Rocket Stove and Infrared Heating

I have been looking at rocket stoves for some time now but never tried to build one. I have built several gasification stoves using 55 gallon drums and modifying stoves just for interest in wood gasification. I found this forum yesterday and it seems people here have a great knowledge for this rocket stove so I thought I would ask some questions about them.
I am wanting to heat a shop, all concrete and steel, with one of these but highly modified. I would not be using a Barrel but would instead you black pipe running horizontal across the ceiling. This would have a reflector around the pipe so as to transfer the heat to the room and heat up items in the room such as the walls, floor and anything that would retain the heat. I have an existing Natural gas Infra-red heating system now but the natural gas has become very expensive to heat with it. I built a imbert gasifier to be used with this type of system but the problem with it is you have to cut wood block 2" to make it work correctly. I would prefer using stick wood instead.
Has any one tried what I am talking about to see if this would work. My only thought that it would not, is the heat being transferred to the Black pipe correctly. I have done several temperature measurements on my infra-red heating tube and know what is to be had at this points for a 50,000 BTU system.
Thank You
Ken
 

Just to clarify, you plan to build something like a rocket mass heater, but instead of conductive heat transfer to masonry packed around the pipe, you're designing for radiative heat transfer from the pipe?

My understanding is founded in theory, not practice, so take this with a grain of salt:

The barrel serves partly to mix the combustion gasses and cause a secondary burn, so I think you might want to include it, or something with the same function, in your design. From what you've described, I think I would design for some turbulent flow on the way into your run of black pipe with its reflector, and some good insulation around that an all the pipe leading to it.

Radiative heat transfer works great at higher temperatures, less so at lower temperatures. Below some temperature, convection will carry away more of the energy than is directed where you want it as IR. Having higher temperatures on exposed surfaces will probably make such a system more dangerous than a standard rocket heater. Also, you might want to run the last section of the pipe through some masonry, to capture more energy before the exhaust gasses leave the system.

Here's my rough draft of the system: pink is insulation, light gray is concrete, dark gray is the reflector. Comments from someone with more practical knowledge would be appreciated.

Thanks Joel,
Except mine would set on the floor and the pipe would be raised to the ceiling height.
This is what I don't know what temperatures are in the pipe of the rocket stoves. On my Infra-red heater the temp closest to the flame is 638 degrees F. then it goes down every 4' to the end to 370F. This is on a 20' section of the heater. This is a 50,000 BTU heater.

Ken

I am sending a drawing of what I am thinking about.

Suggestion: concentrate instead on a vertical burn tube. Insulate around it, and several diameters up the length of the rise. (some of the household systems use as much as 50" for a 7" tube. I'm certain there's a roaring flame at the top, eating away at the barrel lid...
There are impressive videos of things as small as a 4" tube "rocket", insulated about 12", with an uninsulated pipe about 3' tall above it, and it's putting out a roaring jet of flame about a foot tall above that.
Use the vertical tube to help generate a rapidly moving energetic collumn, and then push it through your horizontal heat exchange pipe.


Your decisions come down to mechanics: How to feed it and contain the fire (which produces the heat and smoke to then run into the vertical tube). The standard "rocket stove" model is the horizontal tunnel to the bottom of the burn zone, and you push in as much fuel as you need. When you stop pushing it in, it goes out.
The usual "rocket mass heater" uses the feed pipe for some convenience of letting it gravity feed itself. The "throttle" is in how much fuel you stick into the upright feed.

Other stoves will have what seems more like a normal fire-box, insulated, and a pre-heated secondary inlet leading upward to the base of the insulated vertical burn tube. This seems more like a normal fireplace: build a normal fire, and let the guts heat up to encourage complete combustion.
Either you place a mass of fuel and control the air inlet to control the rate of burn, or you meter the fuel, which either means you feed in the desired amount, or you use something like an automatic pellet feed.
The famous Ashley stove uses a stack of normal firewood, that falls down into the combustion chamber, with secondary pre-heated air inlet and a volume of baffles to burn it all before the flue. The thermocouple that controls it varies the amount of primary & secondary air, so the magazine holds a big lot of wood, and you start the fire in the morning, and that's it. I've heard reports that you build one fire per season, and load fuel & empty out the ash sump as needed.


I suspect that your electrical blower system won't be needed beyond starting it up, and getting the inner tube hot. After that, it should draft on its own.

I like that at every turn, you have it going up higher. You might be able to get away with some down-draft somewhere, but why tempt murphy?

[quote author=Joel Hollingsworth]
The barrel serves partly to mix the combustion gasses and cause a secondary burn, so I think you might want to include it, or something with the same function, in your design.The barrel is a heat exchanger and it also serves to bring the flow from the vertical burn tube down to the lower level of the pipe that people run through a cob bench.
The burn takes place in the vertical tube. Everything after that is ducting to point of use.

The "rocket" burner uses the insulated vertical space to thoroughly mix air & fuel at the point of highest energy release. The length of the vertical insulted run gives it time to mix & burn thoroughly. That's all the encouragement the burn needs to completely combust, in its simplest form.

In the simplest form, no forced draft is needed, nor secondary air. If you over-build things to take the heat, you can use these to strong advantage: After the fan, divert part of the flow to the bottom for primary, and bring the rest of it up around/past the combustion tube and inlet it a few diameters up.

Other considerations... Instead of the piled fire-brick burn tube, think of a steel tube, insulated with a larger outer tube around it. Less mass to pre-heat and get things going (if it can take the heat of forced secondary combustion air).
Somewhere I saw a more-or-less standard "rocket mass heater" that uses a pyrex baking pan built into the cob mass at the bottom, in front of the feed inlet...
I've seen various heat exchangers. Your pipe with the reflector will be interesting, but others have been as simple as the 55 & 33 gallon barrels, or a simple "donut" of chimney pipe, forcing the draft through more surface area.
Your vortex baffles should work, but simply turning and running it through various geometries should do to prevent laminar flow from keeping the hottest part in the center of the tube.
Maximizing surface area, with the same draft area for unobstructed flow is all that's usually built in. Think also of flat rectangle volumes, instead of round pipe.

Thanks JohnF,
This stove uses the same idea of the rocket stove. On the left the hopper where the wood is stacked on end but using a lid on the hopper. Air going in through the pipe input at the bottom. Now reason for this is I can control the amount of heat output but will idle with a flame when the room temperature has came up. The reason for the sealed lid is so I can burn damp wood. Inside the hopper as the heat rises, it will warm the wood inside as it falls down into the burn chamber. I understand about the rocket stove being a manual feed type. There you would heat up the room and when it gets cool you would start another fire. On this one I am trying to make the burn with the blower to create a heat source but when the temperature comes up then the blower would shut off and the stove would drop back to an idle where it would burn only on convection thus saving some wood but staying lit but at a rate not to let the flame go out. Some of this I have done using another smaller stove and it worked. I could get the flame to rise and fall by controlling the primary air into it. You talked about the vertical rise and I have also done that from the same small stove and using tin foil for my reflector could throw the heat away out to about 4 feet. From the small stove I knew it could be done using wood but the next question was how.
The reason to build a horizontal heat pipe is to heat a room 60 feet long and 30 feet wide. Using  a vertical pipe just will not do it because you lose the heat the further away you go to the other end of the room. On the Horizontal pipe it would go the full length of the room and with the reflector would heat both floor and walls at the same time. This is the way my commercial infra-red works now. There is a flame about 5 feet inside a 4" tube on one end. This is great heating as I have used them for 9 years but as I stated it got too expensive to operate. The part you talked about on the barrel as a secondary burn I understand. This is the same thing as putting a shelf in a stove over the flame and letting the smoke travel back over the flame for a re-burn before going out the chimney. This may be where I will get a problem on this stove. I am trying to keep all the heat until it gets to the Black pipe and then extract it there. It may be that I would have to add a secondary air pipe into the end of the black pipe for the flame but this might be dangerous. Let me explain this. I built a double barrel stove but modified. I added a 6" pipe between the two barrels but also drilled 1/4" holes around the short connecting pipe. When it got up to temperature the fire would leap into the top barrel only and burn there causing the top barrel to get red hot. At the bottom where the wood was there was no flame only a blue mist coming off the wood which was the gas from the wood. When I put a piece of tin around the secondary holes the flame would settle back down into the bottom barrel. I later built a control for the secondary air and it worked but finally after 2 years the barrels gave up and I had to thrown them out. So I have not tried anything of this distance like that so I'm unsure what would happen or if this would even happen in this distance from the main flame at the bottom.
I may have to build a small one to see what will happen in this area after this weather breaks.

Ken
 

I am so confused.

So the idea is to heat, but with no mass - right?

Thanks Paul,
To heat mass but not the way the normal rocket stove does.
Below is a picture of my Infra-red heating system. The box on the right end is the burner and electronics. The blacl pipe is 4" and is 40 foot long going out of the building as exhaust. Around the black pipe is the reflector that throws the infra-red frequency across the room. The angle of the reflector is set about 45 degrees and will heat the floor and the walls and anything that is a mass in the building. There is a flame from the burner end that has about a 5 foot long flame, like from a propane torch  going down the pipe.
Here is a experiment I did when researching IR devices. I took a steel pipe black and set it up on blocks. I then used tin foil for the reflector and spaced it over the pipe. I then used a propane torch and held the flame to go down one end of the pipe. Holding your hand under the reflected part you can feel the warmth being transmitted from the pipe for a distance.
What I am trying to do is use the Design of the rocket stove to do the same thing heating mass but a different way. The barrel you use will do the same thing but not transmit across the room unless you use a reflector of some sort. I was confused about the barrels for the rocket stove not being painted black with a high temperature paint because in the case of a black body, the heat will leave it and go to the cooler temperature which is the room.

Ken,  With respect to your Feb 14 design I would suggest putting the 2nd vertical drum back in.  This drum promotes mixing of the exhaust and complete secondary combustion of the unburned "smoke" components (CO, tars, h2 etc) that won't occur with your horizontal run.  If you don't want the drum as a heat source insulate it with Roxul (http://www.roxul.com/home) and the heat will migrate to your radiant system.  Will it work with the suggested changes, yes, provided your radiant heating run is long enough. Once completed you can test if the system is efficient by measuring the exhaust temperature.  On cold days you may have significant resistance to heat moving along your long horizontal sections on startup, ie it won't draw and you get smoke backing into your workspace.  A minor modification can readily fix this, just before the pipe exits the building put in an inverted Y-junction, the point/tail of the Y pointing outside.  One part of the Y attaches to the radiant piping, the other to a fan.  Before starting the stove you start the fan, this blows air past the v-junction and out the exhaust pipe creating a partial vacuum and sucking air through the radiant pipe (sort of like a water aspirator used in chemistry labs).  The air for the fan can come from your room or better yet from outside.  Doing it this way the fan never sees the heated air and therefore can't get fried by the heat.  Start your fire and after a bit you will have heat from your pipes, monitor with either a thermocouple based thermometer or a cheap IR laser thermometer (about $25 including shipping on eBay).  Once you have heat you can turn off the fan.  After a few goes you will have a good idea of how long you need the fan to be on and can put it on a timer.  Once you're to this point it will be flip the timer switch, start fire and forget until you need to reload.  The radiant heat will heat the internal surfaces but not as hot as in the original design so you will have a shorter "comfortable" period if the fire goes out.  Quicker heat but less storage.  In short it would work, some benefits some drawbacks.  Have fun.

Hi Mek and thanks for the insulation info,
I never heard of that before and it seems better than the mix I was looking at as this is flexible.
I think I am in an area that is most confusing to most and I don't understand the rocket stove enough to say for sure what will happen.
I know that if I add the secondary air pipe that I can get a complete burn also but the mixture has to be correct. I think I will have to wait until the weather breaks so I can do some experimenting with the rocket stove first. Here in WV we have had nothing but one storm after another for the last 4 weeks dumping anywhere from 6" to 28" overnight. Today its sleeting on 20" of snow already on the ground and another storm to come sunday.
I will build the rocket stove like you have said on a smaller scale so I can understand it. Then I will modify it and see just what takes place. I purchased one of those IR laser thermometers about 2 years ago but I paid $300 for mine as I needed to be able to change the Emissivity of the metal I was measuring. I think it goes up to 1500 F.

Ken

problem is you dont want a rocket stove and are not designing one at all.
essentials of the stove are the reburn and then the piping the clean exhaust gasses through a mass to heat the mass. the reburn is where most of the efficiency is because it burns off the rest of the pyrolitic gasses. a Rocket stove system is not going to have the heats you want for an IR heating system, its designed deliberately not to. the hottest part of the stove is the space at the top of the heat riser (about 1200 degrees).

what you are looking for and have designed is a controlled stack burn. its going to be dirty and its not going to like small wood. I would look at what you actually want divorced from any type of system.

the closest any type of rocket stove can get is one of the l tube types and your out of spec for those as well.

i might look at  some type of gassifier stack; but off hand i dont know any systems that will work out the way you want.

I do believe that the basics of the "rocket" burner can be made to work here, and work well.
I may have wandered a bit earlier: to some important points:
* Use the vertical insulated burn tube to consume the fuel. With enough air inlet (and some way to control it perhaps) and a tall burn tube, you probably don't need to concern yourself with secondary burn or mixing of fuel/air (it's done in the tall tube).
* go from the top of this, directly to your "black radiator" horizontal run across the ceiling.
This takes the maximum released energy and puts it right into the skin of the HX pipe. Suggest to minimize the distance between the burn tube top and the radiator pipe, if you wish to direct the released heat using your parabolic reflector, otherwise it will furiously warm up the air right there, and whatever is nearest the pipe.

* The "primer" (small heat release at the beginnning of the final run up & out) is a good idea. With your electric fan, it might not be needed. WIth a tall "Rocket" burn tube, the fan might only be needed to keep the draft at start-up, until it heats up the guts.

I maintain that the barrel is not needed. It is the heat exchanger of choice for that design: a flat space at the top of the burn for some cooking utility, and it re-directs the flow back down to the lower exhaust into the cob mass horizontal run. This is the heat exhanger for the "mass heater".
You aren't using this. You're using immediate heat, from the exhaust, right into the room air.

I do not know what success you will have with your controlled stack burn, and self-feeding of the fuel from the stack into the burn area at the base of the insulated vertical burn tube.
You may very well be the one to innovate this with a "rocket stove".

All we've seen in the literature is the "L" and the "J" with their respective methods  (either the continuous manual feed into the lower part of the "L", the other the self feeding, bottom burning sticks of the "J".

If this clears it up a bit:
All that makes it a "rocket" is the insulated vertical burn chamber. This creates a fast moving energetic colllumn of air, by maximizing the time the 3 sides of the fire trangle are present in the most favorable conditions.


I ignored fuel input and everything upstream.. This might very well sit above the floor: you won't need much more than 40" of vertical insulated burn tube for a complete combustion and very energetic flame.
At the top, it'll be furiously hot. over-build as necessary.

Thanks John,
Well you gave me a bit of help with this. I was still going to build a test version of this but from all the posts I was starting to think this might not work. But I'm sorta of hard headed and still will build this test version. I have read about this type of stove and many think its the only stove to use.
There may be many modifications that I will have to do when building this to make it work but that is the fun of it.

Ken

Joel Hollingsworth wrote:My understanding is founded in theory, not practice, so take this with a grain of salt:

The barrel serves partly to mix the combustion gasses and cause a secondary burn, so...

JohnF has convinced me that this barrel isn't necessary for your design.

A vortex might help the insulated barrel to perform as though it is longer. I trust JohnF's assessment that it will easily be long enough for your application, though.

The physics of how a chimney works means that a vortex might not help you on the exhaust, though: The important aspect of a chimney's height is the difference in barometer readings due to elevation. If exhaust gas has traveled farther to reach that lower-pressure atmosphere, it hasn't necessarily done more work (via expansion) in the process. Only releasing it into a lower-pressure environment will cause it to pull harder on the intake.

JohnF wrote:
I do believe that the basics of the "rocket" burner can be made to work here, and work well.
I may have wandered a bit earlier: to some important points:
* Use the vertical insulated burn tube to consume the fuel. With enough air inlet (and some way to control it perhaps) and a tall burn tube, you probably don't need to concern yourself with secondary burn or mixing of fuel/air (it's done in the tall tube).
* go from the top of this, directly to your "black radiator" horizontal run across the ceiling.
This takes the maximum released energy and puts it right into the skin of the HX pipe. Suggest to minimize the distance between the burn tube top and the radiator pipe, if you wish to direct the released heat using your parabolic reflector, otherwise it will furiously warm up the air right there, and whatever is nearest the pipe.

* The "primer" (small heat release at the beginnning of the final run up & out) is a good idea. With your electric fan, it might not be needed. WIth a tall "Rocket" burn tube, the fan might only be needed to keep the draft at start-up, until it heats up the guts.

I maintain that the barrel is not needed. It is the heat exchanger of choice for that design: a flat space at the top of the burn for some cooking utility, and it re-directs the flow back down to the lower exhaust into the cob mass horizontal run. This is the heat exhanger for the "mass heater".
You aren't using this. You're using immediate heat, from the exhaust, right into the room air.

I do not know what success you will have with your controlled stack burn, and self-feeding of the fuel from the stack into the burn area at the base of the insulated vertical burn tube.
You may very well be the one to innovate this with a "rocket stove".

All we've seen in the literature is the "L" and the "J" with their respective methods  (either the continuous manual feed into the lower part of the "L", the other the self feeding, bottom burning sticks of the "J".

If this clears it up a bit:
All that makes it a "rocket" is the insulated vertical burn chamber. This creates a fast moving energetic colllumn of air, by maximizing the time the 3 sides of the fire trangle are present in the most favorable conditions.

I ignored fuel input and everything upstream.. This might very well sit above the floor: you won't need much more than 40" of vertical insulated burn tube for a complete combustion and very energetic flame.
At the top, it'll be furiously hot. over-build as necessary.

JohnF, how many rocket stoves have you built?
If it's more than 20, I'm surprised I haven't met you.

Ernie was on the research team for the Rocket Mass Heaters book (www.rocketstoves.com), and helped test several hundred mockups.  He's been building them in buildings for the last 5 years or so. 
He also knows HVAC and hydraulic steam systems, boat plumbing, and space-to-space firefighting.

So if Ernie says a system is not compatible with rocket stoves, I'd listen.

(I'm married to him, so I tend to listen anyway... most of the time... )

Key points:
A rocket stove is more than an insulated chimney stack.

Both "rocket stoves" and "rocket mass heaters" share elements that are missing from the IR "smoke furnace" design:
- an insulated vertical stack (check)
- a fuel/air feed that's small in cross-section to improve mix & fuel/air ratios;
- at least one right-angle turn between fuel and stack for "splash" mixing;
- a baffle (pot or barrel top) that splashes the exhaust yet again while still hot;
- the principle of heating objects directly at optimal temperatures, rather than warming a large space indiscriminately (rocket mass heaters are fundamentally designed to heat people; rocket cookers put the pot in the center of the action; both provide more heat at useful heights than at the ceiling) and
- a history wherein the original inventors worked together, then split up and took their projects different directions while sharing the same vocabulary. 

If you are controlling the fuel feed and air speed artificially,
- and your heat exchange is supposed to be a quick-burst radiant heater,
- - - and your system is designed to run on an artificially clean-burning fuel at a controlled feed rate, but you're modifying it to take unpredictable fuel loads varying between idle and full burn, using wet wood in a sealed hopper ....

It's not a rocket stove.

Inventing a hybrid rocket stove / wood gassification / radiant pipe heater, in the conditions described, is needlessly complicating your life.  Or possibly shortening it.

Build a rocket stove for fun if you like.  Join us in Coquille this weekend for Pyromania: www.cobcottage.com/workshops

If you think a rocket mass heater is the right technology, build your shop a heated floor or wall that you can use independently of the IR heater.  If it works, just stop using the IR heater.  Or use it occasionally as supplemental or quick heat. 

Another quick alternative is the Pocket Rocket, basically a barrel stove.  Not as classy as overhead heat, but easy to put where you want it.  And easy to build now, while you're figuring out what else you want to do.

If you really want to convert the existing pipe to DIY fuel ...

KenSmith says he's done wood gassification, and that might be the right tool for this project.  If you can trap the gas, then re-burn it to ensure that the only thing reaching the overhead pipe is a creosote-free final product.  It's a messy process, but it is one way to convert a fossil-fuel system to run on available natural biofuels.

A system designed for completely creosote-free natural gas exhaust, will be very likely to clog up when fed any kind of wood smoke.

I've posted before about the dangers of creosote fires in pipes that are strung all across a room.  While high-temperature pipe is likely safer than stovepipe, it's still important to remember that creosote burns really hot.  Your pipe is designed to take a controlled temperature, not a sudden, sticky, super-hot internal fire.

See this post:

Erica Wisner wrote:
...
They used to sell stove pipe in giant S-curves and other fancy shapes.  History responded with a lot of deadly chimney fires. Steel tends to go "sproing" when heated, especially when heated unevenly by burning creosote.  Current building code limits stovepipe lengths to about 6' (? maybe 8'?) so there are de facto expansion joints in any long run; and manufacturers' instructions usually emphasize vertical or near-vertical installation, with straps and clearances from combustibles. 
...
Theoretically creosote shouldn't be a problem with clean-burning stove designs.  But theoretically we never burn wet wood either, nor "damp down" our fires and smolder them through the night.
...

KenSmith plans to burn wet wood, and "idle" the stove,  exactly the kind of burn patterns that can convert ordinary iron pipe into a writhing creosote dragon.

So...

Ernie's warning was a sterner-than-usual version of our standard boilerplate when somebody wants to weld a bunch of stuff together and call it a rocket stove, but leave out the inconvenient parts, and add on some other features the utility companies are charging too much for these days.

"This proposal is significantly different from a rocket stove or rocket mass heater, though it borrows features from those designs.
  - Our experience suggests this proposal neglects key principles that make rocket stoves work well, and carries the usual hazards of amateur wood-stove design. 
  - Of course, you are welcome to ignore our opinions and take your chances on discovering something worthwhile. 
  - Because others may suffer along with you from fire, smoke, CO, or social backlash, we entreat that you research the risks carefully before building, and then test a prototype in a safe location."

Forgive me if I sound like a cranky teacher;
it's 'cause I'm a cranky teacher, and it's late. 

Best of luck with this project, and
let's give KenSmith some space to figure out what he actually wants to do.

Yours,
Erica Wisner
http://www.ErnieAndErica.info

p.s.  A blackbody radiator (in physics) absorbs and emits radiation proportional with its temperature, neither withholding nor favoring certain wavelengths.  Black iron is a pretty good heat sink, conductor, and radiator.  But it won't preferentially radiate instead of absorbing heat - it just emits more than it absorbs when it's hotter than its surroundings, like anything else.  It is a heat exchanger - it emits at its own temperature, after absorbing from the hotter gas.

p.p.s.  The barrel does too matter; build a system with and without one, of any significant length, and you'll see why.

kensmith wrote:
Thanks John,
Well you gave me a bit of help with this. I was still going to build a test version of this but from all the posts I was starting to think this might not work. But I'm sorta of hard headed and still will build this test version. I have read about this type of stove and many think its the only stove to use.
There may be many modifications that I will have to do when building this to make it work but that is the fun of it.

Ken

Ken, it can be pretty simple.  Build the J-tube rocket part, you get lots of heat and clean combustion.  Replace the thermal mass part with your cast iron radiative heater.  It will work, as I've said before faster heat-up and cool down but less staying power so you either will need to feed the fire more often or accept larger temperature swings.  Not a big deal.  You may also need fans to move the heat around a bit, much hotter closer to the stove.

Max

mekennedy1313 wrote:
Ken, it can be pretty simple.  Build the J-tube rocket part, you get lots of heat and clean combustion.  Replace the thermal mass part with your cast iron radiative heater.  It will work, as I've said before faster heat-up and cool down but less staying power so you either will need to feed the fire more often or accept larger temperature swings.  Not a big deal.  You may also need fans to move the heat around a bit, much hotter closer to the stove.

Max

BUT
J-tube rocket stoves don't work with an inside diameter less than 4" - it's been tried, and they just plug up from the viscosity of the air itself in that small a tube.  You might be able to do it with fans, but the burn is likely to be dirty and unreliable.  Pocket rockets do OK at 4" with a short, fast exhaust (not a round-the-room adventure).

AND
you need the inside diameter of the combustion part to be the same as the exhaust part, for rocket stove type exhaust.  So how much stick fuel could you fit in a section of that overhead pipe?

SO
unless that cast-iron pipe is bigger than 5" inside diameter, you gonna be sad.

IF
you use fans, a sealed hopper, oversize burn chamber, etc., it isn't a rocket stove, and you've got to figure out some other way to get it to burn clean so you don't melt your shop down with a creosote fire.  Clean that sucker religiously, and I don't mean "liquid chimney sweep."

IF
you build a standard rocket stove at 8" or 6" with its own thermal mass, you can leave the overhead heater intact and pick your winner.

IF
you already know what you want to build,  then ignore all of us and try it.  Best of luck.  Send pictures.

Yours,
EKW
http://www.ErnieAndErica.info

Erica Wisner wrote:
BUT
J-tube rocket stoves don't work with an inside diameter less than 4" - it's been tried, and they just plug up from the viscosity of the air itself in that small a tube.  You might be able to do it with fans, but the burn is likely to be dirty and unreliable.  Pocket rockets do OK at 4" with a short, fast exhaust (not a round-the-room adventure).

I'd missed the post with the size of his radiator pipe, thanks for pointing that out, it would definitely add resistance not only due to the viscosity but the increased proportion of frictional forces between the gases and the pipe walls.  Let me clarify the statement I made above, it should work if the elements are sized correctly.  What the correct sizes are, I don't know.  As Erica pointed out the work's already done on the thermal mass version so why play around unless you are interested in the development aspects.

HI Erica,
You may be right that what I intend to do with this, that it cannot be called a Rocket Stove. I don't know about that. If a Rocket Stove is to be constructed a certain way, then no it would not be.

Ken

Ken what i see is an attempt to make a controlled pipe fire. a rocket stove uses the hot stack effect for the heat riser. what this means is the draft is all inside the stove; its not dependent on a chimney. the barrel is for capturing the pyrolitic gases and giving them time to finish burning. the cooling of the gasses due to heat loss from the barrel surface helps to "pull" the system a little but not much, to little fall.  if you are looking for a clean burn (by clean i mean on par with a RMH). there's no other way; that i know to do it. if you are looking for a little cleaner than a traditional wood stove then a pipe fire will work sort of. the difficulty is the heat needed to radiate effectively in space. it's really quite alot 670 degrees will heat you at 10 feet eventually. it wont heat the air it will only heat objects which then over time heat the air.

modern shops are an interesting problem to heat. my shops get used for boat building so at any given time i either have very fine dust ( explosive in the right  mixture), solvent fumes (even with good ventilation) , epoxy fumes, and a huge space that needs to be heated. on first blush the last thing you want in your shop is a thing with fire in it. however; (and this is not a plug for RMH's independent of the subject) the fire part of a RMH is low to the floor, the fire is deep in the feed tube, the barrel radiates at a good heat, that if set up right is below the average ignition temp of most solvents (naptha might be a problem).
floor space is an issue in any shop but i have some thoughts on that as well. most shops have a workbench in them that is several inches off the floor and i would look at running the exhaust and thermal mass under the bench. I also like having a wailing chair in my shop (sometimes a seat where you can cry is a good thing when building boats) so the mass can be made into a seat. i also almost always have coffee or tea in the shop so a surface to heat/brew on is a good thing.

a couple observations about a RMH in a shop; the heat is given off over time so you can have a consistent heat for epoxy cure (cuts down the amine blush problems). the mass acts to stabilize both temp and humidity so you dont have big swings in temp or or moisture ( good metal and wood also good for many paints and coatings). if you are doing foundry work having something to pre heat molds in/on is a nice thing to have.

anyhow whatever you decide let us know how it works out. I always like to hear about options for shops.

Ernie,
My shop is a large commercial electronics shop. In one of the pictures I sent is a natural gas infrared heater I have used for 8 years. It heated the floor, walls and all the metal electronics in the shop. I could get the floor heated that you could walk around bare footed as the kids would do and it felt like a water bed. Once the concrete floor was heated up it would heat any connecting concrete floor even out side as the snow would melt on it also. That is what I like about this type of heat. Yes it heated people but I was looking at the mass it would also heat.
Back then Natural Gas was around $5 per MCF. Now its $15 and this is now costly for a 4500 sq foot place.
On these you can also use outside air and there is no cause of explosion because everything would then be sealed to the inside.
I intend to build this to see what will happen and will keep you informed. I have built several different type of gasifiers but nothing like this so its a learning curve for me also. Someone here mention that maybe the best idea was to burn the flame in the vertical channel and heavy insulate it up to the horizontal tube. I think thats the way I am going to try it first on my proto type.

Ken

Thanks Ken
I do know the heating system you have in your shop and they are nice, these days the expense is pretty huge. you might look at heating the slab the Pex tubing has come a long way in the last couple years. and while its a pain grooving the slab to put down tubing is not that hard to do. then you just fill over the tube with levelite. looks like you get plenty of sun in the winter so a solar hot water system might be the way to go.

in an electronics shop you probably have the tooling to make the heaters already and the book gaviotice (sp) has a description on how to make infrablack on copper plate that can be adapted to the thin flashing copper sold in hardware stores. All the acids and oxides are easy to get from various places. ( auto parts stores, pottery supply, ETC.)

just tossing a few ideas out.

Ken, This is an old but interesting topic. If you are still watching this site, did you build it and, if so, how did it go?

I have built and used a radiant rocket stove heater with great success. temp drop from barrel to end of radiant run 1100f to 150f. In a tent so almost no heat from convection (all lost through uninsulated canvas) only radiant heat will work.