if i hook up a full tank of co2 to an empty one, will they equalize?

Question

if it depends on rate, how so? if the temperature drops in the empty one, by how much?

Answer 1

As the HP tank will contain liquid CO2 and, as it expands into the LP cylinder, the LP cylinder will cool down and the CO2 will remain as liquid at a lower temperature. (Refrigeration principle).
(At first, the temperature of the empty tank will fall to near the boiling point of liquid CO2 ..about -78°C but, as liquid level and boil-off pressure increases, the temperature will also increase to correspond with the pressure increase maintaining the CO2 in liquid form.)

As the HP cylinder loses pressure, It's liquid will cool down and, both cylinders will eventually have the same volume of liquid CO2 and the same colder temperature and the same pressure..
In time, as they warm up to ambient temperature, the liquid in both tanks will be at the vapour pressure corresponding to the temperature (at equilibrium) and at equal liquid volume.
The whole process is pure refrigeration principles.

Answer 2

Realistically, one way to really drop the temperature of the CO2 is to allow it to expand rapidly. Not knowing size and vol. involved, I would be worried about freezing condensation on or around the valve or outlet.
Say you have a cylinder, like the large ones welders use, (this is the only type of equipement that I would do this with, since it is strong and the scale is such that you can easily see problems and correct them manually. Larger systems are too hazardous and costly, smaller are to prone to problems that are harder to detect) that is empty, ie 1 atm CO2 and you hook it up in a room to a full bottle at what pressure? Maybe 20-30 atm? You have opened the inlet valve and now you just have to crack the other before the line is at the pressure of the full bottle. So where is the point of inequality? Where the gas is entering the bottle itself. CO2 is not an Ideal Gas. You will have to deal with its z factor and you can probably cool a few cokes by sitting them by the tank. If you want a simple example of what your in for, get a can of room warm coke and the pop the top. The expansion of the little bit of CO2 in it will cool it enough that you can feel the difference in your hand.
Good Luck

Answer 3

The pressure will equalize, whether it is liquid or gaseous CO2. The levels will equalize if it is liquid and they are connected at the bottom. If they are connected at the top, I am not sure. I have the feeling that the first bottle will give off gas until the pressures are equal, then stop.

All this assumes no dip tubes in the cylinders.

Answer 4

They would equalize but it wouldn't be dependant upon rate...
It would be dependent upon the differences in pressure...

When the pressure equalized flow between the two tanks would cease.

Temperature does not play into the transfer of CO2.

Answer 5

Yes they will. It may take a while but eventually they should be identical. Most of the equalization will take place quickly but sooner or later they will have come to the same moles of CO2 in each.