【作者】 刘蕾；

【导师】 解国珍；

【作者基本信息】 北京建筑工程学院 ， 供热、供燃气通风及空调工程， 2010， 硕士

【摘要】 本文通过建立脉动热管性能测试试验台,研究分析了脉动热管不同流型流态对应的工质温度振荡曲线特征,并对脉动热管的运行状态进行了判定与分析。结合流型的变化,研究了变充液率、倾角、加热/冷却流体质量流量,对脉动热管的热输运特性的影响。进而,通过对单一工质添加纳米微粒的途径,研究了脉动热管热输运特性的强化方法。本文首先对脉动热管管内工质的受力进行了初步分析,通过对热电偶合理的布置,实现了对工质受热后的流型流态的非可视化判定:通过温度信号的输出,在不同加热范围和充液率下发现了泡状流、弹状流、塞状流及环状流,并结合所测量的温度值进行了工质流型的机理性分析。进一步结合绝热段温度测点采集值的特征及变化,以及各热电偶布置点的温度采集值特征对脉动热管的运行状态进行了非可视化的判定,并得出判定脉动热管启动和稳定运行的判据。为判定单元式脉动热管的运行及工作状态提供了新的依据,为热管应用于制冷、空调、热能回收等热输运设备寻找最佳传热效率和相应的运行工况提供了有效的实际判定方法。在脉动热管热输运性能的试验研究中,通过改变脉动热管工质的充液率、放置倾角、加热流体进口温度及加热/冷却流体冲刷脉动热管外管壁的流速等,对影响脉动热管运行的几种因素进行了研究。研究发现,当脉动热管启动后,热传输功率随着充液率、倾斜角度的增大而增大;充液率较小、倾斜角度较小时,脉动热管可以在较低的加热流体进口温度下启动。最后,在添加纳米微粒的试验中发现,在单一工质中添加纳米微粒可以大幅度的提高脉动热管的单位面积热传输功率,降低脉动热管的热阻。并且在一定条件下,可以较大幅度的降低脉动热管起振所需的加热流体进口温度,在实现强化传热的同时,还可以降低对加热/冷却介质温差的要求。为进一步应用脉动热管于低温差热输运(例如:空调热回收)装置探索了有用的途径。更多还原

【Abstract】 Pulsating heat pipe(PHP)‘performance test rig was established to investigate the relationship between the flow patterns and the characteristics of oscillating curves of temperature, and the operation state of PHP was analyzed and judged through non-visual method. By combining with the change of the flow pattern, the factors which affected the thermal transport properties of PHP, such as fill ration, inclination angle, the mass flow rate of heating/cooling fluid were studied in this paper. Furthermore, the heat transfer enhancement of PHP was studied by adding nano-particles into PHP working fluid.First, the force of PHP working fluid was preliminary analyzed. Then, through the proper arrangement of thermocouples, the method of determining PHP operating states of PHP by means of non-visualization was obtained: through the output of the temperature sample signal, the bubble flow, slug flow, pushing flow, annular flow was found, and the mechanism was analyzed, which are associated with the temperature measurement values. Further, a new way was used for the first time to determine the PHP’s work states, which includes how to determinate both the start-up stage and the steady stage by the means of non-visualization that is relied on the temperature values of interface between the heating section and cooling section of PHP. This lays a foundation for PHPs’practical used in refrigeration, air conditioning, heat recovery equipment to determine the optimum operating state.The influence of some factors on the thermal transport performance of PHP has been researched. The factors include the working fluid within different fill ratio, inclination angle of PHP heat exchanger and the mass flow rate without heating medium in the heat section and cooling medium in the cooling section. The experimental results show that when the PHPs startup, the heat transfer quantity is increased with fill ratio of working fluid and inclination angles; PHP could startup at a lower heating temperature when the fill ratio and inclination angle at a lower value.Finally, in order to improve the heat transfer capacity of PHP, a kind of nano-particles A was added into a pure working fluid to form a miture.. Experiments with the mixed working fluid found that the heat resistance decreases and the heat transfer capacity increases. Moreover, the inlet temperature of heating medium is significantly reduced under a certain conditions. Therefore, adding nano-particles into the working fluid of PHP could enhance heat transfer and improve the thermal transport performance of PHP, and at the same time reduced the difference of heating and cooling medium temperature. It lays a foundation for the further research the performance of PHP used in low-temperature differential thermal transport, for example: air-conditioning heat recovery devices.更多还原