immage.

Ernie Wisner

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Location: Tonasket washington

posted 15 years ago

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ronie from the fire box to the manifold you got it. like a fluid fire has to have turbulence and it goes up generally; as soone as its on the top of the heat riser it becomes a push system the rules change due to this.

From the manifold to the outlet all the rules change again due to the amount of water vapor and the robbing of heat by the mass.

Woodman try it but i dont think the stove in the drawing will work. you got to many things working against you.

ronie dean

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Location: NW MO

posted 15 years ago

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Wood , I guess, now, that the reason that you are determined to cut out the heart of the rocket heater (the vertical riser) is that you don't want it to heat yer room too quickly and keep the floor cold..?

The diagram you show looks like it would still burn straight up into the load chamber, unless you had a big fan in the exhaust, working constantly.

If you insulate the floor, as Ernie suggests, it will help.

Maybe you could set up a floor heat system by burying tubes or hose in yer floor. Then build a regular RMH - heat water on it- and pour the hot water thru the floor tubing.

Sometimes the answer is not to cross an old bridge, nor to burn it, but to build a better bridge.

Ernie Wisner

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Location: Tonasket washington

posted 15 years ago

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actually you can bury the whole system in the floor. thats what i would do.

i would dig the perimeter insulate it then dig the stove into the floor running the ducting under ground in a roughly circle exhausting it out into a pit or something. what you will have sticking up is the barrel and you should have the top of the feed tube at floor level. remember to insulate under the burning part of the stove (burn tunnel and manifold).

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