Oxygen PPM calculations
I am trying to figure out about how much PPM of O2 my wort is getting. I have searched the forums and haven't found a way to calculate it. Currently I run 3.4LPM in line-4.5BBLs KO temp is usually 66º. Takes me 40 minutes to KO. I know it changes with gravity, I am looking for a estimate for a 14-ish plato beer. Don't mind doing the research myself just can't find a place to start. i know you can by a meter but that isn't in the budget right now. Thanks for the help!
From John Mallet of Bell's a while back:
O2 saturation of water (let's assume wort is the same) varies with temperature and pressure. It will be in the range of 8-12ppm for most craft brewing applications.
For this calculation we will assume that we want 10 ppm in the wort
1 ppm is 1 milligram per liter. (because liter of water weighs 1,000 grams or 1 million milligrams)
If we have a 1 hl brew the calculation would be:
(100 liters/hl) * (10 mg/liter) * (1 gram/ 1000 mg) = 1 gram of O2 per hl.
Now here is the difficult part; this assumes that all the Oxygen goes into solution. Craft brewery wort aeration systems are generally not very efficient. So the way to actually find out what you need to do is to use a DO meter on the wort. DO meters for filtration or packaging applications need to resolve to Parts Per Billion so reading 10 PPM is not particularly difficult with a less costly meter.
To optimize O2 addition I would start testing O2 as the wort enters the fermenter and slowly dial it back until you see the O2 level fall below your specification. (Or until yeast performance degrades)
If my high school chemistry holds true then a standard large cylinder of Oxygen (251 cubic feet) should hold about 10 kg of gas. This is 10,000 grams and should be enough O2 to theoretically bring 10,000 hl of wort to 10 ppm. And that is precisely why I always flinch when any engineer uses the words "should" or "theoretically".