Experimental and theoretical analysis of the impinging stream drying

The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and the mean residence time of particles, and the influence of various factors on drying characteristics were studied. A mathematical model of granular material drying in a semi-circular impinging stream dryer was proposed, in which the flow characteristics as well as the heat and mass transfer mechanisms were considered. Reasonable numerical methods were used to solve the equations. Under various conditions, the calculated results agree well with the experimental data. The unsteady-state drying dynamic equation, as well as the variations of drying rate and moisture content versus time were obtained. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate semi-circular stage number and curvature radius, flow-rate ratio, air velocity, and higher inlet air temperature should be used for enhancing the drying process.