Heat of Fermentation?

[Gregg]

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

[canyon]

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

[Gregg]

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

[sbradt]

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.

[Gregg]

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