Draft Theory Question

[mking7]

Not about my stove though....

But I think the theory will be the same. I have a bbq pit that doesn't draft as strong as I'd like. There are calculators online that give you the volume of the stack needed for x size smoker. So here's my question:

Is it all about pipe volume or do the dimensions matter? Meaning, would a 6" pipe of volume x draft the same as a shorter 8" stack of the same volume?

 

[spirilis]

I think height determines the specific amount of force available for the draft, then internal temperature adds to the effect, but pipe diameter determines how much air/gasses can actually make it through (too small of pipe = appearance of slow draft due to inability to evacuate the gasses fast enough, too large = gasses spread out among the extra volume cooling the gasses so the chimney isn't as hot, which equals less draft)

 

[Jackfre]

The taller the pipe the smaller the pipe you can use...generally! Is yours an open BBQ or enclosed. I guess what I would suggest is to add some single wall pipe of the current diameter and see how it does. If the draft and therefore burn control doesn't improve you may need larger pipe.

In re-reading you post, you say bbq "pit" so I'm assuming an open arrangement. It gets a bit harder because you have all this excess air that mixes with the burned gases you want to vent. Diameter of the hood, height of the hood above the fire, height & diameter of flue, temp of flue gases. You might want to wrap the hood with a strip of sheet metal to adjust the hood height.

Net/net, you are just going to have to do some experimenting. Let us know when the brisket is coming off and we will be glad to come over and comment further. Also, a picture would help.

 

[mking7]

Sorry. In Texas we call it a pit. You may all it a smoker.

 

[mark cline]

I like the chrome wheels and some pin stripping will finish it off.