Low Energy Direct Contact Membrane Distillation: Towards optimal flow configuration

Abstract

Computational Fluid Dynamics (CFD) is used to study the steady state performance of Low Energy Direct Contact Membrane Distillation (DCMD). Two-dimensional numerical model with parallel and counter flow is developed. A case of parabolic flow with characteristic velocity is considered entering the domain from the feed and permeate sides at 40°C and 25°C respectively. The model parameters were measured in the consideration of two dimensional, steady state, and incompressible fluid flow using the complete Navier-Stokes coupled with the energy equation for non-isothermal flow. The feed stream is saline water (4% salinity) which is a mixture of two miscible species, whereas the permeate stream comprises of pure water. Across the membrane the temperature difference creates pressure gradient which is responsible for the transport of energy and vapor mass through the pours of the permeable membrane. The membrane's coefficients of DCMD membrane is evaluated along with the mass flux, heat flux, and temperature polarization factor and results showed a good agreement with the published theoretical work. In view of these plausible results, parametrical study was conducted accounting for parallel and counter flow, different in flow rate and inlet temperature in attempting to achieve optimal operation. In the results section, the mass flux, heat flux, temperature polarization were calculated and discussed based on the simulation.