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Rub-A-Dub 12-15-2007 11:59 PM

Reverse flow
 
Have my firebox monted and getting ready to made my smoker a reverse flow. I have a 6" pipe. Can I use this for the reverse flow or do I need to use plate. I'm at this point in the build and would like some input on what would be best. The smoker is 6 1/2 to 7 feet long. Thanks for the help:-P:-P:-P

Norcoredneck 12-16-2007 04:31 AM

Can't answer but would love to see pics.

Divemaster 12-16-2007 07:16 AM

Quote:

Originally Posted by Norcoredneck (Post 514782)
Can't answer but would love to see pics.

Me too!!! I'm looking at a reverse flow and would love to see what you came up with.

FatDaddy 12-16-2007 07:22 AM

I used !/4" plate for mine. I got the idea turning mine reverse flow after ChromeSporty had his redone. here is the link to mine. It works great. I have seen a friends who has a pipe with hole through out it running the length of his cooker that is welded into his firebox. I dont know how good it works compared to having it done the same way as the langs. which is basically the concept mine is. I dont see how u would get even distribution of heat with just a pipe and then your exhaust on the firebox side. Mine has a plenty of pics of the build
http://www.bbq-brethren.com/forum/sh...t=reverse+flow

smokinbadger 12-16-2007 07:50 AM

Quote:

Originally Posted by Rub-A-Dub (Post 514755)
Have my firebox monted and getting ready to made my smoker a reverse flow. I have a 6" pipe. Can I use this for the reverse flow or do I need to use plate. I'm at this point in the build and would like some input on what would be best. The smoker is 6 1/2 to 7 feet long. Thanks for the help:-P:-P:-P

I'd like to see some pictures too. In the meantime, I can offer some suggestions. Since the point of reverse flow cookers is uniform grate temperatures, in designing one, you need to think about:

1. How best to transfer heat from the hottest air (i.e. just downstream of the firebox) to the coolest (i.e. just before the exhaust stack).

2. How to avoid any unnecessary flow restriction. Since you are essentially doubling the airflow path length compared to a standard offset, this is pretty important.

Both of these constraints would lead me to think that using a divider plate like the Lang design would be better than using pipe. Here are my reasons:

1. The divider plate provides more area for heat transfer between the "forward" and "reverse" flows, promoting more uniform grate temps.

2. The flow restriction is minimized compared to a pipe due to greater hydraulic diameter. The more uniform cross section also prevents local bottlenecks for air flow.

3. Using plate allows the airflow to turn from forward to reverse direction with less pressure loss compared to a pipe.

4. Finally, if you use 1/4" plate, you will have the added advantage of more thermal mass (i.e. specific heat) in your cooker, which will help keep temperatures more uniform during transient conditions like after opening the firebox or smoke chamber doors.

Of course, all of the above is based on considerations of flow and heat transfer. The main thing speaking for pipe is lower cost compared to plate, but I would still go for plate if it were my cooker. Good luck with your project and please post pictures.

Rub-A-Dub 12-16-2007 12:17 PM

Will have some pics next week. I have the firebox monted on the botton with a piece of 6" pipe from the firebox to the main cooking chamber. The firebox is 16" across by 40" long. The chimney will be 4" x 32" long. Will be able to use charcoal or logs. I think I see what you are saying. The pipe would not have the surface area of the plate and would not cover the whole bottom of the cooker to have even heat. Can't get to the cooker untill Tues. The shop is closed untill then.

Here is the website of how I got the chimeny lenght

http://home.nik-martin.com/smoker/Default.aspx

Hope it helps someone.

Sawdustguy 12-16-2007 05:14 PM

I would suggest the Plate. That big hunk of steel acts as a big thermal mass and helps to regulate the cooker temp and temp from side to side.


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