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Firebox efficiency improvement on direct fired brew kettle.

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  • Firebox efficiency improvement on direct fired brew kettle.

    I have been equipment searching online and have found that all direct fired brew kettles in the size range ( 5 barrel) I'm searching have essentially the same firebox design, a box on the kettle bottom that leads to a vent pipe, and often have relatively low efficiencies in part due the fairly small heat transfer area. I had a different idea that I'd like to toss out there to see if anyone see's any inherent insurmountable problems with it.

    The basic premise is the entire brew kettle is effectively inside a giant flue, allowing heat transfer into the kettle not just on the bottom, but all the way up the sides.

    The execution is simple. Take a conventional direct fire rig, and remove the firebox/vent assembly.
    Next, surround the entire assembly with a insulated sheet metal " flue pipe" of perhaps 2" greater diameter than the kettle, going right from the floor to around the same height as the brew kettle. It would have holes near the base sufficient for combustion air.


    Flue gases would spread out around the whole kettle and travel comparatively slowly upwards due to the large effective flue size, rising against the entire vertical surface of the kettle. At the top, it would exhaust into a hood type power venter and outside.

    It would obviously need access plates for maintenance and access to valves ect, but overall it seems like a fairly simple way to get better efficiency, both from the increased heat transfer area, and from the slowing of exhaust gases until they are past the kettle.

    Ok thats it. Point out all the flaws as you see them.

    Thanks,
    Dean
    Last edited by DeaninMilwaukee; 05-21-2013, 06:28 AM.

  • #2
    That could work

    We were forced to convert a steam jacketed 15bbl kettle to direct fire and ended up doing something like you described. I opened up the bottom of the outer jacket and welded a skirt 4/5ths of the way around it and put the 500k btu worth of burners underneath. We then welded 2 three inch exhaust ports onto the top of the jacket and ran exhaust ducting up to the roof. It's ugly and dumps allot of heat into the room, but boils in 30 minutes or less with minimal fuss. It's nice because it channels the hot gases up the sides of the kettle and slows them down.

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    • #3
      Thank you! This is exactly the sort of info I was looking for. Impressed btw with how fast you could hit boil with 15bbls and 500k btu. Your efficiency must be pretty good.


      My math on your 15bbl to boil from mash temp: 4000lbs water, aprox 50 degree temp rise = about 200k btu/hr, so doing it in 1/2 hour means your burner outputted 500k/2 or 250k btu and around 80% efficient.

      We were looking at 400k btu under a 5 barrel batch just to get times down. I may need to rethink my burner sizing.

      Thanks again,
      Dean

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