3 different rocket stove water heater designs, input requested

Hi guys! I have spent countless hours on this site and learned alot of information. I love the efficiency of the rocket stove, particularly the RMH. Unfortunately I'm not too keen on having a bunch of cob in my house but I do like having a wood burning stove in it. My plan is to build a rocket stove that will heat water and cycle it to water storage tanks in the basement. There will likely be four tanks, the hottest two will have electric elements in them as back up. The wood heat will be supplemented by solar thermal evacuated tubes. The farm that this will be built on is North of Saskatoon, Sk, Canada and there isn't natural gas piped in there. Other heating options are heating oil or LP both I think are too expensive and will continue to rise. I have chosen electric, solar, wood since electricity is already ran to all yard sites and it is simple and you only have one bill. The solar and wood will offset the electric bill. There is no shortage of white & black poplar, spruce and white birch near by.

My goal is to extract 50-75% of the heat from the rocket stove through the water and have the remainder convect, radiate into the living room. I am looking for practical experience from anyone who has built or seen a design similar to one of these work. Which would extract the most heat from the rocket stove to the water without lowering the efficiency of the stove?

The first stove has a water reservoir directly on the rocket stove that holds ~45 liters, 24" round x 6" high. In this design the small amount of water would also act as a small thermal mass once the stove has been shut down. I think the temp in the tank will also rise slower so in the event of the system temp rising too high the stove could be shut down before the temp in the reservoir got too high. Surface area is about 452 sq inches and the temp is hottest on that part of the barrel.

The second stove has ~1/2" ID copper pipe coiled inside the barrel and spiraled like a pinwheel at the top. This design could have 28 loops with a circumference of 18" totaling 2400 sq in of surface area, if my math is correct. 18" diameter is 56" circumference x 28 loops + 1500 linear inches x circumference of pipe 1.6 = 2400 sq inches. Plus the area of the pinwheel spiral under the top of the barrel, I don't feel like calculating that haha. This design has more surface area but at a lower temperature along the sides of the barrel but I still think it will capture more heat than design 1.

The third stove combines both the stoves together, it takes the 28 loops along the side and then dumps into the 45 L reservoir on top of the barrel. I built this one because I like having a bit of thermal mass on the stove and I wasn't sure how the pinwheel spiral of pipe would affect the airflow through the stove.

I haven't drawn any of the T/P relief valves yet and this will be a closed system and it will be running on some type of antifreeze since it will need to cycle up to the solar collectors. Barrels 3 & 4 will also have this fluid. Barrels 1 & 2 will contain fresh water. I will be building the stove but the system will ultimately be designed and installed by a licenced plumber.

Line 5: Hot water can make steam, yes I am aware of it and if proper precautions are taken water will not reach that temperature.

Thanks in advance for your input! Calvin

I tried to attached two images, we'll see if they worked...

Calvin Cox : Welcome to Permies, with over 19,000 fellow members you will always find some one here 24/7 who wants to talk about want you want to talk about, many with
widely, or wildly different positions on any topic you pick !

W.O.W., Where to start, I think we both agree that It is the High Temperature Combustion which leads to the great efficiencies of the R.M.H. and the promise of great fuel
savings that attracted you to the R.M.H. in the 1st place. But, that is only the very start, we have to have a controlled way to absorb the heat in a way that continually reduces
Its internal temperatures as it leaves the Heat Riser and falls thru the vertical plane to exit out the transitional area - horizontally to the area where the greatest part of the
Hot Exhaust gases are expected to give up their Heat Energy to the Thermal Mass that they have been Routed through!

By exposing the exhaust gases to the immediate cooling effects of your 3 units, you are cooling the exhaust gases down too soon! This will stop the high speed flow of all the
hot exhaust gases, cooling them down below their combustion temperatures, and even causing the depositing of large amounts of Creosote within the barrel. Much of your
vaunted high efficiencies have been lost and the R.M.H. will transform into a smoke belching monster ! ( low, low efficiencies will result ) Worse is yet to come, eventually you
will succeed in raising the temperature of your water to around 212 F, this is as high as your water can go, an Absolute Temperature that can never be exceeded without sealing
and pressurizing the vessel that contains your hot water !

I need to repeat here that even though your water is now right there at the highest temperature allowed by the rules of the universe, you still have not reached temperatures
that allow efficient operation of your Rocket Stove !

However at this temperature The water in all three models of your' flaming units of death' will flash to steam, 1st- I want you to go to You-Tube land, and check out the Mythbusters
"Exploding Hot Water Heater'- In this case. as Video-taped several times, and reported on U-tube, the whole building was destroyed, the crew came out to look at the remains and 20
seconds later the shell of the tank came down ! - Find it on U-tube now !!!

2nd,and you can rise to this level of enlightenment, without having actually watched 'Mythbusters' , Think the Boston Marathon Bombing with more 2nd and third degree burns!!

Because of the Extremely small diameter of the copper pipe that you used in your #2 and #3 models, the surface area of these small diameter tubes is so much greater than the
mass of the contained water that #2 and #3 will flash to steam before the 1st unit ! (the explosions will be a slightly less dramatic !)

My personal recommendation to you is to consider these 1st simple designs as a small step in a 5 year plan to eventually combine the Rocket Heater into a working Electrical and
Solar system, in truth it must be said that you have barely grasped the fundamentals of the R.M.H.s normal operations , and you have much to learn about the proper sizing and
normal use of any hydronic system, Electrical , Solar or Fossil fuel fired heating unit ! For the 'Safe Growth of the Craft ! ' And your personal safety !!!

Think like fire, flow like gas, Don't be the Marshmallow! As always, your questions and comments- are solicited and Welcomen! PYRO - Logically BIG AL !

[By exposing the exhaust gases to the immediate cooling effects of your 3 units, you are cooling the exhaust gases down too soon!
/quote]
This is something that I haven't heard before (not arguing with you, just new to me). Was under the impression that the goal is to achieve the highest temperature possible and once it leaves the riser, the more quickly it cools, the greater the draw would be because the weight of the gasses increases quickly as heat is absorbed. Please expand on this concept.

Calvin: I totally agree with Al about the danger of the designs presented. While there is very little chatter on this forum about the measurement of heat (BTUs) generated by RMHs, when heating water this is a critical factor. Design #1 @45 liters of water is a little less than 12 gallons or somewhere around 100 pounds. To raise the temperature 100 degrees fahrenheit would require around 1000 BTUs. If my understanding is correct, burning one pound of hardwood can produce around 6,000 BTUs of heat (at 100% efficiency). One handful of wood and.......BOOM! There are commercial steam generators that have coils of tubing in a similar arrangement to example #2--notice the word STEAM! As a former boiler operator, my suggestion to you is to rethink your designs. While the majority of those on this forum want nothing to do with heating water, this is something I am very interested in doing BUT you must not make steam! You mentioned T/P relief valves. Please keep in mind that these must be sized correctly for the potential amount of steam that could be created (once again, BTUs per hour). Have fun but please play safe.

Bill Fox

Bill Fox: - I am just saying that initially we want things super insulated, building R.M.H.s exactly per Ianto Evans, old bricks and minimal insulation,
it used to take up to 3 minutes to 'Hear the Dragon'!

With true Fire brick, and a Perlite and Clay slip chimney wrapped with refractory mineral wool, and insulation of the whole R.M.H. From the cement
floor ( yes this is a tradeoff !) time to 'Hear the Dragon" is down to around 1 minute, this gain and the gain in even Higher Combustion Temperatures
is the result of reducing initial heat absorption Materials.

Actually, I had thought that I had covered that, so thanks for making me make it a little clearer, Again We see this when our neighbor with his Outdoor
Wood-fired Boiler starts up his heating plant, not much efficiency in the beginning due to heat being stolen off of the 'flame front' by the contact with
the heat absorbing cast steel water jacket .and massive amounts of smoke that is by itself lost (potential) heat energy ! Hope this is a little clearer,
and is timely, and helps with a clearer picture in your head.We want to reduce all heat absorption until we have everything up to Operating temps 1st !

For the god of the Craft ! Think like fire, flow like a gas, don't be the Marshmallow ! your comments/questions are Solicited and welcome Big AL !

Al: Thanks for the clarification.

Calvin: I made an error in what wrote because obviously I am mathmatically inert-- I wrote: To raise the temperature 100 degrees fahrenheit would require around 1000 BTUs. If my understanding is correct, burning one pound of hardwood can produce around 6,000 BTUs of heat (at 100% efficiency). One handful of wood and.......BOOM!

This should have read to raise the temperature 100 degrees for 100 pounds of water would require 10,000 BTUs; therefore TWO handfuls of wood and........

Bill

Al, read line 5 in my original post, and thank you for your one suggestion of using larger diameter pipe coils.

Bill, thank you for your great reply! I also had the same understanding as you about containing all the heat possible until the air leaves the heat riser then it's free game to steal energy from. If this wasn't the case wouldn't the barrel be insulated as well?

As you mentioned 1 lb of wood would heat that water in a hurry, theoretically. I have built one of these already but I couldn't get it to draft properly. I think I had wet white poplar. I just brushed the snow off and cut it out of the bush, it was dead fall or dead standing. I have 1 year seasoned white birch for my next test. I built one similar to design #1 except the top of the reservoir was open, no lid, and I just filled it with snow then fired it up to see how long it would take to boil then I would have a bit more info. That was on a 6" round duct feed, burn tunnel and riser all housed in a 55 us gal drum. I think that is marginally enough room to have an adequately tall enough heat riser. So after much tinkering the thing didn't work properly so I never did get to boil the water. The prototype I made a week before did get the top center of the barrel to over 900F, pegged my thermometer.

I was thinking if you can get 900F at the top center of the barrel and alot of people say they have 300F leaving the barrel that would be safe to say you are utilizing 60% of the available heat before it leaves the barrel. Does anyone have any info on how many lbs/hr 49 sq in system would use? Until then I will assume 16 lbs/hr.

16lbs is potentially 96,000 BTU, if the stove is 90% efficient in converting the wood to heat you have 86,400 BTU to play with. Based on last assumption of using 60% of the heat in the barrel you have 51,840 BTU to use in the barrel. If you could capture all 51,840 BTU into the water, which you won't because you'll still be losing some through the barrel walls, you could heat 518 lbs of water by 100F or 51.84 imp gallons, much easier conversion than us gal.

You now need to move 51.84 imp gal, 235L or 61 us gal every hour. That is .86 imp gal per minute. Pretty slow pump. Even if you could capture all 96,000 BTU into the water you would need to move 1.6 imp gal per minute. If you doubled the wood consumption to 32 lbs/hr and kept the 100% efficiency and 100% capture rate you still only need to move 3.2 imp gal per minute.

If I only wanted to run this thing for 4-6 hours a night and I'd like my 50 imp gal tanks at 185F when the stove shuts off for the night, I need to heat tank 1 by 45F = 22,500 BTU, tank 2 by 63F = 31,500 BTU, tank 3 by 81f = 40,500 BTU and tank 4 by 100F =50,00 BTU I need a total of 144,500 BTU. 144,500 BTU spread out over 4 hours is 36,135 BTU/hr. Judging by these rough calculations that don't account for thermal losses to the air the 16 lbs/hr would be too much. 11 lbs/hr would be better. Or I could add more water tanks or have larger water tanks to absorb more BTUs. But as we all know things in practice don't always work as they were planned in theory.

I would love to hear from someone who has tried the coil or the reservoir so I can get an idea of many many BTUs will end up transferring into the water.

Am I missing something here because I don't see what makes these things Big Al's "flaming units of death".

Bill that is great that you have a boiler background that is a great resource in getting one of these rocket heaters successfully converted into a useful water heater. Keep the GOOD suggestions coming.

Am I missing something here because I don't see what makes these things Big Al's "flaming units of death".

For what it is worth I think what you are missing is quite simple. If you heat stored water in a sealed system with a heat source over which you have no control you have a sporting chance of raising the overall standard of the gene pool.
However, if you use an open vented system and move the water, you don't. In the UK the use of a sealed system for any solid fuel appliance is an absolute no no. Uncontrolled heat sources have to have the means to leak the hot water away (by cooling it in some part of the system) in order to maintain safe working temperatures. People were being killed by open fire back boilers which were disconnected when heating systems were introduced, but capped off. They retained a small amount of water which when the fire was lit it had no where to expand to. The result was generally an explosion.

If you Google Dunsley you should find the answer to all your problems. It may take a bit of studying but the inbuilt safety devices prevent problems without a blow off valve in sight. I use one to connect a Propane boiler, a wood burner with back boiler, and have now added a small rocket water heater which I am experimenting with as well. In a properly designed system the loss of the electricity supply will still give you adequate time to get the heat source under control, and even if you don't it will be safe. The rocket alone will raise the temperature of the circulating water to 60c in a couple of hours. This translates to enough hot water in the hot water cylinder for a days use (3 showers and washing). BTu's are great for theory, but they are so dependent on the quality of the fuel that in reality they are at best, only a guide.

Hope this helps.

The statement by Al about the effect of cooling the heat from the riser too soon had me wondering too. As an experiment I added a fan to increase the draw of the flue. He is absolutely right. The temperature of the water in my system rose 30c in minutes with it, but much slower - best part of an hour - without! So the work is not all done in the J tube as I, and I would guess others, had assumed. Thanks for that, it has proved to be one of the most useful bits of info on here.

et al : If we built a rocket Mass Heater with a bypass that let al of the heat go up the chimney until it had stabilized at its peak temperatures and hot exhaust gas velocities,
and then flipped the bypass so that the exhaust gases could give up their heat No problem !

We HAVE to let the R.M.H. come up to Temperature FIRST !!! All of the Exhaust gases must already be consumed, which takes Temps in excess of 1600F and then, down-
stream from the Barrel where it makes no difference to the operation of OUR Rocket, we can proceed to remove as much heat as we can do safely, We must also plan on
exposing water to these temperatures, If our exhaust Temps are in this range and the pump that we are using to move the water thru the system fails, we can have the
water in the Tubing Flash to Steam ! I am sure someone will correct me if i am wrong this is an expansion of 60 Xs, this is an explosive event !

How are you going to turn off your fire when the power goes out, If you try to cap off the top of the Feed Tube to starve it for Oxygen, you are creating the exact conditions
that the movie ''Backdraft'' Immortalized, If you try and remove the cover any time that the combustion chamber of your Rocket is still hot, you will be lucky if all you
lose is your eyebrows ! Big AL !

If our exhaust Temps are in this range and the pump that we are using to move the water thru the system fails, we can have the
water in the Tubing Flash to Steam !

My point exactly. Any pumps used are incidental to the system and the system is not reliant on them. They should not be used inline, but parallel to the return as an assist to flow, (and efficiency of the heat transfer) and not the cause of it. Large bore gravity systems into a separate hot water storage unit/s is the only safe way. Using a pump as the primary source of circulation with an uncontrolled heating unit is insanity. There is no point in heating water you do not have a use for. I have seen a solid fuel system fitted and only capable of working with a pump. In a power cut the householder was shoveling burning coal out of the boiler because the solder on the copper joints was melting!
The potential dangers should not be underestimated, I agree. But there are many ways of doing this safely. Sealed and/or pumped systems are definitely not included. I have serious doubts about high volumes of water at the heat source.

In my opinion, for what it is worth, combining mass storage with water heating is about the worst of all worlds. Build one, or the other, or both. That way they can then be sized to suit requirements. I can't get into the house with a spec of mud on my boots, so sneaking 3 tons of cob in just isn't going to happen. Hence my interest in heating water. If the project proves to be a success, or a failure, I shall post the results as pointers to others attempting to heat water.

I strongly recommend that the Dunsley neutralizer system is looked at if heating water is your thing. I have ad ons of my own to this to further increase the safety for use with a rocket if anyone is interested. I believe this can be done, more importantly, I believe it can be done safely. But I might be wrong............

Paul Jones : Thank You, that was well and clearly stated ! It has been proposed that a really tall Heat Riser could cause the hot exhaust Gases to flow through the Thermal Mass
fast enough to cause them to exit at a high enough Temperature that you are loosing heat recovery and efficiencies! Obviously, heat absorption depends on surface area and the
ability of the exposed material to absorb heat !

As the Heat Riser has to fit under a barrel, and the Barrel has to fit over the Heat Riser and under the rooms ceiling this would be the upper limit, Some increase in gas flow is also
possible with a taller exterior chimney ! I will research the Dunsley system though it will probably be slow going for me !

Take your wife out on an outing the see a Cob House ! You just might be surprised what she would accept ! Keep shooting them at me I will try to keep up ! Big AL !

Thanks for increasing the solutions guys. That is a lot more beneficial than predicting death and Darwin awards. I'm going to experiment with these designs irregardless so it's nice to have some suggestions before I hit the shop.

Paul I tried to research that site and all I found was a company selling wood stoves. Not a lot of water heating info. Do you perhaps have the link?

I am on the same page with parallel pumps, sort of, I like a primary and a secondary in parallel both capable of moving more than enough water to keep the system at a safe temp independently. I work in an industry that plans for failure so we always have a plan B and C for every system. I think it will be wise to have all pumps and valves ran off 12v batteries so will have some time with power outages to keep the system under control. Batteries would be fully charged off grid power. The large diameter gravity system won't work for me since I'm not willing to give up 100 sqft of main floor living space to house my mechanical room. It needs to be down stairs.

Paul do you have any more info that you can share about the design and operation of your system? Always best to learn from someone with practical knowledge.

Al: what you were mentioning about taking heat too early, is that only a problem till the stove hits its ideal operating temp? If you let it get upto temp then start taking heat just outside tbhe riser will stay still have negative effects?

As for dousing the fire, if an over temp was probable a pot of water down the feed would likly do the trick. Other options would be snuffing it or pull the sticks out and toss them in the metal ash pail and out into the snow with them. Not too worried about controlling that aspect. Rockets need a baby sitter as it is so this one would be no different. I'll have temp gauges all over this system linked to one monitoring panel. As well as one analog temp gauge reading fluid temp on design #1.

As always, keep the tips coming!

http://www.dunsleyheat.co.uk/neutralizer%20layouts.html

My system is a variation on this. The installation instructions provided with the Dunsley offer, or did when I bought mine, far more options. It has been working for the last 10 years untouched!

Footprint of 100 square feet? Mine sits in a cupboard with a floor area of less than 2 x 4 feet and that includes the header tank, HWC, Dunsley, pumps, controls, and gas boiler! My solar heating is connected to a coil in the HWC which, had I ordered a Dunsley with enough tappings, would have fed directly into that. Sometimes the water is too hot.

Gravity circulation is God. It is the only safe way to disperse heat. Even my solar is gravity fed so that if I have a pump failure it really wouldn't affect it.

If you must continue down the route you are considering, and who am I to say you shouldn't, think about adding a 50 gallon drum of water above your rocket - open vented - that can gravity feed heat away just in case. If you use a normally open motorised valve your power supply will keep it shut off until the power goes off. You could add a pipe stat to the flow side of the heat exchanger to release the valve if the primary water starts to overheat in normal operating conditions. This tank of cold water will give you ample time to allow your Rocket to burn down. My other thought is if you want to use pipe as a heat exchanger keep it short to lower the water content, but increase the surface area with multiple metal fins. It is far easier to control half a gallon of water that wants to boil than 10 gallons.

It is far better to build in more safety features than you need at the start. If they prove to be unnecessary the option exists to remove them. If they are not there you may not have the option to put them in!

A question for those who might know: Would a CO2 fire extinguisher coupled to a sealing plate for the feed tube be successful in shutting down the fire rapidly?

Thanks Paul. I am all for a non motorized safe system if I can get one that will work for what I need. I had the understanding that you can't gravity feed a hot water tank that is lower elevation that your boiler, is this the case? And also the 4 sqft space will not house enough hot water to heat a 2000 sqft house in -40c with a 40 mph wind. As well as domestic hot water for a family of 6. As I mentioned I would like to store enough hot water for 20 hours of use. I only want to run the rocket stove for a few hours each evening while we're home to babysit it. Ideally the electric elements in the hot water tanks would never have to cut in.

Sorry Calvin I missed the mass storage.

No, it won't gravity feed downhill. So a diagram which may give you something to think about.



The RMS would ideally have 28mm minimum pipework running vertically all the way to the tank. There are limits to horizontal runs and each joint adds resistance to the flow. The lower 50 gallon drum could be reduced in size for quicker heat up of the mass water and lagged. The header tank might be better in galvanized steel than plastic, which won't melt if boiling water does get that high. You really can't avoid the sprung return motorized valve on the top tank for automatic action if the power drops out. This should give you some time to run the RMS down before disaster strikes.

This is just an idea - it needs work. The principles are sound, but I strongly recommend a lot of controlled testing before relying on anything. Please remember that if anything can go wrong, it will!

Hi guys.

I've been looking at several designs for a rocket water heater.

And what comes to mind when considering the factors should be something like in this sketch I made up.

That said, I do have access to wielding equipment and old water heaters.

The design...

* Operating at normal water pressure (might considder two pressure/temp valves on this)
* Added vertical steel fins between the water and exhaust (Size should be tested, as this might induce too much drag on the exhaust)
* Isolating the area above the riser exit to reach sufficient combustion temperatures before it cools off by the walls (Some people that have constructed with water all around and over the inner barrel seems to have issues with getting draft)
* Need to figure out something smart to do with the exhaust (Thing is to be buildt outside in a shed)
* I should move the cold water inlet to a low location and the heated water outlet to the top

Kind regards,
Thor

Thor Elvin Valo : Rather than talk directly about safety, and the dreaded ''Bang - Squish'' when part of the system Malfunctions , Lets talk about maximum load !

We have to have an idea of the climate, and allow for the storm of the Century (Like the old time farmers said Climate is what you expect, Weather is what you get )
to design a system sized to the BTU requirements of the Heat load !

Then we need to consider the TWO buildings

1) the out building and its needs and requirements for insulation, air to air heat exchangers, and make up air


2) The primary Building, its use, occupancy and times of occupancy, and its insulation, Air2air and Make up air requirements!

This should remove most of the potential bottlenecks, and areas where water might 'flash to steam' but such a design should be looked at by a H.E.V.A.C.
Engineer, installed by professionals, and reviewed by a Certified Boiler Tech, and operated only by someone who has had further training in its operation !

Having said that : The Great efficiencies we get with A Rocket Mass Heater are from burning Bone dry Finely split small wood at freakily high Temperatures
allowing for complete combustion!

The Rocket Mass Heater RMH, is designed to work as a space heater, heating the core of your home. In this location, literally within arms distance of the
Homes Core, the frequent needs of the RMH can quickly be met, not as an obstacle in the flow of the days events, but as something tended to with no more
thought than you would use adjusting your eyeglasses !

As such it needs to be located not in some remote corner 'out of the way', But as a Piece of Finely Crafted, Built-in Furniture, a Multi-generational Family Treasure
to be passed on to great and great grandchildren !

After a fine working RMH has come up to temperature, 2-3 large pieces of wood Can be placed in the mouth of the Feed Tube, and will often provide over an
hours fuel supply to the entire RMH and home, Even then your fuel-air mixture should be adjusted within that period !

Again this is just not going to happen if Your RMH is in a remote location !

A partial solution to your situation is to investigate a Batch Fed RMH rather than the Vertically fed RMH that you used for your sketch-up. A batch Fed RMH can be
run with efficiencies closely approximating the Efficiencies of a carefully Tended Vertically Fed RMH. As the name implies, it will allow for loading several hours
worth of wood into itself greatly reducing the amount of attention it must have during the burn cycle, Once again The Size of the heating load determines the
size of the Batch Fed RMH (and how often it must be run ) !!!

Running ether of these models at a remote location requires a mindset willing to accept frequent interruptions of your planned activities to go tend a remote fire!

Remember the more Bells and Whistles you load onto your system to assist you in monitoring you Water jacketed RMH is also increasing failure points !

For the good of the Crafts ! Think like fire, Flow like a Gas, Don't be the Marshmallow! As always your comments and questions are solicited and welcome Big AL

Allen: That good and all, and I really enjoyed your thoughts on the RMS as a family treasure for several generations. I do agree on that.

That said, we did talk about a water heater solution here right? So I will still need a RWH (Rocket whater heater) :3 for my shed. It's purpose will be to heat the water once a day so the residents and guests could get a decent shower each day. It's off grid.


That said, have you seen ZeroFossilFuel's channel on youtube?

He has designed and perfected an adapter for feeding a rocket stove continously with pellets, and it looks like something everyone can put together easily.

This we could easily top up a can for a few hours burntime.


PS: The main building will end up with a RMS if I manage to convince the interior designer. :]

Do you have any good toughts on how to improving this design on a water jacketed rocket stove. (I dont think this is considdered an RMS anylonger)

It's also still an option to make this a open system, as the shed is located higher than the main building therby pressurising enough by itself.


Boom squish! -Thor

Paul Jones wrote:

A question for those who might know: Would a CO2 fire extinguisher coupled to a sealing plate for the feed tube be successful in shutting down the fire rapidly?

Without oxygen the fire cannot burn. The CO2 would also have a big cooling effect, perhaps too quick for some materials (crack!).

Thor : You said you wanted to use a Rocket MASS Heater RMH, with a water Mass substituting for a more conventional MASS, so Yes we should still call this a RMH !

If your Out building is located above the level of you shower point, you will be losing he option of having a Holding tank of hot water filled by Thermo-syphoning
action ! This leaves you with gravity fed showers that initially deliver cold water, or Heavily insulated pipes supply and return lines and a pump, this is complicating
an off-grid hook-up !

If all you are designing your Remote RMH For a Time driven Hot water heater for showers or for showers, cooking and laundry, rather than whole home heating,
you can still get a lot of bang for your buck by running all heated grey water through holding tanks before discharging out to Grey water bio treatment type filters.

I more or less assumed you were trying to create a Whole home heating system, run from a remote location, this would quickly turn a simple Automatically
accomplished action into a drudges task that you would soon find your self making excuses to avoid !

As you have found You-tube I would like to direct you to the You tube web4deb channel while this is a little bit more robust build than you would need for a
simple shower point, it is a more robust system ! For the good of the craft !

Think like fire, Flow like a Gas, Don't be the Marshmallow! As always, your comments and questions are solicited and welcome ! Big AL !

I just found this site, but I wanted to jump right in because Sasakatoon is where I go for serious shopping. I'm currently excited about using a "bubble column condenser" to recover almost all the heat from a wood stove, and some of the pollution. The water could be circulated to other rooms, and used as the main heat transfer medium. It would require a fan. A condenser based on water spray or wet curtains could probably get by on just the water circulation pump or even thermosyphon if you have the room. I'll be getting more details.

Would running the piping in the insulation around the riser in an OPEN loop (open top bucket) to 1) heat the water without turning it to vapor and 2) cool and insulate the riser be a viable option?

No, that would not be a viable (or safe) option. The riser will be up to 2000 F or more on the inside, and you don't want to cool that inner riser surface in any way, you want to keep it as hot as it can stand so the rocket effect works best. The gases leaving the top of the riser will be 1000 F or hotter, cooling to maybe 300 at the bottom of the barrel, so you have an untenable environment anywhere inside the barrel. Putting any water thermal sink outside the barrel is the only safe way, of course designing it so it can circulate fast and freely enough to never reach boiling point.

Hi there I'm new here, but would like to chime in.

What if you had an open system for the boiler and then circulating a vehicle coolant through the piping to transfer heat into your tanks? I was thinking of something like evans waterless coolant, it boils at 375 ferinheight and does not create pressure when it does boil, unlike a glycol and water mix. then you could run a coil of pipe through your water tank and re cycle the coolant into a tank above the stove to gravity feed back into boiler.

I'm new to the rocket stove idea, but would like to build an outdoor (in a garage) heater that i can pipe hot water into my house for radiant heat to lessen my gas furnace operating costs, plus i like warm floors.

here is a video on youtube that shows a good comparison
http://youtu.be/zvzyhI0_U0I

Adam Dombowski : Yes ! Very impressive! I have been out of the heavy trucking industry for years ! This topic needs a great more research, and of course price and
availability are critical links in the chain leading to using this but certainly for system that has never had Water in it -getting down below the critical 3% allowable Water
Contamination is a non issue ! Thank you for bringing this to our attention !

For the Good of the Craft! Big AL!

Adam D. : I certainly can understand your enthusiasm for the unknown possibilities of this product !

Actually there are Two questions that we need to find the answers to, and as I type this it occurs to me that An M.S.D.S. 'sheet' or the placarding requirements for
shipping this stuff may provide the answers !

Water holds heat well we call this effect its specific heat and Water is given ''Pride of place'' and the most important benchmark on the scale at '1' !

There is also the ability of the material to flow heat through itself : _


I'm guessing that many people assume a strong correlation between heat capacity and thermal conductivity, and that weight or density are of utmost importance.
Practical experience tells us --- "cold water is heavy and it makes my fingers cold" --- "cold balsa wood is light and after a few seconds, it insulates and keeps them
warm". But there is much more to it than this. Many materials of similar density have vastly different rates of heat transfer or conduction and there is wide variation
in heat capacity between substances of similar density. Extreme example with red title further down.


Check out these links to the engineering tool box.

Heat capacity --- http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html

Thermal conductivity --- http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

I got this from yahoo answers --- The question posed was --- Why aren't thermal conductivity and specific heat capacity related? Thermal conductivity is the rate
at which a material conducts heat away. It depends on how easily (some of) the electrons can move inside the material. Specific heat has to do with how much
energy is needed to raise an object's temperature, which has to do with the amount of freedom the atoms have in the material. These two properties are therefore
quite different.

For example, compare graphite and diamond. Both are pure carbon. The only difference is crystal structure. Graphite has a specific heat that is about 50% higher
than diamond, because the atoms are more loosely set in the structure (they are set in planes that can slide).

But diamond has a thermal conductivity that is more than 800
times better than graphite, because the regularity of the diamond crystal favors certain directions enormously.

(Much of the above was stolen from a Thread extension By Fellow Member Dale Hodgins as long as I give him credit - - - -)

So we believe that it transfers heat well -its thermal conductivity! In its approved application it does not need a high specific heat the amount of btus it can hold to work
well as a Waterless Cooling fluid ! This is made even more so as it is being pumped to a radiator !

So - Good find, This raises questions and answers will be found ! Thanks again for finding this !

For the good of the craft ! Big AL

Hi
What about this thought (attached image)
It is thermosiphoning, mains cold water feeds into header tank which also functions for relief of pressure and expansion.

The copper coil should be encased with very good insulation, like 150mm cellulose, where the box can be made out of sheet metal or 2 different sized barrels upside down to achieve a cavity to fill insulation.
So the copper coil has lots of surface area within a confined well insulated space to exchange the heat to water. Looks alright? Shall i have a go?

So i have regarded the expansion and pressure regulation with the header tank (not my idea, this is common old methods) that also maintains cold water delivery at all times with the float from mains pressure.

So no explosion danger!

Regarding taking energy away from the required operational heat level of the rocket,
i think by absorbing energy just from the top of barrel, it might work.
I don't think wrapping the whole barrel with a "wet jacket" will work. As you mentioned in this thread before, the rocket will struggle maintaining its temperature to be efficient.

[On conventional "slow combustion heaters" they put "wet backs" inside the firebox. Yes mad. Then the more cluey ones install another loop on top of the loop between wetback and header tank with a temp sensor and switch to determine circulation through wetback ONLY starts at a set min temperature, i think 50 celsius. Therefore the fire is not constantly hit with colder water and thus less creosote is produced.
Of course slow combustion heaters are a big compromise anyhow.]



Let me know if someone can point me out something...
Cheers
Oli

A safe and effective method for water heating has already been developed. It relies on the fact that water under pressure has a higher boiling point than atmospheric water.

An open tank (possibly with float valve to keep the level topped off) sits on or in the exhaust heat flow, on top of the barrel or elsewhere according to desire. A heat exchange coil from the main water storage & use system sits in the water tank (not touching the tank walls or bottom), and circulates heated water to storage, by gravity or pump. Even if the open tank runs dry, the coil will never be subjected to temperatures that will cause its pressurized water to boil.

Hi Glen
So you don't think the insulated space with the coil in my sketch isn't grunty enough to heat the hot water?

and sorry yes i was meaning just to post on this thread.

Many or most of the ideas that people bring here could heat water; the usual issue is safety. Any plan which exposes pressurized water directly to the heated air or metal/ceramic surfaces is potentially dangerous, as those temperatures are likely to at some time exceed 300 degrees F and risk instant steam explosions.

Hi,

I have just started researching this.
My project will include some welding and the hot water tank in the attic, also some 1/2 insulated copper pipe (air conditioning type).
The idea is: inside the bench, just at the stove connection, an heat exchanger should be built using stainless steel chimney pipes with the exterior pipe diameter ~ 4-6 cm higher than the inner pipe for at least 50 cm long.
There also should be a 3-4 degrees drop for the steam condensation to be collected in an airtight container. Also, the slope will help any air in the heat exchanger to go up to the water tank.

Can something go wrong with this?


 

A 1/2" pipe reaching to the attic will have little gravity flow capacity. The bigger this pipe is, the less friction it will have and the easier it will flow.

I note a float valve on the cold water supply. Would this system be pressurized? I'm not sure what the need is for a float valve in a pressurized, potentially constantly flowing system - it wouldn't deplete or overflow. Is the attic tank unpressurized, with just gravity flow to faucets?

Glenn Herbert wrote:A 1/2" pipe reaching to the attic will have little gravity flow capacity. The bigger this pipe is, the less friction it will have and the easier it will flow.

I note a float valve on the cold water supply. Would this system be pressurized? I'm not sure what the need is for a float valve in a pressurized, potentially constantly flowing system - it wouldn't deplete or overflow. Is the attic tank unpressurized, with just gravity flow to faucets?

Yes, it is an unpressurized system, gravity flow. The tank I'm planning to fit is a IBC insulated 1000 liters capacity. I was thinking about 1/2" pipe to heat the water slowly, since the heat exchanger shares the heat with the thermal mass. Even if the water heats in a week, that will not be a problem.

Eduard Popescu wrote:

Glenn Herbert wrote:A 1/2" pipe reaching to the attic will have little gravity flow capacity. The bigger this pipe is, the less friction it will have and the easier it will flow.

I note a float valve on the cold water supply. Would this system be pressurized? I'm not sure what the need is for a float valve in a pressurized, potentially constantly flowing system - it wouldn't deplete or overflow. Is the attic tank unpressurized, with just gravity flow to faucets?

Yes, it is an unpressurized system, gravity flow. The tank I'm planning to fit is a IBC insulated 1000 liters capacity. I was thinking about 1/2" pipe to heat the water slowly, since the heat exchanger shares the heat with the thermal mass. Even if the water heats in a week, that will not be a problem.

1 liter of water = 1kg = 2.2lb.   So you are going to put a literal ton of water in your attic... is your house made of steel? That's a lot of weight for ceiling joists to hold.

Good point! As an IBC is a concentrated cube, it would need to be directly over a load-bearing wall to be safe. Just any old wall might not be good enough; it would need a direct load path to the ground, and maybe an extra steel post in the basement, depending on the specific layout.

Daren Baldwin wrote:

Eduard Popescu wrote:

Glenn Herbert wrote:A 1/2" pipe reaching to the attic will have little gravity flow capacity. The bigger this pipe is, the less friction it will have and the easier it will flow.

I note a float valve on the cold water supply. Would this system be pressurized? I'm not sure what the need is for a float valve in a pressurized, potentially constantly flowing system - it wouldn't deplete or overflow. Is the attic tank unpressurized, with just gravity flow to faucets?

Yes, it is an unpressurized system, gravity flow. The tank I'm planning to fit is a IBC insulated 1000 liters capacity. I was thinking about 1/2" pipe to heat the water slowly, since the heat exchanger shares the heat with the thermal mass. Even if the water heats in a week, that will not be a problem.

1 liter of water = 1kg = 2.2lb.   So you are going to put a literal ton of water in your attic... is your house made of steel? That's a lot of weight for ceiling joists to hold.

No, my house was built in 1872 from stone, no cement nothing. 60 cm (23.6") thick walls, only stone and some clay.

I also found this 6 bar (87 psi) water heater at 68$, corrosion protected. The diameter seems a bit too small 11cm (4.33 in)...