Abstract: Membrane distillation is very promising in the field of wastewater treatment as a means of water recovery method driven by industrial low-temperature waste heat. A variety of new membrane modules with different sizes of semi-cylindrical baffles were constructed by incorporating different sizes of hot liquid flow channels in the air-gap membrane modules. A test rig was set up to systematically investigate the membrane flux and thermal efficiency of the new modules under different conditions of hot and cold liquid inlet temperatures and flow. The results show that the hot feed inlet temperature and flow as well as the cold feed flow are positively correlated with membrane flux, while the cold feed inlet temperature is negatively correlated with membrane flux. Additionally, the hot feed inlet temperature is positively correlated with thermal efficiency. In the new modules, as the size of the semi-cylindrical baffle in the hot channel increases, the membrane flux increases by 4.3%, 6.4%, and 8.7%, respectively, and the thermal efficiency increases by 2.4%, 3.4%, and 4.8%, respectively, compared with the module without the baffle. The results indicate that this new module configuration has the advantages of high flux and high thermal efficiency, providing an optimized basis for the development of high-efficiency air-gap membrane distillation modules.

Key words: air-gap membrane distillation, heat and mass transfer, new flow channel, wastewater treatment