Hydrodynamics and gas transfer performance of confined hollow fibre membrane modules with the aid of computational fluid dynamics

Abstract

The use of gas permeable membranes for bubbleless aeration is of increasing interest due to the energy savings it affords in wastewater treatment applications. However, flow maldistributions are a major factor in the impedance of mass transfer efficiency. In this study, the effect of module configuration on the hydrodynamic conditions and gas transfer properties of various submerged hollow fibre bundles was investigated. Flow patterns and velocity profiles within fibre bundles were predicted numerically using computational fluid dynamics (CFD) and the model was validated by tracer-response experiments. In addition, the effect of fibre spacing and bundle size on the aeration rate of various modules was evaluated experimentally. Previous studies typically base performance evaluations on the liquid inlet velocity or an average velocity, an approach which neglects the effect of geometric features within modules. The use of validated CFD simulations provides more detailed information for performance assessment. It was shown that specific oxygen transfer rates declines significantly with increasing numbers of fibres in a bundle. However, the same trend was not observed when the fibre spacing is increased. A correlation was proposed for the prediction of the overall mass transfer coefficient utilizing the local velocity values obtained from the validated CFD model.

Computation of Global and Local Mass Transfer in Hollow Fiber Membrane Modules

“…Transmembrane flux is then estimated using Sherwood models, therefore again including geometry dependent correlations. Compared to the porous media approach, CFD simulations of resolved hollow fiber packings are often limited to small packings when including transmembrane transport [12] or are only investigating hydrodynamic phenomena if larger packings are examined [13][14][15].…”

Modelling and optimisation of gas-liquid mass transfer in a microporous hollow fiber membrane aerated bioreactor used to produce surfactin

“…(13) is transformed into Eq. (17). The same meth odology was applied to transform back variables into factors (Eq.…”

“…Each relation is valid for the domain 11 < Re < 111, 3.6 10 5 < V L * < 1. The process relationship with a monomial form describing the aeration performances often consider the Schmidt number with a fixed exponent of 0.33 [17]. The Schmidt number, μ/ρD, is a pure material number, that depends only on the agitated liquid properties and on the oxygen diffusivity, D, all considered constant in this work.…”

“…Côté et al [15] obtained experimentally the correlation = Sh Re Sc 0.61 0.363 0.333 (Re varying from 0.6 to 49) to describe mass transfer of membranes using bubble free aeration. More recently, Ka vousi et al 2016 [17] proposed = Sh Re Sc 1,7 0.42 0.33 to describe, by CFD approach, gas transfer performance of confined hollow fibre membrane modules (Re varying from 1100 and 5500). So, we can assume that the Reynolds coefficient of 0.47 in Eq.…”

Novel aeration of a large‐scale flat sheet MBR: A CFD and experimental investigation

“…However, large amount of fundamental research has focused on tubular and hollow fiber membrane modules . Although growing, the literature on two‐phase flow and energy usage for the FS format is still, in general, quite limited .…”