Simulation of forward osmosis process: Modification of mass transfer coefficient and osmotic pressure equations

Abstract

The basis of forward osmosis process optimization problems is having a suitable equation for calculating permeate flux. This relationship should provide an accurate prediction of permeate flux by covering all the physical phenomena governing the process, including internal and external concentration polarization. In this work, by applying the computational fluid dynamic method, the effect of two main parameters, Sherwood number and osmotic pressure, on the permeate water flux prediction have been investigated. Mass transfer coefficient performs a decisive role in calculating the concentration polarization. Consequently, seven widely used equations for calculating permeate flux have been investigated. It was found that only a limited number of these equations provided the ability to predict flux accurately. Moreover, using the Adaptive Single-Objective method, a non-linear relationship between osmotic pressure and the salt mass fraction was presented. This relationship can accurately predict the water flux in the broader concentration range of the draw solution.