Effects of cross-sectional geometry on flow characteristics in spiral separators

Abstract

ABSTRACT As flowing film gravity concentrators, spiral separators are extensively used in the processing of numerous minerals. Appropriate design of their cross-sectional geometries has been known as an effective method to improve the performance of spiral separators. However, limited work has been published on the impact of cross-sectional geometry on flow field characteristics in spiral separators. In this study, the effects of cross-sectional geometries with various parabolic profiles (|x|=m|y| n ) of a spiral separator on the flow film thickness, flow pattern and flow regime were investigated by numerical simulation. The validity of the simulation approach was confirmed by the reasonably good agreement between the predicted and measured flow film thickness in the own laboratory spiral separator. Results have shown that the flow film thickness and the mean primary velocity in the inner and middle troughs are reduced by decreasing downward bevel angle or increasing parabolic index. The dominant region of the secondary flow can be expended inward by increasing the downward bevel angle and decreasing the parabolic index. As the radial position extends inward, a larger downward bevel angle is more conducive to improving the intensity of secondary flow. A wider laminar flow region can be obtained with a smaller downward bevel angle or a larger parabolic index. The flow film thickness has a significant positive correlation with the trough slope in the inner and middle troughs. It is recommended that the matching relationship between material properties and flow field characteristics should be fully considered when selecting the cross-sectional geometry. Thus, this study aids the structural design of the cross-sectional geometries of spiral separators.