Short and fat 250 gal. reverse flow, advice on adjusting parameters for airflow?

Discussion in 'Reverse Flow' started by rikun, Dec 20, 2014.

  1. rikun

    rikun Fire Starter


    I recently got a new tank, which is around 35" in diameter and the straight part is 51" long. I'm going to cut the FB end off and weld a new end plate, since I've found out that it's much easier to work around that flat end. Naturally I'm going to keep the other end to allow for good airflow.

    I have a question for the RF gurus, Dave, Rib, ... How much I should adjust from the Feldon's calculations since this is a short and fat tank?

    For my previous build which was "standard shaped" I adjusted as suggested, 150% for area under the RF plate and for the gap to CC.

    I have not adjusted for the FB to CC opening, should that be also done? My cooking style is mostly hot and fast at around 325F if that affects "tuning".

    I have a lot of space, so I could theoretically still use 1.5 what Feldon says, but I'm going to run into ground clearance problems with the FB.

    What is the minimum height for firebox that would still work okay? I think I'm going to make my FB as wide as the tank and pretty long, but it could only be maybe 15-18" in height. For the vents I'm going to make one lower main vent and one upper vent for better heat transfer to CC.

    Any other advice for short and fast tank? Would you make double doors on both sides even if the racks were slide out?
  2. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Last edited: Dec 22, 2014
  3. novasbc

    novasbc Smoke Blower

    How would you quantify this to be a general application? His tank dimensions sound similar to mine and I hadn't altered any od my calculations based on it.

    If I were to update the calculator I posted later in your thread, is 15% a magic number for what I presume is true for the older tank designs according to my father in law?

    Basically I'd like to get my calculator wiring for all propane tank types. I had no clue that the older vs newer tank shapes mattered.

    I could put a checkbox on it asking if it has more flat sides or more convex and then change the numbers based on that.

    Im heading to the in laws for Christmas and plan on working on my smoker so this conversation was highly enlightening.
  4. lendecatural

    lendecatural Smoking Fanatic

    After looking at a bunch of tanks, I would go with a 0.6 number of D/L ratio. Anything over 0.6 shouldn't be affected by a 15% reduction in area under the RF plate. Of the short and fat tanks I've looked at had a ratio around 0.68 while the newer tanks hover around 0.5 and below.

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