Modeling a closed system with a gas phase at elevated T

[mvoigt]

Hi,

I was wondering if it's possible to model the evolution of a solution, which is placed in a container of fixed volume with a certain head space filled with gas (e.g. nitrogen or air) at 1 atm. The container is sealed and heated, for example to 200 C... Some dissolved CO2 is present in the solution (and some CO2 might be in the head space from the beginning), so the gas and liquid will equilibrate after a while. I tried with the following code

Code: [Select]

USE solution 1 #solution 1 is the solution which is placed into the container before heating
GAS_PHASE 1
  -temperature 25
  -fixed_volume
  -volume 100e-3
  Ntg(g) 1
 
REACTION_TEMPERATURE
200

Does PHREEQC account for the expansion of water in this example, and would this be the correct way (if there is one) to model such a setup?

Thanks in advance!

Martin

[dlparkhurst]

I think it looks OK. The volume of water is not adjusted explicitly, so the volume of gas is fixed. However, the solution density and volume are calculated, so you could estimate the magnitude of the effect.