Predictive modeling of a commercial spiral wound seawater reverse osmosis module

Abstract

A predictive model based on the solution-diffusion theory is proposed for commercial Filmtec 30 SW 2.5″ spiral wound reverse osmosis modules. The model explicitly accounts for longitudinal pressure drop in the retentate channel and spiral pressure drop in the permeate channel, concentration polarization phenomenon, and effect of temperature on water and salt permeability. Using experimental data from literature, it is shown that the Darcy friction coefficients in the retentate and permeate channels fr∝Rer−0.77, fp∝Rep−0.18, the Sherwood number for mass transfer correlation Sh∝Re0.68Sc0.20, and both the water and salt permeability increase with temperature following approximately Arrhenius-type equations. The mathematical model with parameters derived from the experimental data can reasonably predict water and salt fluxes as well as pressures under various combinations of feed conditions of temperature, flow and pressure (average error ≤4%). The dependence of concentration polarization on recovery, temperature and feed rate is analyzed and compared with an empirical formula from Filmtec.