Combination of computational fluid dynamics and design of experiments to optimize modules for direct contact membrane distillation

Abstract

The design of membrane distillation modules is an important issue that must be addressed for it to be practically implemented. Herein, a combination of the design of experiments (DOE) and computational fluid dynamics (CFD) was developed to evaluate the interaction between variables of module geometry and how they affect the performance of a direct contact membrane distillation (DCMD) process. A three-dimensional CFD model was developed to calculate flux, the performance ratio (PR), and the permeate-to-feed ratio (ϕp) as functions of the height, length, and width of the channel in a plate-and-frame DCMD module. The CFD model was validated using experimental results in a laboratory DCMD system. Based on a DOE with a central composite design (CCD), CFD simulations were carried out, and response values were obtained for each combination. The results show that length is the most important factor affecting flux, and height is the most important factor affecting PR and ϕp. However, the effect of module width was not significant compared with that of the other variables. Based on the results, a set of regression models were developed to estimate flux, the PR, and ϕp, and these estimations match the CFD simulation results well. Using the derived models, the dimensions of the DCMD module were optimized to simultaneously increase water productivity and energy efficiency.