Can you really reverse the flow of a vertical collum of air?

Discussion about Reverse Flow Smokers
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noname
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Can you really reverse the flow of a vertical collum of air?

Post by noname » March 20th, 2019, 11:13 am

Im looking into vertical smokers and like the idea of reverse flow but 2 local builders have each said basically the same thing. The smoker wont reverse the flow, what happens is a flow of air will develop from the heat source to the base of the smokestack. A great example is a chimney in your home. The flow of fresh air comes in your house (doors windows) and directly to the fireplace, it doesn't rise up, push cold down then the cold somehow finds a way past the fire to exit the building, and its proven that some houses are actually colder due to this.
So, Does a vertical reverse flow actually reverse the flow or not really?
Has anyone taken temperatures from the bottom to the top at different levels at the same time? What were your results?



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Re: Can you really reverse the flow of a vertical collum of air?

Post by Big T » March 20th, 2019, 7:56 pm

Most guys on the forum don't think that RF is needed to even out the temps in a vertical smoker. I don't have a vertical RF but there are a lot of them out there and the guys claim that they're pretty even in temperature from top to bottom. I also would think that there wouldn't be a market for them if they didn't work because eventually everyone would get tired of fighting different temps in the cook chamber. I've heard that it does take a little time to establish a good draft so you have to keep them closed as much as possible or wait for the draft to re establish. I don't think you can compare a smoker to your fireplace because a smoker has an outside air intake and sends the heat and smoke out the stack and into the cook chamber. In order to compare that to a fireplace, you'd need to pipe the chimney back into your house and see what happens. This is just my thoughts on the matter and of course I could be wrong.


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Re: Can you really reverse the flow of a vertical collum of air?

Post by LeonardK » March 20th, 2019, 8:38 pm

Hi

Two years ago I started learning about different kinds of smokers. It started I wanted to just build a nice 38 inch tall grill about 24x23 inside nice big racks leaving lots vert space to put baffles, water, etc planned two racks with about 8 or 10" space.

Then switched to that vert reverse flow idea where fire below goes up 3" sides then down over meat racks to exit damper at the bottom. Never did that but have heard different things about them working either good AND bad.

I just built a rev flo with 16" pipe 36" long

But before in reading all kinds smokers 1st one I found after that vert rev flo was on the Amazing Ribs site the Inverted Flame smoker, burns wood on top in small stainless box with suction conduit draws smoke and fire down to bottom of Cooking Chamber then up thru and out damper by means at end using a fan.
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Next discovery the Gravity Feed with insulated cabinet, sure looks like a good smoker. Like that ins cabinet and still intend to build one.

Chronologically tho, I then came to build the more standard horz rev flo smoker out of 16" pipe. Working good and I love the way it smokes.

During researching reading the other kinds plus a friend who had a 36" pipe rev flow 8 ft long, poorly designed, damper too small and used way too much wood and fuel to cook, checked it against the pit calc and it was wrong.

But I had thought of an idea just might use one day for variation in outcome..... why do you have to let all the smoke go and like if you DO have a flow problem.

The Inverted Flame idea made me think of putting a metal fan blade on a long shaft using food grade grease on bearings to draw smoke at the damper and re-circulate into the bottom of cooking chamber.

For my friend w/ 8ft rev flow, before he turned it into an offset, I was thinking how would this work with a fan at the 180 drawing the smoke/fire thru?

Well just a few interesting thoughts about re-circulating smoke with motors or helping the flow move when it won't work.

Don't have any motors on mine, it works. But some day I might use this idea.




Leonard
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Dirtytires
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Re: Can you really reverse the flow of a vertical collum of air?

Post by Dirtytires » March 20th, 2019, 8:46 pm

Guess it really comes down to how much time you have to tinker/adjust your original design.



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Re: Can you really reverse the flow of a vertical collum of air?

Post by Gary_G » May 16th, 2019, 8:20 pm

I built a vertical cab with this in mind....I have three exhaust stacks, low middle and high. The heat is forced up the side walls and gets out through the lowest hole.Image

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Ah, here is a construction photo that shows the vent stack holes. My cabinet is insulated and it has a gravity fed charcoal firebox and I use a stoker fan all the time.

So I have a modified up/down draft with assisted convection.

BTW... firebox rebuild is on the list of projects for this summer. New Firefox will have lateral xfer tubes to make sure the heat goes up the sides of the cabinet, to the top where it makes a turn towards the center and washes over the meat on the way back down. The meat cools the hot air, and the lower temp air exits the vent stack holes.

At least that is how I try to run it. Image


Regards,
Gary

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Re: Can you really reverse the flow of a vertical collum of air?

Post by Pete Mazz » May 17th, 2019, 4:28 am

Does a vertical reverse flow actually reverse the flow or not really?
Of course they work. No one would build them if they didn't. I'm in the camp that they're overly complicated for what's needed.


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