The relation of bed depth, particle density, and particle size to the local coefficients of heat transfer of internally-heated fluidized beds of solids

Abstract

The variation of the local coefficients of heat transfer with bed depth, particle density, and particle size were studied using a pyrex pipe four inches in diameter as the fluidizing vessel. The fluidized solids investigated were aerocat cracking catalyst, having a geometric-mean particle diameter of 0.00262 inch and an absolute density of 136.6 pounds per cubic foot; tabular alumina, having a geometric-mean particle diameter of 0.0138 inch and an absolute density of 238.8 pounds per cubic foot; silica gel, having a geometric-mean particle diameter of 0.0187 inch and an absolute density of 135.1 pounds per cubic foot; and superbrite glass beads, having a geometric-mean particle diameter of 0.0138 inch and an absolute particle density of 179.5 pounds per cubic foot. The heating element was a 230-vo1t, 1750-watt, copper-sheathed rod having a diameter of 0.25 inch. Temperature measurements were made with 20 B and S gage, iron-constantan thermocouples insulated with fiber-glass braid over glass wrap. Air varying in temperature from 80 to 85 °F and in humidity from 0.000 to 0.004 pound of water vapor per pound of dry air was used as the fluidizing medium.