Evaluation of Thermal Efficiency of Membrane Distillation under Conductive Layer Integration

Abstract

The role of high conductive layer integration in the performance of the of direct contact membrane distillation (DCMD) processes is investigated. In particular temperature polarization coefficient (TCP), mass flux and thermal efficiency are evaluated for the baseline setup and after integrating a thin superconductive layer on the membrane surfaces. A countercurrent flat-plate baseline module for the desalination of saline water at 1.3 mole% aqueous NaCl was developed using a flat-sheet electro-spun PVDF membrane. The validate numerical model is based on a 2D steady state, conjugated heat, and laminar Navier-Stokes flow subject to the actual thermal and velocity flow conditions. A combined Knudsen and Poiseuille flow model is integrated to estimate the permeated mass and heat flux. The model simulates the flow in two adjacent channels representing the hot saline feed channel and the colder fresh permeate channel. The two channels are thermally coupled by the super-hydrophobic membrane and the additional two superconductive feathering layers to the membrane. Although, the baseline results were in line with numerous literature work on DCMD, the integration of superconductive membrane feathering showed insignificant improvement. The maximum achieved gain was 1% in the TPC, 0.5% in the mass flux and 0.2% in the thermal efficiency and in despite of the different parametrical variations in operating velocities (Re=10, 50, and 100) and temperatures (50 oC and 75 oC) to exasperate this influence.