Effects of Inter-Particle Force on Particle Behavior and Heat Transfer around a Horizontal Tube in a Fluidized Bed

实验研究了颗粒的内聚性及其附聚对水平管周围颗粒行为和传热特性的影响。通过改变流化空气的湿度来控制由于液体桥引起的颗粒间内聚力。通过测量床层压降和目视观察定量评价了粘性颗粒流化床的总体行为，采用3种实验方法研究了粘性颗粒在水平管周围的行为和传热特性。其中之一是同时测量的颗粒的行为（空隙率和颗粒速度）和瞬时局部传热系数在同一位置上的管表面上。其他测量方法是使用微型摄像机从管内部观察管表面上的温度和颗粒。周围的温度分布 ...更多信息 通过使用热敏液晶片使加热的管可视化。并利用Newral网络法计算了换热系数的分布。通过从管内投射激光光片的方法，观察了颗粒和气泡在管内表面的行为，得到的主要结果如下：当颗粒间力随着流化空气的相对湿度增加而增加时，管周围的空隙率变得更高，并且管上表面上的颗粒的运动被抑制，因此，管周围的传热系数明显降低。颗粒间力的增加导致的管周总平均传热系数的降低可以通过使用由床层压降估计的沟流指数来很好地关联。提出了一种从管内投射激光光片的可视化新方法，该方法可以清晰地区分与管壁接触的颗粒和气泡。少

The effects of cohesiveness and subsequent agglomeration of particles on the particle behavior and heat transfer characteristics around the horizontal tubes were experimentally studied. The inter-particle cohesive forces due to a liquid bridge were controlled by changing the humidity of the fluidizing air. The gross behavior of the fluidized bed with the cohesive particles was quantitatively evaluated by measuring the bed pressure drop and visual observation.Three kinds of experimental method were used to study the particle behavior and heat transfer characteristics around the horizontal tube. One of these is the simultaneous measurement of the particle behavior (void fraction and particle velocity) and the instantaneous local heat transfer coefficient at the same location on the tube surface. The other measuring methods are the visualization of the temperature and the particles on the tube surface from the inside of the tube using a micro-video camera. The temperature profiles around … More the heated tube were visualized by using thermosensitive liquid crystal sheet. And the heat transfer coefficient distributions were calculated from them by Newral network method. The behavior of the particles and the bubbles on the tube surface were visualized by throwing a laser light sheet from the inside.The obtained main results are summarized as following : When the inter-particle forces increased as the relative humidity of the fluidizing air increased, the void fraction around the tube became higher and the movements of the particles on the upper surface of the tube were suppressed, and consequently, the heat transfer coefficient around the tube became significantly lower. The decrease of overall average heat transfer coefficients around the tube by the increase of the inter-particle forces can be well correlated by using the channeling index which is estimated from the bed pressure drop. The new visualization method by throwing the laser light sheet from the inside of the tube was proposed and it can clearly distinguish the particles making contact with the tube surface from the bubble. Less