Mathematical model for heat transfer mechanism for particulate system

摘要

Various theoretical models for fluidized bed to surface heat transfer have been considered to explain the mechanism of heat transport. The particulate fluidized bed which is the common case for liquid–solid fluidized bed is much simpler and homogeneous and transport operation can be easily modeled. The heat transfer coefficient increases to a maximum and then steadily decreases as the bed void fraction increases from that of a packed bed to unity. The void fraction εmax at which the maximum value of heat transfer coefficient occurs is a function of the solid–liquid system properties.An unsteady state thermal conduction model is suggested to describe the heat transfer process. The model consists of strings of the particles with entrained liquid moving parallel to surface, during the time interval heat conduction takes place. These strings are separated by liquid into which the principal mode of transfer is by convection. The model shows a dependence of heat transfer coefficient on void fraction and on physical properties, which is consistent with the results of experimental work.