Analysis of the shear force caused by slug bubbles tracking in the hollow fiber membrane module.

The performance of bubbles in the hollow fiber membrane module has been explored to overcome the membrane fouling in many studies. In this study, to obtain a better strategy, the process of slug bubbles tracking under different crossflow velocity and aeration intensity has been explored in the tubular system. Based on an in-suit investigation method, Fiber Bragg Grating (FBG) sensing technology, the bubbles velocity, coalescence number, travelling distance, interference aera were investigated in the slug bubbles tracking process. Besides, computational fluid dynamics (CFD) models were used to simulate the slug bubbles tracking process. Moreover, the correlation of slug bubbles with the fiber packing density during tracking and coalescence was further analyzed. The results from experiments and simulations show that the bubbles tracking promotes the increase in bubble velocity, with a maximum increase of 91.46 %. And the bubbles tracking and coalescence phenomenon mainly occurs in the area between 0.6 and 0.9 m. Besides, during the bubbles tracking process, the wake zone induced by the bubbles had a significant increase in the range of 30.26 %-137.05 %. Pulse flow alternating with pulse bubbles increases the bubble coalescence rate from 28 % to 44 %, enhances the velocity of slug bubbles and increased their travelling distance. Numerical model shows there is a correlation between packing density and slug bubble velocity and the optimum bubble velocity was observed at a packing density of 333.33 m2/m2. Besides, the process can also be optimized by reducing the fluid velocity and increasing the aeration intensity. The regularity of formation and development of bubbles tracking helps to further refine the control of gas-liquid two-phase flow.