Discussion Forum

Hi,

I am trying to model a membrane separation unit (a thin flow channel) where permeate (low concentration) is continously removed, while the retentate (high concentration) is recirculated to a feed tank, where it then enters the membrane unit again. Hence the inlet concentration as well as the concentration in the module will increase over time. I would like to integrate over time the mole flow and volume flow which exits the model in the form of permeate and use this to continously calculate the inlet concentration.

I imagine it could be set something like writing the variable Cin=(N0-Nout)/(V0-Vout) where N0 and V0 are set starting amounts of moles and volume and Nout and Vout are variables and the total removed amount of moles and volume at any time. Then write Cin under inflow for transport of diluted species. I have probes set up which give the outflow at any time in mole and volume (mole/s and m3/s), and have tried calculating Nout and Vout as integrals using integral probes, the integration function (intop1) and line integration under derived values. These all seem to integrate along the lenght of the boundry and give a value in m * mol/s or m^4/s. But I of course want to integrate over time and get an answer in the value m^3 and mole.

Would this be possible to do and what would be the easiest way?

Thanks