MODEL COMPARISONS FOR DYNAMIC k L a MEASUREMENTS WITH INCOMPLETELY MIXED PHASES

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Abstract
Oxygen transfer coefficients for gas-liquid systems can be determined by dynamic response experiments. Calculation of the unknown k L a parameter involves analysing the step response data with a model which suitably describes the gas and liquid phase mixing phenomena as well as the electrode dynamics. Various combinations of plug-flow, disperion-flow and well-mixed models are proposed to describe particular gas-liquid systems. Through Laplace transformation, the first moments are calculated in terms of the model parameters. From experimental step response data, the first moment is obtained as the area above the response curve. Using the tabulated relations, dynamic k L a response data can be analysed for many particular gas-liquid oxygen transfer situations. Comparisons between the moment relationships serve for the calculation of the errors in k L a which would be incurred when using an incorrect two-phase model. In general, approximate models may lead to large errors.