MEMS微型回路脉动热管启动、传热及运行机理研究

Micro heat pipes have been a topic of intense research in the academina of heat pipe in recent years due to the significance of applications in cooling of thermal micro-system,including but not limited in microelectronic chip. This research aims to systematically study, both experimentally and theoretically, a novel style of micro heat pipe - - the MEMS micro closed loop oscillating heat pipe (micro-CLOHP). With the aid of high speed visualization study and integrated heating and temperature measurement approach, the start-up behavior and factors affecting the occurrence of start-up of a micro-CLOHP will be investigated. Then, the effects of microchannel geometrical structure, characteristic size, working fluid and gravity on the thermal performance of micro-CLOHPs will be discussed and find a way to achieve bulk circulation flow of working fluids within the closed loop and thus heat transfer enhancement. To reveal the operation mechanism of micro-CLOHPs, several primary driving forces which contribute to the self-oscillation of working fluids in micro-CLOHPs will be confirmed taking into considertion the scale effect, shape effect, as well as the liquid-vapor phase interface characteristics. This research will enrich and develop the theory of OHPs, and lay a theoretical foundation to understand the mechanism of liquid-vapor phase interface motion and thermo-hydrodynamic characteristics within highly confined space coupled with both evaporation/boiling and condensation. Also, it will provide a new approach for the cooling of thermal micro-system, especially in microelectronic chip cooling.

微型热管是近年来国际热管学界研究关注的热点，对包括微电子芯片在内的热学微系统冷却具有重要的应用价值。本项目拟对一种新式微型热管- - MEMS微型回路脉动热管开展系统的实验研究和理论分析，借助高速可视化显微观测手段和集成加热/测温技术，研究确定热管启动发生的条件和过程特征，获得通道结构尺寸、工质种类和重力等对其传热性能的影响规律，寻找工质在热管微通道回路内实现自循环运动以强化传热的有效途径。在综合考虑尺度效应、形状效应和相界面特性影响的基础上，寻找并确定影响热管自激振荡的若干主导作用力，揭示其相变传热运行机理。本项目的研究将丰富和发展脉动热管研究理论，并为理解微尺度受限封闭空间内蒸发/沸腾和凝结相变共存状态下的相界面运动行为和流动传热机制奠定理论基础。同时，也将为热学微系统（特别是微电子芯片）的冷却提供新的思路和方向。

微型热管是近年来国际热管学界研究关注的热点，对包括微电子芯片在内的热学微系统冷却具有重要的应用价值。本项目借助MEMS技术设计并制作了一种高效的微冷却器件——硅基微型脉动热管，通过可视化显微观测手段和集成加热/测温技术，研究并确定了热管启动发生的条件和过程特征，获得了通道结构尺寸、工质种类和重力等对其传热性能的影响规律。首先，借助高速可视化显微观测手段研究了微型脉动热管内工质的相变过程、汽液相界面振荡运动及流型发展演化情况，发现了两种不同的启动模式（无核化和核化启动），并首次观察到热管微通道内的Leidenfrost（莱登佛罗斯特）效应；其次，通过集成加热/测温技术和PWM（脉冲宽度调制）控制方法模拟了芯片“热点”发热特征，由此掌握了微型脉动热管在不同热负荷模式下的自适应调节能力和整体温控性能。同时，提出了毛细管内气/液塞状流（泰勒流）接触角滞后和毛细压降的理论模型以及预测脉动热管运行管径下限（或最小管径）的理论模型，为后续更准确模型的建立以及微型脉动热管的设计制作给出了理论指导。通过本研究，丰富和发展了脉动热管理论，为理解微尺度受限封闭空间内蒸发/沸腾和凝结相变共存状态下的相界面运动行为和流动传热机制提供了理论支持；同时也为热学微系统提供无需外加动力装置的新型高效微冷却方式提供新了思路和方向，对其它微小型汽、液两相传热器件（特别是封闭器件）研究具有很好的参考和借鉴意义。