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Collection of physical quantities related to RMH  RSS feed

 
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This is an old text I posted some weeks ago in an other thread. But I got no feedback. Please do not call me obtrusive, I am just interested in this values. I hope to have more success in this new thread with a new name/title.

Collection of physical quantities related to RMH

I was looking in the Internet for some physical quantities of Rocket-mass-heaters but with little success.
Is someone here who can give me some hints where to find them?
Or did someone measured them and can tell me the values?
Please have a look at the attached image. Several points are marked which are interesting for measurement. Of course, not many people have the technical equipment to measure all of them but one might know one value and an other one an other value. If enough people will contribute we will finally get a general impression of what happens in an RMH.

Description of what quantity can be measured at the different Points:

Point 1. Feeding opening.
i.) How much wood you feed ? Unit = [Kilograms / hour]. Put the wood on a scale before you put in in the RMH. Cords are quite useless in this context.
ii.) Speed of air entering the feeding opening. Unit = [meter / second]. You need an Anemometer for this.
iii.) Flow rate of air entering the feeding opening. Unit = [m³/s] = volume /second. Some Anemometers can measure this too. You need to type in the area of the opening. If you know this its easy: Flow [m³/s] = speed [m/s] x area [m²]. But what is the area if the opening is blocked by the wood? In this case a feeding barrel is useful. If you do not have one put, for the time of the measurement, a short tube on the opening and use the cross section of that tube, see Fig 4.
iv.) Humidity of the wood. Unit = [%]. There are small and relatively cheep electronic apparatus which can measure this.
v.) Relative humidity of the air. Unit = [%]. You need a Hygrometer.

Point 2. Combustion chamber. Temperature. Do not forget to tell the Unit °C of °F or what ever you use. I would suggest °C.

Point 3. Exit of the heat riser. Between the top of the heat riser and the bottom of the barrel. Temperature.

Point 4. Gas inside the barrel. Temperature. At this point the gas lost a part of its heat to the bottom of the barrel (cooking plate)

Point 5. Gas inside the barrel. Temperature. Just before entering the thermal battery.

Point 6. End of the horizontal tube.
i.) Temperature
ii.) Amount of condensed water. Unit = liter / s = volume per seconds. Better would be kg/s



Point 7. Exit of the vertical chimney. Temperature, soot, CO content and ii.), iii.) and v.) of Point 1.

Point 8. to 12. Surface temperatures. An Infrared-thermometer is probably the best choice for this.

I suggest to use SI units (International system of units, kg, m, °C or K, liter …) but I know, not everyone is used to this. Therefore, what ever unit you use, do not forget to write it next to the numerical value.

Is someone here who measured the thermal efficiency of a RMH, or who knows such a value?
Thermal efficiency = (energy that remains in the living room) / (entire energy contained in the burned wood).
In other words the thermal efficiency is the ratio between what you really get, to what you would like to have. You would like to have all the energy contained in the wood in your living room but you get just a part of it. The rest is blown out the chimney.
With averaged values from Point 1, Point 6 and Point 7 the efficiency can be calculated.
I am afraid no one will read such a long text – so I stop here.

best regards
Peter

P.S. The name of the image “Fig 4.” makes sense in the old thread, here it is the only image.
Fig4.jpg
[Thumbnail for Fig4.jpg]
 
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Peter Peterson : I hope that you will be willing to have a little patience with your fellow members. Much of what you want will be revealed soon*, but most fellow members
remember past skeptics who have in the face of mere anecdotal evidence from the majority of your fellow members been unwilling to bend to 'the will of the people'

Considering a requirement to be willing to experiment, and a total investment of a few hundred dollars (often Less!) and a long week-ends worth of time, when faced with
people who actually want Quantifiable/Qualifiable Evidence before they make the move forward, many builders shrug off the demands for more information as 'not worth
their time'

For the 1st time ever, 12 'Wood fired Heater' Manufactures have been selected finalists to be judged according to initial costs and efficiencies*, as such this will be the 1st
time an outside agency will be in charge off testing and testing results ! I am sure that more people than myself will weigh in with the dates,and exact place. A full line up of
units to be tested was posted in a recent ' Popular Mechanics ' and can be retrieved by a careful Google search !

With over 100,000 D.I.Y. rocket mass heaters made to date, I would expect a spread of 30% -40% in individual efficiencies, with these One-of-a-kind, hand built units I
would still expect an individual unit to fall below builders expectations by 10%, or exceed their expectations by 5%, even with careful handcrafting by professionals ! I
would also expect this to be the range over any test group large enough to be quantifiably significant !

My current understanding of this round of testing, is that the individual builders will have between now and mid-november to prove to themselves that the units being turned
over to the Testing Body is the best that they can expect to produce, this still leaves us with the need to prove longevity and the ability to re-produce the results of the testing
body, but is a major step forward !

*My understanding is that the above mentioned tests will occur in Washington D.C. in November this year! HOPE YOU CAN WAIT THAT LONG! For the Good of the Craft! !
Tthink like fire, flow like a gas, Don't be the Marshmallow ! As always, your comments and questions are solicited and are Welcome ,PYRO - Logically BIG AL !



 
Peter Peterson
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"HOPE YOU CAN WAIT THAT LONG! "

Yes, of course, I will wait.
Thank you very much for spending your time answering my question.
Peter
 
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Peter and Allen,

You might try the Donkey proboards and see what data has been posted there. Peter van den Berg did quite a bit of testing and he has the gear with which to do it.

If you go to the Dragon Heaters blog, you will find a recent set of data about temperatures and efficiency which relates to our "castle" build. It does not use a barrel for radiating heat or a bench for thermal mass. Instead, the heat is stored in bells made from chimney flue liners. We put temperature sensors in many of the locations which you have in your illustration. We used a piece of testing equipment which was able to tell us the amount of CO, O2, and so forth in the exhaust.

As far as the contest which Allen mentions, it is being put on by the Alliance for Green Heat and you can find the information about it at www.forgreenheat.org. As far as I know, the committee which chose the finalists did not select any entries which are based on the type of j-tube rocket design discussed on this board. When I read some of the press releases now, I have the impression that what they are looking for is computer technology applied to the burning process...you know, something using electricity to open and close air vents, etc.

Unfortunately.

Cindy
 
Peter Peterson
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Cindy, thanks for the hints!
Sounds interesting but I might need some time to find out what “Donkey proboards” are and how to go to “Dragon Heaters blog”.

Less happy makes me your info: “the committee which chose the finalists did not select any entries which are based on the type of j-tube rocket design discussed on this board”.

First time I heard about Rocket-mass-heaters was some month ago and I still do not understand why they are not more known, more spread, more considered in the world. I personally do not have one but theoretically the principle sounds really ingenious and superior to any other wood stove I know, but I do not know the practical drawbacks. Are there any that explains why RMHs are widely neglected?

regards
Peter
 
Cindy Mathieu
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Peter,

Donkey (a guy's nickname) Proboards is available at donkey32.proboards.com
The nickname of the site is Rocket Stoves...Experimenter's Corner...Answers Questioned


Dragon Heaters blog is at http://blog.dragonheaters.com/ The discussion I mentioned is under Dragon Notes|Dragon Burner Masonry Heater with flues. There are 5 parts. Part 4 has most of the data. We manufacture a cast refractory burn tunnel which can be used in any rocket heater design instead of bricks.

My theory as to the answer to your last question is that understanding of j-tube rocket heater design started in the permaculture world only 20 or so years ago. It hasn't spread too much beyond that so far.

I don't know why the committee for the contest made the choices they did. We spent a lot more time preparing our entry for a j-tube design (which was rejected) than we did on the batch box design which was accepted. The entries were on paper; they got about 30 of them and accepted 14. I don't know how many, if any others, were for a j-tube design. I understand that one or more of the finalists had to drop out because they can't build their masonry heater in the time allowed.

Cindy



 
Stinging nettles are edible. But I really want to see you try to eat this tiny ad:
What would you cook first in a rocket oven?
https://permies.com/t/89866/cook-rocket-oven
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