Flow of granular material through vertical slots

The relationship between the dimensions of a vertical slot and the mass flowrate of granular solids flowing through it has been investigated. Most experiments were with rape seed and casein. The solids were discharged from a rectangular vessel 165mm x 155mm through slots up to 400mm long and 70mm wide. Flow rates varied from less than 0.001 kg s{-1} to more than 2 kg s{-1} and were correlated with the product of an effective flow area and the square root of the hydraulic mean diameter of this area. For a specified material, the dead space corrections to slot length and width that gave a best fit of the experimental data had different numerical values. The weight of a discharge vessel, at conditions for which only part of the slot height was occupied by the solids flow, was found to correlate quite well with flow rate.