HEAT TRANSFER FROM AN IMMERSED FIXED SILVER SPHERE TO A GAS FLUIDIZED BED OF VERY SMALL PARTICLES

Results of unique heat transfer measurement in beds of fine, cracking catalyst particles, fluidized by air or helium gas, are compared with predictions from a theoretical model presented in the literature, and also with an earlier established empirical correlation. Moreover, the results have been related to dense phase flow conditions around a silver heat transfer probe by a simple turbulence model. A maximum heat transfer coefficient of h = 2300 W/m(2)K has been measured in a bed of 14 mu m (average diameter) particles, fluidized by helium gas. The data collected, and the model developed, can be used for the design of heat transfer tubes in fluidized beds of fine particles as for instance in fluid catalytic cracking (FCC) of crude oil heavy residues. The FCC is one of the most important conversion processes in the petroleum refineries.