Numerical simulation of membrane desalination in a conjugated heat transfer configuration: Role of spacers

The performance of the Direct Contact Membrane is assessed via the Computational Fluid Dynamics (CFD) simulation. The developed conjugated heat numerical model from the authors' previous work is used t investigate the role of spacer on the flow and DCMD metrics. The feed (hot stream) and permeate (cold stream) channels are subjected to uniform Navier-Stokes flow and are thermally coupled with a hydrophobic membrane polyvinylidene fluoride (PVDF) in conjugate heat transfer formulation. Depending on the membrane properties (permeability, thickness, pour size, conductivity, etc.) a temperature, and therefore, a pressure gradient across the membrane is created leading to vaporizing, transporting, and condensing the feed at the permeate side. This work investigates the influence of the spacers in modifying the thermal and kinetic boundary layers, i.e. adjustment of surface temperature, heat flux, and shear stress. The DCMD membrane mass transfer coefficient is evaluated additional to the temperature polarization factor (TPF) and thermal efficiency. Results showed a significant change in Temperature, Nusselts number, and surface shear stresses when spacers are introduced as the boundary layer became fully turbulent which enhanced the mass and heat flux but to a smaller extent.