Numerical Simulation Of The Particle Circulation Flow Characteristics Of The Liquid Solid Exterior Circulating Fluidized Bed Heat Exchanger

The technology of circulating fluidized bed has already been largely applied in chemical,mechanical,atoms energy and so on. The situation of liquid-solid two phrase flow is quite complicated. In order to further understand the behavior of particle circulation in the liquid-solid exterior circulation fluidized bed, on the base of the present experimental study done by others, by the method of numerical simulation, using software of STAR and CCM+, further observe the behavior of particle flow, simulating of the position and diameter ratio of the nozzle,which is the key part affecting the particle flow. Moreover, plan to replace the nozzle by venturi tube, which better help particle circulation in the tee-assembly. By the numerical simulation, it will much easily observe the behavior of particle, such as pressure,speed,turbulent kinetic energy, vorticity, the particle track, in the tube. After simulating the nozzle and venture tube structure,we find out that the nozzle position determine the up-down vortex and the nozzle diameter ratio determine the counterpressure in the nozzle exit,which will affect vortex. the nozzle affection toward the circulation effect of the particle in tee-assembly will be determined by the counterpressure and vortex. the bigger of the counterpressure in the nozzle exit, the smaller of drop pressure caused by the nozzle, the smaller the resistance is,the better the result will be. when simulating venture tube and the nozzle in the same situation, the venture tube will speed up the particle circulation than the nozzle does.The result says: the different position and diameter of the nozzle will affect two phase pressure, speed, turbulent kinetic energy, vorticity. When the nozzle postion is L=0mm, the counterpressure in nozzle exit is lower, the affection of vorticity entrainment is in the right level, the nozzle diameter ratio is 0.375, the speed in the nozzle exit and the change of the turbunent kinetic energy will better supplyKinetic energy toward the particle,which will circulate properly. After replacing the nozzle by venturi tube,it founds out the counterpressure in the tee-assembly is one time bigger,moreover the whole pressure is smaller, resistance is lower. When the contraction length of venture tube is 150 mm, the drop pressure in theventure tube is lower, the counterpressure in contraction part is lower, the resistance is smaller. When the depth-diameter ratio is 4, the counterpressure in contraction part is smaller, the change of drop pressure is stable, the flow wave is small, energyconsumption is small. And moreover, the vortex, formed in the horizontal tube,will affect faraway and effectively stop the particle deposit caused by gravity.