CO2 volume in kegged beer

[Simonh82]

I'm carbonating a beer at the moment. My usual process is to hook up the keg full of cold beer to the gas and set it to 50PSI. I leave it out in my brew shed for about 20 hours and then bring it in and connect to the gas in my kegerator at 14PSI. A few more days at that pressure and it is perfect.

At the moment my kegerator gas has run out and the brew shed is so hot I don't want to leave my beer out in it to boil. Instead last night after kegging I pressurised the headspace to 60 PSI and disconnected it and put it back in my fermentation fridge set at 2°C. This evening I checked again and was surprised that there was almost no pressure left in the head space. I reprssurised to 70PSI and put it back in the fridge.

Can anyone help me work out how many volumes of CO2 will be in the beer after this second dose of CO2. There would have been about 0.75 vol of CO2 in solution after fermentation. There was probably 600ml of headspace in the keg and I can't be exact but when. I pulled the PRV there was only a very small pfff, so I think most of that CO2 has gone into solution.

Can anyone point me in the right direction?

 

[Drunkula]

If there was barely a whisper of expulsion at 2c then you can estimate it at 1.59 volumes. Then lets say that little sealer blast took it to 1.6. You really need to know more but just put the temperatures into:

https://www.brewersfriend.com/beer-priming-calculator/ Don't worry about the headspace in this case.

 

[stz]

< 1.603, but likely a bit less.
https://calistry.org/calculate/vanDerWaalsCalculator

You'll need a and b constants for co2.
https://www.engineeringtoolbox.com/...-Waals-equation-constants-gas-law-d_1969.html

You can now calculate how many moles of co2 will occupy 600ml of space at a give temperature at both 60 and 70 psi. You don't know how much absorbed between the first and second blast and how much you let off when pulling the PRV, but I'm assuming it all absorbed and didn't go pssfft to make life easier, but if you had a pressure gauge you could have known. co2 is 44 moles per gram. You can now work out how many grams/l this all was. Then you can turn convert that into volumes.

Phew! Interesting how close it is to the other reply!

 

[peebee]

Using a more workman approach:

You've, say, 20L of beer. It'll have about 1 volume of CO2 (20L) dissolved in it from fermentation (tad less). So you want to dissolve another "volume" (20L of CO2) to get it up to 2 volumes (hellish fizzy, but not for some). So you fill the 1/2L airspace with roughly 4 atmospheres (1 atmosphere is roughly 15psi, 1 bar). So, that's 4x 1/2L = 2L of CO2 dissolving in the beer … only 18 more to go!