Improving the performance of direct contact membrane distillation utilizing spacer-filled channel

This study describes the effect of the presence and filament orientation of spacers on the flow pattern and heat transfer enhancement for a commercial direct contact membrane distillation module. In this research, both experimental and computational fluid dynamics (CFD) simulations are carried out when the two sets of spacer filaments are oriented at an angle of 45° to the channel axis and also when the top filaments are oriented at an angle of 30°, 45°, 62° and 90° while the bottom filaments are being parallel to the direction of flow. Fluid flow and heat transfer through empty and spacer-filled channel at various filament orientations and Reynolds number are simulated. Besides predicting the Nusselt number and total drag coefficient, the simulated results allow deeper understanding of the role of spacer presence and its filament orientation in fluid and heat flow structure. It is found that the degree of enhancement in heat and mass transfer depends on filament orientation of spacers. The simulated results show that when the two sets of spacer filaments are oriented 45° to the direction of flow, the wall shear stress and the Nusselt number are pronounced and increased by approximately two times over the empty channel.