EXPERIMENTAL-DETERMINATION OF THE MASS-TRANSFER BOUNDARY-LAYER AROUND A SPHERICAL BIOCATALYST PARTICLE

An oxygen microsensor was used to determine the thickness of the boundary layer outside a spherical biocatalyst particle in liquid flow. Different particle diameters and fluid velocities were used. The results were compared with correlations available in the literature using the superficial liquid velocity. The measured thickness of the boundary layer appeared to be smaller than the thickness calculated with the literature correlations. The reason for this disagreement could be that the local liquid velocity existing in the measuring equipment was higher than the superficial velocity used in the calculations. No experimental distinction could be made between the results obtained with different particle diameters. The diameter dependence is small at high Re numbers, while at low Re numbers the measuring error was too large due to vortices. However, it is clear that care must be taken when using correlations from the literature to predict external mass transfer resistance. © 1990.