ISA of exhaust pipe

Hello there, i am planning to build a rocket mass heater, and as i have a very long exhaust tube, i want to know how this 5meters long exhaust tube will increase the ISA of the proyect.
The tube is 20 cm diameter.
Thank you very much, this forum has very nice info about everything. BEST wishes.
Nacho

Hi Nacho;
A 20 cm pipe is apx. 8" in diameter.
At 5 meters long it is almost 16.5 feet long.
This will work fine for an 8" J tube rocket mass heater, in fact, it could be almost 10 meters long depending on how many bends you place in line.
Each 90-degree turn is a 5' deduction in length.
An 8" RMH can push up to 50' of horizontal pipe.

thomas rubino wrote:Hi Nacho;
A 20 cm pipe is apx. 8" in diameter.
At 5 meters long it is almost 16.5 feet long.
This will work fine for an 8" J tube rocket mass heater, in fact, it could be almost 10 meters long depending on how many bends you place in line.
Each 90-degree turn is a 5' deduction in length.
An 8" RMH can push up to 50' of horizontal pipe.

Thanks for your answer, my pipe has not bending, It is vertical all the way.
I am working on a Batchbox rocket, 8" with the sizes provided in the bbr web. The question is that i am afraid because i do not know if the pipe area counts the same in calculating the ISA.

If you have a 200mm chimney (exhaust) then you can build a 200mm or a smaller size system.
However, one forum member has said you can use a smaller size chimney than system size, I dont think that is always a good idea. Generally speaking if you have a 200mm chimney you would build a 200mm system.

Fox James wrote:If you have a 200mm chimney (exhaust) then you can build a 200mm or a smaller size system.
However, one forum member has said you can use a smaller size chimney than system size, I dont think that is always a good idea. Generally speaking if you have a 200mm chimney you would build a 200mm system.

Yes, i am not oversizing, the entire proyect is 200mm or 8"

Hi Nacho,
The length of the chimney pipe won't influence your batchrocket system in a negative way. As far as I know, even a 10 meter high chimney won't have a negative impact on a given system. In your case, a 200 mm chimney, straight up and 5 meters high would be ideal. A higher chimney would produce more friction along its walls, that's true. But at the same time it produces a stronger draft due to the height of the air column.

In short: a 200 mm system is correctly tuned to a 200 mm chimney. The table gives you the correct ISA, nothing to worry about.

Peter van den Berg wrote:Hi Nacho,
The length of the chimney pipe won't influence your batchrocket system in a negative way. As far as I know, even a 10 meter high chimney won't have a negative impact on a given system. In your case, a 200 mm chimney, straight up and 5 meters high would be ideal. A higher chimney would produce more friction along its walls, that's true. But at the same time it produces a stronger draft due to the height of the air column.

In short: a 200 mm system is correctly tuned to a 200 mm chimney. The table gives you the correct ISA, nothing to worry about.

Ok, thank you very much, i am very excited planning the bbr, i hope It will be good. I'll keep posting.

Please note that I have said that my 8" J-tube system works fine with a 6" chimney which has positive natural draft. I would not try to reduce the chimney on a batch box system, as that delivers heat faster than the same size J-tube.