AN EXPERIMENTAL INVESTIGATION ON FORCED-CONVECTION HEAT-TRANSFER FROMA CYLINDER EMBEDDED IN A PACKED-BED

Forced convection heat transfer from a cylinder embedded in a packed b ed of spherical particles was studied experimentally. With air as the working fluid, the effects of particle diameter and particle thermal c onductivity were examined for a wide range of thermal conductivities ( from 200 W/m K for aluminum to 0.23 W/m K for nylon) and three nominal particle sizes (3 mm, 6 mm, and 13 mm). In the presence of particles, the measured convective heat transfer coefficient was up to seven tim es higher than that for a bare tube in crossflow. It was found that hi gher heat transfer coefficients were obtained with smaller particles a nd higher thermal conductivity packing materials. The experimental dat a were compared against the predictions of a theory based on Darcy's l aw and the boundary layer approximations. While the theoretical equati on was moderately successful at predicting the data, improved correlat ing equations were developed by modifying the form of the theoretical equation to account better for particle diameter and conductivity vari ations.