Membrane and spacer evaluation with respect for future module design in membrane distillation

In the case of membrane distillation (MD), the membrane is the core component, but in a full-scale module a spacer is also required in the flow channel. It is increasing mixing and thus the heat and mass transport to the membrane. In this work commercially available membranes and spacers for full-scale module design are evaluated. Special attention is paid to the pressure drop and the heat transfer properties of different spacers. It is shown that MD modules need to be operated in a different flow regime than other membrane processes due to pressure drop limitations. Especially spacers with a high mean mesh size as well as spacers with a high mean mesh size to thickness ratio show good results. Pressure drop and heat transfer characteristics are combined in order to assess the most suitable spacer. For the evaluation of the membranes, Liquid Entry Pressure (LEP) and flux are measured. It is confirmed that membranes with a low pore size show high LEP values. Furthermore, it can be shown that membranes with a high pore size dM to thickness dM ratio showed the highest flux.