Degree Name

Doctor of Philosophy


Department of Mechanical Engineering


There is hardly an industry which does not employ gravity flow bins for the storage of bulk solids. Conseauently there has been considerable activity and research to provide the engineer with information that will enable him to design bulk solid storage facilities for unobstructed and predictable flow. There also has been an increasing tendency in industry to handle finer materials which has led to considerable difficulties especially in cases where the actual flow rate was considerably less than plant capacities.Such misfortunes have prompted a number of investigations in this field in an endeavour to understand the flow of fine materials and to make suitable modifications to gravity flow bins to improve the flow situation.

This thesis is concerned with the prediction of the flow rates of fine bulk solids from mass fLow bins and hoppers. In this initiaL treatment the two-phase nature of the flow will become apparent. The analysis requires the imultaneous consideration of the continuity of the bulk solid and the interstitial fluid,and the inclusion of the effects of the interstitial gas pressure gradients in the equation of motion of the flowing bulk solid.

This analysis will be applied ihitially to an incremental element of bulk solid,the flow through which is described by a number of partial differential equations whose solution requires considerable numerical effort. An approximate analysis is then be developed by considering the flow through an assumed element . Three non-linear total differential equdtions result which also require numerical techniques for their solution.

By making suitable assumptions for the forni of the flow stress field ,analytical solutions for the flow rate, the interstitial gas pressure distribution and the flow stress field are obtained for channels with or without surcharge. Pesults for coarse bulk solids are then derived by neglecting the effects of interstitial fliud pressure graaients.

The predicted flow rates compare favourably with observed flow rates from an experimental pLane flow bin.

It must be stressed that this is only an initial treatment, extensive work still is required to completely understand and predict the flow of general bulk solids from bins.

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