Effect of flow deflector on the flux improvement in direct contact membrane distillation

This study experimentally investigated the influence of flow deflector on the performance of direct contact membrane distillation. A total of seven modules, including a smooth membrane module and six flow deflector modules were fabricated and tested. Effects of the number of flow deflector, deflector height, and the placement of deflectors are examined. The smooth module reveals a comparatively abrupt change of water flux when the inlet velocity is around 0.25 m s− 1, and a plateau is seen for the water flux ratio vs. the Reynolds number for modules containing flow deflectors. Depending on the arrangement of flow deflectors, the maxima occur at a Reynolds number of 500 for D1 and 650 for the others. The plateau for module having more flow deflectors has shifted toward a lower Reynolds number while the pressure drop ratio does not reveal such a plateau. For the same pumping power, the test results show that the water flux for smooth module are smaller than that of all flow deflector modules, and it is applicable to all temperatures. It is also found that modules with more deflectors become more and more competitive at a higher feed temperature but are less effective when the velocity is high.