Flux enhancement during ultrafiltration of produced water using turbulence promoter

Concentration polarization and membrane fouling remain one of the major hurdles for the implementation of ultrafiltration of produced water. Although many applications for ultrafiltration were already suggested, only few were implemented on an industrial scale. Among those techniques, turbulence promoter can be more simple and effective in overcoming membrane fouling and enhancing membrane flux. As for the result that turbulence promoter increase fluid velocity, wall shear rates and produce secondary flows or instabilities, the influence of turbulence promoter was investigated on permeate flux during produced water ultrafiltration and the potential application of this arrangement for an industrial development. Experimental investigations were performed on 100 KDa molecular weight cut-off PVDF single-channel tubular membrane module using four kinds of turbulence promoters. It is observed that the significant flux enhancement in the range of 83%--164% was achieved while the hydraulic dissipated power per unit volume of permeate decreased from 31%--42%, which indicated that the using of turbulence promoter is more efficient than operation without the turbulence promoter. The effects of transmembrane pressure and cross-flow velocity with and without turbulence promoter were studied as well. Among the four kinds of turbulence promoters, winding inserts with 20.0 mm pitch and 1.0 mm wire diameter showed better performances than the others did.

Experimental and CFD Studies on the Performance of Microfiltration Enhanced by a Turbulence Promoter

This paper reports experimental and computational fluid dynamics(CFD) studies on the performance of microfiltration enhanced by a helical screw insert.The experimental results show that the use of turbulence pro-moter can improve the permeate flux of membrane in the crossflow microfiltration of calcium carbonate suspension,and flux improvement efficiency is strongly influenced by operation conditions.The energy consumption analysis indicates that the enhanced membrane system is more energy saving at higher feed concentrations.To explore the intrinsic mechanism of flux enhancement by a helical screw insert,three-dimensional CFD simulation of fluid flow was implemented.It reveals that hydrodynamic characteristics of fluid flow inside the channel are entirely changed by the turbulence promoter.The rotational flow pattern increases the scouring effect on the tube wall,reducing the particle deposition on the membrane surface.The absence of stagnant regions and high wall shear stress are respon-sible for the enhanced filtration performance.No secondary flow is generated in the channel,owing to the streamline shape of helical screw insert,so that the enhanced performance is achieved at relatively low energy consumption.

Heat Transfer Augmentation in Developing Flow Through a Ribbed Square Duct

An experimental study is conducted to investigate the heat transfer augmentation in developing turbulent flow through a ribbed square duct. The duct is made of 16ram thick bakelite sheet. The bottom surface of the ribbed wall having rib pitch to height ratio of 10 is heated by passing a c current to the heater placed under it. The uniform heating is controlled using a digital temperature controller and a variac. The results of ribbed duct are compared with the results of a smooth duct under the same experimental conditions. It is observed that the heat transfer augmentation in ribbed duct is better than that of the smooth duct. At Re=5.0× 10^4 , the mean temperature of air flowing through the ribbed duct increases by 2.45 percent over the smooth duct, whereas in the fibbed duct Nusselt number increases by 15.14 percent than that of the smooth duct with a 6 percent increase in pressure drop.