Analysis of wall shear stress on the outside-in type hollow fiber membrane modules by CFD simulation Recep Kaya a , Gokhan Deveci a , Turker Turken a,b , Reyhan Sengur a,c , Serkan Guclu a , Derya Y. Koseoglu-Imer a,b , Ismail Koyuncu a,b, ⁎ a National Research Center on Membrane Technologies, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey b Department of Environmental Engineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey c Department of Nanoscience and Nanoengineering, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey HIGHLIGHTS • CFD simulation of hollow fiber membrane module has been studied. • Tangential module configuration had higher shear stress distribution. • Experimental results are in accordance with CFD simulations. abstract article info Article history: Received 7 February 2014 Received in revised form 22 July 2014 Accepted 24 July 2014 Available online xxxx Keywords: Hollow fiber membrane module Shear stress CFD Simulation Crossflow filtration In this study the effects of shear stress distribution and pressure loss on two different hollow fiber module types through have been investigated. The CFD simulations are based on the numerical solutions of the Reynolds averaged Navier–Stokes equations on three dimensional module geometries. The fluid flow inside modules is modeled using a realizable k-ε turbulence model. Module geometries consist two different types of inlet and outlet. One of the modules has normal and the other has tangential inlet and outlet. These two module types are investigated by CFD simulations and results are verified with experimental studies. Based on the simulation results, it has been observed that tangential inlet and outlet create rotational flow inside the module and this causes higher shear stress when compared to normal module geometry. The velocity profiles inside the modules and average pressure drop between inlet and outlet ports are presented. For tangential module configuration, the distribution of velocity inside the module is more homogeneous than the normal module configuration. Average pressure drop between inlet and outlet ports for both module configurations is nearly the same in steady state simulations. The results of the experimental studies are in accordance with the simulation results. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Membrane filtration has a wide range of applications for water and wastewater treatment. However the performance of most pressure driven membrane systems suffers from concentration polarization, fouling and scaling, which decreases module productivity by reduced flux, increase of energy consumption, etc. [1,2]. Membrane fouling occurs by particle accumulation on the membrane surface, which forms a cake layer that plugs the pores entirely. These effects are highly dependent on suspension composition, membrane properties and hydrodynamic conditions [3]. To alleviate these adverse effects, shear stress should be investigated as a hydrodynamic condition in the mem- brane module. Computational Fluid Dynamics (CFD) is a powerful tool for understanding the flow dynamics inside a module body. CFD is the science of predicting fluid flow, heat transfer, mass transfer, and related phenomena by solving the mathematical equations which govern these processes using a numerical algorithm. It signifi- cantly reduces the cost, time and risk associated with running repeated experiments [4]. CFD can characterize flow conditions in various situations and has been widely used for studying flow dynamics. For estimating important parameters such as turbulence conditions and shear stress on membrane surface, CFD can be a useful simulation tool. Shear force is an important parameter for scraping the cake layer particles from the membrane surface [5,6]. It is well known that high shear rates on the membrane influence particle back transport from the membrane surface which in turn reduces the concentration polari- zation and cake formation in cross-flow filtration [1,7]. Many studies Desalination 351 (2014) 109–119 ⁎ Corresponding author at: National Research Center on Membrane Technologies, Istanbul Technical University, Maslak, 34469 Istanbul, Turkey. Tel.: +90 212 2853473; fax: +90 212 285 6667. E-mail address: koyuncu@itu.edu.tr (I. Koyuncu). http://dx.doi.org/10.1016/j.desal.2014.07.033 0011-9164/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal