Numerical Simulation and Optimal Design of AGMD-Based Hollow Fiber Modules for Desalination

To improve the permeate flux and to keep the advantage of the high thermal efficiency in air gap membrane distillation (AGMD) for desalination, the optimal design of countercurrent AGMD of the hollow fiber module (AGMD-HF) is proposed. The module is basically composed of hydrophobic porous fiber tubes for feed flow and nonporous tubes for cold flow. The set of mathematical model equations for the entire module is derived from rigorous mass, momentum, and energy balances of both the feed side and the cold side coupled with the simultaneous mass and heat transfer across the membrane. The temperatures across the membrane and along the length of the module are simulated. The sensitivity of the process performance to operating conditions along the fiber length is investigated over a range of temperature and the flow rate. It is found that in the AGMD-HF domain, air/vapor dominates the heat and mass transfer resistances, which are comparable with the available experimental results in the literature. An attempt ...