CORRELATING LOCAL TUBE SURFACE HEAT-TRANSFER WITH BUBBLE PRESENCE IN A FLUIDIZED-BED

A fifty-one millimeter outside diameter heat transfer tube of thirteen millimeter wall thickness was fitted horizontally into a cold bubbling bed of sand and fed with a supply of hot water. The surface of the tube was instrumented with five miniature thermocouples and, in addition, two pressure taps were drilled into the tube to infer bubble presence from vertical pressure gradients. The relationships between bubbling frequency and bed height as well as bubbling frequency and fluidizing velocity are reported. The correlation between transient temperature and differential pressure data shows the influence of bubble events on the local tube heat transfer. Velocity of a bubble at the tube surface could also be inferred from multiple thermocouple data.