Estimating the mixture friction factor for the dense-phase transport of particulates in horizontal pipes with inner longitudinal spiral slots

Abstract

This research was devoted to establishing a dimensionless model for estimating mixture friction factor based on the Buckingham Theorem. An experimental test-rig with conveying pipeline of 40 mm I.D was designed, assembled and used to collect the data needed to model the mixture friction factor. Experiments were carried out in four levels of slot depths (0, 0.35, 0.55 and 0.9 mm), three levels of air pressure (100, 200 and 300 kPa) and three pipeline lengths (3, 6 and 9 m). Conveying tests with three particulate materials of mung bean, corn, and polyethylene pellets were completed using three replications. Static air pressure across the conveyor, mass flow rate of discharge solids and inlet air mass flow rate were measured during the tests. The model developed can estimate the mixture friction factor within the range of variables studied. The comparison between predicted and measured mixture friction factor showed no significant difference. According to values of R 2 , RMSE, reduced chi-square and MRD parameters, mixture friction factor modelling of the pneumatic conveyor had good accuracy. Other results showed that the mixture friction factor was 65% less than that of pipelines with inner trapezoidal slots studied earlier, therefore lower upstream pressure was required for dense-phase pneumatic conveying of particulate materials in the new conveyor. The developed model showed acceptable error in predicting pressure drop from the experimental data.