Topic
Mass transfer coefficient
About: Mass transfer coefficient is a research topic. Over the lifetime, 7827 publications have been published within this topic receiving 168354 citations.
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TL;DR: In this article, a three-dimensional model for convection, diffusion, and reaction in a porous, heterogeneous system has been implemented, which is used to analyse the influence of hydrodynamics and structural heterogeneities on mass transfer and conversion processes of solutes in biofilm systems.
158 citations
TL;DR: In this paper, the effects of the relevant process parameters on the permeate flux have been studied, taking into account the mass and heat transfers across the hydrophobic membrane, and the equivalent film heat transfer coefficient and the overall membrane mass transfer coefficient can be obtained from the experimental data.
158 citations
TL;DR: Results of this modeling study clearly indicate that only evaluation of overall conversion rates or mass fluxes can describe the correct biofilm conversion, whereas interpretation of local concentration or flow measurements as such might easily lead to erroneous conclusions.
Abstract: This modeling study evaluates the influence of biofilm geometrical characteristics on substrate mass transfer and conversion rates. A spatially two-dimensional model was used to compute laminar fluid flow, substrate mass transport, and conversion in irregularly shaped biofilms. The flow velocity above the biofilm surface was varied over 3 orders of magnitude. Numerical results show that increased biofilm roughness does not necessarily lead to an enhancement of either conversion rates or external mass transfer. The average mass transfer coefficient and Sherwood numbers were found to decrease almost linearly with biofilm area enlargement in the flow regime tested. The influence of flow, biofilm geometry and biofilm activity on external mass transfer could be quantified by Sh-Re correlations. The effect of biofilm surface roughness was incorporated in this correlation via area enlargement. Conversion rates could be best correlated to biofilm compactness. The more compact the biofilm, the higher the global conversion rate of substrate. Although an increase of bulk fluid velocity showed a large effect on mass transfer coefficients, the global substrate conversion rate per carrier area was less affected. If only diffusion occurs in pores and channels, then rough biofilms behave as if they were compact but having less biomass activity. In spite of the fact that the real biofilm area is increased due to roughness, the effective mass transfer area is actually decreased because only biofilm peaks receive substrate. This can be explained by the fact that in the absence of normal convection in the biofilm valleys, the substrate gradients are still largely perpendicular to the carrier. Even in the cases where convective transport dominates the external mass transfer process, roughness could lead to decreased conversion rates. The results of this study clearly indicate that only evaluation of overall conversion rates or mass fluxes can describe the correct biofilm conversion, whereas interpretation of local concentration or flow measurements as such might easily lead to erroneous conclusions.
157 citations
TL;DR: In this article, the effects of process variables on the volumetric liquid phase mass transfer coefficient of oxygen, k L a, in a stirred bioreactor were investigated by the static gassing-out method.
156 citations
TL;DR: In this paper, two multiphase flow microfluidic devices based on the use of droplet flow to enhance the mass transfer performance have been specially developed, and the performance data has been obtained by monitoring the extraction of succinic acid from n-butanol to aqueous drops containing NaOH.
156 citations