Hydraulic drag of dense beds consisting of particles of different shape

Formulas derived by different researchers for the hydraulic drag of a dense bed consisting of particles of different type (balls, pellets, particles of arbitrary shape) are compared. Similarities in the dependence on the temperature and filtration rate are sought in terms of the reduced hydraulic drag coefficient. The dependence of the hydraulic drag on the porosity is practically unaffected by the shape of the particles. A formula is recommended for the hydraulic drag of a pellet bed with natural packing, with a low content of fines. On that basis, the energy losses in the bed itself and in the whole gas–air channel of roasting machines may be determined.