Effect of helical structure on ozone mass transfer in a hollow fiber membrane contactor

The aims of this work were to investigate the ozone mass transfer in a helically wounded hollow fiber membrane contactor in dependence on operating conditions and to study the effect of the helical membrane structure on the ozonation performance compared to linear fiber arrangement. The role of the mass transfer resistances and the fiber geometry were investigated by means of a mathematical model. The ozone flux was found to increase with increasing gas pressure, ozone gas concentration, gas and liquid velocities. In contrast, for a high ozone dosage low liquid velocities should be preferred. The helically wounded structure of the hollow fibers was found to enhance the ozone flux up to factor 7 comparing to linear fibers due to arising secondary flows inside the fiber lumen and an orthogonal flow at fiber shell. Especially at high Reynolds the mass transfer resistance of the liquid boundary layer in a helical fiber membrane contactor is significantly reduced, so that the resistance of the gas boundary layer gains importance. The mass transfer resistance of the membrane remains low comparing to the overall mass transfer resistance. The possible application fields for ozonation purposes using helical fiber membrane contactor and economic benefits compared to linear fiber membrane contactors could be derived based on the gained ozonation results.