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Post by Donkey on Feb 9, 2012 15:47:58 GMT -8
The barrel is reversed, in actuality the bigger you make the barrel, the more heat you'll get from it (with practical limits). In THIS case, heated gasses are trying to move up and are being pumped (in effect) down and out. A wider gap will slow the pumping action, giving the heat more time to hang out in the barrel area. I know it's not technically a bell, but it will act a bit like one. As a general rule, if you want more heat from the barrel, make the gap larger. I have found this to be true in a couple of stoves that I've built in the last couple of years. It's counter-intuitive, but seems to be true none the less. A tighter gap up top will create a hot spot, as the book says. A tighter gap around the sides just seems to run the gasses through faster, so they end up in the bench earlier, leaving less heat behind in the process. So far, barrels seem to heat a room faster if the gap is larger. I could be wrong, but that appears to be what I've been seeing.
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Post by Donkey on Feb 9, 2012 15:28:21 GMT -8
Yep. Look up the T.E.G. Thermo-Electric Generator. Also, there's the Stirling Cycle Engine, which has been around for a LONG time and some folks have used them for converting waste heat to kinetic energy and/or electricity.
Seems to me that if the intent is to make electricity, the TEG or some kind of thermo-couple would be the way to go, fewer conversions.. On the other hand, if the intent is to use the electricity to turn some gizmo or provide some kind of kinetic motion, the Stirling Cycle would be my choice for the same reasons..
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Post by Donkey on Feb 8, 2012 8:21:03 GMT -8
Right.. The "scrape the walls" thing is all about heating a pot from below. If you don't "scrape the walls" with the flow in those conditions, you'll be wasting heat. This is a condition where heated air is flowing straight up and out of the gizmo and the pot is placed in the way of the flow to catch some heat before it leaves.
The barrel is reversed, in actuality the bigger you make the barrel, the more heat you'll get from it (with practical limits). In THIS case, heated gasses are trying to move up and are being pumped (in effect) down and out. A wider gap will slow the pumping action, giving the heat more time to hang out in the barrel area. I know it's not technically a bell, but it will act a bit like one. As a general rule, if you want more heat from the barrel, make the gap larger.
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Post by Donkey on Feb 5, 2012 20:11:03 GMT -8
edit: dug out the road base today and relaid it mixed with clay slip. There is immediate improvement! I've been re-thinking the straight sand, pour it in and cap it theory.. Sand, even with high grain diversity, has holes in it. Gaps between the grains that act like insulation. Lately I've been thinking that it seems better to mix it in with slip or something. More direct contact between all the bits for better heat conductivity and flow. 'Course, the sand's been working, so...
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Post by Donkey on Jan 28, 2012 10:39:45 GMT -8
Seems to me that what would be great is if it could be done without a blower, If the rocket stove itself provided the draft to do the job.
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Post by Donkey on Jan 26, 2012 18:06:32 GMT -8
Yep.. I was thinking about it but never tried it out. I seemed too complicated for what I wanted to accomplish at the time. I built the sauna (which is chronicled here somewhere) without the gasifier.
I still love the idea though and would be fascinated (and overjoyed) to see it pulled off.
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Post by Donkey on Jan 26, 2012 18:00:08 GMT -8
I got no numbers either, but I have seen barrel tops and 1/4 inch steel plate glow cherry red. This suggests around 1500 at the top of the heat riser. This IS rare, normally these stoves don't get that hot at the barrel, normally you don't WANT it that way either. I see (black) metal stove pipe (in 8 inch stoves), on a regular basis, turn to melted crumbles. Though use black pipe, I get it from the dump and use it as a sort of expendable mold, to hold a pearlite/clay mix till it's dry and somewhat fired.
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Post by Donkey on Jan 25, 2012 9:21:52 GMT -8
Canyon, I've often wondered if you could weld up a complete stove with a port on the top to pour in pearlite and a water tank built in for mass/hot water. It would stand up on legs and be quite light for transpo.. I know, it's a bit off topic, but you've just reminded me.. Waddya think?
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Post by Donkey on Jan 25, 2012 9:13:14 GMT -8
Let me preface by saying that I'm NOT an extreme weather guy. I've lived my life (so far) in very mild, forgiving climates. Now, I have done a lot of work WITH cold weather guys and have picked up a few bits of info. Mostly, I'll just steer clear of the bit's I know nothing about and let those who do answer for them. So- my partner and I are planning a major addition to her tiny off-grid house. While almost tripling the floorspace, our little place will be in the 600ft2 range (I said it was small, right?). It's currently a 200 ft first floor with a small sleeping loft. The addition will be a two story cube tacked onto the side. RSMH have been on our radar for a few years now and we've decided to attempt to make one the primary heating system for our new home. I wanted to run a few things by the collective, and hopefully get a little more info on a few ideas I've had. Any information or tips on constructing a space with a RSMH in mind would also be super helpful. We're in Northern New York (Basically Canada), Hardiness Zone 3. We hit -20F a couple times this year, and sustained sub-zero temps happen a few times a season. I'd place the stove and it's thermal mass as close to the center of the space as is convenient. If you park it against an external wall, you WILL loose heat directly to that wall (and then outside) without getting any human benefit. Yes, insulation will slow the loss of heat, but ONLY slow it. Remember, you get no (personal) benefit of heat flow that you cannot place yourself inside of. So let me do my rant, and please excuse if you are nerdly enough that this info is old.. Heat DOES NOT RISE. Heat travels in all directions equally, faster through good conductors, slower through insulative materials. Heated fluids (air, water, etc.) on a planet (or spinning container (centrifugal force)) convect, warmer fluids being less dense are shoved up by the cooler, heavier stuff going in the opposite direction. Convection (heated fluids rising) is a property of fluids, NOT HEAT. Heat, coming off of convecting fluids travels in all directions equally (assuming equal conductivity). OK.. I got that out of my system. Simplicity is your friend, adding moving parts pumps and complex systems is asking for a failure in those parts. If your system relies on those complex bits to work, when they fail in the depth of winter, you might have a real problem on your hands. IMHO it's better to run exhaust piping through the floor than a glycol loop. To that, I think Canyon's got it right. Once again, Canyon said it well. You need ample, well placed openings to allow for convection. I don't think that running mass up to the second floor is necessary. It's good to remember that while ample mass for storage is good, it needs to be balanced with appropriate fast radiance. My stove here at home has little to none of metal, fast radiant surfaces. It takes an hour or more to feel much heat coming from the thing. I plan to tear parts of it down and add a barrel or some other metal surface to fix this. The "barrel" (doesn't HAVE to be a barrel, just some kind of sturdy metal container) helps with draft, cooling flue gasses and all that. It also radiates heat instantly, starting to warm the space right away and it will continue to radiate almost as long as the bench is warm. Since you'll be heating the upstairs with warm air, don't forget this important detail. You'll be venting into the space rather than the stove, warmed through the bench. Interesting idea. Well.. The thing will be directly connected to the outside whether the stove is running or not, probably bringing in outside air all the while. I think it's a neat idea, I'd size it a little larger (since it's ventilating the house instead of just the stove) than the stove needs. I'd also put some kind of adjustment on it, a sliding door or something to regulate it and/or shut it off when needed. I've done this with some success in my stove.. I'd say doing it properly is dicey, not sure I did it quite right. I'll let someone else pipe in here.. ( ) Do yourself a favor. Build a couple/few temporary stoves outside first, include some of the options that you want to the best of your ability. These things can be finicky, they need tuning and there are some critical proportions that are non-obvious. Try to make your mistakes in a way and place that is safe before you move it inside. When you do finally build it inside, you'll have a MUCH better grasp on what to do. Good luck, and don't forget to let us know how it goes!
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Post by Donkey on Jan 20, 2012 8:28:36 GMT -8
As mortar, I usually just use clay slip. That is clay rich earth, mixed with water, put through a sturdy fly screen. IMHO, the thinner the joints are the better. Mortar is for holding the bricks apart, NOT sticking them together, gravity holds 'em together (with a remarkable mount of stickiness from the clay, but let's ignore that.)
If I need something thicker than just the slip (big voids or the bricks rock around on a high point) then I'll mix in wood ash (to the slip mixture) to a bread dough consistency. Use as little as you can get away with and still do the job. The works can then be puttied up from the outside with the clay/ash mix, filling the holes, etc.
That's it. No fancy mixes, no store-bought gunk, no toxics (besides the lye naturally found in wood-ash. Wear gloves) It'll last for a good long time and when it's time to take things apart again, no problem. You will be surprised how resilient the clay/ash mix can be. If you got good clay, it won't come apart too easy.
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Post by Donkey on Jan 18, 2012 8:29:24 GMT -8
Concrete is likely to crack (heat shock). Still.. Cracked or not, it'll hold up the works.
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Post by Donkey on Jan 18, 2012 8:11:01 GMT -8
No sweat.. Umm... Wood doesn't burn either...
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Post by Donkey on Jan 17, 2012 21:03:18 GMT -8
Heat travels in ALL directions equally. HEAT DOES NOT RISE!!! Heated fluids will move by convection in a gravity well.. This is a property of fluids, not heat itself. (can you tell this is a peeve of mine?)
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Post by Donkey on Jan 16, 2012 19:26:21 GMT -8
I've often wondered if there was a low tech solution to this. Could heat pipe technology be adapted to work? These little passive coolers are used in the Al/Can highway to help keep it frozen.
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Post by Donkey on Jan 15, 2012 9:58:19 GMT -8
OK, so what's needed is a pot burner that fits well just under the heat riser. It should probably fit snugly so that any air passing by MUST enter the pot area, maybe some vanes to guide airflow into the right spot. I suppose that if the stove is to be strictly an oil burner, the feed box and burn tunnel won't be needed. Seems more fun (to me) to make an oil burner gizmo to modify a standard rocket stove..
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