Which transport equation, which scheme, which model???
 

Hi all,
My project is related to filling a tank with hydrogen. The inlet mass flow is 1 kg/s and the the tank initially has 1 kg hydrogen inside. So, technically after 5 seconds, the mass inside the tank should reach to 6 kg.
First, I used Peng-Robinson equations and after checking the final result by using integrate variables in paraview I found out the final mass was much less than I expected. Then, I changed the transport equations to perfect gas. In that case, the mass inside the tank reached to 9 kg.
I have tried different schemes including linear, upwind and linearUpwind schemes and I also tried both kEpsilon and kOmeqaSST models but none of them influenced the final result that much.
I am using openfoam 5 and the rhoCentralFoam is the solver. What is the problem do you think and how can i deal with it?

Best regrads,
Masih Mojarrad