Experimental and Numerical Investigation of Hollow Fiber Membrane Module Length and Aeration Intensity

Abstract

The matching relation of module length and aeration intensity in hollow fiber membrane cleaning process was investigated. Five module lengths (0.6, 0.8, 1.0, 1.2 and 1.4 m) at three aeration intensities (3, 5 and 7 L/min) were experimentally tested. Flow fields around hollow fibers were evaluated numerically with computational a fluid dynamics (CFD) approach. Shear stress and velocity distribution were affected by the hollow fiber membrane module length and aeration intensity. The high flow velocity over a shorter membrane module caused extra consumption of aeration energy while the low flow velocity over the top of a longer membrane module was not be sufficient for effective washing under the same aeration intensity. The maximum length, meeting the range of fluid velocity (higher than 0.21 m/s), was defined as the optimized module length when the aeration intensity is settled. Combined experimental and numerical investigation demonstrated that optimal module lengths were 0.6 and 0.8 m at aeration intensities of 5 and 7 L/min. In addition, poor washing occurred in five module lengths at the aeration intensity of 3 L/min. Optimal matching relation between module length and aeration intensity was beneficial to alleviate membrane fouling and decrease energy consumption.