• Post Reply Bookmark Topic Watch Topic
  • New Topic

pebble style rocket mass heater in paul's office  RSS feed

 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I was getting asked questions about the rocket mass heater in the thread about the wooden box style shippable core thread. And since the questions really aren't about the box core, then I thought I would start a new thread.

Is there anything that can explain the performance, or practical use of the dual exit flue area? Does this dual exit flue have beneficial/practical use because of variable outdoor wind, or during cold start-ups?... or maybe this is just the way your lab testing apparatus is setup.








All of the rocket mass heaters at basecamp are experimental. The one in the office is loaded up with the most experiments.

The lever you see is connected to a baffle inside the duct designed to direct the exhaust either through the roof or through the wall. When you route through the roof, the stove pipe collects radiant heat from the barrel and then the vertical pipe will pull exhaust as well as the heat riser pushing. Unfortunately, when we flip the lever, the pull in the stove pipe is so strong that the exhaust is still pulled up - so the baffle is probably blocking only 95%.

The problem with this particular exhaust through the wall is that it has two extra 90 degree turns. So it isn't a very fair comparison. We were going to route it straight out the wall, but there was a stud there.

I can say that this rocket mass heater is working quite well. The firebox is 7 x 7 x 16. Two loads of wood will take the room from 55 degrees to 85 degrees and that will be all the fire we need for one day.

Ernie and Erica came back and installed an external air intake. And then it got very cold out and it has stayed cold. But here are a few things I learned:

819) When it gets really cold, the vertical stove pipe pulls really hard 24x7. So you get a really rockety burn when you are burning. And when you are not burning, then all of the room air is pulled through the system, warmed by the mass and your mass warmth is pulled outside.

820) Ernie, Erica and I all agree that air intake MUST come from down low - to avoid creating anything resembling a competing chimney. And, when it gets really cold outside, the uninsulated vertical air intake starts to act like a push to the system as the intake is warmed by room temp air. So the air intake itself seriously cools the room with this heat exchange. And then pushes really cold air into the rmh which then starts to cool the whole mass.

821) We need to insulate the air intake.

822) We need a way to completely shut off the air intake outside.

823) We need the ability to completely shut off the vertical stove pipe at the roof.

824) When the temperatures are not so cold, I think we need to have an external riser and barrel to draw air through the system from the wall.




 
Satamax Antone
gardener
Posts: 2254
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
54
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Paul, make a bell on that vertical chimney. At least you'll trap some heat. I have been impressed by bells! Quick one, two barrels atop of each other, one intake one exhaust at the bottom. Two of thoses after a six incher, and you should trap all the heat. When the burn is done, why don't you put a lid on the feed? filled with some rockwool, there shouldn't be much draft!
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
It's good to know that Newton's law of cooling still applies. LOL
http://amrita.vlab.co.in/?sub=1&brch=194&sim=354&cnt=1
 
Len Ovens
pollinator
Posts: 1452
Location: Vancouver Island
29
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:

The lever you see is connected to a baffle inside the duct designed to direct the exhaust either through the roof or through the wall. When you route through the roof, the stove pipe collects radiant heat from the barrel and then the vertical pipe will pull exhaust as well as the heat riser pushing. Unfortunately, when we flip the lever, the pull in the stove pipe is so strong that the exhaust is still pulled up - so the baffle is probably blocking only 95%.


All flue shutoff valves shields etc. in North America are only 80% by law for "safety" reasons. (read to avoid law suit from stupidity) If you look at the the Russian peasant stoves (oven heating etc) they have quite a large compartment that has a door over it while burning in the flue path. The flue sticks up a few inches in there and then continues over head. After the fire is out (use your nose) they put what to me looks like a small garbage can lid over top of the bottom flue to block it 100%. Then close the outer door. The are also guillotine style cutoffs that modern stove/heater makers use for the same reason.... though in NA they are of course only 80% If you are trying to make something that will pass permit... the last 20% is something you will have to deal with one way or the other. The most obvious thing of course in a sealed system like the RMH is to seal the intake 100% which is safer anyway from idiots.



819) When it gets really cold, the vertical stove pipe pulls really hard 24x7. So you get a really rockety burn when you are burning. And when you are not burning, then all of the room air is pulled through the system, warmed by the mass and your mass warmth is pulled outside.


good to know. Blocking the air intake 100% should fix that. I think the intake is square and so a wood or metal square that is bigger than the intake with a square of rockwool attached that just fits might work well.


820) Ernie, Erica and I all agree that air intake MUST come from down low - to avoid creating anything resembling a competing chimney. And, when it gets really cold outside, the uninsulated vertical air intake starts to act like a push to the system as the intake is warmed by room temp air. So the air intake itself seriously cools the room with this heat exchange. And then pushes really cold air into the rmh which then starts to cool the whole mass.


This is an area that needs to be studied from more than a heating view point IMO. The heater is not the only thing that needs fresh air, the people do to. The minimum air exchanges required be law are good for survival, but not for health. I would suggest a minimum of 4X the allowable minimum so the population inside can thrive not merely exist. so...

821) We need to insulate the air intake.

I would rather say the air intake should start outside of your insulated mass of earth lower than the rest of the intake so that the earth mass can warm that air on its way in. I would have this air enter at some distance from the heater so that people (and pets who are more sensitive to low oxygen) get first crack at it. The heater can have what I breath out.

822) We need a way to completely shut off the air intake outside.

I would say Never. It would be ok for keeping the home warm while all occupants are outside... but remember the stupid factor when someone decides to leave it closed "cause its a little warmer".

823) We need the ability to completely shut off the vertical stove pipe at the roof.

Yup. but not legal. Closing the intake may have the same effect... try it as it is safer and therefore to be preferred.

There are a lot of stupid people around... or better yet, smart people who sometimes do stupid things (Len raises hand). When it comes to smoke and sealing air entrance, these things should be always at the foremost in the mind. My feeling is that the heater can not be considered on it's own but only as part of the whole living environment. Do not listen to a building contractor on this as current building practice in my opinion gives homes that while more energy efficient, are sick homes based on profit over occupants well being.
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Do I dare ask you to post the first 818 observations on the pebble stove?
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Jim LaFrom wrote:Do I dare ask you to post the first 818 observations on the pebble stove?


A lot of it went into the recent podcasts.

 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Blocking the air intake 100% should fix that.


I'm thinking that I would need to block the intake and the outgo. Otherwise, the vertical will just do a big heat exchange through the night.


I think the intake is square and so a wood or metal square that is bigger than the intake with a square of rockwool attached that just fits might work well.


So maybe just mount some sort of manual plug outside?


The heater is not the only thing that needs fresh air, the people do to.


Today I've been running it without the air intake. The draw is plenty strong enough. And yesterday there was a smell of smoke in the air - it makes me think that I might have a leak somewhere. So that made me think that there is another perk to pulling the air out of the room instead of from outside - to just make sure you get every spec of smoke out of the house.

It also made me think about one place where cob is better: everything about it is extremely well sealed. Without tape.

I would say Never. It would be ok for keeping the home warm while all occupants are outside... but remember the stupid factor when someone decides to leave it closed "cause its a little warmer".


Keep in mind that this is very experimental. This is not for just anybody to use - this is for me to use.

At this point, the design in place is such that if you shut off the air intake - you draw air from inside the room.

 
S Bengi
Posts: 1359
Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even distribution
9
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I totally agree with pulling the air from inside the room.
That way fresh air can enter enter the room then the fire chamber vs just the fire chamber.
There will be a little smoke back when the fire is just lit or if a crazy strong gist of wind blows in the wrong direction.
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Likes 3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I wonder if there might be a collection of ways to get more pump when you need it. Each with a good baffle to turn it on and off.

One good outdoor baffle could be whether to route the exhaust into a riser/barrel pump or just shoot it straight outside. After all, if you leave a pump like that connected all the time then it will drain your thermal mass.

Another good baffle is the one that erica has in this video where you can shortcut the mass in order to get the fire started:




 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Paul,
you said, 822) We need a way to completely shut off the air intake outside.

I think have your answer. In wood working dust collection systems, they have such things called "BLAST GATES" They come in various sizes 2 1/2", 4.6,8 + they are effective for maybe 98%-100% shutdown depending on the system and whether or not these things are pressurized, by overall pretty effective in the workshop scenario. LEGAL DISCLAIMER- these are NOT for use with any wood burning appliance, including wood stove, rocket stove and RMH's and you didin't hear it from me. Hope it furthers the empire.

http://www.amazon.com/8-Diameter-Industrial-Blast-Gate/dp/B00E1O2O2S/ref=sr_1_fkmr3_3?ie=UTF8&qid=1385331967&sr=8-3-fkmr3&keywords=8+inch+blast+gate
 
Albert Sindlinger
Posts: 3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Wondering about the wood box as a container for the mass? Could one use a metal stock tank to hold the system instead of the wood? Would the metal containment from the stock tank cause problems for the working efficiency of the stove?
Thanks, Al
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Paul,
Again referring to #822.
I'm surprised you are trying this. Erica had made reference to this wood stove site in an older video of hers (or maybe post) and "The Myth" of using an outdoor air source. Maybe the stove is trying to tell you something. Granted this is all just an experiment but this is one more thing to check off the list
http://woodheat.org/outdoor-air-supplies.html
 
                    
Posts: 238
Location: AR ~ozark mountain range~zone7a
9
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Unfortunately, when we flip the lever, the pull in the stove pipe is so strong that the exhaust is still pulled up - so the baffle is probably blocking only 95%.

The problem with this particular exhaust through the wall is that it has two extra 90 degree turns. So it isn't a very fair comparison.


You might try the EITHER OR approach to the flue, EITHER vertical chimney, OR horizontal chimney to find a fair comparison of performance. The interesting manifold & valve assy. currently between the two types of chimneys is probably affecting flue flow regardless the position of the valve, and also possibly affecting the flue/heat loss (819) when the RMH is not being fired as well as under full load. Most home installations will only require one chimney, be it horizontal or vertical, you might test your new unit temporarily dedicated both ways, albeit it isn't as much fun with only one chimney and no lever to flip around with.

james beam

 
Hans Quistorff
pollinator
Posts: 765
Location: Longbranch, WA
41
chicken goat rabbit solar tiny house wofati
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Reading through the Canadian studies and thinking about the way most of the mass has been set up for RMH, I had the thought of putting room make up air intake from outside lower than the mass and running it under the mass to pick up heat that radiates down then enter the room by coming up through the end of the mass. This would supply partially warmed fresh air to the occupants and be more resistant to back drafting.

If such a room make up air system worked well then I think a passive vent tube over a rocket stove used for cooking with a slide valve for 100% closure would be nice. I am very sensitive to oil vapors in the air particularly pork fat.
 
Len Ovens
pollinator
Posts: 1452
Location: Vancouver Island
29
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:
So maybe just mount some sort of manual plug outside?


Maybe some pictures will help. All of these are from this page:
A story about an abandoned village. (Quite interesting in it's own right)

This first one is open but shows the inside quite well:

You can see the flue sticking up from the bottom. The chimney continues overhead. (brick)

The next one shows the cap and the outside door (not from the same heater though)


While all of this seems to be brick work, I see no reason this could not be done with cob or insulated tin.

This is a "just for fun picture". The sleeping platform over top of one of the ovens.


These homes are new enough to be stick built rather than stone, cob, sod or brick as they would have been in earlier times. They were also poorly insulated and situated in a colder climate than your project is. In other parts of the this site they show small brick heaters in the middle of the living area with tin pipes going to the main chimney. Apparently these pipes were straight at whatever angle they had to be.... I can imagine they posed a hazard to people moving about in the room, but then they grew up learning to be careful, not like todays world where fear of law suit makes for people growing up in padded cells heated to 72F at all times
 
Len Ovens
pollinator
Posts: 1452
Location: Vancouver Island
29
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Here is the best picture of a guillotine flue shutoff I could find just now.


The frame can be seen in place and the blade to the left. The blade slides from left to right to block the passage off and to the left to open it. It is operated by a pull handle. Most of these seem to be custom made. This is very similar to the waste gate on the sewage tank of an RV. (too bad those are only 4inch) In this case it shuts off flow to a bench (or maybe it shuts off a bypass route to the flue).
 
Bill Kearns
Posts: 159
Location: E Washington steppe
4
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Maybe some pictures will help. All of these are from this page:
A story about an abandoned village. (Quite interesting in it's own right)


Utterly fascinating! Thanks for posting that!
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Jim LaFrom wrote:Paul,
Again referring to #822.
I'm surprised you are trying this. Erica had made reference to this wood stove site in an older video of hers (or maybe post) and "The Myth" of using an outdoor air source. Maybe the stove is trying to tell you something. Granted this is all just an experiment but this is one more thing to check off the list
http://woodheat.org/outdoor-air-supplies.html


I'm surprised too.

This is not a slam dunk decision. I remember the first time I was exposed to the "ziplock bag argument" when i suggested air intake from the outside. I think I have mentioned that several times. And then last spring I got into a long, rich discussion about it with Ernie and Ernie's dad - who also has a rocket mass heater. And then Ernie, Erica and I have hashed it out a dozen times since. Here are some notes.

At this point in time I am thinking that the direction I want to move toward is to have a system that has lots of control - something where I can turn things on and off as needed. I like the idea of having some draw when starting the fire. I like the idea that if I start to get some smoke back I can adjust things to be a little rocketier. If the system is too rockety (and a lot of heat is escaping outside) I can slow things down a bit.

And, of course, this particular heater has the primary function of solving some of the problems we've had in the rocket mass heater world.

Erica and I have talked about some ideas with putting heat sink fins on the duct work in the gravel to make sure we extract more heat before it goes out the wall. We've also talked about ideas on sealing the duct without gluey-tape.

 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Len Ovens wrote:
This first one is open but shows the inside quite well:

You can see the flue sticking up from the bottom. The chimney continues overhead. (brick)

The next one shows the cap and the outside door (not from the same heater though)



That looks like the sort of thing I am looking for!

 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Paul, you said

At this point in time I am thinking that the direction I want to move toward is to have a system that has lots of control - something where I can turn things on and off as needed. I like the idea of having some draw when starting the fire. I like the idea that if I start to get some smoke back I can adjust things to be a little rocketier. If the system is too rockety (and a lot of heat is escaping outside) I can slow things down a bit.

And, of course, this particular heater has the primary function of solving some of the problems we've had in the rocket mass heater world.

Erica and I have talked about some ideas with putting heat sink fins on the duct work in the gravel to make sure we extract more heat before it goes out the wall. We've also talked about ideas on sealing the duct without gluey-tape.



I think I understand what you are saying. You want the controllability of a fuel source like LNG, Propane, or Gasoline. The problem with wood is you can't immediately shut down that fuel source and then get it back up to temp at your will. Also the chimney system isn't pressurized, so it is DEPENDING on that heat to carry the exhaust air out. If you achieve 100% efficiency in reclaiming the heat then you start getting yourself into backdraft problems because all there is left, is cold air in the last portion of the system. The reason some of these systems are under performing is because the venting system gets too long or has too many bends which causes structural restrictions (turbulence) to air flow. You can add fins or add length either way gets the job done, you just don't want to do it too well.
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
If it is a really cold day outside, I wand to adjust things to be less rockety.

If it is a cool day outside (55 degrees) I want to adjust things to be more rockety.

There are things that can be controlled. I want to control them.

I prefer to have air pulled out of the room instead of having air pulled from outside. Most of the time. For that 10% of the time I want air to be pulled from outside, I want the option.

When the fire is out - i want to make sure that the air moving through the system is at a FULL STOP.

If the exhaust is leaving at 140 degrees, I want to fix that.

I do not need perfect. But I do want better.
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:If it is a really cold day outside, I wand to adjust things to be less rockety.

If it is a cool day outside (55 degrees) I want to adjust things to be more rockety.

There are things that can be controlled. I want to control them.
Don't we all!
paul wheaton wrote:

I prefer to have air pulled out of the room instead of having air pulled from outside. Most of the time. For that 10% of the time I want air to be pulled from outside, I want the option.

When the fire is out - i want to make sure that the air moving through the system is at a FULL STOP.

If the exhaust is leaving at 140 degrees, I want to fix that.

I do not need perfect. But I do want better.

There is something called Physics and we can't fight that. If you pull air out of a room there is something is that is going to replace it . In HVAC terms this is called makeup air. (cool air?) You will either depressurize the room if it were totally airtight or air will find it's own way in. Nature abhors a vacuum. (Permaculture principle )
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
There is something called Physics and we can't fight that.


Is there a point in this somewhere that I am suggesting that we fight physics?

If you pull air out of a room there is something is that is going to replace it . In HVAC terms this is called makeup air. (cool air?) You will either depressurize the room if it were totally airtight or air will find it's own way in. Nature abhors a vacuum. (Permaculture principle )


Which is entirely the point. I prefer to have the stale, stinky air removed from the room and replaced with fresh air from outside. Yes, the air from outside will be cold - and it is coming in while my rocket mass heater is running.


 
Chad Johnson
Posts: 46
1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Has someone tried an adjustable bell (barrel) height to control the amount of rocket?
 
Satamax Antone
gardener
Posts: 2254
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
54
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:
Which is entirely the point. I prefer to have the stale, stinky air removed from the room and replaced with fresh air from outside. Yes, the air from outside will be cold - and it is coming in while my rocket mass heater is running.




Paul, in the pellet worls, thare is a tipe of tube where the flue is concentric with the fresh air. The flue on the inside, and fresh air outside. Thus heating up the fresh air. Tho, it's not needed. It could be mimicked with two tubes in a rocket. Mind you, you'd have to have some leftover heat to warm the intake air, and, obviously, you can't make it run in the bench, so you would have to separate the two tubes at some point.

http://www.poujoulat.co.uk/produit/38/17/1/concentric-chimney-system-for-gas-fires-amp-pellet-stoves/pgi-pellets.html
 
Len Ovens
pollinator
Posts: 1452
Location: Vancouver Island
29
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Wow I can answer two posts in one

paul wheaton wrote:If it is a really cold day outside, I wand to adjust things to be less rockety.

If it is a cool day outside (55 degrees) I want to adjust things to be more rockety.

There are things that can be controlled. I want to control them.


And I think this is something that can be achieved. I am going to add another term to things here. "Ballast gas" This is air that is not being used to help the heater work(move the exhaust out) or to produce heat. Too rockety would be too much ballast gas in the system. This ballast gas is being heated by the fire... sucking heat into itself and then leaving the system with that heat too.

Right now the intake air is being controlled by the fuel blocking the intake, though I have seen a brick set across the feed too. It seems that at most, the intake for air needs to be 1/4 the riser CSA. There are two reasons for this (well that I can think of): The first of course is keeping the ballast gas in check. the second in my experience, is that the primary burning area at the bottom of the feed tube stays too cool and doesn't burn well. The intake area (as in CSA) needs to be controllable. I did this by sealing the fuel feed and instead using a second air intake that could be controlled. This is about the time I found out that any damper I could buy was only 80% cutoff. Not only were there holes in the plate, but the 6inch damper plate was only 5inches in diam... I ended up using bricks. The trick is to provide just enough air for a full burn, but no more. (in practice, just over)

paul wheaton wrote:

I prefer to have air pulled out of the room instead of having air pulled from outside. Most of the time. For that 10% of the time I want air to be pulled from outside, I want the option.

When the fire is out - i want to make sure that the air moving through the system is at a FULL STOP.

If the exhaust is leaving at 140 degrees, I want to fix that.

I do not need perfect. But I do want better.


sealing the system at fire out is just good sense. As you can tell by my pics above this is not a new idea.

Jim LaFrom wrote:

There is something called Physics and we can't fight that. If you pull air out of a room there is something is that is going to replace it . In HVAC terms this is called makeup air. (cool air?) You will either depressurize the room if it were totally airtight or air will find it's own way in. Nature abhors a vacuum. (Permaculture principle )


Yes, but we want the air to come in under the best conditions that physics allows. We want to make the best use of that air. We already know we will have air coming into the room aside from any direct feed. We don't want a sick house after all. I can't really speak for Paul, but my Goal would be to have as much fresh air entering the home as I can without it affecting the comfort of the home or removing all our heat either. I also wish to stay away from any active system outside the effects of the burn itself. This means being very careful in design of the living space and the air entrance. The living space should be set up so as not to have people in the way of any cool draft created and have the fresh air enter the dwelling in such a way that it travels some distance through something warm before it can be felt. It is not just designing a heating system that works well, but designing the home around that as well. In this case, Paul is setting aside some of the home design elements (not ignoring, but not studying just now) and finding out what the heater itself needs to work best. Then the home can be designed around those parameters.

One more thing, I would really like to see the flue gas (bad term for no flue ) recombine with the outside air at lower than room temperature. Still within what physics will allow of course. I think this is possible, at least in really cold weather, shoulder seasons may be more difficult. I am not sure the flue gas will be less than room temp when it exits the house itself, but the gas should be cooled in such a way the heat can be of use in any case. (such as warming up incoming air)
 
Hans Quistorff
pollinator
Posts: 765
Location: Longbranch, WA
41
chicken goat rabbit solar tiny house wofati
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Len Ovens wrote:Wow I can answer two posts in one

paul wheaton wrote:If it is a really cold day outside, I wand to adjust things to be less rockety.

If it is a cool day outside (55 degrees) I want to adjust things to be more rockety.

There are things that can be controlled. I want to control them.


practice, just over)

paul wheaton wrote:

I prefer to have air pulled out of the room instead of having air pulled from outside. Most of the time. For that 10% of the time I want air to be pulled from outside, I want the option.

When the fire is out - i want to make sure that the air moving through the system is at a FULL STOP.

If the exhaust is leaving at 140 degrees, I want to fix that.

I do not need perfect. But I do want better.


sealing the system at fire out is just good sense. As you can tell by my pics above this is not a new idea.

Jim LaFrom wrote:

There is something called Physics and we can't fight that. If you pull air out of a room there is something is that is going to replace it . In HVAC terms this is called makeup air. (cool air?) You will either depressurize the room if it were totally airtight or air will find it's own way in. Nature abhors a vacuum. (Permaculture principle )


Yes, but we want the air to come in under the best conditions that physics allows. We want to make the best use of that air. We already know we will have air coming into the room aside from any direct feed. We don't want a sick house after all. I can't really speak for Paul, but my Goal would be to have as much fresh air entering the home as I can without it affecting the comfort of the home or removing all our heat either. I also wish to stay away from any active system outside the effects of the burn itself. This means being very careful in design of the living space and the air entrance. The living space should be set up so as not to have people in the way of any cool draft created and have the fresh air enter the dwelling in such a way that it travels some distance through something warm before it can be felt. It is not just designing a heating system that works well, but designing the home around that as well. In this case, Paul is setting aside some of the home design elements (not ignoring, but not studying just now) and finding out what the heater itself needs to work best. Then the home can be designed around those parameters.



That is why In my earlier post I suggested bringing in the make up air under the mass storage where it would be warmed by heat that otherwise would take a long time to reach the room. Then it would be comfortable and healthy for people and the fire to breath before it exits again. When the fire path is blocked there will still be air exiting through unsealed portions of the building, the make up air for that can continue to be heated by the mass before entering the room.
 
Allen Herod
Posts: 18
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Maybe this has been tried. Forgive me, I haven't read all the RMH stuff but here's my brainstorm (possibly a brain fart). I saw some discussion on the intake coming from inside or outside. I'm on the bandwagon that it needs to come from inside for healthy air exchange. Now for my brain fart... What about an exhaust recirculation back into the burn chamber, much like a turbo charger on a diesel engine? On a turbo diesel engine (I believe this is the concept) fresh air is pulled in but exaust is also forced back into the intake (via the turbo, driven by exhaust pressure) creating more fresh air draw (kind of like a siphon effect) but also recirculating heat that would otherwise be lost out the chimney. Maybe it has been tried and failed or is already part of the system and im missing it. Seems like a possibility to me and should boost the initial heating up of the system at the very least? It would possibly increase air exchange in the room but also generate more heat in return. Point me in the right direction if I am missing something.
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Allen Herod wrote:Maybe this has been tried. Forgive me, I haven't read all the RMH stuff but here's my brainstorm (possibly a brain fart). I saw some discussion on the intake coming from inside or outside. I'm on the bandwagon that it needs to come from inside for healthy air exchange. Now for my brain fart... What about an exhaust recirculation back into the burn chamber, much like a turbo charger on a diesel engine? On a turbo diesel engine (I believe this is the concept) fresh air is pulled in but exaust is also forced back into the intake (via the turbo, driven by exhaust pressure) creating more fresh air draw (kind of like a siphon effect) but also recirculating heat that would otherwise be lost out the chimney. Maybe it has been tried and failed or is already part of the system and im missing it. Seems like a possibility to me and should boost the initial heating up of the system at the very least? It would possibly increase air exchange in the room but also generate more heat in return. Point me in the right direction if I am missing something.


I think the goal for this project is to have everything be done as 'passively' as possible. (No other energy inputs.) As you well may know, turbo chargers involve compressors and re-circulation under pressure which is nice for the technology in cars, jets and watercraft but for the purposes of this discussion/ brainstorming session we are looking for as simple as possible. Those Turbos need other energy inputs and at the end of it all would be a net energy loss.. Just re-venting the smoke back into the fire chamber without some sort of closed loop would just force smoke into the room because of the open feed tube. Secondly cooling the smoke too much, without forced air circulation would kill any draw to vent to the exterior resulting in SRS, smoky room syndrome.

Any ideas of forced air movement, turbocharging, outside air sources really need to be focused into a 'batch fed', airtight, system. Essentially a wood burning stove.Keep brainstorming though. We need to keep those neurons activated.
 
kevin Davis
Posts: 16
Location: North Central New Mexico 7.000'
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Now for my brain fart... What about an exhaust recirculation back into the burn chamber,

Allen. I like that concept. I think I know what you mean by the turbo concept but not in this situation. I'm thinking you mean to re-plum the exhaust into the feed chamber like a closed loop. I would think also that O2 would still need to be introduced also.
My shop is so leaky that it wouldn't hurt the human and cat if oxygen was taken from the room, but in a tight house, a way would have to be found to find more combustion air .
So, if there is just co2 coming from the flue and not combustible, why bother? Now my little brain is scrambled.

Paul, at fire out I use a plate of steel over refractory wool covering the firebox. Climbing up to the roof I can feel no heat coming out of the flue. Seems to work just fine. Over an 8 hour no burn my bench gives up maybe ten degrees.
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
My brother and I had a few chats. he has ordered the steel to make two guillotine style shutoffs. One for the stove pipe going to the roof and one for the air intake.

He wanted to make one for the wall exhaust also - but I said lets let that one come a week or two later. Because we might learn some things about the first two and want the third to be slightly different.

We still need some sort of really good lid on the chamber over the wood feed.

Today I got cocky when starting the fire and ended up with smoke in the room. I really wish I could have said "activate maximum rockety!" Once I got the fire going good, then I was really glad that it pulled the air out of the room - get that smoke out of here!

Tim added bigger windows to the office. I watched the wild turkeys go by twice today. Another perk is that the window is now a little further away from the fire bits. Tim is also mounting a point for a lamp over the wood feed.

I'm now thinking about the wall exhaust. I want to be able to experiment with the outdoor passive pump and the straight shot outside.

Another thing that came up today. We seem to have just heaps of winter projects. And the more we talk about it, the more we think how great it would be to have six more people out here. But, damn, it's cold outside. Today, Jocelyn and I talked a little bit about setting up two bunks over the mass. One bunk would be right over (on?) the mass and the next would be a few feet up. The duct going outside could be shifted. And the the electronics-on-the-shelf needs to be moved anyway.


 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:My brother and I had a few chats. he has ordered the steel to make two guillotine style shutoffs. One for the stove pipe going to the roof and one for the air intake.

He wanted to make one for the wall exhaust also - but I said lets let that one come a week or two later. Because we might learn some things about the first two and want the third to be slightly different.

Another thing that came up today. We seem to have just heaps of winter projects.


Paul,
Just curious. I would think both of Tim and your time were valuable than this. Amazon has these gates for what I would consider reasonable. (http://www.amazon.com/8-Diameter-Industrial-Blast-Gate/dp/B00E1O2O2S/ref=sr_1_1?s=hi&ie=UTF8&qid=1385675451&sr=1-1) Why are you trying to reinvent the wheel (blast gate)? Much easier to knock out the other projects at hand when you use other people's labor and innovation and then do what you best.
 
paul wheaton
master steward
Posts: 21976
Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I wanna see the other side.

Plus, we're talking about keeping the gate insulated.
 
Satamax Antone
gardener
Posts: 2254
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
54
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
paul wheaton wrote:I really wish I could have said "activate maximum rockety!"


Paul, when i start my rocket from cold, i put few sticks in criss cross fashion, and pour a glass of denatured alcohol on top, then set light to it. Only do this if starting from cold. But it works far better than paper. Gets a very strong draft in the first few seconds, and lights up the wood. I also use it to prime the tube.
 
Allen Herod
Posts: 18
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Jim LaFrom wrote:
Allen Herod wrote:Maybe this has been tried. Forgive me, I haven't read all the RMH stuff but here's my brainstorm (possibly a brain fart). I saw some discussion on the intake coming from inside or outside. I'm on the bandwagon that it needs to come from inside for healthy air exchange. Now for my brain fart... What about an exhaust recirculation back into the burn chamber, much like a turbo charger on a diesel engine? On a turbo diesel engine (I believe this is the concept) fresh air is pulled in but exaust is also forced back into the intake (via the turbo, driven by exhaust pressure) creating more fresh air draw (kind of like a siphon effect) but also recirculating heat that would otherwise be lost out the chimney. Maybe it has been tried and failed or is already part of the system and im missing it. Seems like a possibility to me and should boost the initial heating up of the system at the very least? It would possibly increase air exchange in the room but also generate more heat in return. Point me in the right direction if I am missing something.


I think the goal for this project is to have everything be done as 'passively' as possible. (No other energy inputs.) As you well may know, turbo chargers involve compressors and re-circulation under pressure which is nice for the technology in cars, jets and watercraft but for the purposes of this discussion/ brainstorming session we are looking for as simple as possible. Those Turbos need other energy inputs and at the end of it all would be a net energy loss.. Just re-venting the smoke back into the fire chamber without some sort of closed loop would just force smoke into the room because of the open feed tube. Secondly cooling the smoke too much, without forced air circulation would kill any draw to vent to the exterior resulting in SRS, smoky room syndrome.

Any ideas of forced air movement, turbocharging, outside air sources really need to be focused into a 'batch fed', airtight, system. Essentially a wood burning stove.Keep brainstorming though. We need to keep those neurons activated.


I figured I might get some turning wheels with this idea... A turbo charger (technically) DOES NOT involve "outside power" to turn a compressor. You may be confused with a super charger that is belt driven by the engine. A turbo differs, in that it is driven by wasted exhaust fumes(no electricity or belts turn it), making it at least somewhat "passive" in my opinion. If it weren't there, yes there would probably be less energy input (in this case more or less wood). However, that little extra input comes out exponentially on the other side (hypothetically in a RMH, more heat). In my mind, this system wouldn't even need the "turbo" to create the same effect. Instead, if the pipes ranged in size and were on the proper plane to work together, it should, in my theory, naturally aspirate... just the same as a draw is created thru the intake and out the chimney I think, unless we have a math genius out there, experimentation would be the only way to prove or disprove this theory.... And I personally know a "mathmetician" (spelling?) with a masters degree that couldn't solve a simple geometry problem for me a few years ago, so I would have doubt in any mathmatical "proof" against this. I know "turbo" sounds like alot of energy and waste but it doesn't have to be. Just food for thought.
 
Allen Herod
Posts: 18
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Kevin, not exactly a closed loop. Yes, a loop but there is still chimney exhaust and outside oxygen coming in to feed the fire.
 
Len Ovens
pollinator
Posts: 1452
Location: Vancouver Island
29
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Allen Herod wrote:
I figured I might get some turning wheels with this idea... A turbo charger (technically) DOES NOT involve "outside power" to turn a compressor.


Ja, the early two stroke diesels were super charged, but most newer four strokes are turbo (Len has one). The pressures involved in even a lower compression gasoline engine are still much higher than with the RMH. Even then, the turbo doesn't do much good until the engine RPM passes a certain point. Below that point it is often bypassed because there is a net loss in power. The RMH just doesn't have the working pressure to turn a turbine.

However, some of that activity does happen right at the top of the barrel where the gas from the center of the riser hits the barrel top and goes down the side of the barrel just a bit before curving back in and up to form a spinning torus. (a similar idea is used in some masonry heaters too but not torus shaped) This does reintroduce the spent flue gas back into the still burning gases. The pump effect made by the flue gas expanding and contracting (becoming lighter and heavier) is actually pretty delicate... which is why there is much discussion on things like exhausting and smoke back in the first place. The RMH riser/barrel combo helps to make a j-tube feed and wall exhaust work where they might not in an open fire place. The high mass allows the burn to be "furious" without over heating the room. It is very much a balancing act all the way through. Every change in one area requires change in other areas.
 
bob day
Posts: 352
Location: Central Virginia USA
14
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
i know this wouldn't work for the roof vent, but could the wall exhaust be sealed with a dryer style flap--just a plastic(?) door hinged at the top that gravity closes, but is light enough for the exhaust pressure to open easily, this could keep out bugs other times of the year as well

 
Allen Herod
Posts: 18
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I'm not necessarily suggesting the use of an actual turbine in the system (unless absolutley needed to make the circulation happen), just the recirculation concept, if even possible, for added efficiency. I realize the pressures are NOWHERE near the same. I agree that any change down the line in this manner is going to change intake and burn (recirc. could be shut on and off as needed with a flue) and as I said previosly, various size pipes would be needed to make the pressure/draw happen and still should not let smoke off in the room with controling of the recirculation. Maybe you wouldn't open it until a good fire was going. And, I think you are incorrect about the operation of the diesel turbo not functioning until a higher rpm, as diesel engines are designed to operate high torque at low rpm anyways. Yes there is more recirculation pressure created (and you actually hear the turbo wind up) at higher rpm, but the turbo is running even at idle.... trust me, even at idle, the turbo on a diesel engine would try to suck your hand in if you put it up there (I've put my hand up there, lucky to still have all my digits). I thought this would start a good discussion. If the concept worked, I guess we could then call it a "TRMH"

As I said above, I believe the vertical plane of a recirculation system would be very important for this to properly work. (IE. the recirc. port would probably need to be as low as possible, due to the low pressures... AND pipe size will have an effect.

One more edit: Think about the natural draw already happening from the burn and the siphon effect... Siphoning can happen with air just barely skimming over an open port. Just a 1/2 inch recirc pipe might make a signicant difference in burn.
 
Jim LaFrom
Posts: 36
Location: Truckee, CA
3
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Allen,
The point of a RMH is that it has been found to be one of THE MOST EFFICIENT Heaters that has been proposed. There are figures, (I believe somewhere) that put the efficiency in the 95% efficiency range. This turbo stuff would do what exactly? Try to burn the last 5%? I don't think that is a reasonable pursuit at this time. Most modern home forced air gas systems would LOVE to get to 95% efficiency. We are able to do this with a regenerating fuel source (Wood) and a couple hundred dollars with little to no ongoing costs for future fuels, if you are the Craig's list kind of forager type of person.

The types of things that need to be addressed, in this thread at least, are issues of...
- controlling heat output, ease of creating that second call for heat which might be in 10 mins or 5 hours from now.
- damping down the heat firebox and dumping heat loads after a cycle. Then having an air tight seal around the firebox so that the cold air doesn't come rushing back down the primary ignition exhaust vent.
- having an air tight seal on the feed tube when not cycling so the room isn't getting back drafted smoke and CO.
- having an efficient means of transferring heat and exhaust gas to a mass via ducts, or other means.
- finding the optimal length and/or number of bends in the duct system to create as large a mass as possible without reducing draft from the stove. This will need to be recalculated for each manifold sized system.
- once a cycle of heat has ended, does damping the end of the exhaust system help to prevent the stored heat from continued flow from the stove. How much difference in sustaining a bed temperature within a certain specified
range. Do the added dampers (blast gates) preserve the heat within the system without threatening air quality?
- determine most effective material for storing this collected heat. IS COB the only solution to thermal mass? Would a water tank be more effective?
- after all that can this whole thing be automated enough to run without nannying it.

I thought I had a decent understanding of turbo jets, and pulse jets and turbines in general. With your comments I went back to Wikipedia to refresh my thoughts. All I saw were engines that required compressors that were running off of electricity or another gas generator engine. In some styles there were fans involved that further compressed the incoming air. Those prop fans were also run by electricity. The only other option was for planes flying at high rates of speed which by that speed were able to pressurize air by the mere slicing through that wind stream. Those fans are POWERED by electricity. Through circuit boards the compressed air is mixed with fuel in a timed cycle which provides propulsion because of the series of controlled explosions that all happen within the sealed engine. Once again, we need external energy inputs. As for recycling exhaust, how does one figure out when the exhaust is finally ready to be dumped as opposed to being recycled for the now hundreth time. There can be no way of determining between newly made exhaust and the recycled exhaust. The extra turns cause friction in the system and a cooling effect is created rather than any additional warmth. I would be pleased to listen your explanation of how a compressor gets charged without any energy inputs, or how without a compressor or hurling a RMH out of a jet fighter at 30,000 ft will the air become compressed. We aren't even talking about a sealed system (which would be VERY DANGEROUS on the hobbyist level.) I guess I will leave finding those answers to you.


 
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!