What will happen if I do this....

[Kaiser]

my guess is that he set the pressure to 38 but took off the feed... the co2 will dissolve and not stay at 38 but go down to a more gentile 12 or so... depends on several factors though.

This is an interesting approach. Knowing the volume of beer, the volume of the head space and the temp of the beer, you could calculate the pressure that is necessary to get all the necessary CO2 in the Keg with one shot.

Disconnect the gas line and let it sit or shake to reach equlibrium (or however this is spelled). At that point you should have the perfect amount of CO2 in the beer given that there were no leaks.

I wonder if the pressure would be beyond what you can get from a regulator or put into a keg before the pressure release engages.

Kai

[bub]

Jesus Christ Kai...
you think too much, you are making Doc look like a lightweight with these "math" things you talk about
Here is the best way to make beer...
Uhhhh that looks good.
water hot, grain crushed, green pellety things in hot stuff
make cold, put white stinky stuff in and watch it bubble. (can't wait for the comments on that one)

You guys and your science.... jeesh
BUB

[Kaiser]

You guys and your science.... jeesh

If I could brew every day, I'd probably wouldn't be thinking so much about it .

But this is one the aspects of brewing that I like so much: The application of engeneering and scientific knowledge that I thought was going to go to waste after I left college.

Kai

[jimc]

You guys and your science.... jeesh

If I could brew every day, I'd probably wouldn't be thinking so much about it .

But this is one the aspects of brewing that I like so much: The application of engeneering and scientific knowledge that I thought was going to go to waste after I left college.

Kai

OK, I'll bite. So someone check my math.

Lets say we have 4.5 gallons of beer in exactly a 5 gallon keg so the headspace is 0.5 gallons. If the beer is at 50F (10C) the solubility of CO2 in water (couldn't find it for beer...) is 1.3cm^3 CO2/g H2O. That makes the volume of CO2 already in the beer 17L. If we want to carbonate to say 2.5vol we need a total of (4.5gal*2.5*3.8L/Gal) 42.6L. Subtract what we already have 42.6-17 = need to add 25.6L CO2 into the 1/2 gal headspace. You can estimate with PV=nRT to find the pressure required in the 0.5gal or 1.9L head space to put ~26L of CO2.

I come up with 150-200 PSI depending on the carbonation level

I haven't thought it through completely, but does anyone see an obvious mistake?

-Jim

[JB-Brewer]

I would say it would be in the ball park... cause if I need a quick carb I'll boost my pressure to 30 PSI and throw on a disconnect to the out tube and shake for a few mins. That means my 30 psi is consistinly goin in there for 3-5 mins and carbing her up. My simple math gives me 30 psi x 3-4 mins = 150-200 psi. I'm a math major. thank you, bye.

[bub]

Ok you math tools...
your theory would be correct IF the pressure was instantaneous... however you have to consiter the time it takes to get lets say 100psi in... during this time some will have dissolved into the beer.

WTF why the hell do I care.. I was just baiting the hook...
Bar wench... beer me.
BUB

[Kaiser]

during this time some will have dissolved into the beer.

For a first order caculation, this should be ignored. Otherwise we are talking about differential mathematics here.

Kai

[jimc]

during this time some will have dissolved into the beer.

For a first order caculation, this should be ignored. Otherwise we are talking about differential mathematics here.

Kai

I ignored any CO2 dissolving into the beer when I did the calcs. I also assumed CO2 behavied as an ideal gas (which it doesn't) but the numbers should be close enough to get us in the ball park.

Jim