split exhaust into four separate exhausts?

One of the examples that sticks in my mind is a 6'' pipe will flow 4x what a 3'' pipe will flow, not just double, Its
Total Cross Sectional Area, and friction loss at the walls X the distance you must flow your gas/or liquid !

I saw this earlier before I made my first post and just a little bit ago I had a thought.

If you set up a 6 inch system right up until the Mass part and then split it into 4 separate 3 inch exhausts, could you potentially run each one of the 3 inch tubes to a mass in different rooms?
And when you begin to run them to the outdoors, Would it be better to run them separately to the outside or could you run them all back together and back into a 6 inch tube?
Now I am thinking running them back together wouldn't be a very good idea, in my head I keep thinking that you would end up with a choking point. Unless you had a way to make sure it kept flowing in the correct direction.

Let me know what you think.

Jason E. Smith : This IS thinking outside the box, and we DO need a lot of thinking like this to make the '' Rockets of Tomorrow " ! But in the most practical sense -

You are adding to the complexity of the system , and greatly increasing its costs ! Four times as many pipes, 4Xs the cost and the fittings to split / gang One pipe

into 4 and then back again is going to be very pricey !

This has been discussed before and the costs involved in this is enuf to make me uninterested in this experiment ! So far One-one has reported success with this

project ! For the Good of the craft ! Big AL

Well I kinda figured doing what I asked would make things much more complex and expensive.

But I never said someone had to do it, I just want to know if someone who is more experienced than myself thinks it might be feasible.

The only real way this would be useful is if someone (like myself) had multiple rooms they wanted to heat.
I want to build a RMH to heat my house. And I am thinking the way I will do it is by figuring a way to transfer heat into the existing duct work.

But as I also read and know, air especially moving air does not retain heat well at all.

And thinking about that and what you had posted 2 years ago got me to thinking of a potential way to make a single RMH heat multiple smaller rooms.

Thus my Brain concocted the 4 way split.

I wouldn't be able to afford 90% of the materials to do that project, but if I was able to I could put smaller Mass heaters in 4 rooms of my house on the first floor.
For example, one in the kitchen, second in the living room, third in one of the bedrooms, and the fourth in the second bedrooms.
If I were able to pull it off, it would heat my entire basement, first and second floor all while saving money on my utilities.
And to tell you the truth, it might cost a little extra to build it, but would likely save a home owner more money in the first year than they spent on it.

And just to prove my point for that.
Over the summer I usually only spend around $400 to $500 on my electric bill. During the winter I spent well over $2000 this year, last year was over $3000.
I have already been looking up ways to get the supplies I need to as close to free as possible. The barrel would cost me around 8 to 10 dollars, the duct work for a normal exhaust (not the 4 way) would only cost me about $20 at a local secondhand store that sells used items out of houses that have been torn down. For a single mass I could get all the supplies I need for free because I know several people who live just out of town on a farm. Other than making the Cob and getting the fire bricks, this is already looking like it's going to be super cheap to build. I will say over the summer I will probably spent about 150 to 200 dollars on all the materials I need to make my first RMH.
That is going to cost me around a tenth of what the electric company charges me.
So while it would cost extra to do the 4 way system I asked about, it would save myself thousands in the first year I had it.


So anyway back to my question.

Does anyone think it would work?

Jason, key words to search for on the internet.

Path of least resistance.

Boundary layer,

friction drag

If you are absolutely sure you can equilibrate such a system, go for it.

Myself, i would pass.

Satamax Antone wrote:Jason, key words to search for on the internet.

Path of least resistance.

Boundary layer,

friction drag

If you are absolutely sure you can equilibrate such a system, go for it.

Myself, i would pass.

I am a trained Electrician, I know all about the path of least resistance.

There is always a way, It could be as simple as making sure the tubes are all the same length or just a matter of putting a duct fan in the lines to force them all to move.

The way you guys talk is as if it's impossible to do.

If you are sure it can be done, go for it. I wouldn't waste my time on this.

Satamax Antone wrote:If you are sure it can be done, go for it. I wouldn't waste my time on this.

I am only sure of three things.
1:I love my beautiful daughter, she is the best thing to happen to me.
2:I will probably spend the rest of my life fighting with the Veteran's Affairs to get my knee fixed.
3:I will probably die before that happens.

I will likely experiment with it after I have built my main one. If I am lucky I will be able to before next winter, but probably not.

Jason, just to explain my point of view on the subject, immagine, that you've managed to make four perfectly equal channels, that draw the same. With the same incline. With the same amount of elbows, all oriented the same, to reach a single chimney.

But you have around one of thoses, you have left few stones in the cob, more than in another one. Closer to the pipe, that what you want. But even to that level of detail, it counts. These accumulate more heat, and they keep it longer. And, then, you have your stronger pulling leg.

I would rather play with one or two bells, and conduction through the walls.

But since you said, your house is from 66, it's most certainly not a massonry wall one. I don't know how you guys can stand baloon or stick framing, in the US. Worse bit, it's my job, partly, to make such structures. But i like thick stone walls!

Well, rant off.

Satamax Antone wrote:Jason, just to explain my point of view on the subject, immagine, that you've managed to make four perfectly equal channels, that draw the same. With the same incline. With the same amount of elbows, all oriented the same, to reach a single chimney.

But you have around one of thoses, you have left few stones in the cob, more than in another one. Closer to the pipe, that what you want. But even to that level of detail, it counts. These accumulate more heat, and they keep it longer. And, then, you have your stronger pulling leg.

I would rather play with one or two bells, and conduction through the walls.

But since you said, your house is from 66, it's most certainly not a massonry wall one. I don't know how you guys can stand baloon or stick framing, in the US. Worse bit, it's my job, partly, to make such structures. But i like thick stone walls!

Well, rant off.

My house is 66 years old it was built in 1950. And the walls are drywall with little to no insulation on the outer walls.

Now when you start giving examples of why it would be hard to do, THAT satisfies my curiosity better than just saying " it would be difficult so I wouldn't try it."

The major part of figuring things like this out is contemplating what could go wrong and figuring out ways to fix it before it happens.

The main thing my brain came up with was when the 4 smaller exhaust joined back into the bigger one. I figure that it would hit that junction and if it didn't have initial assistance it would bottle neck or try to go backwards down one of the smaller exhaust.

Well, this question comes back regularly, that why you got a laconic reply

I have a few builds behind me, and I would not try a multi channel heater.


I don't know how is your neighbourhood. But as far as cheap and easy insulation goes. Pile up small size strawbales against your walls. cover the prevailing wind side with a tarp during the winter. Can't remember in US r values, but it's around R40 or so. Once roten, after may be ten years, change it. And you're good for ten more years. Hold with wire. I had calculated here, in france, it would cost me about 1100 euros to cover 250m² of wall. And that would be repaid in few months for you, with your electric bills!

I forgot to say, the bale system is also interesting, because the bottom bales compost over time, and you can even grow mushrooms on theses.

Hi,

as I read this split-run-challenge I spontaneously began to do some math:
One 6" duct and four 3" ducts do have the same CSA, however the wall length (circumference) of four 3" ducts is double to that of a 6" duct, hence I assume double the drag per run length.
If you subtract a boundary layer of say 0.2 inches the ratio between the circumferences gets somewhat better, but the "flow-open" CSA of the 4 ducts becomes smaller than that of the 6" duct.

At this point I would say "try, but with a fan", but it gets worse:

Suppose you have no forced air supply double drag means half the recommended maximum run length through the mass, for a 6" system that translates to 22 1/2 feet instead of 45 feet straight run, no bends.
Divided by your four runs you have 5 1/2 feet per run, straight, without any bends. But if you want to heat four rooms and channel these short runs into a room and back to a combined chimney you will have to subtract substantially more length from each run for the required bends

At this point I would say: IMHO not possible.
But please correct me if my logic or math is wrong.



Ralf

Satamax Antone wrote:Well, this question comes back regularly, that why you got a laconic reply

I have a few builds behind me, and I would not try a multi channel heater.


I don't know how is your neighbourhood. But as far as cheap and easy insulation goes. Pile up small size strawbales against your walls. cover the prevailing wind side with a tarp during the winter. Can't remember in US r values, but it's around R40 or so. Once roten, after may be ten years, change it. And you're good for ten more years. Hold with wire. I had calculated here, in france, it would cost me about 1100 euros to cover 250m² of wall. And that would be repaid in few months for you, with your electric bills!

Sadly I live in an Urban area, I could probably get the straw bails, but after setting them up I would have Code Enforcement breathing down my neck telling me to remove them or they would fine me.

My neighbors house is roughly 10 feet or 3 meters from mine.

Ralf Siepmann wrote:Hi,

as I read this split-run-challenge I spontaneously began to do some math:
One 6" duct and four 3" ducts do have the same CSA, however the wall length (circumference) of four 3" ducts is double to that of a 6" duct, hence I assume double the drag per run length.
If you subtract a boundary layer of say 0.2 inches the ratio between the circumferences gets somewhat better, but the "flow-open" CSA of the 4 ducts becomes smaller than that of the 6" duct.

At this point I would say "try, but with a fan", but it gets worse:

Suppose you have no forced air supply double drag means half the recommended maximum run length through the mass, for a 6" system that translates to 22 1/2 feet instead of 45 feet straight run, no bends.
Divided by your four runs you have 5 1/2 feet per run, straight, without any bends. But if you want to heat four rooms and channel these short runs into a room and back to a combined chimney you will have to subtract substantially more length from each run for the required bends

At this point I would say: IMHO not possible.
But please correct me if my logic or math is wrong.



Ralf

|

So according to your math, as long as there is a forced air system in place, it could theoretically work?

Hi Jason,

well, this is new territory, I suppose no one has tried this so I can´t say it it will work.
What I can definitely say is that if a forced air system breaks down in the middle of a burn, may it be because of mechanical failure or a power outage, you will be in trouble.
Even a small amount of smoke back into an enclosed room is already very nasty.

Jason E. Smith : Yes, With a forced air system and feedback controls from the Individual Ducts it is possible ! You now have a system that is furthered complicated

by a requirement for outside Electrical Power. With the loss of your Grid-tied Electricity due to a winter storm ( and 100 year storms occurring every Decade now )

You will ether need a back-up Elect Energy source, or lose your ability to heat your House !?!!


So- price of system, an over-complicated system, and possibly being unable to use the system in a major storm event,- and tho this system has been discussed

in these pages, no one has yet come back here to say they have a working prototype ! - and then there is your code enforcement officer !!


Please do continue to feel comfortable in bringing any idea to these pages,that is how we will get to the builds of tomorrow, and prototype any thing that strikes

your fancy! And Excuse us if we respond with '' Been there, done that, got the teeshirt, wore it out, used the rag to polish my low-quarters '' - we all started where

you are right now !


For the good of the crafts Big AL

Ralf,

I know that no matter what forced air system was in place it would require frequent inspections, cleanings, and maintenance. It look likely need to be checked daily to make sure it doesn't break down unexpectedly. And in the case of a power outage I have multiple back up systems in my home to provide myself at the very least about 4 hours of DC 12v. Which I also have an invert to supply myself with 120v if needed.


Allen,

I understand that my theory makes the RMH much more complicated and increases the chance for failure.
But as I continue to think of problems I think of ways to makes sure the problems don't happen.

Right about now I want to build it so I figure out a way to make it work.
Time to pull out the sketch pad and draw some designs.

One thing you can look at for inspiration is automotive exhaust systems. Getting multiple pipes from multiple cylinders in the most efficient way possible is one of the best performance per dollar enhancements that can be done to an engine, so there is all kinds of performance information on this subject that can be utilized for a rocket stove/mass heater.

Ralf Siepmann wrote:Hi,
as I read this split-run-challenge I spontaneously began to do some math:
One 6" duct and four 3" ducts do have the same CSA, however the wall length (circumference) of four 3" ducts is double to that of a 6" duct, hence I assume double the drag per run length.
If you subtract a boundary layer of say 0.2 inches the ratio between the circumferences gets somewhat better, but the "flow-open" CSA of the 4 ducts becomes smaller than that of the 6" duct.

When I think about this, particularly the surface area, I think about how much heat the exhaust is losing. If you made on long mass with 1 x 6" pipe vs 4 x 3" pipes, the exhaust of the 3" pipes would be lower temperature than the exhaust of the 6" pipe for a given length. It has more surface area to dump heat into the mass. This would work great for a mass oven (something I am working on), but counterproductive for long distances. Also, making the exhaust too cold can cause smoke back issues. You could run the exhaust back by the bell, but that makes the possible length of exhaust run an even shorter distance from the fire box.

The other thing is the amount of heat being produced (BTU's). A given firebox/duct combo size will only be able to put out so much heat at once. Splitting it up 2 ways or 10 ways with the same flow potential doesn't make it produce any more heat. A bigger system is needed. A larger batch with an appropriate single exhaust system should be able to carry more heat a further distance from the firebox than a multi tube exhaust system. A dual exhaust could be used with a central firebox and exhaust going in either direction with a unified mass going between two rooms which would help get more even heat across the mass (more even heat between rooms).

If you need to warm up a number of separated rooms then it might be beneficial to take stock of what needs the most heat and how to get the heat there. If one room isn't inhabited and just needs warmth to avoid pipes freezing then maybe adding vents in the door/wall or perhaps even a thermostatically controlled fan could bring some heat from a room with a RMH to a room without one. Popping holes in the walls up high and blowing in loose fill insulation like cellulose fiber can help retain heat. Multiple mass heaters may be the only efficient way to heat spaces that are not adjacent to each other.

Jason E Smith wrote:

Satamax Antone wrote:Well, this question comes back regularly, that why you got a laconic reply

I have a few builds behind me, and I would not try a multi channel heater.


I don't know how is your neighbourhood. But as far as cheap and easy insulation goes. Pile up small size strawbales against your walls. cover the prevailing wind side with a tarp during the winter. Can't remember in US r values, but it's around R40 or so. Once roten, after may be ten years, change it. And you're good for ten more years. Hold with wire. I had calculated here, in france, it would cost me about 1100 euros to cover 250m² of wall. And that would be repaid in few months for you, with your electric bills!

Sadly I live in an Urban area, I could probably get the straw bails, but after setting them up I would have Code Enforcement breathing down my neck telling me to remove them or they would fine me.

My neighbors house is roughly 10 feet or 3 meters from mine.

And you tell them, it's removable, and as far as you know, you're still entitled to store your belongings the way you want

Four separate tiny (3") circuits would be totally impractical without powered circulation, but four 4" circuits could run concurrently if you have a balancing damper on each of them (normally inaccessible so somebody doesn't happen to shut them all off at once) to adjust relative flow rates. I still would be skeptical of it working well.

A more practical method if you must have heat sources in different parts of the house would be to run the duct through them in sequence, possibly balancing the amount of transfer surface and mass in each area to accord with the duct temperature and heating load. This would have to be a fairly straight-line system; a half-dozen elbows would drastically reduce the total duct length you could support. F Styles ran his duct and mass in a nearly straight line through several rooms to the chimney. This of course is only possible with certain room layouts.

Well I decided that if I am still living here long enough to build an RMH, I will likely instead of making a multi-exhaust system I will knock out the wall in the middle of the house and build the mass there.
It would be much easier to accomplish that rather than the trail, error, (which might lead to a fire) and time involved in designing and implementing the multi-exhaust RHM.

If that is possible for you to do, I think it would give the best, most reliable results.


And just for the sake of correct math, in regard to Ralf's post:
"for a 6" system that translates to 22 1/2 feet instead of 45 feet straight run, no bends.
Divided by your four runs you have 5 1/2 feet per run,straight, without any bends."
As the four small runs would be concurrent and not sequential, you would not actually have to divide by four; the multiple ducts would be theoretically equivalent to a single 6" duct for flow purposes. You would still have to subtract for any elbows, making multiple masses likely to be impractical.