自湿润流体重力热管传热特性

发布时间：2018-05-16 12:46

本文选题：重力热管 + 传热强化　；参考：《山东大学》2015年硕士论文

【摘要】：重力热管是一种高效传热元件,具有结构组成简单、加工制造方便,生产成本低廉等优点,可广泛应用于工业生产的各个换热场合。随着近年来国家对能源环境问题的重视,强化重力热管的传热性能成为重力热管研究的重要热点内容,作者通过查阅相关文献,掌握重力热管强化传热研究现状,现有的强化传热方式可大体分为：采用高效工质、进行管内表面处理及设置管内插件等。其中采用高效工作介质进行重力热管性能强化是当前的研究热点,自湿润流体作为新近提出的一种高效工作介质,在重力热管中的应用研究较少,还不够全面。因而本课题选用自湿润流体作为重力热管工质,对自湿润流体重力热管的传热特性进行深入研究。本文以自湿润流体重力热管作为研究对象,通过改变实验设计参数对其基本传热特性进行了研究,通过与水工质重力热管进行对比,对其强化传热特性、小倾角强化特性及复合强化特性进行了研究。主要研究工作及结论如下：1、通过查阅相关文献,对重力热管强化传热研究现状进行了综述,掌握了重力热管的基本传热理论及自湿润流体的强化传热机理。2、完成了重力热管的加工制造及实验台搭建。制作了两种工质的重力热管,设计并搭建了实验所用的实验平台,确定了热管性能测试实验方案及实验数据处理方法。3、实验研究了自湿润流体重力热管基本传热特性。得出如下结论,重力热管热阻随加热功率、倾角及充液率的增大均先减小后增大；最佳倾角随加热功率的升高而减小；实验得出最佳充液率为热管蒸发段容积的180%左右。4、实验研究了自湿润流体强化传热特性,得出结论如下：自湿润流体能够减小重力热管的启动时间,但启动温度有所升高,随着功率的升高,启动时间及启动温度逐渐接近水工质；水平放置时,自湿润流体降低重力热管热阻、增大了传热极限,大幅改善重力热管性能；垂直放置时对重力热管性能略有恶化。5、实验研究了自湿润流体小倾角强化传热特性,得出结论如下：小倾角时重力热管运行温度、轴向温差及热阻高于水工质热管,但传热极限显著提升,因而相比水,自湿润流体在小倾角下仍有一定应用优势。6,、实验研究了垂直放置时自湿润流体及内螺纹表面结构复合强化作用对重力热管传热特性的影响,得出如下结论：复合强化作用可以降低重力热管运行温度,减小热阻,增大蒸发段及冷凝段换热系数,全面强化重力热管的传热性能。
[Abstract]:Gravity heat pipe is an efficient heat transfer element, which has the advantages of simple structure, convenient manufacturing and low production cost. It can be widely used in various heat transfer situations in industrial production. With the attention paid to energy and environmental problems in recent years, the enhancement of heat transfer performance of gravity heat pipe has become an important hot topic in the research of gravity heat pipe. The existing heat transfer enhancement methods can be divided into: efficient working fluid, tube surface treatment and installation of tube plug-in and so on. It is a hot topic to strengthen the performance of gravity heat pipe by using high efficiency working medium. As a newly proposed high efficiency working medium, self-wetting fluid has little application in gravity heat pipe and is not comprehensive enough. Therefore, the self-wetting fluid is chosen as the working medium of gravity heat pipe, and the heat transfer characteristics of the self-wetting fluid gravity heat pipe are studied in depth. In this paper, the basic heat transfer characteristics of self-wetting fluid gravity heat pipe are studied by changing the experimental design parameters, and the heat transfer characteristics are enhanced by comparison with the water working fluid gravity heat pipe. The characteristics of small dip angle strengthening and composite strengthening were studied. The main research work and conclusions are as follows: 1. By consulting relevant documents, the current situation of heat transfer enhancement in gravity heat pipe is summarized. The basic heat transfer theory of gravity heat pipe and the mechanism of heat transfer enhancement of self-wetting fluid are mastered, and the manufacture of gravity heat pipe and the construction of experimental bench are completed. The gravity heat pipe with two kinds of working fluids was made and the experimental platform was designed and built. The experimental scheme of heat pipe performance test and the experimental data processing method were determined. The basic heat transfer characteristics of self-wetting fluid gravity heat pipe were studied experimentally. The following conclusions are drawn: the thermal resistance of gravity heat pipe decreases first and then increases with the increase of heating power, inclination angle and liquid filling rate, and the optimum inclination angle decreases with the increase of heating power. The experimental results show that the best liquid filling rate is about 180% of the volume of the evaporative section of the heat pipe. The heat transfer characteristics of the self-wetting fluid are studied experimentally. The conclusion is as follows: the self-wetting fluid can reduce the starting time of the gravity heat pipe, but the starting temperature is increased. With the increase of power, the starting time and starting temperature are close to hydraulic quality, the self-wetting fluid reduces the heat resistance of gravity heat pipe, increases the heat transfer limit, and improves the performance of gravity heat pipe greatly. The performance of gravity heat pipe is slightly deteriorated when placed vertically. The heat transfer enhancement characteristics of self-wetting fluid with small dip angle are studied experimentally. The conclusions are as follows: the operating temperature, axial temperature difference and thermal resistance of gravity heat pipe are higher than those of water heat pipe with small dip angle. But the heat transfer limit is obviously raised, so the self-wetting fluid still has a certain application advantage under the small dip angle compared with the water. The influence of self-wetting fluid and the surface structure of the internal thread on the heat transfer characteristics of the gravity heat pipe under vertical placing is studied experimentally. The conclusion is as follows: the combined strengthening effect can reduce the operating temperature of the gravity heat pipe, reduce the thermal resistance, increase the heat transfer coefficient of the evaporation section and the condensing section, and enhance the heat transfer performance of the gravity heat pipe in an all-round way.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK172.4

【参考文献】