溢流式筛孔板热水塔内单气泡的可视化实验  

Visualization Research on Bubble in Overflow Sieve Plate Hot Water Tower

作　　者：包泽彬 王亦飞[1] 胡晨辉 于广锁[1] BAO Zebin;WANG Yifei;HU Chenhui;YU Guangsuo(Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education,Institute of Clean Coal Technology,East China University of Science and Technology,Shanghai 200237,China)

机构地区：[1]华东理工大学洁净煤技术研究所煤气化及能源化工教育部重点实验室,上海200237

出　　处：《华东理工大学学报（自然科学版）》2019年第1期23-30,共8页Journal of East China University of Science and Technology

基　　金：国家重点研发计划(2017YFB0602802)

摘　　要：以煤气化渣水回收系统中的蒸发热水塔为研究对象,对热水塔内孔径为5 mm的塔板上单气泡的形成和运动特性进行了可视化实验,借助高速相机和图像处理方法得到了气泡整个生长周期的形变过程及运动特性。实验结果表明:气泡的生长周期分为3个阶段:形成区、上升区和振荡破碎区。气泡等效半径在形成区迅速增大,在上升区和振荡破碎区缓慢增加;气泡长径比在形成区呈衰减变化,而在振荡破碎区变化规律性较差;蒸汽气泡的y向形心运动速率先增大后平稳波动,氮气气泡的y向形心运动速率处于一直增加的状态,但在振荡破碎区的运动规律较差,蒸汽和混合气体气泡在冷凝过程中均出现了中空现象。对于混合气体气泡,氮气流量的增加导致气泡形成和破碎的时间变短,阻碍了蒸汽传热冷凝。Based on the evaporating water tower of the circuit bottom ash sluicing system,the formation and movement of the single bubble emerging from an orifice with diameter of 5 mm in the middle of tray were investigated by visual experiments,with the water flow rate of 150,200,250 L/h,the steam flow rate of 5 kg/h,and nitrogen flow rate of 0.1632 kg/h and 0.3264 kg/h.The life time of bubbles was recorded by high speed camera and the characteristics of bubble deformation and movement were obtained by image processing software.The results show that the life time of bubble is divided into three parts on the basis of pictures:formation region,rising region and oscillation region.The bubble deformation and movement are obtained in each part.The equivalent radius of bubble increases rapidly in the first region because of the gas influx and grows more slowly in the latter two regions.The aspect ratio of bubble changes from large to small in the formation region,while it changes irregularly in the oscillation region.The vertical velocity of centroid of steam bubble increases at the beginning and then fluctuates.However,the vertical velocity of centroid of nitrogen bubble increases over time due to the lacking of mass transfer.The motion law of bubble in the oscillation region is hard to describe.The hollow phenomenon is found in both steam and mixture bubbles through the condensing process in the experiment.The effect of non-condensable gases to the transmission process is also discussed.With the increasing of the nitrogen flow rate,the time of formation and oscillation region decreases for the mixture gas bubble,leading to the deterioration of heat transfer in the tower.The result of this paper can be a theoretical guidance for evaporating hot water tower operation.

关 键 词：塔器 气泡 气泡运动 可视化实验 不凝性气体 

分 类 号：TQ026.2[化学工程]