溢流式布膜铝板液膜厚度和润湿特性实验研究  

Experimental Study on Thickness and Wetting Characteristics of Liquid Film on Aluminium Plate with Overflow Type Distributor

作　　者：万智华[1,2] 厉彦忠[1] 苏长满[2] WAN Zhihua;LI Yanzhong;SU Changman(School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China;Institute of Building Intelligence,Jiangsu Vocational Institute of Architectural Technology,Xuzhou,Jiangsu 221116,China)

机构地区：[1]西安交通大学能源与动力工程学院,西安710049 [2]江苏建筑职业技术学院建筑智能学院,江苏徐州221116

出　　处：《西安交通大学学报》2020年第4期35-43,共9页Journal of Xi'an Jiaotong University

基　　金：江苏省住房和城乡建设厅科技计划资助项目(2016ZD56)。

摘　　要：为了探索高雷诺数(Re>700)时平板降膜厚度规律和溢流式布膜方式下的润湿特性,设计并搭建了垂直铝板降膜实验台,采用电容测厚技术测量了Re为660~1390时冷态水膜瞬时厚度的变化情况。利用文献数据着重分析了流动长度和Re对平均液膜厚度的影响,并通过图像处理法计算了加湿过程的润湿面积。实验结果表明:在研究工况范围内,随着Re的增大,液膜厚度的最大值、最小值、平均值、标准偏差、波动振幅均存在上升趋势;不同流动长度处液膜厚度存在较大差异,拟合出流动长度L为0.43 m处的平均液膜厚度的经验关联式,计算值和实验值的相对误差控制在±6%范围内;层流向紊流转换的临界Re约为500,临界Re之后的平均液膜厚度随Re的增长速率要高于之前的;在Re为15~200时,润湿比随着Re增加呈现波动增大的趋势,预测平板最小润湿流量约为0.27。A test rig based on falling film on the vertical aluminium plate is designed and built to obtain the film thickness characteristics under high Reynolds number(Re>700)on the plate and the wetting properties with overflow type distributor.The instantaneous film thickness of cold water without heating is measured by the capacitance probe technology under Re ranging from 660 to 1390.Effects of flow length and Re on the average film thickness are emphatically analyzed by comparing with literature data.The wetted area in wetting process is measured by the image processing technology.Experimental results show that the maximum value,minimum value,mean value,standard deviation and fluctuation amplitude of liquid film thickness all show an upward trend with the increase of Re within the studied Re conditions.The thickness of liquid film varies greatly at different flow lengths.An empirical correlation of average liquid film thickness at flow length 0.43 m is obtained by fitting,and the relative errors between the calculation formula and the experimental data are controlled within±6%.Moreover,the critical Re under which the flow patterns transform from laminar flow to turbulent flow is about 500.After the critical Re,the average liquid film thickness increases with the increase of Re at a higher rate than those before the critical Re.When Re is in the range from 15 to 200,the wetting ratio fluctuates and increases with the increase of Re.The minimum wetting rate of the aluminium plate is predicted about 0.27.

关 键 词：降膜 竖直平板 液膜厚度 润湿 溢流式 分布器 

分 类 号：TB657.5[一般工业技术—制冷工程] TK124[动力工程及工程热物理—工程热物理]