Simulation and multi-objective optimization of heat and mass transfer in direct contact membrane distillation by response surface methodology integrated modeling

Abstract

Membrane distillation (MD) traditionally utilizes low-grade thermal energy to drive vapor transport through hydrophobic membrane pores for water treatment. The concurrent enhancement of water flux, thermal efficiency and water productivity to achieve the global optimization of MD is still a challenge. In this work, a new simulation and optimization approach is proposed by integrating theoretical heat and mass transfer models with response surface methodology to investigate the complicate interaction effects of various influencing factors on heat and mass transfer parameters, including overall mass transfer coefficient, feed/permeate side heat transfer coefficients, membrane surface temperature and temperature polarization coefficient, in direct contact membrane distillation (DCMD). The operating and module configuration variables show important interaction effects on enhancing the heat and mass transfer in the membrane module. The significantly elevated heat transfer coefficient on account of the combined high feed temperature, short module length and high feed velocity leads to a great improvement of water flux and thermal efficiency. The ultimate global optimum conditions for the high water productivity were determined where the high levels of heat transfer coefficient (5905W/(m2·K)), temperature polarization coefficient (0.66), water flux (63.0kg/(m2·h)) and thermal efficiency (0.83) all synchronously approach to their own pinnacles. The results indicate that it is an effective way to take advantages of the interaction effects of operating conditions with module configuration parameters to achieve the overall enhancement of MD performance.