Effects of pore spacing on drop size during cross-flow membrane emulsification—A numerical study

The design and pore distribution of the membrane are important factors in cross-flow membrane emulsification. To determine the effects of hydrodynamics and drop interaction on drop size, drop formation has been studied numerically using computational fluid dynamics (CFD). Oil with a viscosity of 7.0 mPa s was used as the dispersed phase and water was used as the continuous phase. The conditions studied were pore spacing of 10, 15 and 20 times the pore diameter (20 μm) at a highly dispersed phase velocity of 0.18 m/s, and 10 times the pore diameter at a low velocity of 0.019 m/s. In the case of short pore separation and a low dispersed phase velocity, the drop formation process was uniform, resulting in an emulsion with a narrow drop size distribution, and a dispersed phase flux of 500 L/m2 h. At the higher dispersed phase velocity, the shortest pore separation gave a polydispersed emulsion, whereas pore separations of 15 and 20 times the pore diameter gave nearly monodispersed emulsions, and the flux of the dispersed phase reached 3400 L/m2 h.