Comparison of hollow fiber module designs in membrane distillation process employed lumen-side and shell-side feed

摘要

In the present work, randomly packed, curly fiber, spacer scattered, and spacer knitted modules were fabricated and their performance in direct contact membrane distillation employed lumen-side feed and shell-side feed was investigated, respectively. Experimental results showed that the flux of different module configurations in shell-side feed operations were lower than that in lumen-side feed operations. Modified modules showed higher flux compared with randomly packed module and the spacer knitted module had the best performance with 51.8% enhancement at 328 K in lumen-side feed performance. The module flux increased as the feed flow rate increased, and all the modified modules showed relative high flux even at a low feed flow rate, which confirmed the fluid improvement caused by the spacers or wavy geometries. The overall heat transfer coefficient of modules ranged from 704 to 1,961 W/(m(2) K) in lumen-side feed operations, while that was lower to be 425-645 W/(m(2) K) in shell-side feed operations. In addition, higher heat transfer coefficients and temperature polarization coefficient were observed with modified module configurations. The sodium chloride tracer response technique was used to reveal the shell-side flow pattern and distribution for various module designs. Results showed that the modified module configurations can provide a better flow distribution in shell side with longer residence time and smaller variance, thus higher thermal efficiency and flux could be accomplished.