We present a new module of the software tool PoreChem for 3D simulations of osmotic

processes at the cell-element scale. We consider the most general fully coupled model (see

e.g., Sagiv and Semiat (2011)) in 3D to evaluate the impact on the membrane performance

of both internal and external concentration polarization, which occurs in a cell-element

for different operational conditions. The model consists of the Navier–Stokes–Brinkman

system to describe the free fluid flow and the flow within the membrane with selective

and support layers, a convection–diffusion equation to describe the solute transport, and

nonlinear interface conditions to fully couple these equations. First, we briefly describe the

mathematical model and discuss the discretization of the continuous model, the iterative

solution, and the software implementation. Then, we present the analytical and numerical

validation of the simulation tool. Next, we perform and discuss numerical simulations for

a case study. The case study concerns the design of a cell element for the forward osmosis

experiments. Using the developed software tool we qualitatively and quantitatively investigate

the performance of a cell element that we designed for laboratory experiments of

forward osmosis, and discuss the differences between the numerical solutions obtained

with the full 3D and reduced 2D models. Finally, we demonstrate how the software enables

investigating membrane heterogeneities.