Eugene Howard

I realize this thread is about bells and such, but perhaps related..........as I think of original rocket mass heater design.........j-tube, barrel riser and cob style bench as thermal mass..........you light up the fire and keep it going for a short while until thermal mass heats up......then let fire go out and ride the radiant heat of the thermal mass for as long as it lasts.  Rinse and repeat.

What happens if you just keep the fire in the j-tube going........continuous? Does the whole thing ever reach an equilibrium point or does it just keep getting hotter in the room to the point it eventually drives you out? Once the thermal mass heats up, what happens to flue temps? Do they start rising also to point where you are no longer storing heat but losing it up the flue/chimney?

So yet another question.........if I were to use lump charcoal as my source of fuel (vs wood), would these rocket heaters.......batch or j-tube......work as well, or even at all? My guess is no.........or at least not nearly as well.

Some observations..........youtube videos from well known sources.........

First up.......one of my favorites.......but what I note is the size of the fuel load........and how it burns.......and how vortex waxes and wanes thru stages of the burn So what happens downstream of batch box when the flames go out? Where does the radiant heat from still burning charcoal go?



Next up.......will use a Liberator as example of a j-tube...........this is NOT a batch system.........a continuous burn that does not vary......meaning all components of the fuel......charcoal and gases........all burn at same time.......and as soon as fuel runs out, all heat generation stops. Unless a thermal mass is installed downstream, the heating stops. In practice.....as folks are using these.....it gets to be a problem.



And lastly what in my mind may represent best of both worlds.............with a twist..........replace the batch box of the masonry heater with a j-tube running thru appropriately sized bell........which BTW.......takes us back to the original rocket mass heater.......with j-tube, barrel riser and cob mass. But all components of the fuel burn at same rate and can burn continuous for as long as it takes to heat the load of the mass to see you thru?



OR........combine the lovely flame and vortex of the FOX batch system, as core for a masonry heater. The FOX batch system could be a commercial made outfit no different than one of the truly horrible heatilator type pre-fab fireplace cores. Do that and maybe we can take these mainstream into homes all over the place?

Many apologies..........yes I do tend to get the terms flue/chimney and stack height cross threaded........stack height sometimes used with BBQ smokers, which I'm also interested in. I'll try to use flue from now on to refer to......well......the flue. BTW, with BBQ smokers, taller stack heights are used to increase the draw, power and heat generated inside smokers. Stack size, both in diameter and height matter. Those also include dampers which are used to slow down rate of burn (smokers can get "rockety" too if allowed to take off and go.........), so dampers are used to slow down rate of burn and to force heat and smoke to back up into the smoke chamber. Offset smoker designs going thru an upheavel as designers are trying to direct the heat thru the smoker chamber to spread it out evenly for better use and results. Top down cookers gaining in popularity over traditional bottom up cookers. One should think it would be settled science by now, but it's not.

Also, thought of yet another factor that might affect chimney / flue slow downs or reversals.......and that is a source of make up burn air. Way back when, our houses and buildings were drafty, so source of make up air was easy.......there was no shortage of cold air coming in........but as homes become better built and tighter........they run out of burn air. Initially this was couched in terms of not wanting to burn heated interior air thru our wood heating appliances, but past that.......a tight house runs out of air.......basically the stove pulls a vacuum and stalls when it runs out of make up burn air. May not apply to everyone, but I suspect it may apply to some.........and some of those not aware of what is going on.

So a few observations and perhaps clarifications......

Perhaps what makes the batch box more powerful is there is a larger stack of wood all burning at same time.......vs the j-tube which has one or a few sticks burning at a single point of flame........the tip of the spear?  Like twin 4 barrel carbs vs. a 2 barrel on a gas engine? Perhaps the analogy does hold up if you think of the heating of the mass as the load on the engine?

Peter's explanation of the draft temp condensation issue is very helpful. Had never seen it put that way, but does make sense. So taking that forward........some mitigation remedies...........

1. Hotter stack temps.......don't stall the engine with too much load?
2. Less stack height? Can recall issues when folks put rockets in basements and ran flues up 2 or 3 stories and they didn't work? So short stacks to chimney top vs tall? Then there would be issues with inside chimney stacks vs. outside?
3. Does it matter if chimney flue pipe is single or double wall?

Seems like there are a lot of engineering variables to consider.......and perhaps some guildelines set forth as something to consider and follow?

This is a commercial boiler setup that comes as close to continuous burn potential as any. Use wood chunks vs. sticks of firewood?

Have given the situation OP describes a bit of thought, and it occurs to me what is needed is to graft the rocket concept onto a central heat distribution system. I am aware of one direct application...........gasification boilers.........and another older system that uses hot air convection......same as with most forced air heat systems.

Commercial made gasification boilers.......both updraft and downdraft can be purchased, but are fairly expensive. The most common in US are the outdoor boilers. Nearly all of those are batch burn of firewood. But move on to the euro market and there are larger boilers that use biomass.......aka.....wood chips with automated feed systems. Very expensive.

As a kid, the home we lived in had a wood or coal fired forced air furnace. My grandparents had a big two story home that had a similar furnace in it. I don't know the mechanism, but a fire in the firebox heated an enclosed area above, and then the hot air was pumped thru ductwork like any other forced air furnace. I can't remember how the heat exchanger was setup. My dad built a 28 x 40 shop and it is also heated by a stationary wood burning floor furnace, with blower. No other  ductwork or heat distribution. Not even radiant heat as the firebox has an insulated jacket around it.

I found this photo on another site of a one of build a guy uses to heat his uninsulated metal shop. Both radiant and convection heating......

He runs a hot fire in the heater, and heat exchanger are the pipes that run thru the firebox. But imagine a batch box running off to the side and exhaust routed thru this like a bell........and heat output ducted so it could be pumped around?

Lastly, am curious if anyone has ever used wood chunks.........about tennis ball sized chunks in either a J-tube or downdraft gasifier? One that could be employed as a continuous burn?

Question on ISA.

Is the internal surface area related to the size of the fuel load in the batch box? As in one load of fuel will heat this much area?

Or.......if you ran a 6 inch J tube.......and just kept it going.........if you had an ISA say 150% the maximum for the batch box......would it eventually get it up to temp?

OK, am familiar with them. May even be registered there. Will check it out.

Merry Christmas to all!!!

The other forum? Permies? Or........?  

Big fan of your videos. The burns are impressive. Always thought something like the unit shown in the video could be made into a central core that could be made commercially, then shipped to a build site to be installed in a masonry heater to replace countless ineffecient conventional fireplaces.

If starved for entertainment and looking for a new direction, am wondering if something similar could not be developed as a down draft unit, which could then be fed continuous like a J-tube, vs. a batch box? Keep feeding it until you get your thermal mass where you want it, then let it burn out?

Either way, for widespread appeal, the glass door to watch the fire burn will be important. Being able to also watch the vortex burns is the cherry on top.