Computational Fluid Dynamics Modeling of Pressure-Retarded Osmosis: Towards a Virtual Lab for Osmotic-Driven Process...

Area of Science:

• Membrane Science and Technology
• Renewable Energy Systems
• Computational Fluid Dynamics (CFD)

Background:

• Pressure-Retarded Osmosis (PRO) offers potential for clean energy generation from salinity gradients.
• Accurate modeling of PRO requires understanding complex interactions between fluid flow and osmotic fluxes.
• Existing models often struggle with the geometrical complexity and flow regimes found in real PRO modules.

Purpose of the Study:

• To develop an efficient and high-fidelity 3D Computational Fluid Dynamics (CFD) framework for osmotically driven membrane processes.
• To accurately model osmotic water flux and reverse salt flux by coupling CFD with analytical solutions for concentration polarization.
• To investigate the impact of external (ECP) and internal (ICP) concentration polarization on PRO and Forward Osmosis (FO) performance.

Main Methods:

• Developed a two-way coupled CFD framework integrating a CFD solver for ECP with an analytical model for ICP.
• Simulated 3D flow within membrane modules, accounting for complex geometries and flow regimes (laminar to turbulent).
• Validated the model against experimental data for various PRO and FO case studies.

Main Results:

• The CFD model accurately predicts osmotic water flux and reverse salt flux, capturing all concentration polarization effects.
• The model demonstrates flexibility in simulating both PRO and FO processes, comparing ECP and ICP contributions.
• Successful simulation of a lab-scale PRO module across a wide range of Reynolds numbers, from laminar to turbulent flow.

Conclusions:

• The developed CFD framework provides a robust and efficient tool for high-fidelity simulation of osmotically driven membrane processes.
• The model accurately accounts for concentration polarization effects, crucial for optimizing energy harvesting in PRO.
• This approach enables comprehensive analysis of PRO and FO performance under diverse operating conditions and module designs.