汽-液-固三相循环流化床蒸发器的可视化分析

在热模条件下,采用电荷耦合器件图像测量和处理系统,对汽-液-固三相循环流化床蒸发器内固体颗粒的运动、分布及相应的传热特性,进行了可视化研究．热通量的变化范围为3150～5 825 w·m~(-2),固体颗粒含率的变化范围为O％～2％．研究中定性地分析了由启动到正常运行的不同阶段,汽-液-固三相循环流化床蒸发器内的流动和传热特性．结果表明,汽-液-固三相循环流化床蒸发器的启动阶段是一个非稳态过程;在汽-液-固三相循环流化床蒸发器的稳态操作过程中,加热管可分为液-固两相段和汽-液-固三相段;固体颗粒的加入,增加了沸腾段的高度,并且对产生的汽泡有破碎作用;加热管中固体颗粒平均轴向运动速度低于循环管,而固含率高于循环管．

Visualization Analysis of Vapor-Liquid-Solid Three-Phase Circulating Fluidized Bed Evaporator

In the condition of heating, by using the charge coupled device ( CCD) image measurement and dealing system, the visualization study was made on the movement, distribution and heat transfer of the solid particles in the vapor-liquid-solid three-phase circulating fluidized bed evaporator( CFBE). The heat flux varied from 3 150 W ?m ~(-2) to 5 825 W ?m ~(-2) , and the additive solid particle holdup varied from 0% to 2%. The characteristics of different operating periods in the vapor-liquid-solid three-phase CFBE were qualitatively analyzed. The results show: the start-up period of the vapor-liquid-solid three-phase CFBE is an unsteady progress; in the steady operating progress, the heating tube can be divided into vapor-liquid-solid three-phase section and liquid-solid two-phase section; the additive solid particles raise the height of boiling section, and also may break up the bubbles; the mean axial velocity of solid particles in the heating tube is higher than that in the circulating tube, while the solid particle holdup is lower than that in the circulating tube.