Please Check My Numbers - Reverse Flow - 36" X 24" X 3/8"

[DB Myers]

23.25 ID X 36 Long X 3/8 Pipe = 15284 sq in
FB/CC opening = 61"
RF Plate Opening from Firebox = 61"
Area Under RF Plate - 61"
RF Plate Open End = 61"
Firebox = 19" Tall X 20.5" Wide X 16" Deep = 6232 (33% = 5087sq in)
FB to CC - Radius 11.62 x Segment 5.25 = Segment of 71.848 sq in" - 1.5 lip (8.366 sq in) =63.48 sq in
Chord AB 19.437
Chimney = 3.5" X 3.5" X 0.7854 X 35 = 336.74
15248 X .022 = 335.45

Thanks

 

[daveomak]

29.25 ID X 36 Long X 3/8 Pipe = 15284 sq in 24,191 cu. in.
FB/CC opening = 61" 97 sq. in.
RF Plate Opening from Firebox = 61" 97 sq. in.
Area Under RF Plate - 61" 97 sq. in.
RF Plate Open End = 61" 97 sq. in.
Firebox = 19" Tall X 20.5" Wide X 16" Deep = 6232 (33% = 5087sq in good
FB to CC - Radius 11.62 x Segment 5.25 = Segment of 71.848 sq in" - 1.5 lip (8.366 sq in) =63.48 sq in
Chord AB 19.437
Chimney = 3.5" X 3.5" X 0.7854 X 35 = 336.74
15248 X .022 = 335.45 532 cu. in.
532/.7854x4x4 = 42" 4" stack
532/.7854x5x5 = 27" 5" stack (34"x5" my choice)....

Radius 14.625.... segment height 6" .... Chord AB 23.6"..... Segment area 99.1

 

[DB Myers]

Thanks, I screwed up though, it was late. The smoker is a 24" (23.25 ID), 3/8 in pipe by 36". I don know where i got that ID from (beer). Would you please check again? Sorry to waste your time.

 

[daveomak]

No problem.... I want you to build the best smoker possible.....

23.25D x 36L x .7854 = 15,284 cu. in.

x.004 = 61 sq. in.

x 0.33 = 5,043 cu. in. FB or larger

x 0.001 = 15 sq. in. or so for FB air inlet area.... Generally 20% upper inlet and 80% lower inlets are good...

x 0.022 = 336 cu. in. for the exhaust above the CC....

336 / .7854 x 4 x 4 = 4" dia. stack 27" above the CC.. I would go with 4", 34" above the CC...

Chord AB, RF plate width 19.1"

Segment area 67 sq. in.... Good...

Click on the link below to view the circle calculator numbers...
https://screenshots.firefox.com/xXN6lwYii5Dj2cvy/www.1728.org


....

 

[InThePittBBQ]

Dave I see you helping lots of people with these calculations, good on you for lending a hand that's awesome!

 

[daveomak]

My pleasure.... Have a great day...

 

[DB Myers]

No problem.... I want you to build the best smoker possible.....

23.25D x 36L x .7854 = 15,284 cu. in.

x.004 = 61 sq. in.

x 0.33 = 5,043 cu. in. FB or larger

x 0.001 = 15 sq. in. or so for FB air inlet area.... Generally 20% upper inlet and 80% lower inlets are good...

x 0.022 = 336 cu. in. for the exhaust above the CC....

336 / .7854 x 4 x 4 = 4" dia. stack 27" above the CC.. I would go with 4", 34" above the CC...

Chord AB, RF plate width 19.1"

Segment area 67 sq. in.... Good...

Click on the link below to view the circle calculator numbers...
https://screenshots.firefox.com/xXN6lwYii5Dj2cvy/www.1728.org


....

Hi Dave,

I have a couple of problems. The entrance to my back yard will only allow me to have a 27" tall stack with the base that was welded prior to discovering that. In addition, the welder wants to use a 4" x 4" square stack as that is what he has and likes to use. Would 19" or 20" above the cook chamber work with that size and still and create enough draft? It would appear that a square stack that is much taller would have too much volume.

I was also curious as to why the stack length is always listed as above the cook chamber. Mine will exit the side of the cook chamber above the firebox. Does the elbow and pipe getting to the top of the chamber figure in the calculations for stack volume?

Thanks for your help!

 

[daveomak]

4" square will work.... Make it a 2 piece stack... weld on outer tabs to the top section, so it slides over the lower section... Drill a couple holes so a pin will hold it in place... Or a hinge and have it tip... lots of fixes available...
Sacrificing performance is not in my vocabulary...

 

[DB Myers]

So are you still saying 34" even though it is 4" square? That would be 544 CI above the CC. Isn't that too much volume?

 

[daveomak]

The "effective" area of a 4" square tube is the same as a the effective area of a round 4" tube....