Experimental Study of Shear Flows and Convective Heat Transfer Characteristics of Granular Materials

Citation

Patton, James Scott (1985) Experimental Study of Shear Flows and Convective Heat Transfer Characteristics of Granular Materials. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/f3ja-cj26. https://resolver.caltech.edu/CaltechETD:etd-11022004-085416

Abstract

An experimental study of granular material shear flows and convective heat transfer characteristics are presented in this investigation. A rectangular chute was used to obtain the results. The experiments were conducted with two sizes of glass beads. In addition, some information was obtained on the shear stress of polyethylene pellets.

The bulk flow properties are used to evaluate the wall shear. The development of a method for determining the bulk density allowed for more accurate calculation of the flow quantities. A derivation of a compressible open channel equation is given for determining the wall shear. The wall shear is presented in terms of several forms of the Froude Number and solid fraction. The experimental results show that the friction coefficient (the ratio of the shear stress to the normal stress) is not a constant but increases with the Froude Number. The presentation of the wall shear as a function of a wide range of solid fractions is the first experimental work that can be directly compared to analytical and computational investigations.

The convective heat transfer properties of flowing granular materials were investigated by examining the flow over a flat heating plate. The method for determining the bulk density of the flow also proved revealing for the heat transfer studies. By using this method, a unique curve for each material was produced in terms of a special Nusselt Number and Peclet Number. The results clearly show that the Nusselt Number reaches a maximum and then decreases for higher values of the Peclet Number. A derivation for convective heat transfer to a flowing granular material is given to predict the heat transfer properties over a wide range of flow conditions.

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