通气环套内垂直圆柱表面核沸腾传热研究  

Nucleate Boiling Heat Transfer on a Vertical Cylindrical Surface in the Annulus with Air Introduction

作　　者：苗君[1] 王军[1] 谢建[1] 沈自求[1] 

机构地区：[1]大连理工大学化学工程研究所,辽宁大连116012

出　　处：《高校化学工程学报》2003年第2期134-140,共7页Journal of Chemical Engineering of Chinese Universities

基　　金：国家自然科学基金资助项目(50176007)

摘　　要：研究了带有同心套管的垂直圆柱形加热表面在环隙中通入空气时的核沸腾传热性能.结果表明,通入空气使沸腾传热系数有所提高,并且加热表面温度有所降低.通入空气也会增强自然对流传热,而且这种增强幅度比沸腾时更大.在实验条件下,通气可使沸腾传热系数提高39.63%～80.50%,壁面温度可降低1.39～2.58℃,自然对流时通气可提高传热系数380.09%～482.52%.为此对上述实验结果用扰动增强和'界面汽化热阱'效应增强的机理来进行了分析.实验还在恒定热流率下考察了气速对沸腾传热系数的影响.结果表明, 沸腾传热系数随气速提高先增加后降低.用Mashima 和Ishii的两相流模型进行了计算,结果说明了这种气速影响的原因是由于由泡状流向弹状流流型的转变.Nucleate boiling heat transfer on a vertical cylindrical heated surface with a concentric outer tube was investigated when air was introduced into the boiling liquid. It was found from the experimental results that air introduction can significantly enhance the boiling heat transfer and make the temperature of heated surface lower. Also, the experimental results obtained at a liquid temperature below the boiling point showed considerable enhancement of convective heat transfer by the air introduction and the heat transfer enhancement caused by the introduction of air in this case was larger than that in nucleate boiling. Over the whole test range, the introduction of air can increase 39.63% to 80.50% in the boiling heat transfer coefficient and decrease 1.39-2.58°C in the temperature of heated surface. Also, the introduction of air makes 380.09%-482.52% increase in the convective heat transfer coefficient. The results were analyzed by two heat transfer enhancement mechanisms, i.e. the heat transfer enhancement by an increased disturbance and the enhancement by interfacial vaporization heat sink effect. Heat transfer coefficient was also measured at different air superficial velocities when heat flux remained constant. The experimental results showed that the heat transfer coefficient increases with the increase air velocity at first and then a decrease in heat transfer coefficient is observed with a further increase in air superficial velocity. It can be proved by the result simulated by using Mashima and Ishii two-phase model that the effect of further increase of air superficial velocity will decrease the boiling heat transfer is due to the change of the flow pattern from the bubble flow to the slug flow.

关 键 词：通气 环套 垂直园往表面 核沸腾传热 界面汽化热阱 

分 类 号：TQ021.3[化学工程]