Low Energy Desalination via DCMD: The Role of Superhydrophobicity and Optimal Flow Conditions

The role of superhydrophobicity on DCMD performance is assessed using polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) electrospun membrane sheet coated with tetrafluoroethylene oligomers (OTFE) particles followed with hot pressing. This led to infuse and deposit ~2-3 μm of OTFE layer on the surface of the PVDF-HFP membrane without compromising the pore size distribution nor the membrane permeability. Nominally the membrane is tested and reported to achieve 99.9% salt rejection and 14kg/m2.hr permeation flux. A mid this successful fabrication and assessment, high fidelity computational model that based on conjugated Navier-Stokes flow for the flat membrane DCMD system is developed to assess the sensitivity of the hydrophobicity under different flow conditions (i.e. temperature, velocity or Reynolds number), and membrane properties (i.e. porosity and conductivity). Results shows the pronounced and outstanding performance of the superhydrophobic DCMD membrane when integrate with low conductivity, high porosity and subjected to favorable high and safe operating temperature and Re flow. Under these conditions, an additional improvement of 20%, 22%, 15% can be achieved in the permeation flux, thermal efficiency and temperature polarization coefficient (TPC) metrics, respectively.