Dryer vent stack extension mod....question?

[geek with fire]

Dryer vent stack extension mod....question?

I keep meaning to ask this question when anytime this mod is discussed; but always seems I would be hijacking someone else's thread. Thought I would start my own.

Perhaps I need to do a search and do more homework, but I don't understand what keeps most of the heat and smoke from wanting to travel under the grate and up the stack when you extend it down to the grate. Are we to assume here that the heat and smoke goes strait up when it enters the chamber and therefore has be forced back down by the extension. I haven't yet added this mod to my chargriller because I don't yet fully understand how it effects the airflow. Ejamakate me!

 

[ikebbq]

From my understanding, by extending the chimney down to grate level, it is evening out the heat from the top of the cooker to grate level. Also, since heat and smoke rise, the extension keeps more smoke in the chamber to circulate around the meat. Might have to experiment a little to see how much effect it really has.

 

[glued2it]

one of my offsets has the stack at the grate level from the factory. I haven't quite worked out the science myself either. seems like it would track too much smoke in the chamber. With the theory of smoke just kissing the meat as flows by seems to be contradicting. I'm doing some experiments of various temps throughout the entire cooking chamber before adding the mods to the smoke n pit.

 

[geek with fire]

So whether or not I am crazy is another matter all together. It looks like at least I'm not the only one who has questioned the theory behind this mod. Thanks! (Disclaimer: I'm not bashing anyone here. I haven't even tried it. I'm just curious about how it works)

 

[capt dan]

I use it in my silver, and it has slowed my fuel use, and helped keep my temps better regulated. After that mod, I added the heat plates w/holes.
Tomorrow, I am making an expanded metal charcoal box for the fire box. I am hoping to make less visits to the smoker for adding more lump!

 

[bbq bubba]

O.K. Heat rises, heat leaves the firebox and head's straight for the exhaust.
If the exhaust is at grate level, the heat is forced into a swirling effect until it reaches the exhaust and escape's.
Betwen the intake and exhaust there's a "drawing effect" that the air follow's, your just detouring the heat n smoke from going straight out to circulating in the smoker before exiting!!

 

[nh3b's]

Im pickin up whatchya layin down here Bubba. Nice mod.

 

[glued2it]

I understand the concept behind it. It has always been in the back of mind if there is enough airflow for the smoke. How is the smoke going to kiss the meat as it passes by if it's trapped in the chamber. none the less I still have good temps at grate level.

I'll be interested in my test results.

So I guess what I'm wondering is a quality issue and not fuel usage issue.

But explain this one as well. using a baffle that is pointed downward using a system that rises(heat) seems that you would be wasting heat through the fire box as it raises higher the the output of the baffle level.Plus ruining the finish of the fire box. Is there enough airflow to push the heat out? Who's the aeronautical engineer here?That's who I want to talk to.

I think the baffle is a good idea but needs to be rengineered

 

[morkdach]

well i havent got to drive the train yet but heat and smoke rises and will head to the highest and closed place to atmosphere.bring the vent lower and heat entire chamber above food racks for more even temps my thought on the subject any way

 

[walking dude]

if the heat swirls, so will the smoke.........it will "KISS" the meat as it goes by........tho i don't understand kiss........i want that smoke STOMPING ON MY MEAT.........not kissing it..........in my ecb, the smoke has to go by the meat.........under it......over it around it.......permeating i am hoping......not kissing it.........ack

 

[peculiarmike]

Bubba is dead on the mark.

 

[gramason]

I extended the pipe in mine, and I have more even, steady temp.