Carbonating in keg, high psi but low carbonation

[bracconiere]

Higher temperatures don't slow down force carbonation. They actually speed it up slightly.

i'm curious as why it takes like 15 minutes of shaking to burst at 45psi, and 80f, but only like 2-3 minutes at 45psi at 40f?

this how long it takes my co2 cylinder to lose ~1oz....?

 

[doug293cz]

i'm curious as why it takes like 15 minutes of shaking to burst at 45psi, and 80f, but only like 2-3 minutes at 45psi at 40f?

this how long it takes my co2 cylinder to lose ~1oz....?

The over pressure is much higher at 40°F than at 80°F, and the over pressure is one of the variables that controls the rate of carbonation. And, as carbonation proceeds, the over pressure at 80°F the over pressure drops off faster than it does at 40°F, so the rate slows down faster at the higher temp. The rate starting out slower, and slowing down faster as things proceed causes things to take longer at 80°F.

For carbonation, the rate is controlled by absolute (more correctly partial) pressures, which are gauge pressure + 14.7 psi.

Say the beer starts out at 0.8 volumes at the end of fermentation. At 40°F the equilibrium pressure is 8.6 psi absolute. At 45 psi gauge, the absolute pressure is 45 + 14.695 = 59.7 psi absolute, thus the pressure difference is 59.7 psia - 8.6 psia = 51.1 psi. At 80°F the initial equilibrium pressure is 16.8 psia, and the initial pressure difference is 59.7 psia - 16.8 psia = 42.9 psi. So the initial rate of absorption at 40°F is 51.1 / 42.9 = 1.19 faster then at 80°F. If the final carb level is 2.5 volumes, then the equilibrium pressure at 40°F is 29.9 psia, and at 80°F the pressure is 52.4 psia. The pressure deltas (which control rate) at the end of the process are 59.7 - 29.9 = 29.8 psi at 40°F and 59.9 - 52.4 = 7.5 psi, and the absorption rate difference at the end is 29.8 / 7.5 = 4.0.

Brew on

 

[bracconiere]

So the initial rate of absorption at 40°F is 51.1 / 42.9 = 1.19 faster then at 80°F.

so dissolved co2 from fermentation, ~0.8vols would basicallly be standard atmosphereic pressure, add that. i don't see where 14.695, and 16.8 come from though...

well i was googling, and had an idea...if i hit the sweet spot to form 'liquid' co2 in the keg at something that would NOT blow the keg, so under say 60-70psi...would i be able to get the liquid into the keg, then just give it a day or two to settle?


damn i just saw something about 50psi, and had a crazy thought, liquid 750-1000 isn't it, duh

(sorry for hijacking beervoid! )


edit: and would it matter if the co2 was warm and beer cold? my co2 is usually at 80f and just the beer i'm carbing is 40f...because 1.19 times faster just doesn't seem like what i experience...

 

[beervoid]

What temperature are the kegs at? It takes forever to carb a room temp keg, but it sucks up the Co2 in the cold kegerator/keezer.

2c

 

[bracconiere]

2c

maybe temp is just a BIT lower and they froze? maybe...?

what did they feel like when you said you were going to shake them?

 

[beervoid]

maybe temp is just a BIT lower and they froze? maybe...?

what did they feel like when you said you were going to shake them?

No, I can take samples they are fine.

 

[bracconiere]

No, I can take samples they are fine.

has this been covered, could the gas poppet be clogged? like pull the spund thingy off, give it a quick push see what comes out?

 

[beervoid]

has this been covered, could the gas poppet be clogged? like pull the spund thingy off, give it a quick push see what comes out?

Def not clogged no, I got 6 kegs im keeping an eye on atm.

 

[doug293cz]

so dissolved co2 from fermentation, ~0.8vols would basicallly be standard atmosphereic pressure, add that. i don't see where 14.695, and 16.8 come from though...

...

edit: and would it matter if the co2 was warm and beer cold? my co2 is usually at 80f and just the beer i'm carbing is 40f...because 1.19 times faster just doesn't seem like what i experience...

The rate of CO2 absorption is controlled by absolute pressure. Gauges read the difference between absolute pressure and atmospheric pressure (14.7 psia.) So, to get absolute pressure, you have to add 14.7 psi to the gauge pressure. Carbonation charts and calculators take care of that under the covers, because the only thing a brewer can measure directly is gauge pressure.

The 1.19 ratio is an estimate of the original rate difference. At room temp the rate quickly drops off as the pressure differential between the applied pressure and equilibrium pressure goes down. At chilled temp, the rate also goes down, but much slower than at room temp. As you get close to the target carb level the rate difference is closer to 4X. And the analysis here is oversimplified, so actual differences could be more or less.

Brew on

 

[bracconiere]

man i just scrolled up, this is the science forum! sorry for intruding! (i did read it though and look forward to the scientifically explained answer)

i'll trying to googling sugar solutions and carbonation as a parting thought...