Performance improvement of countercurrent-flow direct contact membrane distillation in seawater desalination systems

The modeling equations for the temperature distribution and pure water productivity in a parallel-plate direct contact membrane distillation module under countercurrent-flow were derived theoretically with the use of the mass balance on each subchannel. The analytical solution is obtained by using the separated variables method with an orthogonal expansion technique extended in power series. The pure water productivity, average Nusselt number, and temperature distributions of both hot and cold feed streams are represented graphically with the feed velocity and the inlet saline temperature as parameters. The improvements of device performance were achieved under the countercurrent-flow operation. The influences of operation and design parameters on the pure water productivity are also discussed.