Mass Transfer in Hollow fiber Module for Reverse Osmosis seawater Desalination

摘要

With regard to mass transfer in a seawater flow channel of a hollow fiber module used for seawater desalination, the seawater flow channel in an infinitesimal space is taken as a model of a plow channel in a circular tube and between similarly parallel flat plates.An analytical solution of velocity distribution and a numerical solution of concentration distribution are obtained from fundamental equations by use of a separation procedure of variables. As a result, the ratio of concentration polarization on a membrane surface is determined by salt rejection and a dimensionless volumetric flux of water through te membrane, that is, a product of the volumetric flux of water through the membrane and the half width of the flow channel are divided by a diffusion coefficient.It has become clear that under practical operating conditions, the ratio of concentration polarization can be ignored. There is almost no difference between a seawater flow channel model with parallel flat plates and another model in the form of a circular tube. On the other hand, the calculated thickness of a concentration boundary layer is much larger than the width of the seawater flow channel in a conventional equation of mass transfer, which is expressed as a function of Reynolds number. It seems that this may be mistaken for a non-uniform flow not related to diffusion resistance.