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Thread: Heat of Fermentation?

  1. #1
    Join Date
    Nov 2007
    Posts
    93

    Heat of Fermentation?

    Currently calculating cooling requirements, specifically for fermentation. Unfortunately, all my reference books are in storage so I'm having to use educated guess and secondary sources, so :

    Estimate 4kg fermentables per 100 litres wort.
    Heat of fermentation 652.4 kJ/kg
    Fermentation proportions over 5 days : Day1 8% : Days 2-4 27% : Day 5 11%

    I know the overall load is relatively small compared to liquor/wort cooling, end-of-fermentation cooling, cellar, etc., but I would like to have a reasonable estimate.

    Does this look about right? Comments appreciated.

    Thanks,

    Gregg

  2. #2
    Join Date
    Aug 2006
    Location
    Homer, Alaska
    Posts
    93
    There are many variables including some you can't plug into an equation. What
    yeast? Ale or Lager can make a huge difference. Specific strain can make a big difference and specific pitching temp or if allowed to rise some can also,and or course # of generations/strength/viability. Fermenter geometry can make a difference as well. Believe it or not the moon and other cosmic forces even can make a difference. I imagine you are trying to size refrigeration? You can only get a rough estimate on a time line like that. If that's all you need and you are fermenting with a basic ale yeast I'd say your daily percentages are roughly ok except day two and three should be higher say 33% and 30% respectively and day one should be higher as well I guess...
    canyon

  3. #3
    Join Date
    Nov 2007
    Posts
    93
    Thanks. As you say, there are many variables, so I just need an approximation. Any comments on the 652.4 kJ/kg heat of fermentation?

    Gregg

  4. #4
    Join Date
    Jan 2006
    Location
    Lawrence, KS
    Posts
    215

    heat of fermentation

    fermentation generates 252 BTUs of heat for every lb of extract lost. For Ales, in our brewery, I look at a peak rate of fermentation of 0.4 P/hour (That's generous but better to aim high). Using the formula:

    (P+259)*P*B/100= lbs extract/hour

    Where P is the peak P/hr and B is the volume of fermenting beer (in Bbls)

    gives 14.5 lbs/hr for a peak rate if 0.4 P and a volume of 14 Bbls.

    Take that times 252 and you get a cooling load of about 3,660 BTU/hr

    FYI, I usually use 0.15 P/hr for calculating lager loads.
    Steve Bradt
    Free State Brewing Co.
    Lawrence, KS

  5. #5
    Join Date
    Nov 2007
    Posts
    93
    Thank you, Steve; our figure of 652.4 kJ/kg converts to 280 BTU/lb, close enough to your 252 BTU/lb. The details of your fermentation heat calcs. are useful too.

    Gregg

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