Flow frictional resistance in pneumatic conveying of solid particles through inclined lines

The frictional behaviour of fully suspended dilute flow of granular solid particles in air through the transport lines of various angularities, α, with the horizontal plane in the range of 0°≤α≤30° is presented in this paper. The friction factor determination is based on the measurements of local static pressure gradients. The experiments were mainly directed to determine the effects of transport line inclination, particle physical characteristics, the ratio of mass flow rate of particles to that of air, Mp/Ma, and the flow Reynolds number, Re, on the two-phase friction factor. A variety of solid particles whose average diameter, dp, and apparent density, ρp, being in the respective ranges of 75.5 μm≤dp≤275 μm and 467.95 kg/m3≤ρp≤824.17 kg/m3 were used, with 5%≤Mp/Ma≤30%, at 50 000≤Re≤100 000, for this purpose. The results were expressed in terms of two-phase friction factor, fp+a, correlations proposed under the light of the state of art. The experimental data was also evaluated via solids friction factor, fs, correlated previously by Özbelge [Int. J. Multiphase Flow 10 (1984) 459] based on a theoretical analysis of vertical upward flow fields [Int. J. Multiphase Flow 9 (1983) 437] as well as to confirm the validity of the method in non-vertical upward flows.