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wdwalter 11-29-2012 09:11 PM

Heat generation during fermentation
 
Is there any way to calculate the difference in ambient temp and wort temp using OG and yeast pitched? Everything I have seen says about 5-10 degrees higher for actively fermenting wort. Is there any way to actually nail this down with a little math?

hoppymonkey 11-29-2012 09:15 PM

Quote:

Originally Posted by wdwalter (Post 4633761)
Is there any way to calculate the difference in ambient temp and wort temp using OG and yeast pitched? Everything I have seen says about 5-10 degrees higher for actively fermenting wort. Is there any way to actually nail this down with a little math?

I don't believe so, There are too many variables involved. Basically the more active the fermentation the more the temp rises.

Golddiggie 11-29-2012 09:22 PM

Ummmm, that's what thermometers are for, to completely take any guesswork out of it. In it's simplest form, you have the fermometer (stick on the outside of the fermentation vessel). At the top end of the scale you have thermwells with probes sent down them to give a temperature reading (with the opening of the thermowell blocked off to keep the temperature in it stable.

BTW, yeast is a living thing and will react/act differently in different brews. Even if you brew the same recipe you can have different temperature increases depending on other variables. I don't see how you could get all of them figured out, in such a way that a brewer wouldn't need to enter a dozen (or more) pieces of data.

Phunhog 11-29-2012 10:32 PM

Not to mention that it will depend on the conductivity (glass, plastic, stainless) of your fermentor.

Golddiggie 11-29-2012 10:53 PM

Quote:

Originally Posted by Phunhog (Post 4633937)
Not to mention that it will depend on the conductivity (glass, plastic, stainless) of your fermentor.

That's why I use a thermowell going into the middle of the ferementer, sealed at the opening, with a digital probe going down into it. The probe goes almost to the bottom, and has a display placed on a shelf nearby. That way I don't need to worry about ambient temps influencing the reading. :D I have all my fermenting caps set up that way. :D

SpeedYellow 11-29-2012 11:03 PM

And don't forget the temp difference will change every hour or day too, since activity changes. So a graph of temp difference versus time would look like a broad bell curve. You *might* be able to approximate the temp difference as a function of CO2 output for a given container type. But that probably doesn't help much.

What's the point of this exercise anyway?

Golddiggie 11-29-2012 11:10 PM

Quote:

Originally Posted by SpeedYellow (Post 4634017)
And don't forget the temp difference will change every hour or day too, since activity changes. So a graph of temp difference versus time would look like a broad bell curve. You *might* be able to approximate the temp difference as a function of CO2 output for a given container type. But that probably doesn't help much.

What's the point of this exercise anyway?

Point??

phoenixs4r 11-29-2012 11:12 PM

No, there is no way to calculate the projected temperature change using the variables you listed, other than simply, up. As others have pointed out you can monitor it.

KuntzBrewing 11-30-2012 12:04 AM

5-10 degrees higher with air, 3-5 in cooler full of water up to beer level. General rule of thumb

SpeedYellow 11-30-2012 12:54 AM

My lagers don't like your rule of thumb. I usually see more like 3-5F with lagers. Seems to be a bit lower than my ales. YMMV. :)


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