【作者】 柳春清；

【导师】 卞永宁；

【作者基本信息】 大连理工大学 ， 流体力学， 2011， 硕士

【摘要】 作为换热设备的基本结构单元,二维及三维流路内流体的流体力学特性以及质量和热量的传递强化机理等受到了广泛关注。目前,相关的实验及数值模拟研究已经得到了脉动流场下三维波壁管内在不同操作条件下质量和热量传递强化的最佳振动频率,但各个最佳振动频率之间的关系尚未明确。本文主要关注了脉动流场下三维正弦波壁管内的流动特性,重点考察了脉动流场下三维正弦波壁管内的质量传递强化与不同操作条件下的振动频率的关系,并得到不同操作条件下的最佳振动频率,进而明确不同操作条件下最佳振动频率之间的关系,为高效热质传递设备的设计和传递强化技术的科学研究提供参考。本论文的具体内容如下：第一章主要针对国内外已有的相关研究进展进行总结,阐述不同流场下各种形状的二维和三维流路内的流动特点。截至目前的研究成果表明,定常流场下二维和三维流路内的研究结果比较成熟,实验和数值模拟结果基本吻合；而在脉动流场下,相对于二维流路的研究成果,三维流路的研究成果仍显不足,特别在确定三维波壁管热质传递的最佳操作条件方面,尚待完善和深入。第二章介绍了本研究所采用的实验装置、实验原理和相关实验设备的操作方法。实验装置包括波壁管流路系统和电化学测量系统,实验将以相关的流体力学理论为基础,将电化学技术应用于本实验研究得到质量传递速率。第三章给出了相关的实验结果和不同操作条件下的最佳振动频率,进而找到不同操作条件与最佳振动频率之间的关系。实验结果表明,振动频率对质量传递强化有显著影响,不同振动分率以及净流动雷诺数Res条件下皆存在一个获得最大质量传递强化效果的最佳振动频率；提高脉动振动分率有助于传质强化,同时在中等净流动雷诺数Res下可以获得较好的传质强化效果；不同振动分率下最佳振动频率与净流动雷诺数Re。呈递减的线性关系,且随着振动分率的增加,净流动雷诺数Res的影响在增大。上述结果对于实际换热器的传递强化操作具有重要的指导意义。第四章对本研究的成果进行了总结。第五章指明了未来可拓展的研究内容。更多还原

【Abstract】 As the basic structure unit of heat exchanger equipment, the characteristics of fluid mechanics and the mechanism of heat and mass transfer in 2-D and 3-D wavy-walled tube have been focused widely. The current experiments and numerical simulation works out the best Oscillatory frequencies for heat and mass enhancement in 3-D wavy-walled tube under different operational conditions, but the connection of the Oscillatory frequencies between different operational conditions have not been clarified. This investigation mainly focuses on the flow characteristics, the relationships between mass transfer enhancement and oscillatory frequencies under different operational conditions in 3-D wavy-walled tube. Through the obtained data of optimum oscillatory frequencies, the article also demonstrates the relationships between different optimum Oscillatory frequencies under different operational conditions, which provide references to the design of efficient heat and mass transfer equipment as well as the research of technique of heat and mass transfer. The details are as follows:Chapter 1 summaries the development of relevant researches of various scholars home and abroad. It elaborates the flow characteristics in different 2-D and 3-D channels under different flows. The present study shows that the research of 2-D and 3-D channels under steady flow is convincing, and the experimental results comply with the numerical results well; however, the research in 3-D channels under pulsatile flow appears less convincing than that in 2-D channels, it is yet to be improved and extended specially on determining the optimum operational conditions in 3-D channels.Chapter 2 introduces the experimental equipments, principles and related operation procedures. The experimental devices include wavy-walled flow system and electrochemical measurement system. Based on related theory of fluid mechanics, the experiment applies electrochemical technology to measure mass transfer rate.Chapter 3 demonstrates the optimum Oscillatory frequencies, and indicates the relationships between different operational conditions and optimum Oscillatory frequencies through analyzing the experimental results. The experimental results shows that oscillatory frequencies have a significant impact on mass transfer enhancement, it must exist an optimum oscillatory frequency that corresponds to the best mass transfer effect under different oscillatory fraction of the flow rate and net flow Reynolds numbers; Higher oscillatory fraction of the flow rate contributes to a better mass transfer enhancement, and it can obtain better effect for mass transfer enhancement under medium net flow Reynolds number; The optimum oscillatory frequencies show a decreasing linear relationship with Res under different oscillatory fraction of the flow rate, meanwhile, the effects of Res increases with oscillatory fraction of the flow rate increasing. The above results have an important guidance on actual operation of heat exchanger.Chapter 4 summarizes the achievement of this article. Chapter 5 points out the possible contents of future research.更多还原