Peterberg Batch Box Dimensions

[pinhead]

Attached is a spreadsheet which calculates the dimensions of a Peterberg Batch box according to the desired Heat Riser diameter:
Peterburg Batch Box Dimensions Calculator.xlsx (18.26 KB)

Peterberg Rocket Stove Calculations
Heat Riser Dimensions	Inches								Millimeters
Diameter	3	4	5	6	7	8	9	10	75	100	130	150	180	200	230	250
Length	21-10/16	28-13/16	36	43-3/16	50-6/16	57 10/16	64-13/16	72	540	720	936	1080	1296	1440	1656	1800
Base	2-3/16	2-14/16	3-10/16	4-5/16	5-1/16	5-12/16	6-8/16	7-3/16	54	72	94	108	130	144	166	180
Box Dimensions
Width	4-5/16	5-12/16	7-3/16	8-10/16	10-1/16	11-8/16	12-15/16	14-6/16	108	144	187	216	259	288	331	360
Height	6-8/16	8-10/16	10-13/16	12-15/16	15-2/16	17-4/16	19-7/16	21-10/16	162	216	281	324	389	432	497	540
Depth	8-10/16	11-8/16	14-6/16	17-4/16	20-3/16	20-3/16	25-15/16	28-13/16	216	288	374	432	518	576	662	720
Port Dimensions
Width	1-1/16	1-7/16	1-13/16	2-3/16	2-8/16	2-14/16	3-4/16	3-10/16	27	36	47	54	65	72	83	90
Height	4-12/16	6-5/16	7-15/16	9-8/16	11-1/16	12-11/16	14-4/16	15-13/16	119	158	206	238	285	317	364	396
Depth	2	2	2	2	2	2	2	2	50	50	50	50	50	50	50	50
P-Channel
Width	1-1/16	1-7/16	1-13/16	2-3/16	2-8/16	2-14/16	3-4/16	3-10/16	27	36	47	54	65	72	83	90
Height	5/16	7/16	9/16	10/16	12/16	14/16	1	1 1/16	8	11	14	16	20	22	25	27
Overhang	5/16	7/16	9/16	10/16	12/16	14/16	1	1 1/16	8	11	14	16	20	22	25	27

EDIT: Here are the equations.
EDIT: Now with 3 through 10 inches and 75 through 250 mm.

Given: Heat riser DIAMETER = D

Base B = D*.72
Riser Height = 10*B

Box Dimensions
Width = B*2
Height = B*3
Depth = B*4

Port Dimensions
Width = B/2
Height = B*2.2

P-Channel Dimensions
Width W = B/2
Height (thickness) = ((3.14(D/2)^2)*.05/W

[pinhead]

And if you don't have Excel or don't want to open a spreadsheet, here's a screenshot...



And here's a cross-section of the stove:

[petect]

Very Nice! It seems to work just fine.

It downloads as Read Only - rename it when you save the file and it work.

For those who don't have excel, post your numbers here, and hopefully someone can run them and post the results.

Pete

[sierramog]

I was able to open file using OpenOffice.org, free download.
Thanks!

[smarty]

Thanks for the screen shot, the mac spreadsheet thing didn't work, so the table is very handy.

Where it says "calculated base" what does this refer to? It seems obviously related to the height whatever it is.

Also the ratio between CSA and height decreases as you go up in system size according to a constant pattern. So the ratio between height and CSA of the 4" system is pretty much double that of the ratio between height and CSA of the 8" system, and three times the ratio of the 12" system.

What the formula underlying this - sorry maths was never my strong point - there is some pattern to it is there not?

cheers.

[pinhead]

The "calculated base" is simply a "constant" in the equations used to calculate the dimensions. I'll see if I can find Peterberg's post explaining how the numbers are calculated.

EDIT: Here are the equations.

Given: Heat riser DIAMETER = D

Base B = D*.72
Riser Height = 10*B

Box Dimensions
Width = B*2
Height = B*3
Depth = B*4

Port Dimensions
Width = B/2
Height = B*2.2

P-Channel Dimensions
Width W = B/2
Height (thickness) = ((3.14(D/2)^2)*.05/W

[bernardbon]

Hello,

I can not find the formula to calculate the dimenssion primary air.

Could anyone help me?

Bernard,

[peterberg]

Primary air is 20% of heat riser cross sectional area.
(3.14*(D/2)^2)*20%.

[bernardbon]

Thanks

[Donkey]

Mar 18, 2013 11:06:57 GMT -8 pinhead said:

The "calculated base" is simply a "constant" in the equations used to calculate the dimensions. I'll see if I can find Peterberg's post explaining how the numbers are calculated.

I haven't seen the answer to this yet.
How is the "calculated Base" arrived at?
What does it represent?

[peterberg]

The original calculation was done by Jim (jham) from Southern Virginia.
This is the thread where he explained his calculations.

He elaborated about it by PM, but I'd think it's alright to publish this here:

Oct 12, 2012 at 6:11pm
Hi Peterberg,
I wanted to get back to you sooner about the way I attempted to derive the measurements of my stove from your sketchup example but I have been busy at work and home. So....here I go.

I took your measurements and saw that by using bricks in the sketchup model you had made every linear measurement a ratio of a basic unit. Because the clearest ratio you talked about was the 3 to 2 ratio of the firebox opening, I took the firebox opening and divided the height by 3 to use as the basic unit. So 1 unit = 108mm.
I then just converted all the linear measurements of your model into multiples of the basic unit. The only measurements that were not a simple multiple of the basic unit was the width and height of the burn tunnel. I just rounded those values (burn tunnel W and H) to simple multiples of the basic unit (108mm) and came up with W=54 (.5 units), H=216mm (2 units).
To figure out all the values for my stove I started with the diameter of the heat riser pipe (100mm) I wanted to use, and got the c.s.a of the heat riser 7850mm2. I then multiplied that times 4 for the c.s.a of the firebox and got 31400mm2. To get my basic unit of linear measure for my stove I then took the formula for the c.s.a of the firebox opening and plugged in the numbers I knew: 3 x unknown single unit x 2 x unknown single unit=31400 (the c.s.a of firebox). I then solved the equation to derive the single unit: 6 x unknown unit squared=31400

unknown unit squared=31400/6

unknown unit squared=5233

unknown unit=square root of 5233 or 72mm

I took that basic unit and plugged it in to unit measurements I had figured out from your model. As an example, the heat riser height on your model was 11 units high (108 mm x 11=1188mm) so mine was (72mm x 11=792mm). I apologize if I am not doing a very good job of explaining myself, math is definitely not my native language

I think that this method of scaling worked well because the stove works well. I have sealed and insulated the heat riser more carefully since the last time I posted and the stove is working better than ever. I am going to start a thread today asking for some design help with a planned application. Thank you again for all your data you have shared.

Jim

Later on, I've done some recalculations myself and arrived at this conclusion:
It is entirely possible to culculate the base dimension by taking 72.36% of the diameter of the riser. So, define the riser diameter, preferably the same as the exhaust pipe, and do this simple math.

[Donkey]

I find it interesting that the port (referencing the .XL file) has a SMALLER CSA than system size.
For a 6 inch system, the system CSA is 28.26 inches and the port is 20.52 inches.
Is this correct?

[satamax]

Aug 27, 2013 8:39:44 GMT -8 Donkey said:

I find it interesting that the port (referencing the .XL file) has a SMALLER CSA than system size.
For a 6 inch system, the system CSA is 28.26 inches and the port is 20.52 inches.
Is this correct?

Donkey, iirc, in the thread peter said to me 65 to 70% csa for the port.

[Donkey]

Seems so..
Constants (in ANY formula) tend to point at a law of some kind (physical, mathematical, etc.)
It'd help to know what the 72.36% means.

[peterberg]

Actually, in the model Jim calculated the port is slightly larger than 72% of system size. Minus the overhang of the p-channel it will come down to the 70% target.

The reason why the port is narrower than system size: it promotes a higher air velocity in the port itself and slows down immediately behind it. This do promote a very effective turbulence without adding more air into the fire. Supplying more air as a method to induce turbulence is being used by everyone who like to promote better combustion, with the obvious disadvantage of cooling the fire and enlarging the amount of excess air.

I've tried smaller and wider ports as well, results were not as good. So yes, the constant could be 72.36% but the question of why isn't answered.

Tantalizing, don't you think?