Influence of Heat Exchanging Tubes on Local Heat Transfer Coefficient in Fluidized Bed Reactor

Abstract

Fluidized bed reactors are widely used in a variety of chemical industrial processes for extremely exothermic reactions. But the performance of the reactor could be impacted if the exothermic reaction’s heat isn't removed sufficiently. Understanding and analyzing the heat transfer mechanisms occurring in the reactor is crucial to improving the reactor’s overall performance as well as the chemical process. The investigation was carried out in two stages) one tube heater, five internals equipped with one tube heater). In both stages, the heat transfer probe was moved to different places around and inside the center and the range of gas velocity was 0.2–0.48 m/s. A sophisticated heat transfer system was used to investigate locally and instantly how a bundle of vertical heat-exchanging tubes affects the heat transfer coefficient (HTC) in a gas solid fluidized bed. The experiments were conducted on 0.13 m inner diameter Plexiglas fluidized bed reactor by using silica sand as particles with size of 600 µm and fixed packing height 35 cm. The heating element consists of solid brass shell, a heater and flux sensor. The heat transfer probe dimensions 12 mm diameter and 8 cm length. The thermocouples were 10 cm above distributer. The local heat transfer coefficient (LHTC) increase with increasing fluidizing velocity. There is a different behavior of HTC at various local position of tube heater in comparison with other different tubes position. When there are vertical internals present in the center, the HTC increases by 31% for different gas velocities. A comparison of local heat transfer coefficient with internal tube and without internal tube gives a reasonable result.