EFFECT OF PARTICLE TO BED DIAMETER RATIO ON PRESSURE-DROP FOR POWER LAW FLUID-FLOW IN PACKED-BEDS

In this work, new measurements of pressure drop tor the flow of purely viscous power law type fluids through fixed beds of spherical particles are reported. In particular, the effect of column to particle diameter ratio on pressure losses has been investigated. It is also demonstrated that the existing correlations result in the values of friction factor which differed widely from each other, especially for highly shear thinning behavior. Based on the present data as well as data available in the literature, extensive comparisons have been made with the predictions of a selection of methods available in the literature. It appears that the method proposed by Christopher and Middleman reproduces 290 data points with the minimum overall average error of 12.7%, albeit it rises to a maximum of 70%. It is shown that the predictions can be improved by incorporating the column to particle diameter ratio into the analysis. Using this notion, a new predictive equation has been developed that predicts the results of the same 290 tests with an overall average error of 10.9% which rises to a maximum of 62.8%, slightly lower than in the method of Christopher and Middleman.