CO2 Volume changes

[r8rphan]

Can anyone tell me how much % wise a certain volume of CO2 in a carboy at 66 degrees will change when the carboy is lowered to 39 degrees?

I'm wanting to leave my 1" blow off tubes installed when I drop the temp for cold crashing... Want to make sure I don't suck the star san from the blow off buckets into the corny... 1" blow off tubes are a little over 5 feet long, probably three and a half feet long before the liquid would be drawn in by gravity...

They are 6.5G carboys with 5G of beer in them...

 

[motobrewer]

it would take quite a bit of suction to pull 1" cross section of fluid 5 feet.

 

[AiredAle]

Here's a rough estimate:

volume change - convert temps to Kelvin, use PV = nRT equation, you get V1/T1 = V2/T2, so if you know V1, the headspace in your carboy, you can calculate the new gas volume V2 at T2 - say 6000 ml (1.5 gal more or less).

So. V1 * T2/T1 = V2 substituting 6000 ml * 280 K / 292 K = 5750 ml, for a volume change of 250 ml.

Volume of your hose, say 2 cm inside diameter or 3.15 cm squared area, times 100 cm open length of hose, you get 315 ml of free hose volume.

So, volume change 250 ml, open hose area 315 ml. I would switch to airlocks with a minimum of vodka in them; this is too close for comfort, and you might get overflow since the blowoff hose is curved at the top.

 

[motobrewer]

Here's a rough estimate:

volume change - convert temps to Kelvin, use PV = nRT equation, you get V1/T1 = V2/T2, so if you know V1, the headspace in your carboy, you can calculate the new gas volume V2 at T2 - say 6000 ml (1.5 gal more or less).

So. V1 * T2/T1 = V2 substituting 6000 ml * 280 K / 292 K = 5750 ml, for a volume change of 250 ml.

Volume of your hose, say 2 cm inside diameter or 3.15 cm squared area, times 100 cm open length of hose, you get 315 ml of free hose volume.

So, volume change 250 ml, open hose area 315 ml. I would switch to airlocks with a minimum of vodka in them; this is too close for comfort, and you might get overflow since the blowoff hose is curved at the top.

lol

 

[r8rphan]

Yeah, this is the third batch since I started using a fermentation chamber... And the last two started getting what looked like an infection was possibly forming after switching to airlocks and cold crashing... minor, didn't hurt the beer, but saw what I thought was infection forming, and there was mold on the PVC fittings I use with a no hub coupling at the top of the carboys.. Never had that problem before using the ferm chamber...

So I was hoping to not have to change to airlocks this time, keeping the carboys full of CO2...

There was some mold building up inside the box at various places, so I scrubbed it down good with bleach/water before this batch... So maybe it won't be an issue now...

was making me nervous...

BTW, the tubing is 1" ID, not OD..

 

[r8rphan]

Deleted post (duplicate)