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Post by marthale on Mar 8, 2019 22:25:29 GMT -8
I have been thinking about making a Rocket mass heater with a super insulated thermal mass.....
But here is the twist....
Imagine that you have the standard Rocket Mass heater with barrel, with pipes that go thru cob to heat the cob.
Now, what if this was outside and the pipes that go thru the cob and the cob was in an insulated box, and on top of this box was an insulated chimney that routed the heat into the home via a window, then a insulated chimney.
I would be using the heated thermal mass like a heat exchange pipes on the bottom heating the mass, and pipes on the top taking that stored heat and releasing it into the home at a fixed rate.
I was thinking that one could setup a tent in the home and have this heat constantly feeding that tent thru the night....
I having a mobile home considered making this directly under my trailer so that I could cut a hole in the bottom of my floor that would allow heat to come up from the thermal mass, and the rest of the mass would be highly insulated.
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Post by gadget on Mar 8, 2019 22:50:27 GMT -8
My first concern with a RMH that is outside is who gets to go out every 10 minutes and feed the fire?
I see your challenge with a mobile home and am guessing that is why you want the RMH outside due to the size and weight?
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Post by marthale on Mar 9, 2019 7:20:05 GMT -8
Yes, the plan is to use a 8 inch tube combine with Peter's marvelous batch box design to heat a large mass up quickly ( in theory ) I have never had a rocket stove mass, but I have seen a COB oven operate, and I have seen them heat up a huge mass that stays hot for days.
Perhaps what I need is a cob oven design so that I can heat up a huge mass and then pull the air out via blower as I need it.
I am thinking perhaps a dirty cob oven style would save me much tubing.
Yep I want a a fire that heats up a large thermal mass then trap that heat for me to siphon off of it. That is my theoretical design.
I was watching a film on kilns last night and I was looking at how they would use the heat off the kiln to dry out other clay material as it cooled down. I am thinking there is a ratio of surface area to the rate the heat can escape....
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Post by DCish on Mar 9, 2019 10:22:22 GMT -8
Another thought... any time you move heat and try to exchange it there is loss. If you're poking holes in the floor anyway, how about a hole in the floor for feeding a J tube that is below the trailer. A hyper-insulated flue pipe could lead under the trailer to whatever rooms you are trying to heat, and a tee that leads up to a barrel in each room you are trying to get heat to. The first barrel would be the smallest since it'll be the hottest, with each one progressively larger / cooler. If you are mindful to keep your harvest surface area within spec so that you have enough heat left over to run the chimney, it should work just fine. You could stack some bricks inside or outside the barrels to add some mass to help smooth out the heating curve, and if you add enough mass to create structural concerns, you could build up support from the ground under the floor to pass the weight directly to the ground so that you don't over-stress the trailer itself. This system would certainly require priming to get going, but should be relatively straightforward to install, and ought to work. For a kid's birthday party I once built an 8-foot, dry-stacked, horizontal brick tunnel with 6' of chimney pipe balanced on one end and a brick missing on the other end to form a fuel feed. After priming it lit well and was smokeless in no time. It was a great butt warmer... until it got too hot to sit on. After an hour and a half I had three layers of brick splits over the first foot of "bench" by the fuel feed, 2 layers for the next 2', and a single layer for the rest, and it was mostly uniform heat from one end to the other. I didn't run it other than that once for that brief period, but it gave me appreciation for just how versatile configurations can be.
One variable I'd want to test in advance is how well a single, upward-pointing tee feeding a barrel bell would work. Presumably hot flue gasses would stream in and cold ones would stream out with no problem, as in general bell / stratification chamber function, but it would be worth doing a mock-up in advance, just to be sure, and to tune barrel sizes before cutting holes in floors.
Whatever way you go, do keep us posted!
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Post by coastalrocketeer on Mar 9, 2019 12:11:36 GMT -8
I am planning to do a similar design, batchbox feeding outdoor thermal mass, but with an open water tank at the top of the masonry bell, with a few layers of R-15 rock wool insulation around and above that masonry bell and water tank sides and top, and all inside a shed built of metal framing, siding, and roofing.
Water from the heated tank will be cycled to/from 55 gallon “mass” drums in various rooms of the house directly by 12v pumps, and a coil of copper in the tank will feed our DHW tank either pre-heated, or fully heated H2O, depending on the temps in the rocket heated tank.
Each 55 gallon drum will hold about 450 pounds of H2O as thermal mass, and act as a giant radiator. If they last a couple of years before rusting out that will be fine, as I can easily monitor their condition, and get new barrels cheap.
Smaller 15 gallon barrels in each room could work for a smaller structure like yours, and give you the mass storage, slow release effect.
The main heated tank could be right in your largest space, with the cob/masonry mass in the crawl space insulated, and the heat lost through the top would be lost into your home...
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Post by marthale on Mar 11, 2019 7:04:09 GMT -8
I am planning to do a similar design, batchbox feeding outdoor thermal mass, but with an open water tank at the top of the masonry bell, with a few layers of R-15 rock wool insulation around and above that masonry bell and water tank sides and top, and all inside a shed built of metal framing, siding, and roofing. Water from the heated tank will be cycled to/from 55 gallon “mass” drums in various rooms of the house directly by 12v pumps, and a coil of copper in the tank will feed our DHW tank either pre-heated, or fully heated H2O, depending on the temps in the rocket heated tank. Each 55 gallon drum will hold about 450 pounds of H2O as thermal mass, and act as a giant radiator. If they last a couple of years before rusting out that will be fine, as I can easily monitor their condition, and get new barrels cheap. Smaller 15 gallon barrels in each room could work for a smaller structure like yours, and give you the mass storage, slow release effect. The main heated tank could be right in your largest space, with the cob/masonry mass in the crawl space insulated, and the heat lost through the top would be lost into your home... Yes, I have even thought of doing with my my large bath tubs heating the water to say 180 degrees, then when done pulling the plug on the tub, when it gets the right temp time for a bath ;-) Or rather drop a pump in the bathtub run the line up and now you have a shower with the water that is heated in the bath tub.
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Post by gadget on Mar 11, 2019 7:58:47 GMT -8
I'm going to agree with the idea of using water to move the heat. I am a big fan of hydronic heating. I use to not be but now that I understand how well it works I think it is the best option for moving heat around to remote locations. I have a hydronic system in my green house. I have 330 gallons of heated water under my grow beds. I also have a water loop in the ground beds. It holds a ton of heat. I use 1 insulated 55 gallon barrel buried in the ground as a go between everything and every sub system shares the same water from this central barrel.
It doesn't have to be expensive to do hydronics if your creative and keep it safe. Do your home work and build it right. Yes, its more money then cob and vent pipe but I think its worth the initial investment for way better performance.
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