joseph
Junior Member
Posts: 66 
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Post by joseph on Sept 25, 2014 11:06:21 GMT -8
Water barrel inside the bell, yes. Inside and high, actually poking through the top a little for ease of access. We will build an (removable) insulated cap for it. This stove is going where a different design existed. I have a metal stand that will hold it up, it needs some cutting down, as it's too narrow around the tank to act as a bell. .... How high will the water barrel be above the top of the riser? Does the hot exhaust impinge directly upon the bottom of the water barrel, or is there some kind of shield or deflector? - joe |
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Post by Donkey on Sept 26, 2014 9:05:36 GMT -8
No deflector. Gap will be large enough for good flow, that is all.
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joseph
Junior Member
Posts: 66
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Post by joseph on Sept 28, 2014 11:21:39 GMT -8
No deflector. Gap will be large enough for good flow, that is all. When first starting the stove, when the hot riser air hits the cold water barrel, it will cool and contract considerably. It will fall down to the bottom of the bell, and sideways out to the chimney. Will it be able to go up the main chimney? - joe |
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Post by Donkey on Sept 28, 2014 11:26:35 GMT -8
It should.. It's going to depend on the surface area of the water tank. In this case, is small, around 15 gallons (sorry, don't know the surface area yet.). I plan to insulate the inner wall of the bell with perlite/clay. We'll see.  |
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Post by johndepew on Sept 28, 2014 17:27:45 GMT -8
How long do you figure it would take for this system to get up to operating temperatures, assuming the thing is fired once a day or even less often? Obviously that depends on the amount and quality of insulation keeping the heat in, but I'm curious about what implications this would have for daily routine in a residential setting.
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Post by Donkey on Oct 2, 2014 20:08:46 GMT -8
We will be building one this weekend (starting tomorrow). The tank that we will be using is out of the old system that I had here. It reached full temperature (in the old system), depending on the initial temperature of the water (solar assist) after between 2 and 3 loadings of wood. It's an 8 inch system and 2 loads of wood burn down in about a half an hour (depending on the wood).
This new system should come to heat better, as it will be better insulated and the tank will set inside of a bell, which should be more efficient in terms of heat intake to the water.
We should have first results by Monday.. I'll keep y'all appraised.
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Post by timbee on Oct 4, 2014 18:43:30 GMT -8
Hi all i don't get around on the internet much so was surprised when Matt Walker pointed this thread out to me when we were discussing ideas for water heating at the innovators event at Paul Wheaton's place. There are now about half a dozen rocket water heaters kicking around the place that i have either built or friends have built that seem to be standing up to daily use in the real world okay. Iv'e long wanted to even further simplify the water heater by having the mass on the ground and feeding the hot gasses in sideways as per Donkeys sketch but early tests showed extreme stratification of heat so that there was a thin layer of boiling water at the top of the barrel that was absorbing huge amounts of energy in the phase change and dumping it out of the system as fast as i could put it in. I think the trick will be to induce uneven heating of the water so as to generate a convection current in the barrel and stop stratification. By introducing the riser inlet below the top of the barrel i think there is a good chance that donkeys system will induce the convection needed. To get the barrel bottom nearly on the ground i am/will be trying some baffles to get the uneven heating going. One problem with this approach however is that if we are introducing the heat at the top and baffling so the the gasses pass down one side of the barrel and up the other we will have a system that will turn into an air heater after the stove goes out Not good. We could add a second series of baffles and send the gasses to the bottom of the barrel one more time to stop this but its starting to add a little more complexity and i like easy cheap simple so i will be trying just some short baffles either side of a bottom outlet to stop shortcutting of gasses straight to the outlet. The trouble with using baffles is that while the delta T on the riser inlet side will be good the delta T on the other side at the top will be woefull as the induced convection current will be rolling the hottest water towards much cooled gasses lowered heat transfer so i think the slightly raised approach of Donkeys is superior but will pretty much use the same amount of materials as my standard system which is more efficient. However it's not all about efficiency, i love the idea of having everything mounted to the lid and no sealing problems and very easy replacement of components. One of the biggest problems people seem to have building these systems is coiling the copper pipe in through small openings ( 3" x 2" or so) . Having it hanging from the lid in the upright system is much easier. One other thing to note is with donkeys system you will still tend to have some stratification which may be a good thing as if you arrange your copper coil so it sits predominantly towards the top of the tank it means you will be able to extract usable heat more quickly than the tank above system which due to bottom heating tends to mix quite violently and so the whole mass of water comes up to temperature more evenly (slowly) . May not be a problem with systems that are heated daily but for quick start up may be a consideration
Cheers Tim
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Post by Donkey on Oct 5, 2014 6:37:47 GMT -8
Nice one, Tim.
We're in the process of building one right now. Constraints of the building have forced us to put the tank on top of the riser. Heat will leave the riser and strike the bottom of the tank directly before going above into a "bell chamber". This should provide the violent mixing you are talking about.. I didn't think about all of this before, just constrained by the space to do it in this way.
The drawback is that it's going to be taller than I wanted and will make checking water levels and fiddling with the bits a little more difficult.
I'll post images of the build in a few days.
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JJ
Junior Member
Posts: 56
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Post by JJ on Oct 5, 2014 8:36:29 GMT -8
Nice one, Tim. We're in the process of building one right now. Constraints of the building have forced us to put the tank on top of the riser. Heat will leave the riser and strike the bottom of the tank directly before going above into a "bell chamber". This should provide the violent mixing you are talking about.. I didn't think about all of this before, just constrained by the space to do it in this way. The drawback is that it's going to be taller than I wanted and will make checking water levels and fiddling with the bits a little more difficult. I'll post images of the build in a few days. Looking forward to seeing those pics K. I never thought about putting the tank on top of the riser. I had just thought about wrapping copper tubing around the heat riser and then connecting it to cpvc or something along those lines. Haven't experimented with it yet. I'll be very interested to see how it turns out for you. I have to admit - I've just been building typical rocket mass heaters for two years now or so...but I think it's time for me to delve into the depths of stuff like this too. I'll be having several underground greenhouses up and functioning in the spring that will be year round (so I've incorporated rocket mass tech into them for the Michigan winters). It will be interesting for sure... |
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Post by jetset on Oct 5, 2014 12:31:35 GMT -8
Alright, alright, ALRIGHT! There! Ya got me to sign up for an account so I can chip in and get some feedback too, I hope you're all happy!   First question up, how do I make sketchup files available for your viewing pleasure? My primary objective is a small system to preheat 15gal (56.78L) batches of water going into the hot water heater. The setup as I see it in my head will be a 15gal drum plumbed into the house line submerged in a 55gal (208.2L) insulated drum of water that will be pumped into the bottom of a 20gal (75.71L) drum (on its side, and for those interested its surface area is @11.8ft 2 (1.2m 2)) within an insulative bell. This drum is to be vented so there is no chance of the boom squish (shouldn't that be boom scald or boom shrapnel, why the squish?) mentioned previously in this thread. And finally it will return via gravity flow out the much larger opening on top to the 55gal drum. And for those skipping ahead to the last page of this thread (as of this posting) allow me to reemphasize that if you're going to play with fire that's fine. However, if you're going to play with fire AND water please look up mythbusters water heater on youtube and then take the time to really understand what you're dealing with. (How was that Donkey?  ) So, I guess the first thing I could use input on is planned use of materials. Starting with the core (4in square (10.16cm) system btw) and first section of riser I plan to use Rutland's castable refractory cement and surround it in 4in of perilite. For the remaining sections of riser my plan is to make a 4:1 mix of perilite and refractory cement. Finally, for the bell, even though I would love to just make the top bottom and sides as single pieces I've read here that big pieces typically end up being big puzzle pieces. So, my thought is to make 4in x 4in x 8in (10.16cm x 10.16cm x 20.32cm) bricks out of a 4:1 mix of perilite and masonry mortar. Well, without being able to post a visual that's it for now. Thanks everyone, take care, and God Bless! Jacob |
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JJ
Junior Member
Posts: 56
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Post by JJ on Oct 5, 2014 14:21:53 GMT -8
Alright, alright, ALRIGHT! There! Ya got me to sign up for an account so I can chip in and get some feedback too, I hope you're all happy! First question up, how do I make sketchup files available for your viewing pleasure? My primary objective is a small system to preheat 15gal (56.78L) batches of water going into the hot water heater. The setup as I see it in my head will be a 15gal drum plumbed into the house line submerged in a 55gal (208.2L) insulated drum of water that will be pumped into the bottom of a 20gal (75.71L) drum (on its side, and for those interested its surface area is @11.8ft 2 (1.2m 2)) within an insulative bell. This drum is to be vented so there is no chance of the boom squish (shouldn't that be boom scald or boom shrapnel, why the squish?) mentioned previously in this thread. And finally it will return via gravity flow out the much larger opening on top to the 55gal drum. And for those skipping ahead to the last page of this thread (as of this posting) allow me to reemphasize that if you're going to play with fire that's fine. However, if you're going to play with fire AND water please look up mythbusters water heater on youtube and then take the time to really understand what you're dealing with. (How was that Donkey? ) So, I guess the first thing I could use input on is planned use of materials. Starting with the core (4in square (10.16cm) system btw) and first section of riser I plan to use Rutland's castable refractory cement and surround it in 4in of perilite. For the remaining sections of riser my plan is to make a 4:1 mix of perilite and refractory cement. Finally, for the bell, even though I would love to just make the top bottom and sides as single pieces I've read here that big pieces typically end up being big puzzle pieces. So, my thought is to make 4in x 4in x 8in (10.16cm x 10.16cm x 20.32cm) bricks out of a 4:1 mix of perilite and masonry mortar. Well, without being able to post a visual that's it for now. Thanks everyone, take care, and God Bless! Jacob I didn't know you needed water to make fire. ~feeling confused (that was a joke.) =-D |
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Post by matthewwalker on Oct 5, 2014 17:34:00 GMT -8
Hey Tim! Great to see you here my friend. I was thinking about the design stuff we talked about as I was traveling home today from the East Coast...I had a lot of time to think. Maybe just run the flue gas down the one side using the baffles and then under the barrel and out to the exhaust without going back up. Insulate the heck out of the far side, and avoid the temp mismatch of the complete circuit. I dunno, just a thought, might still be a bunch of power left in the flue gasses at that point, but that's just a sizing issue. I might have to knock one together here to play with in the coming weeks now that I'm done traveling for a bit. Sure wish I could have stayed long enough to see yours make me a hot shower.
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Post by jetset on Oct 5, 2014 18:26:00 GMT -8
I didn't know you needed water to make fire. ~feeling confused (that was a joke.) =-D LOL! To make fire no, to make hot water it's pretty essential. Or perhaps you're suggesting I should just get at it and build something. Truth be told I do have a 6in (15.24cm) square L-tube I use to boil sap down to maple syrup. Problem is it's made of 1/4in (.64cm) steel, so at some point based on what I've read here I'm looking at a rebuild. That's why I'm looking for input on the materials I'm thinking of using right now In hopes that this will last a substantial amount of time. Thanks and God Bless Jacob |
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JJ
Junior Member
Posts: 56
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Post by JJ on Oct 5, 2014 18:42:53 GMT -8
I didn't know you needed water to make fire. ~feeling confused (that was a joke.) =-D LOL! To make fire no, to make hot water it's pretty essential. Or perhaps you're suggesting I should just get at it and build something. Truth be told I do have a 6in (15.24cm) square L-tube I use to boil sap down to maple syrup. Problem is it's made of 1/4in (.64cm) steel, so at some point based on what I've read here I'm looking at a rebuild. That's why I'm looking for input on the materials I'm thinking of using right now In hopes that this will last a substantial amount of time. Thanks and God Bless Jacob I am by far not the best person based on experience to ask about the rebuild. I have mastered the typical rocket mass heater and have experimented with it a lot - just not with water yet. Just for the sake of gaining commonality with you - we live in Michigan and have numerous maple trees on our property and use rocket tech to produce our syrup as well We use typical fire brick rocket stoves for that. I was reading that you want to retain heat for 15 gallons of water. I had once today had an idea - based on Donkey's idea of putting the water heater tank inside the bell - and then thought to myself, why couldn't the water heater tank go "inside" of another tank "inside" of the bell as long as the space between the water heater tank and the other tank that were both inside of the bell was insulated? You'd definitely want some type of heat retention between the water tank and the hot air in the bell - especially if you're going to be heating 15 gallons of water, no? I mean - you don't want just "warm" water so the insulation would have to be thinner...but at least it would be a continuous retention of heat inside that bell so that the water was still hotter even after the stove went out? Just a thought. I only just learned about the russian "bell" technology today and am still researching so what do I know anyway lol. PS: YES! Get on it! The best thing you can do is get to tinkerin so your trial and error process gets over faster! (This coming from a bona fide bohemian-blood gypsy, 3rd generation American  |
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Post by jetset on Oct 6, 2014 2:29:18 GMT -8
Michigan huh, well I'm not too far away here in New York. Missed the Maple season this past spring, I was visiting My wife in the Philippines and was gone the exact two weeks the sap would have been flowing. Lord willing we will hopefully be done with the immigration paperwork and she'll be here for that first delicious harvest of the year this spring.
You're right that putting the main water tank with the batch barrel in it inside the bell and directly above the riser would be ideal, but the height restrictions of the basement prevent that as an option. Thus, the reason for removing that off to the side. I do have a couple concerns with what you were suggesting. It sounded as though you were talking about putting the batch barrel which would be connected to the water line going to the hot water heater inside of another barrel with insulation around it. This gets you into a situation where you're heating a pressurized system essentially directly which is not good. Also, once you use the water in the batch barrel the heat is gone till you fire again. By placing the batch barrel in another barrel of water (basically replacing the copper coil in Donkey's original post with the batch barrel) which is vented you do two things. First, it's safe because the water in the main barrel can only get up to boiling because it's not pressurized. Second, think of that main barrel of water as your bench mass. every time you draw off some water the water coming in will get preheated.
I'd like to do a batch system for two reasons. First, my water comes from a spring on our hill and by the time it travels all the way to the house there's quite a loss of pressure do to the length of the run so a couple hundred feet of copper tubing isn't really an option. Second, and perhaps more importantly, the "moths fluttering out of my wallet" indicate I don't have money enough for that much copper.
Think of the bell system like this. Take your typical bench mass and turn it vertically. Then, instead of making a continuous run of flue pipe you simply have open cavities where the hot gasses can accumulate give off their heat to the mass sink to the bottom and flow either to another bell or the flue connected to the chimney. It basically allows you to have the same thermal battery but in a much smaller footprint.
Take care and
God Bless!
Jacob
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