Performance Analysis and Optimization of a Hollow Fiber Air Gap Membrane Distillation System

A comprehensive investigation of the performance and optimization of hollow fiber air gap membrane distillation (HF-AGMD) is presented. A detailed mathematical model is developed for the membrane distillation process based on heat and mass analysis, considering the geometrical parameters. The model is validated against experimental data to ensure its accuracy. Using this model, a systematic parametric study is conducted to examine the effect of feed temperature, feed and coolant flow rates, fiber length, pipe diameter, and fiber count on both the feed and permeate sides. In addition, a genetic algorithm (GA) is integrated with the model to maximize productivity and gain output ratio (GOR) and minimize specific thermal energy consumption (STEC) considering fiber distribution, channel geometry, module length, and operating parameters to elucidate and quantify the trade-offs between water productivity and energy efficiency in hollow-fiber AGMD systems. Results show that high feed temperature and turbulent flow enhance permeate flux and GOR, while excessive fiber counts or large diameters may induce laminarization and reduce efficiency. In the parametric study, the HF-AGMD system achieved a maximum permeate flux of 23.8 kg m⁻²h⁻¹, a maximum GOR of 1.17, and a minimum STEC of 550 kWh m⁻³, demonstrating competitive thermal and productivity performance within the investigated operating range. The GA optimization yields an optimal configuration with a maximum GOR of 3.49, a minimum STEC of 184 kWh/m³, and a daily productivity of 32.45 kg/day. The study findings provide practical design and operation guidelines for tailoring HF-AGMD systems toward scaling-up and commercialization.