Solar energy assisted direct contact membrane distillation (DCMD) process for seawater desalination

• Solar assisted DCMD system for seawater desalination.
• Improved two dimensional dynamic model for unsteady state conditions and membrane fouling.
• Model predicts the permeation flux with time for different operating conditions.
• Solar-MD system proved suitable for long term operation of approximately around a half year.

Development of a solar assisted direct contact membrane distillation (DCMD) system for seawater desalination and an improved mathematical model to predict the permeate flux for unsteady state conditions were investigated. Different types of commercially available polytetrafluoroethylene (PTFE) membranes were used in a solar-DCMD system for seawater desalination. Membrane properties, such as the liquid entry pressure (LEP), pore diameter, effective porosity and pore size distribution, were characterized for each membrane. A two dimensional (2D) flat-plate dynamic model with heat and mass transfer mechanisms was used to predict the permeate flux under different operating conditions. Good agreement between the numerical simulation and experimental results were found. Long-term fouling phenomenon in the DCMD system was experimentally and theoretically examined. The experimental heat energy consumption ranged from 896 kW h/m3 to 1433 kW h/m3, and the gained output ratio (GOR) ranged from 0.44 to 0.70. The solar-DCMD system was run continually for more than 150 days for seawater desalination in Korea. During day time, more than 77.3% of the heating energy was supplied by solar energy. In particular, in the month of September, 95.3% of the heating energy was supplied by solar energy.

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