【作者】 商福民；

【导师】 刘登瀛；

【作者基本信息】 华北电力大学（北京） ， 热能工程， 2009， 博士

【摘要】 随着高新技术的发展,许多设备单位面积热负荷越来越高。而这些承受高热负荷场合又常常需要冷却,并要求换热设备小型或微型化。传统热管因微型化将受到携带极限限制而面临挑战,自激振荡流热管的应用有望解决这一技术难题。本论文针对回路型自激振荡流热管的热传输特性,运用实验研究的方法,率先从被动强化传热的角度出发,通过自激振荡流热管分别采用非均匀截面结构、不等径结构、管内工质为Cu-H2O纳米流体时的热传输功率以及对壁面温度特性的对比分析,研究其热传输及自激强化传热特性。在此基础上,运用理论分析的方法,对自激振荡流热管内的物理过程进行合理的简化,构建其内部流动及传热的数学模型,通过计算和对比分析,研究其热传输及自激强化传热特性。实验自激振荡流热管材料为黄铜,总垂直高度480mm。其中,冷凝段150mm,加热段和绝热段共330mm,总弯头数8个,热管倾角55°。非均匀截面结构是在内径3mm等截面热管基础上,将加热段和绝热段加工成垂直交错布置、断面为椭圆形结构型式,工质为蒸馏水,充液率为42%。不等径结构同样是在内径3mm等截面热管基础上,将热管中部相间管段变成内径1mm的结构型式。其中,不等径段长度220mm,工质为蒸馏水,充液率74.5%。工质为Cu-H2O纳米流体的热管内径2mm, Cu-H2O纳米流体的充液率分别为40%、43%、58%、60%、67%,Cu粉体积份额分别对应1.0%、0.50%、0.30%、0.10%、0.05%。实验研究得到的主要结论：(1)自激振荡流热管采用非均匀截面结构可以起到强化传热的作用,但加热功率必须要达到使热管的循环动力足以克服非均匀截面所造成的流动阻力。(2)自激振荡流热管采用不等径结构可以达到强化传热的目的,在中等热负荷情况下,强化传热效果比较明显,尤其是热源在变径区域的情况。(3)Cu-H2O纳米流体作为自激振荡流热管工质,在很大程度上可以起到强化传热的作用,但只是辅助性的,而决定其热传输功率的关键因素应是充液率。理论分析方面,主要研究管径、充液率、冷热端温差等因素对管内工质的受力、传热及振荡特性的影响。考虑到前期实验研究工作具体情况,理论研究重点放在加热段传热特性的计算分析上,而被动强化传热特性主要针对非均匀截面结构进行了研究。通过对比分析,理论计算结果与相对应的实验研究结论基本符合。结合下一步的研究工作,对自激振荡流热管技术在太阳能热利用、电子元器件散热以及低温余热回收等领域的应用进行了探讨。更多还原

【Abstract】 With the development of modern new high-technology, higher and higher thermal requirement per unit on many devices is demanded because of the miniaturization or microminiaturization of cooling or heat exchanging equipments in the high heat load situation. Traditional heat pipe is facing the challenge for the micro-sized devices, and the application of self-exciting mode oscillating-flow heat pipe is expected to solve this technical problem.In this paper, experiment is performed to investigate the characteristics of heat transfer and Self-Exciting enhanced heat transfer of the looped uniform SEMOS HP. The heat transfer characteristics were analyzed by comparing the wall temperatures of the SEMOS Heat Pipe with uniform structure, non-uniform structure, and the pipe with Cu-H2O nano-fluids as thermal exchanging medium. Then, by using theoretical analysis, it simplifies the physical process of SEMOS HP and builds the internal flow and heat transfer mathematical model, and then qualitative research also has been done on heat transfer and Self-Exciting enhanced heat transfer characteristics by calculating and comparing analysis.In the experiment, the material of self-excited oscillation flow heat pipe was brass, the total vertical height was 480mm, and the condensation section was 150mm, heating and insulation section were 330mm in all, the total numbers of elbows is 8, and heat pipe inclination is 55°. Non-uniform cross-section structure is based on the uniform cross-section heat pipe with 3mm internal diameter, the heating and insulation section is changed into vertical segment staggered layout, the cross-section was oval-shaped structure, the working fluid inside the heat pipe was high-purity distilled water, filling rate of working fluids was 42%. For the non-uniform heat pipe, the main part diameter is 3mm also, the central tube sections is changed into lmm diameter. The length of the non-uniform section was 220mm; the working fluid was high-purity distilled water, filled rate 74.5%. For the Cu-H2O nano-fluid heat pipe, the inner diameter of 2mm, Cu-H2O fluid-filled nano-fluid rates is 40%,43%,58%, 60%,67%, the volume fraction of Cu were 1.0%,0.50%,0.30%,0.10%,0.05%, respectively.The main conclusions of experimental research: (1) Self-excited oscillation flow heat pipe using non-uniform cross-section structure can achieve the purpose of enhancement of heat transfer, but the heating power must be high enough, so that the circulation power can overcome the flow resistance caused by the non-uniform cross-section.(2) The non-uniform structure self-excited oscillation flow heat pipe can enhance heat transfer performance, this effect is much better on medium heat requirement and especially the heat source is located in non-uniform structure section.(3) Cu-H2O nano-fluid as self-excited oscillation heat pipe working fluid can also help to enhance heat transfer, but complementary, the key factor to determine its heat transfer performance should be the filling rate.The target of this theoretical analysis is to investigate the working fluid stress, heat transfer and the performance oscillation influenced by diameter, the rate of fluid-filled, temperature difference between the hot and cold-side and so on. The emphasis is the calculation and analysis of heat transfer characteristics of heating section. For passive enhanced heat transfer, the studies focus on calculation and analysis for the non-uniform section. Through comparative analysis theoretical calculation results tallied basically with the corresponding experimental conclusion.Combined with the next step researches, the applications of self-excited oscillation flow heat pipe on solar thermal technology, electronic components heat transfer and low temperature waste heat recovery are discussed.更多还原