Learning Forum

[soubhanik.nath]

I am doing a steady-state simulation and reporting the profiles of mole fraction, molar concentration, static pressure, absolute pressure, and total pressure, at a wall. My operating pressure is 2.1 Torr and ideal gas law is being used. The static pressure at the wall is calculated to be 0.38 Torr. 

However, when I use the molar concentration to calculate the partial pressure at the wall through the ideal gas law, I get a partial pressure which would correspond to the operating pressure of 2.1 Torr and not the calculated static pressure (or operating + static) at the wall. Why is this so? Shouldn't the values calculated at a surface be calculated using the actual partial pressure at that surface? 

I am using these equatiosn:

1) p_A = c_A R T

2) p_A = x_A P

[Ahmed Hussien]

I am not sure what you mean here, but please ensure you are using absolute pressure in your calculations — that is:
P_abs = P_operating + P_static. This is the pressure used in the ideal gas law and for calculating partial pressures based on molar concentration.