BTU's Required For A Given Volume Of Cook Space??

[Q-Dat]

Didn't know where to post this question so here it is.

I'm wondering if there is a formula or a reference out there that can help me figure this.

For example If I have a 120 gallon tank that is 24"x64" including the caps, I want to know what kind of achievable temp range O could have with a 35,000 BTU pellet burner on one end.

Thank you to anyone that has the knowledge to help me out here.

[Pete Mazz]

If you think in terms of a propane grill you should be able to achieve pretty high temps. Most bigger grills are in the 40,000 BTU range and can reach 500 deg or more.

[Q-Dat]

So what would be the correct part of the forum for this?

[Big T]

I'd say you found the right section of the forum to ask a question.

[Q-Dat]

Sorry. I guess I misunderstood what this forum was for. Based on the description on the board index page I figured the mods would move it to the correct place where more eyes would see it.

[Big T]

I didn't mean to sound like a smart eleck , this truly is the right place for your question. Frank is the btu guy and I'm sure he'll see your question in this forum.


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[Q-Dat]

No you didn't at all. This is one I definitely didn't expect an instant answer to.

[Tom_Heath]

Yes this is defiantly a Frank question.

[The Czar]

I'm thinking it's possible....

[Q-Dat]

I'm thinking it's possible....

I think so to but I would hate to spend the money build it and then find out that either it can't or that it has to run wide open to handle the load.

[Q-Dat]

Yes this is defiantly a Frank question.

Would it be appropriate to PM him on this?

[Big T]

You could try, I don't personally know Frank but from what I gather he's a pretty busy guy. I think he usually gets on here every few days or so.

[Frank_Cox]

Howdy.... Prepare to be BTU'd....
ok so,if you were going to get precise with a number then it depends on several things...

• the cook temp required
• the "product load" as in weight and entering temp.
• the desired time to reach the finished internal temp
• the desired cook chamber temp
• and finally the volume of the cook chamber and heat loss

so forgetting I said all of that and getting back to reality (because nobody really wants to do all of that math and I would hafta ask for help with it also....) a more practical way of figuring it out would be the BTU capacity of the fuel being burned and how much is used per hour... well that's easy! BTU's of wood on average are around 8500 btu's per pound. so if you got the pit running and then weighed each split before you put it in the pit on the reload then how often you add that amount of wood you can then calculate it out. I'm gonna guess each split (Fist size in diameter) weighs about 3 pounds and I usually add that much once per hour to Mack so, 3x8500=25500 BTU's / hour or BTU/H. That is fairly close to the same volume pit your asking about.

[Big T]

You asked for it and you got it

[Frank_Cox]

correction... some wood is known to be as little as 6300 BTU's per pound so here is a handy reference to BTU capacity of different species
Click here : Firewood BTU Ratings Charts for Common Tree Species

[Rev.Mike]

[Q-Dat]

correction... some wood is known to be as little as 6300 BTU's per pound so here is a handy reference to BTU capacity of different species
Click here : Firewood BTU Ratings Charts for Common Tree Species

correction... some wood is known to be as little as 6300 BTU's per pound so here is a handy reference to BTU capacity of different species
Click here : Firewood BTU Ratings Charts for Common Tree Species

Wow ok thank you very much! So if I interpret you correctly you are saying that this same size tank with an offset fire box would need roughly a 25,000 BTU fire?

[Frank_Cox]

not an exact number but a good estimate. what are you planning to build?

[The Czar]

I think my brain just farted

[Clover Ridge Smokers]

In case anyone is wondering what it looks like inside Frank's brain, here's a PIC.

[Puff]

Let me be frank about this....Oh No thanks.

[Q-Dat]

not an exact number but a good estimate. what are you planning to build?

Basically a pellet cooker that will have a cross flow along the lines of the Jambo. Strictly a comp pit so sacrificing cook space by putting the burner inside for the sake of achieving the desired flow. I don't cook a ton of meat for comps so with a two or three tiered rack setup on the side opposite the burner i should have plenty of room.

[forty_creek]

At first read I thgt I was back in chemistry for the fourth time around...chemistry kicked my arse in college.
All BTUs aside that made sense. Thanks Qdat for asking a sir OB1-Frank for the BTUing


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[Q-Dat]

Please forgive the ever so crude drawing, but this is the basic concept of what I want to do. Nothing to scale obviously, just to illustrate the desired heat flow.

[Frank_Cox]

so, I think you will find that in the case of a pellet hopper the BTU content will not be the issue as much as the required air flow needed to get the cook chamber to temp and keeping it there. a standard 36,000 BTU hopper assembly (smoke Daddy one in this case) moves about 130CFM of air. I would think that would be on the low end. good thing is you can always install a convection fan or even another hopper and put them in parallel on 1 controller.