There is a white glue that comes with the replacement door seal .  It hardens really well.

Pour some into the open space to wet the seal and press it down with a flat stick so it is sealed again.  

The glue will dry and make it air tight.  Check the inside at that point to see how it looks.

If there is a bend in the door, opening a small gap for a significant part of its length, don't despair.  Replace the whole seal again and press it shut to let the glue set.  Presto.

Cheap and easy.

Don't try to bend the metal back. Not worth all the risks.  

This "cure" might glue the glass to the metal frame at that point.  It will still expand a little from heat.  Therefore it is not suggested you make a similar repair on the other side(s).  Better to re-seat the glass with a new seal and glue.  A new seal is much puffier than an old one so it seals all gaps.

This is the general case installation guide (not showing the particulars of the passage through a floor or ceiling).

Crispin

I have an update on the chimney termination above the roofline.  

I wrote that I would find the installation manual for Kyrgyzstan which cites the updated Russian national building code (I think 2016 or so).  

It is not "one rule for all".   Please see the attached schematic.

+++++++++++++
Within 1.5m of the ridge, it should be 0.5m above the ridge.
Within 3m of the ridge, same level as the ridge.
More than 3m from the ridge, at a line descending 10 degrees from the ridge.
+++++++++++++

Of course there is no problem to be higher than any of these values.

Crispin

Greetings

I confess at the beginning I am a stove designer.

The leak between the chimney sections when you "do anything" is a key indicator that you have positive pressure inside the upper chimney created by the local environment and positive pressure at the bottom created by the buoyancy of the hot exhaust.  Otherwise the leak would not occur. The pressure inside the chimney would should always be negative compared with the room(s).

Key to solving this will be addressing what is going on at the top of the chimney. Wind can easily blow air down a chimney for all the reasons mentioned by others.  

I was surprised by the chatter about vane hoods being a problem re durability. These draft inducers are common enough around the world. The rotating (spinning) type are very reliable so why would a swinging one be a problem?

Various static induction or more correctly "eduction" designs have been made going back centuries.

Let's concentrate on your upper installation. It sounds as if everything is fine, but you have positive pressure inside the stack which should not be the case.

In the Russian national standard, they have a different approach to the eternal dimension spec. The 10 feet rule is not applied in the building code. The rule is: take the top of the peak and draw a line at ten degrees down towards the chimney. The stack exit must be above that line. I can't remember if it is one foot above but certainly it must not be below it.

We used that standard when creating an installation manual in Kyrgyzstan and never had draft problems with stoves that were much more efficient than the usual crap. More efficient usually means with a lower gas exit temperate (but not always). So less draft available, but no trouble.

These installation specs are in the building code, not the stove performance standard such as CSA B415.1 which applies in Canada and the USA. (A new update is coming in a couple of months, BTW.)

Explore the 10 degree clearance idea, and see if your chimney would pass the standard applied in most of Eastern Europe and Central Asia.

Second, temporarily remove whatever cap you have to see if it is responsible for creating positive pressure at the top. Maybe it's fine. I haven't used that draft-creating cap in the photo before, but it looks interesting. It has no moving parts. If it doesn't work, send it back for a refund.

Third, regarding the make-up air - try opening various upstairs windows instead of the nearby door. Windward side, leedward side, find out what doesn't work. Ruling things out is as important as finding conditions that work. If it suddenly solves the problem it points to an architecture problem (building layout etc).

Fourth, the comment about trees might be significant. I don't thinl you have a stove problem. You have an architecture problem. If it was me, I'd immediately put on a swinging vaned hood while seeking other solutions.

Fifth, if you raise the top of the chimney, check with the rules about the support and the "vee" of sheet metal that diverts snow around it. It should be able to pass a WETT inspection even if your municipality or insurance company doesn't require it.

Lastly, Permies readers can reach me using crispinpigott at outlook dot com. I can dig out the graphics on the chimney top dimensions and slope.  It might be on my website at www.newdawnengineering.com in the library, stoves, Kyrgyzstan. There is an English version somewhere.

Stay well
Crispin

Apologies if this posted twice.

Ted:

Unfortunately there is quite a bit of misdirection in the replies below and not wanting to offend anyone I will try to give you some guidance in principle and for your application.  Please everyone, tolerate my alternative interpretations as just that.

>I remember somebody saying that if you close up a chimney with a baffle that is just a metal plate that closes over it, that it would be friction and slow down the fire.

This is correct, such a device is called a chimney damper for the reason that you "dampen the fire" in the sense of slowing down the burn rate. A damper is quite permissible provided that it is not able to close off the chimney completely. There are often regulations about this where the area can be reduced by 2/3 leaving 1/3 open when fully closed.   This is essential for late fire emissions to escape.  Most stoves (including rocket mass heaters) have poor combustion in the late fire due to high excess air (far too much air for the fire's requirement) and poor control over it.  

Mostly, it is not a good way to control a fire's burn rate. In all cases possible, the system should be constructed so as to limit the ingress of air, not the egress of gases. When the entrance is limited, and the chimney is pulling, any leaks permit air to enter the stove, whereas in the opposite case the gases inside try to leak out.  A negative draft maintained on the top of a fire should be about 20 pascals if you can arrange it.  That is very little, but it means a warm chimney pulling and air entering the stove through the controller with the entrance as the restriction on the system.

CO leaking out of the stove into the room is not heavier than air. CO2 (44 mole mass) is and sinks, but not CO. CO is almost exactly the same density as air (28 mole mass) and disperses very effectively throughout the room causing problems. The mechanism is it displaces oxygen on the red blood cells so it lowers the oxygen carrying capacity of the blood.

>Does a hose nozzle work as a venturi or a restriction?  

Anything that reduces the flow up a chimney will reduce the exhaust gas flow rate.  The temperature of the chimney above and below the restriction will change if you change the amount of that restriction.  This will affect the total draft on the stove. Generally speaking, all stoves in the USA have exhausts that are too large in diameter to work properly, the chimneys are too large in cross-section, and the exit temperature is too low to be effective.  That is a pretty broad condemnation, but it is just how it is.   Most stoves require a barometric draft regulator but do no get it. If the chimney is hot enough to work properly it tends to generate thermal runaway: more heat leads to more firepower leads to more heat in the chimney leads to more firepower.  That is not how most people want their devices to operate.

Draft in a chimney is a source of "power".  You could use a fan, but a warm chimney is capable of "doing work".  So a chimney is really a natural fan.  The power available can be directed in various ways: You could turn the energy into a "suction" on the fire and the air entrance (the preferred option). You could dissipate the energy creating a high velocity flow gases past the restrictive plate you are considering, slowing down the total flow.  Given any constant temperature in the chimney, the available energy could pull a lot more air quickly, or more slowly but having a high flow rate past the restriction point.  You may have a reason for wanting that.  You could use a small diameter chimney so the energy was dissipated along the whole pipe length limiting the flow to a certain desirable rate.  Usually that is a good idea.  The main point is there is energy available and you can choose were it is applied.  It might be at the secondary air entrance adding velocity (one of my favourite design ideas.)

Now for your main motivation:

>...also at the same time be a restriction that would allow soot to burn up completely (actually in a restriction that speeds it up, soot particles should shrink just on that).  

What you describe is a fire that is not burning cleanly, followed by some attempt to fiddle with the flow rate of the gases in order to reduce the smoke generated.  It is already too late. If the fire is not burning cleanly in the first place, it is far better to burn better than to try to clean up what should not be there. Slowing down the gas flow rate in the chimney is very unlikely to correct a bad combustor design.  That is not how things work.  Poor combustion has several classic causes so addressing them is a better approach.

>...but really burn up those soot particles and shrinking them too

Smoke particles don't "shrink".  They grow, rapidly.  You are quite correct that they are combustible. Smoke is almost entirely made up of unburned fuel and water vapour. A small amount of a typical stove's emissions is ash, not the products of incomplete combustion. Creating good operating conditions for combusting biomass requires meeting certain conditions.

One is an oxygen level of about 8% to 10% in the exhaust.  This is air which is not required to burn the fire.  Biomass is not as easy to burn as gaseous fuels which can tolerate very low excess air levels (even 1% or less O2). If you have 18% O2 in the exhaust, that is 600% excess air and it FAR too much to burn cleanly.  

The calculation is:  Measured Oxygen %/(21% minus measured Oxygen %)  The answer is the excess air factor, so multiple by 100 to get %.  
Note that it is not the total air demand, which is Excess air + 100% also called "Lambda".

All that unwanted excess air cools the combustion.  Slowing down the exhaust does not guarantee the O2 level will drop. It might, it might not.  It depends on the architecture of the stove.  But one thing for sure, it should not be more than 10% when running on high power. If you have a technically sophisticated burner, you can get it down to 6% but that is not for the ordinary hacker. Instrumentation is required.

You are correct that if you burn the smoke it will yield more heat.  However burning the CO gives far more heat than burning the smoke. C to CO yields about 8 MJ per kg of fuel. CO to CO2 gives more than 24 MJ/kg.  So if you lose a lot of energy to CO (bad combustion), you can get it back by burning the CO instead of carefully venting it outside. Emitted CO is a called a "chemical loss".

To keep CO burning needs about 820 C above the combustion zone. This is NOT provided by blowing harder on the air supply, which will just force more cold air though the chamber, cooling the fire. Blowing on a charcoal or coke fire like a blacksmith usually create a lot more heat, but huge amounts of CO.  Such a fire is not a good example of clean combustion at all.  Hot, yes, but not clean.

To get a clean, hot burn, your fuel load should match the grate area and a lot of other things.  Most stoves have:

too large a grate
too large a fire chamber for the typical fuel load
too much primary air
too large a chimney diameter
too little insulation around the combustion zone to maintain a hot fire needed to light the CO produced
too low an operating temperature
too little draft or
Too much draft without a barometric draft regulator

Putting an air control at the air entrance is how to control the fire intensity.
Secondary air (if supplied) should be approximately twice the primary air supply and where possible, preheated. If you want to burn wet wood, the primary air has to be preheated (big emissions reduction).

Most stoves have far too much primary air so any secondary air is just a waste of energy as the air goes in, is not used or needed, and carries heat up the chimney.

Very clean burns can be obtained without any grate - see Masonry Heaters available from the Masonry Heater's Association website. If the floor of the chamber is made from firebrick, effective combustion can be maintained for a long time. Recent developments in combustion include placing a layer of small stoves (20-30mm) over the whole fuel bed (still no grate).  This may not suit people burning 24/7 however, try it and see the difference.  It reduces smoke generation a lot in some cases.

Very high performance stoves (called HELE for high efficiency low emissions) have a surprisingly low chimney gas velocity of 150 to 250mm per second in a chimney that is about 1 square inch (6.5 cm^2) per kW of firepower. When you compare that with what is usually provided or "required" you may be surprised.

General rules are: burn first, clean and hot.  Then transfer heat to some surface, then vent what is needed to operate the chimney properly. Do not use a chimney as a heat exchanger save for the first few feet.  Once heat enters the chimney, keep it there to operate the draft into the stove properly. You gain nothing from a warm chimney after it departs the heated envelope, i.e. above the ceiling.

Good luck with your investigations. Modern HELE stoves can be see (drawings and all) in the Library of www.newdawnengineering.com under Library / Stoves, then by country.  One you might check out is the KG2.5 under Kyrgyzstan.  Have a look at the function of the "flame tube" which burns smoke and CO as it enters the heat exchanger. It is so effective that the top of the heat exchanger serves as a third cooking position.  The Kyrgyzstan project is quite interesting. You can read about the development of the main stoves here:

https://openknowledge.worldbank.org/handle/10986/31282
(click the download button)

A precis is available at https://openknowledge.worldbank.org/bitstream/handle/10986/31774/Beyond-the-Last-Mile-Piloting-High-Efficiency-Low-Emissions-Heating-Technologies-in-Central-Asia.pdf

And the dramatic impact it produced on people here:

https://www.nature.com/articles/s41533-019-0144-8.epdf

Stay well.
Crispin

The stove is indeed a coal stove, though that is not the only model we used. Altogether 4 different stoves were developed, initially in Tajikistan, of which 2 were specifically for biomass in any form (dung is a very important fuel at high altitude).  Now there are 6.  There had never been a stove in Central Asia before which could burn dung without the addition of some sticks and wood.  The oft-assumed unburnability of dung was shown to be incorrect. It can be used to heat a home at -30C and cook properly, if operated in a new manner (back lighting) and if there is a "flame tube" incorporated into the heat exchanger.

It was decided to report the KG4 series in this document because it highlighted that if a concerted effort was made to apply modern engineering, assessment and testing, it was possible to produce a coal burning stove that was about as clean as propane. We won't quibble about numbers, it is just important to show that profoundly clean coal combustion is possible and that people dependent on it should not be denied access to modern engineered solution. In short, a pro-poor policy of doing what we can with what they have, given that nothing else will be done that helps them. We are also attaching the false claim that all solid fuels are "inherently dirty" - a position promoted by those advocating gas and liquid fuels. It's nonsense.

Touring the Kyrgyz uplands last year in February was shocking in some ways. People are so poor it is tragic, and they have terrible living conditions because of the poor stove designs and condition. Everyone over 40 is said by the Chief pulmonologist to have COPD. Everyone with one of these KG4.3 stoves was so-o-o happy. In most cases the stove saved more fuel expenses than they received per month from government in welfare payments.  The stove saves enough fuel to pay for itself after 4 months. So the issue is access, not affordability. All the designs and drawings are available at my website (in the public domain) www.newdawnengineering.com in the Library/Stoves/Kyrgyzstan then folder KG4.3 or 4.4 (there is a small difference in the overall length of those two versions).

In principle, the same combustion system (cross draft gasification) could be used to burn wood but we are not there yet.

This needs a new Forum category: Domestic space heating and cooking.

There is a new technical paper in the World Bank’s Open Knowledge Repository:

“World Bank Group. 2019. Advancing Heating Services Beyond the Last Mile : Central Asia Pilot Experience with High-Efficiency, Low-Emissions Heating Technologies. ESMAP Paper; World Bank, Washington, DC. © World Bank.

Please ask readers to download a copy from the website as it counts the number, and that ultimately influence pro-poor policies.  This paper on HELE stoves is downloadable from the following webpage:
https://openknowledge.worldbank.org/handle/10986/31282 or http://hdl.handle.net/10986/31282

Please share the link widely.

The direct link to the PDF is
https://openknowledge.worldbank.org/bitstream/handle/10986/31282/134620-WBAHSWEB.pdf?sequence=1&isAllowed=y

The document provides a detailed description of how one of the cooking and heating stove technologies used in the Kyrgyzstan Winter Heating Pilot was developed.  It is a comprehensive discussion of the social and technical factors that contributed to the success of this Pilot, producing significant impacts on health, income and comfort of people living “beyond the last mile”. A link is provided to the full set of drawings and some photos archived in the ESMAP Library.

The point of saying “beyond the last mile” is that whatever are the current plans to extend modern heating and cooking services, there are a large number of people who will not be reached. This group of 500m people “beyond” are, now and in the medium term, dependent on burning solid fuels (biomass, dung and coal).  The question addressed is: What can we do for this group of low income, deeply rural and hardly accessible families which suffer all the negative consequences of chronic cold, poor combustion, indoor leakage of smoke, inconvenient drudgery and a dire lack of access to modern energy?  How can we bring modern science and engineering to these spatially and culturally diverse groups?  

The article proposes a comprehensive approach and describes how this was done in highland, rural areas of Kyrgyzstan. It covers in some detail how the KG4.3 crossdraft stove was developed over 9 years and the scientific cooperation between groups in several countries that led to the development of this HELE technology.

This document can be used to inform policy in multiple ways. If we are to eventually bring modern energy services to everyone, which will take time, there are highly beneficial interventions which can be made a low cost per person, even in poorly served regions using carefully crafted technology transfers. Apart from all the social and health benefits, the project also makes positive impacts on everything from local employment, the social status of women, emissions of CO2, Black Carbon and PM2.5.

Two further papers reporting the health benefits of the project have been submitted by the Dutch International Primary Care Respiratory Group to the WHO Bulletin and npjPCRM (Primary Care Respiratory Medicine) which conducted a Fresh Air-sponsored study of the impacts of the stove and low pressure boiler replacements.

Please circulate the links given above to anyone who you think is interested in these topics.  Stove designers will find a good deal of technical information about construction and principles of combustor operation, as well as guidance on how to interact with the communities in which it is intended to provide such modern heating and cooking services.  This crossdraft technology has already been replicated in China, Kyrgyzstan, Mongolia, Russia, Poland, South Africa and Tajikistan. A few photos are provided.

Forthcoming: Complete details on construction of three versions of the technology will be included in the final report from the World Bank-funded UB-CAP Project in Ulaanbaatar, Contract C-5039-MN/KLTA-01.

Best regards
Crispin

There is a whole book printed privately by TATU, then called the ECATU, now a branch of the Eastern Cape Agriculture Department on building with gabions. It was dated about 1982 and has been used in hundreds of building in the Eastern Cape. There is a manual device from New Dawn Engineering that can make the gabions by hand called a Netwire Board. There is also a heavy duty version for making earth dam walls called TriNet based on the same principles. See www.newdawnengineering.com for ideas. /products /wire /fencing Something like that.

It is possible to contact Cecil Cook cec1863@gmail.com to ask how to get a copy of that Roneo publication. It used both the gabion style wire and soil cement bricks, in-filling between wooden posts. It was very cheap and relatively insulating. The TATU offices in Mthatha were made using that system.

Regards
Crispin

Two more photos.

Brick greenhouses in China:

China Agricultural University has an experimental farm in Haidian North (Beijing) with several of the greenhouses described above. I am attaching several photo taken of these from inside and out.

This one is attached to the Biomass Stove Testing Laboratory which is run by the CAU College of Engineering at which I am a supervising 'visitor' (grad students, stove design and testing protocols).

The greenhouse is used as a storage facility though there are some biochar experiments going on in the photos. That is why it is not full of plants.  The fuels and stoves are stored prior to testing. All the stoves in the photos are low pressure boilers (hydronic heaters) made in Hebei Province. Testing is part of a clean air initiative for 18m farmhouses.

As described above the greenhouse top and south are curved, with a descending cover. The ropes and handles hanging from the ceiling are to control vents. There is a fan visible in the west wall. The building to which it is attached is occupied by not heated, it is just convenient to use the back was as part of another structure.

I can confirm that it is warm enough to grow things all year though I didn't pay much attention to what, or for how long. The structure was destroyed by the local government who declared that it had been built on 'farmland' illegally. No comment. The 'destroyed' picture shows the West wall, the fan and a bit of the structure - bricks.

The thermal mass of the walls is very large. I did not calculate the heat storage and return, but it is a substantial structure. There is every reason to think it is capable of keeping temperatures above some given value for a given period based on ordinary calculations. The length to width ratio would be important in that if it is really long, the influence of not having light enter on the east side is less important. I suspect the ratio is about 1:4 East:South. Although the West wall shelters the 'house from late sun, light still hits the inside of the East wall so the loss isn't all that much.

The metalwork is modern with modern conventional vents and levers. Nothing is automated except the fan thermostat.

Crispin in Muizenburg

Yes. Quotations come from Thabsile Shongwe. Sea Freight is possible. Air freight is sometimes cheaper. Other times it is better to make your own.

You can click on any of the email links to send an email to Thabsile (a lady).

There are masses of photos available of these technologies in use - just a taste on the web. Many have been on the market for 20 years. For home construction also see the hand operated rock crusher. There are 90 in Haiti.

The idea of using 'fencing' as a deterrent or structural element is good in that you can make by hand precisely what you need. For example if you are making Square Mesh on site, you can make a single sheet of 'fence' as wide as you want - no joints for example over an entire roof.

You may have seen the Diamond Stucco Mesh on the same website. This was specifically designed to make a wire product that could hold cob or plaster without and backing - sort of like a chicken wire that is sized to hold plaster. It has a thickness of about 5mm meaning if you push it against a mould, the cement still gets behind half the wires and onto the other half.

The purpose is to be able to add a very strong reinforcement to plastered things like hay bales without investing a lot of money.

The Diamond Stucco Mesh machine is also used to make stainless steel mesh for bird cages. Unlike chicken wire (rigid hexagonal holes) it is stretchy so it can form over complex shapes like barrels. The machine is not easy to learn to use it - it takes a few days. Experts make about 25 m^2 per day (14mm holes). There are no machines in North America.

The Square Mesh has been made by hand down to 30x30mm. It is used to make gabions with internal dividers. The usual size is 76mm (3") holes.

The savings over buying fence may not be much where you live - check the cost of plain wire in bulk per kg and fence per kg first. The difference is the available savings. Most places it is 40% but watch out. Same warning for barbed wire.

If there is any interest in making water tanks from cement and mesh I can forward drawings for making a mould based on a galvanised corrugated iron water tank. We made dozens of such moulds for thousands of tanks in Southern Africa. The finished tank is 40mm thick (1-1/2"). Sizes were 1000 and 2000 Imperial gallons (4500/9000 litres)

Gabion making by hand.

There is a set of hand operated equipment (two actually) for producing gabions from plain galv wire.

The idea is to make one of three types of mesh, then fasten it to a wire frame that is held on a large spindly jig. Then fold it up.

The three types of mesh are Diamond mesh (chain link) and Trinet which has triangular holes and Square Mesh which looks like diamond mesh turned 45 degrees. All three can be hand made under a tree.

The website is www.newdawnengineering.com under fence products.

The Trinet jig product was designed for Dam construction and bad be made with quite thick wire. The others are normally 11 gauge or thinner, 12 gauge being most common (2.5mm).

On the thermodynamic side I can make two small contributions.

The angled riser AKA chimney: a chimney's draft is related to its average temperature (of that section) and its vertical height, even if it is on an angle. Your system consists of several sections with different drafts, at least one of which is negative (being a Rocket Mass Heater). There is a draft calculator in the library at bioenergylists.org (search for draft calculator nigel). You can use it to determine the sum of five or eight sections, can't recall which. At least five.


Second, the 'corrugated' flexible pipe sections which you can use for elbows: the flow 'restrictions' which these represent is not really because of the bumpiness. It is that they have a more effective heat transfer rate (higher surface area) than a straight smooth surface. In short, they drop the temperature more, reducing the heat available at the exit thus reducing the net draft on the system because it will be cooler at the end.

You have two main sources of draft: the initial internal chimney (use bricks) and the final exhaust. The sum of these is your total draft, pretty much. You should measure the temperatures involved at the end to prove you have 'some draft' at the late fire stage when things are the most dangerous. The heat stored in the bricks of the internal riser help greatly at that time.

Generally speaking feeding into the leg of a Tee is a bad idea, rather use a branch Y + 45 degree elbow on one side then a 90 degree elbow for the other direction, which doesn't have to go directly opposite because you can rotate it on its axis. The combination has less flow resistance that a tee heading off in two directions.

In that same draft calculator there is a section on the left which you can use to 'burn' your fuel and it will tell you the gas flow rate if you know the excess air level (separate discussion). The flow rate can be used to calculate the total flow resistance of the proposed pipe network using conventional HVAC methods. The bottom line is that below about 10 feet per second 'resistance' to flow is not significant, and is far outweighed by changes in total draft caused by small changes in temperature (as can quickly be seen using the draft calculator) and chimney height.  

There are municipal rules for the exit height of the pipe above the roofline for very good safety reasons (to do with wind).

It is common here in Central Asia to wrap the outside portion of the chimney in insulation to improve/conserve the draft at the end.

Good luck
Crispin in Bishkek

Congratulations Andy

Great achievement.

>Based on the available stove pipe having a 15 cm diameter (5.9 inches) it is essentially a 6" system.

Do you think this is adequate? People think pipes are expensive so cost matters a lot. There is a pipe making machine at GIZ in the West end (they have a rented workshop). There is a bending break with a cutter attached, a roller and a seaming machine, all hand op. The chimney pipes are made locally so you can get any size you need by asking them for it. The common sizes at the market are 95, 108 and then the big one. Elbows can be sourced locally. The Korean TLUD briquette stoves with a heat exchanger beside them have a 90 elbow at the bottom of the stack.

>The Mongolian ladies from the community laughed with delight when they sat on the bench today and felt the warmth on their butts.

That is very comfirming. The lower portion of the ger is space that is lived in!

>...I had the idea to place one of their round bottomed cooking pots in the feed tube ring.

Were you burning wood or coal?

I have a list of retailers/importers selling firebricks, both of Chinese and Russian origin, stuffed away somewhere. Let me know if you need it. Some keep a little stock. Some don't. Expect them to be in the Tg1400-1600 range each.

A stove development and training cnetre is about to get started and it would be good if you could give either a class or field demonstration (or both) to the staff of that centre-to-be. The idea is to work with people who are doing-the-doing on the ground to offer them theoretical and practical back-up, product testing and social science impact assessments. The latter as we all know is often missing from 'technical development'. User acceptance, opinions on the fueling, functions, cost, flexibility and durability must be part of the hardward development. That means bringing the formal sector producers into more contact with the users. A very helpful study was done by Cecil Cook the American about a year ago that raised some eyebrows and legitimate issues. It seems old hippies can still make a contribution and get attention.

Would the RMH benefit from a cast iron top where the pot sits? CI is quite cheap. It would be easy to produce at the artisanal level by one of the township foundries. Ditto for the grate.

I wish you success in the coming season.
Crispin

Dear Andrew'n'All

YOu are really hitting the nails on the heads with that post. Congrats.

>Focusing on the original question about burning coal in an RMH, if one retained the J-tube Rocket configuration, what adaptations must be made to deal with burning coal?

The original downdraft stove was a J stove. With a flat J Iguesss you could say. So far there is not an available downdraft stove though I taught several artisans to make them. One surprised me by calling it a Russian name and he knew how to light it, andreally loved the performance. He got a 13 hours burn from a single load by putting a choke ring in the chimney. So they are known in Mongolia.

The huge advantage of a downdraft is that when burning high volatiles coal like Nalaikh (which is about 2/3 of domestic consumption in UB) it deals really well with the volatiles and the refuelling emissions which are horrificon a traditional stove. Remember the trad stove is a wood stove with bricks in it.

>Would one keep the downdraft configuration, or would a crossdraft or a dasifier/pasifier work better?

I have seen some pretty wild things tried in UB so I remain open to anything that will burn. I put a video on YouTube about the stove with the rotating grate - that was off-the-wall crazy and partly worked. Would have been better if it was made to tighter tolerances. Thermal eff was 35% tho.

>Is there still a risk of runaway burning?

I really think not. The coal burns pretty much like wood - you have to restrict the primary air to slow it down which is a problem with the trad stoves because of the poor fit of the ash drawrs, as I said.

>Would one need to inject secondary air at some point, heated or otherwise?

That is really likely. As the primary air is necessarly restricted because of the high volatiles, secondary air is needed. With hte GTZ 7 series stoves this was provided by running it through the grate at the low-level end where the coke is. It is an odd way to do it but it sure worked well. Very little additional secondary air is needed on top of that. As others have suggested above, restricting hte primary air at the entrance of the RMH will provide negative pressure in the firebox limiting the chance that anything will leak out.

>I would guess that a refractory combustion chamber would be a requirement. Would cast refractory be sufficient, or would kiln fired material be necessary?

To avoid a general discussion, yes and in the case of Ulaanbaatar, I suggest using the widely available (meaning three outlets or more) of the Chinese boiler liners. They are about $1.25 each and are really well made, can take tremendous thermal shock and are cheaper than the Russian ones. Mentioned above was the need to deal with higher temperatures. Quite right. Metal does not last when exposed to the coal fires at high revs, so to speak.

>Is the startup time for coal significantly longer than wood?

Definitely, especially as the fuel is 25% moisture. It is often frozen like a popsicle when it put in.

>If so, would some sort of draft inducer be necessary to maintain draft until the system is heated up?

In short yes, but what kind? The nest answer seen so far is the heat exchanger bypass which is a hole approx 40 x 50mm leading directly to the chimney bypassing the heating box. The box is made slightly larger to compensate for the heat bleed. It brings the stoves up to temp quickly and has been adopted by several manunfacturers. This is of course not necessary on the RMH.

>Addressing the issue of condensation, would a feasible solution be to make sure the flue in the bench, or whatever the mass is shaped like, is sloped to drain with a trap placed inside the heated structure at the bottom of the chimney, or before the exhaust vent perforates the exterior wall?

I was hoping Ianto or someone with experience would comment on this aspect. How is the condensation dealth with? Is it drained outside or pooled and evaporated later?

>Addressing cooking, I get the feeling that making a single combo stove for the cold extremes of Mongolia may become a case of "Jack of all Trades, Master of Nothing."

Yeah, a serious possiblity. The thing is, the population is in a state of flux and there are definite market segments for specialised products which the RMH might be one. In its favour is that they are used to mass walls which they call heating walls. I have heard one report of a fixed heating wall in a portable ger.

>While the barrel over the internal chimney of a heating stove may be used to make or warm tea, or slow cook, I don't know that it will be able to cook a meal in a 20 liter wok without some major alterations.

The cooking height is a non-negotiable so this has to be considered. Possible cooking locations are the horizontal portion between the firebox and the vertical hot chimney, or on top of the chimney which is too high for short women to put 10 litres of soup. Woks slosh easily.

>Could a cooking top be fabricated to fit the barrel, something that would lift the wok above the chimney to maximize heat at the top of the barrel, and make a good airtight seal at both the barrel and the wok?

The problem is still going to be the height. Making tea might fly.

>Would it be safer to put the cooking unit ahead of the internal chimney?


Exactly. Possible, as they say.

>Would it be simpler to just buy one stove to cook with and another to heat with?

We have available at least some social anthropoligical survey material (American, Cecil Cook) indicating that above a certain income level there is a strong preference for electric hotplate cooking, like a rice cooker and so forth. People also cook with bottled gas if they can afford it. This is also the group that a) has more money and b) probably lives in a house that the RHM could heat.

One must be careful when interviewing because if you ask about stoves, they tell you things that relate to the importance of 'storing heat' (which most stoves do poorly) and portability, even if it is in a fixed installation. It is a hangover from being nomads. We found the same in South Africa. What people think about stoves (which drives their purchases) is different from their use of them and the cost of using them.

People mistake a small smouldering fire as the stove 'storing heat'. The thermal mass of the stove is not large at all but this capacity rates highly on surveys.The reason is they have such a flash-in-the-pan massive fire followed by some smouldering coals. They mostly have never seen a stove that has continuous heat for a long time like Roger Lehet's vertical masterpiece. Have you seen it BTW? Mother Earth has picked it up as a promo technology through their fairs, somehow. He deserves the victory.

Incidentally I met with Adam Perry of Cob House fame together with Cecil Cook at the East London airport on Wednesday. We didn't talk RMH - no time - but got to see each other. He is examining the spread of soil-cement building technology in the old Transkei where is has displaced cinder blocks in low income housing in some towns. Cecil is an adjunct prof at the Univ of Fort Hare and Adam is studying there. There is a strong AT connection in there too I expect.

Stay well

Hi Ernie

Pleased to meet you.

>A few points i would like cleared up and then i need to bow out due to being a moderator and the water already passed.

I am not following the 'water already passed'. Is the thread so old no one is interested any more? That happens....

>1. direct heated chimney? Are you referring to the heat riser?

Is that a reference to another post? I am not sure what a direct heated chimney is - I was trying to describe the traditional stoves as presently used. They have a steel pipe which is often fairly loose on a very short (way too short) stub on the back right (usually) corner of the heat exchanger. The heat exchanger on the traditional stove is a rectangular box behind the combustion chamber.

As for the RMH the central riser is what I presume you meant by the heat riser, yes?

>2. damper? a bit of steel is better than a brick in some way?

I was describing what they use. The common practise is to make a cut with a hacksaw in the chimney and insert a piece of approx 0.6mm flat galv sheet. In virtually all cases I have seen the damper is not capable of closing off the chimney completely. Many stoves have no control on the chimney but do use the ash drawer as a controller epecially during ignition. In general the ash drawers are too loose and do not seal well enough to limit the excess air entering the stove. This leads to two common problems: runaway burning in the first 45 minutes and a negative thermal efficiency in the last 90 minutes. A typical burn is 4-5 hours.

>3. internal pressure? where do you see this as a problem?

If the fire is running well and the damper on the chimnmey is closed enough, the stove is under a positive pressure as gases build up in it and leak into the room. This is so common a phenomenon that people are careful to avoid the condition because when it happens it kills everyone in the house, or makes them very sick. It is not just the CO, there are a lot of poorly burned volatiles in a stove that is choked on the chimney side unless the coal is completely coked by then.

>4. you subsidizing the RMH?

Not me that's for sure. I have no money. But I can train people. In order to have any stove subsidised it has to be tested for emissions and thermal efficiency. I believe the RMH will easily pass the % efficiency rating. To my knowledge there is no unit available in UB for testing for emissions. Was the one mentioned above completed?

Very briefly, the emissions test is the measurement of the CO and PM2.5 emitted during an ignition, a burn until 90% of the burnable mass has gone, then a refuelling and a similar burn. The result is expressed in PM mass per megajoule delivered into the home. That takes care of the thermal efficiency number in the same calculation. Basically it is a measure of how much pollution per unit of heat gained by the house. The current target is an 80% reduction in PM 2.5 relative to the baseline (which is 788 mg/Net MJ). The best stoves are in the 3 nines range (99.9% better than the baseline). The 72,000 MCC sponsored TLUD's are in that range.

>Who has asked you to do this thing?

No one. Just looked like a really good idea. I don't want to estimate the uptake, but a demo is probably warranted. Roger pointed me to the USA work and it seemed to have (parts of it at least) a good fit in some circumstances. I will raise it as a possible design if and when I can, to local producers to see what the uptake is. They are a very easy people to introduce new technologies to. Adoption can be quite rapid. So is rejection. Cooking capability is a big issue and if the women don't like it they won't use something even if it is free. There are strong relationships between the families and their stoves. Second hand stoves are rarely sold outside the extended family.

I believe the RNH will be more applicapable to the many thousands of people who are building fixed housing than gers (because it is a nomadic, temporary house). The use of thermal mass walls is widespread in fixd housing though they obviosuly suffer from not having a proper method for dealing with the condensation. The combination of fuel moisture and combustion moisture is on the order of 450 litres per month condensing inside the wall. Lots of issues. The RMH will have to deal with that too if it is a condensing unit (which I believe from what I read, the best ones are). Handing condensate when it is -40 outside is an issue.

Regards......

Thanks. Robert van der Plas and I have discussed refusing to subsidise any stove that creates a positive pressure in it because of the obvious risk from leaky, artisanal stoves. The cast iron tops are a particular concern as they have (often) multiple rings. The finish is 'as cast' and has zero resistance to internal pressure.

The placing of air entry controls is standard advice at the lab. A lot of design info is shared there because we can show directly on the screen what the effect is - very convincing.

At present I would at least consider a damper that was partial. Still open-minded in case an innovation pops up. Dampers are widely used - a sheet metal slider. But a traditional stove with a well run damper tops out at about 60% eff which is well below target. We have to have more radical designs.

Greeting Friends of RMH's

I was introduced to the RMH by Roger Lehet some time ago and read the books/material I was able to locate. I am delighted that someone is trying to build one in UB (Ulaan Baatar). It believe the construction of the heat exchange, at least in princple, has great potential for increasing the system efficiency well above the baseline stoves (which is 53% as presently determined).

A couple of updates for those who follow the developments from some distance and might not get news easily:

The laboratory build by the Asian Development Bank operated almost continuously for about 1 year which was enough time to test a few dozen proposed improved stoves. Significant reductions in smoke were attained with a maximum thermal efficiency increase of 30% (to 83%) for a few. This is still not a condensing system, which I believe Ianto has achieved on the long bench systems. Great. The WB and ADB do not develop stoves so those which are hitting the market since about August 2011 are what projects have decided to promote. The main projects are MCC, XacBank, GIZ (ex-GTZ) and a company owned by a large mining company that wants to work on the air quality problem. There are about 30 local manufacturers of stoves.

The major project at the moment is the MCC (Millenniun Challenge Corp, Washington) which is subsidizing portable top-lit updraft coal stoves made from cast iron nad sheet metal. They have placed about 72,000 in the past 7 months which is about 50% of the ger-dwellers' stoves. There has been some leakage into the rural areas which I was encouraged to hear although not part of the plan. It means wider adoption of a new technology - not always something easy.

XacBank is providing finance to really poor people and as the payback on saved fuel is a matter of a few weeks, and given they have 2 years to pay, it is a no brainer for those needing to save money. The typical ger-dweller uses 4.5 tons of coal a year. They can cut that in half.

I have recent news from Prof Lodoysamba that the refuelling issue (TLUD's are hard to refuel if you are not careful about when it is done) has been succesfully resolved with widespread understanding that is has to be a fairly large refuel (with wet lignite which cooled the chamber) followed by immediate re-lighting. This allows 24/7 operation. The technique was developed at the ADB lab and shared with the trainers - it seems to have been completely transmitted to the general population so it won't be lost.

Anecdotal reports of better quality air in the city were received but I want to see it before I believe it. There are lots of sources of smoke and dust. Let's hope it is working. The PM2.5 emissions from the new stove are dramatically lower than the traditional ones, primarily because of the elimination of the smoky start-up cycle. That accounted for more than 85% of the smoke from any burn.

Back to the RMH. The possiblity of a condensing system for town-based gers and of course the thousands of small fixed dwellings is very attractive. As people can afford it, they build something permanent and that tends to drive up their coal consumption and emissions. Little attention is paid to solar orientation so lots of work needed there. Insulation is well understood but considered expensive. The RMH could easily be added to the thermal mass walls that are popular, though not exactly optomised.

Whatever is built, it has to be able to cook as well as the current technology. This is not going to be traded away unless there is an alternative cooking system (electric or bottled gas). These are popular among people with a bit of money so if they are cooking that way, an RMH cold be added to the house.

It is very important that the combustion process, above all the ignition sequence, be tailored to reduce the possiblity of roading cold fuel on a hot fire. This is the source of the vast emissions of smoke from the traditional stove. The regular box (well described above) is actually a Russian wood stove that has pretty good performance if the front door is kept closed. Radiant heat from the sides is strongly desired as knee level or else the top of the get is warm and the floor where the kids are is freezing. Some people burn wood (pallets especially) all winter but not the majority by far.

For those who want to work on a coal fired RMH the characterisation of the fuel wil be important. It is approx 25% moisture. Of that which remains it is 50% volatiles (easily lit) and 50% carbon. That is approximately the same analysis as wet wood. The desired burn rate is about 0.75 to 1.25 kg per hour for a heat output of 4 kW to 10 kW or so. Remember that there will be a desire to have less heat from the drum and more heat invested in the mass storage so it averages what can be a flaring fire followed by a slow burn. A flaring fire can easily overheat the home. The fuel tends to 'take off' once it gets a chance to burn. The coal from Baganuur (further away but even cheaper that Nalaikh) is worse actually with oil detectable in it.

Any advice on how to reduce the direct heating from the chimney while retain the draft system (which I like a lot) and increasing the storage in thermal mass will be shared with any and everyone.

Last point re cooking, plan to have to boil 4 sheeps heads at a time in a 20 litre wok. Milk is pasturised in 20 litre batches. You can thus see there is a heck of a lot of power required by many families. The traditional stove can be stoked to that level (25 kW) but that does not mean all stoves must do it. It is just that is the sort of question people ask when kicking the tires.

Best regards
Crispin