狭缝通道内核态沸腾中的气泡动力学研究  

Study of the Bubble Kinetics in Nucleate Boiling Inside Narrow Gap Passages

作　　者：郭雷[1] 张树生[1] 程林[1] 陈雅群[1] 

机构地区：[1]山东大学热科学与工程研究中心,山东济南250061

出　　处：《热能动力工程》2011年第3期299-303,371,共5页Journal of Engineering for Thermal Energy and Power

基　　金：国家重点基础研究发展计划(973)基金资助项目(2007CB206900)

摘　　要：为加深对狭缝通道内核态沸腾气泡动力学机理的探索,对宽度为2 mm的I-形和Z-形两种不同截面形状的狭缝通道内核态沸腾展开研究,通过数值模拟的方法探究不同壁面接触角对气泡生成及长大过程的影响,不同狭缝形状与流动压降的关系,计算中考虑了重力、表面张力和壁面黏附的作用。发现:壁面接触角的不同对气泡的形态有很大影响,壁面接触角越小,产生的气泡越趋近于圆形,气泡脱离壁面的时间越短,反之,气泡越难脱离壁面;接触角的变化对换热系数也有影响,壁面接触角越大,气泡覆盖的面积越多,壁面热阻越高,传热系数降低;表面张力在狭缝通道沸腾换热过程中所起的作用要远远大于重力;气泡的成核对边界层产生强烈的扰动,泡底微层的存在具有强化换热的作用;Z-形通道较I-形通道换热系数有所提高,但流动压降明显增加。To deepen the exploration of the mechanism governing the bubble kinetics in nucleate boiling inside narrow gas passages,studied was the nucleate boiling in narrow gap passages of two different sectional shapes,i.e.I-shape of 2 mm wide and Z-shape.By adopting a numerical simulation method,the influence of different wall surface contact angles on the bubble formation and growth process and the relationship between the gap shapes and flow pressure drops were investigated.During the calculation,the effect of the gravity force,surface tension and wall surface adhesion were taken into consideration.It has been found that the wall surface contact angles exercise a very big influence on the morphology of the bubbles.The smaller the wall surface contact angle,the more close to a circle the bubbles produced and the shorter the time for the bubbles to depart from the wall surface.Contrarily,it is more difficult for the bubbles to depart from the wall surface.Any change in the contact angle also influences the heat exchange coefficient.The bigger the wall surface contact angle,the more the area covered by the bubbles,the bigger the heat resistance of the wall surface and the smaller the heat conduction coefficient.The surface tension plays a role far bigger than the gravity force in the boiling heat exchange in the gap passages.The nucleation of bubbles will lead to a strong disturbance to the boundary layer.The existence of the tiny layer at the bottom of the bubbles can function to intensify the heat exchange.The heat exchange coefficient of the Z-shaped passage is somewhat improved compared with that of the I-shaped passage and the pressure drop in the flow process,however,increased conspicuously.

关 键 词：核态沸腾 狭缝通道 气泡动力学 

分 类 号：TK124[动力工程及工程热物理—工程热物理]