The Effect of Inlet and Outlet Configuration on the Performance of Hollow Fiber Direct Contact Membrane Distillation

Abstract

Abstract Hollow fiber microporous membranes have been used widely in membrane distillation (MD) for seawater desalination applications due to their high surface area. The configurations of feed inlets and outlets significantly impact the performance of hollow fiber direct contact membrane distillation (HF-DCMD). An increase in feed inlets and outlets can also profoundly affect the system’s performance by reducing the concentration polarization at the membrane surface and increasing the mass transfer rate. These aspects are critical when designing and optimizing HF-DCMD systems for various applications such as water desalination and wastewater treatment. Computational fluid dynamics (CFD) simulations were implemented to investigate the performance of HF-DCMD for a desalination process. The effect of inlet and outlet configuration in a tubular shell filled with hollow fiber membranes is examined in modules with a 31% packing ratio. The feed solution with a concentration of 35 g/L NaCl flows in the shell side while the permeated water flows inside the hollow fibers. The Navier-Stokes, mass and energy transport equations for laminar flows are solved with a coupled boundary condition to model the desalination process in the module. Various feed inlet and outlet configurations are considered, including one with an inlet and outlet normal to the shell’s axis (at the shell’s end surfaces) and others with inlets and outlets parallel to the axis. The module with an inlet and outlet at each shell end parallel performs better than other configurations. The permeate flux is enhanced by approximately 153% when four feed inlets are placed at the side wall of the shell. On the other hand, the study observed a slight increase in water production when multiple feed outlets are used.