Heat Transfer to Pneumatically Conveyed Glass Particles of Fixed Size

Abstract

The phenomenon of heat transfer to an air stream laden with solid spherical particles flowing up a vertical tube with constant heat flux was investigated experimentally and analytically. Two particle sizes, 30 and 200 microns in diameter, were employed. The air flow conditions were held constant at Reynolds numbers of 13,500 and 27,400 while solids were added up to gravimetric ratios of seven. The analytical treatment parallels available solutions for single-phase flow. An approximate solution was obtained under the assumption that the difference in the temperature of the two phases is small, and that the radial temperature profiles of the two phases in the fully developed region are similar. Qualitative agreement with the experimental results is obtained. Large changes in the local Nusselt number were obtained in the experiments using 30-micron particles, in contrast to small effects due to 200-micron particles.