200 mm Batch Box in 3 storey building - ISA calculation

[paganodimelito]

I'm building a 200 mm Batch Box in a 3 storey building:

ground floor:
- fire brick core
- oil drum over the riser as primary bell for immediate heat (and as cooking surface)
- adobe bench
- 4 m of vertical uninsulated steel pipe to go to the first floor

first floor:
- adobe bench
- 4 m of vertical uninsulated steel pipe to go to the second floor

second floor (attic):
- 2 m of vertical uninsulated steel pipe (continuing from the first floor)
- exit trough the wall (0,5 m of horizontal insulated steel pipe)
- final chimney (2 m of vertical insulated steel pipe)

I have a doubt on how to calculate the total ISA. Should I include alle the ISA of the vertical uninsulated steel pipe?
It it is the case, that would leave very little room for the benches.

[martyn]

One issue i see is a 200mm batch box has a 5’ high riser so your cooking hight will be at eye level?

[peterberg]

All bare chimney pipe will extract heat, but the highest heat is transported in the faster streaming center part of a vertical pipe. My guess would be: half of the pipe's internal area need to be in the calculation, at the very least.

[fiedia]

paganodimelito ,

With this set up, the second bench may never get warm enough to heat the second floor (see this thread). May be you can insert a bypass to get smokes to flow from your barrel either through the whole house (including first floor bench) or directly to the second floor bench.

My non insulated vertical pipes never really heated the room upstairs. the radiating surface was not sufficient. I even tried to make a 4m long circuit of horizontal pipes which got warm but without real heating efficiency. Worse, smokes condense in the contact of such cold walls and water drips sometime along the pipes. Soot deposits faster on the non insulated surfaces which you have to clean more often. If you have the choice, build a nice bench or bell to extract and store heat and insulate your pipes. 

[paganodimelito]

Jun 15, 2021 12:04:08 GMT -8 martyn said:

One issue i see is a 200mm batch box has a 5’ high riser so your cooking hight will be at eye level?

Yes, it will just be for herbal infusions or soups, it will ne accessed standing on the bench

[paganodimelito]

Thank you for the advice, here are some updates on the construction:

pictures: photos.app.goo.gl/NyKzeaNQaqHnZd6X8


The whole construction is insulated from the floor with a 10 cm layer of Leca clay balls whetted in clay slip, covered in a thin layer of coarse adobe.


The base of the burn chamber is laid out with 3 cm thick firebricks, while the base of the riser is made with 6 cm thick firebricks standing on their side.

 
The walls of the chamber are built with 6 cm thick firebricks and a mortar made of clay slip and very fine sand (less than 0,5 mm grains).


The roof of the chamber is made of 5 cm thick refractory slabs.

 
The octagonal riser is made of 3 cm thick firebricks.


The whole core is left to dry.


 
The flue going upstairs is installed with a 45° elbow and a horizontal cut with 10 cm clearance from the floor.
For the bench a catenary curve template is made of plywood, base with 40 cm, height 35 cm, considering the 10 cm clearance of the flue, the curve in contact with the hot gases is 60 cm.

 
The bench is built with stones and coarse cob. An inspection port is placed in front of the flue. Bench length is 200 cm.


The space between the bench and the wall is filled with Leca clay balls whetted in clay slip.

The core will later be covered in 13 mm thick ceramic wool, the riser with a double layer. It will then be plastered with clay-sand mortar and 7 mm fiberglass mesh.
A standard steel drum will be placed on the riser as primary bell.
The burn chamber will be insulated from the wall with Leca clay balls whetted in clay slip, and encased in regular bricks.
The bench will be completed and covered with adobe with a minimum total thickness of 15 cm from the top of the catenary.
A second bench will be made at the first floor.
If the temperature is too low at the first floor, I might add a bypass on top of the back of the first bench, I'm thinking 100 mm insulated pipe, and insulate the 4 m of flue going upstairs.

The ISAs are as follows:
1,78 m2 - barrel
1,53 m2 - (estimated) lower part of primary bell (going from the barrel to the bench)
1,20 m2 - bench 1
1,26 m2 - flue 1 (accounting for 50% of ISA as Peter suggested)
1,20 m2 - bench 2
2,20 m2 - flue 2 (accounting for 50% of ISA as Peter suggested)
9,17 m2 total (ideal is 9,41)

now time for questions:
- is the 10 cm clearance between the flue and the floor enough for flow dynamics (see pictures)?
- do you think a partial bypass of bench 1 will improve heat distribution? is it worth it?
- I have read donkey32.proboards.com/thread/2464/door but I still need advice on how to firmly install the door frame on the burn chamber, is there any information available?
- any other thoughts?

[fiedia]

Regarding the door, you can weld one or two anchors behind the top of the door frame and insert them in your second skin

Regarding flue clearance, I think that you have to keep at least the same cross section all the way with PI*D*H = PI*D²/4 or H=D/4. So for a 200mm diameter, a clearance of 50mm min.

Why do you plan to use 100mm pipe for the upper bench ? I thought one has to keep at least the HR CS all the way.

[capscut]

this is a very interesting project, I will be happy to see you fire it up. good luck with your build!