Simulation of heat and mass transfer with cross-flow hollow fiber vacuum membrane distillation: The influence of fiber arrangement

Two factors (fiber row space and intersection angle) of fiber arrangement in hollow fiber vacuum membrane distillation (VMD) module design were studied through simulation works for optimizing the configuration design. The flow field in the module and the permeate fluxes were simulated while the feed inlet velocity was varied from 0.02 m/s to 0.08 m/s. The temperature polarization coefficient (TPC), concentration polarization coefficient (CPC) and the vapor polarization coefficient (VPC) in the modules were discussed based on the average values of the whole configuration. The experimental validation of the simulation models were carried out and good agreement was achieved. The results show that the fiber arrangement can significantly influence the performance of the modules. High permeate flux and VPC values can be observed in modules with row space 2.5 times of the fiber outside diameter and intersection angle 60° or 90°. The TPC and CPC values first increase but then decrease when the row space or the intersection angle enlarges. The enhancement of feed inlet velocity increased the value of TPC and VPC as well as the permeate flux in all simulated modules.