【作者】 李楠；

【导师】 马学虎；

【作者基本信息】 大连理工大学 ， 化学工程， 2015， 硕士

【摘要】 脉动热管是一种新型高性能传热设备,无传统热管的毛细芯结构,由包含蒸发和冷凝的毛细管或多个U形槽道组成。因其结构简单、易于加工制造、传热量高等特点,有着广泛的用途,在大功率LED散热方面有着很好的应用前景。脉动热管的通道直径较小,工作介质在通道内部形成间隔的汽弹和液弹,蒸发段和冷凝段的温度梯度引起的压差是液弹脉动的驱动力。由于脉动热管集显热传热传递和潜热传递于一体,管内复杂的汽液两相流致使目前其机理依然不是十分清晰。为此,许多学者针对影响脉动热管性能的影响因素展开了广泛研究。脉动热管中液弹的运动行为对其传热性能有着至关重要的影响作用,通过改善液弹的脉动状况可以有效提高脉动热管的工作效果。因此,本文基于改变脉动热管的通道结构来研究其影响作用。本文在均一矩形通道结构热管研究的基础之上,设计加工了另外四种不同结构的脉动热管。在通道中引入了半圆形截面结构和不同水力直径的渐扩渐缩通道结构,完成了不同充液率条件下的可视化实验和传热实验。同时,设计了小型多通道双面矩形热管设备,研究了固定充液率条件下,倾斜角度对热管传热性能和启动性能的影响。通过以上研究,为提高脉动热管传热性能和不同安装环境下的适用性提供实验支持,并探索热管在大功率LED散热方向的应用可行性。实验研究表明,矩形截面结构的脉动热管由于具有尖角结构,能够促进液弹的脉动并改善蒸发段的液体回流情况,因此具有更好的传热性能。渐扩渐缩通道中液体运动时受到两侧不同壁面的影响作用而出现非对称型汽液相界面,并促进了液体内部的掺混作用,同时蒸发段凹槽内液体的残留会减小干壁面积,促进液体蒸发。相比于1#均一通道热管,3#渐扩渐缩热管在充液率为30%、50%和70%时传热性能分别提高了4%～32%、4%～25%和6%～18%。然而,水力直径较小的4#热管,液弹的受到较大的阻力作用,导致其传热性能变差。针对双面矩形通道热管的研究发现,倾斜角度越大,重力在液弹运动方向上的分力越大,热管传热性能越好。加热功率越大,热管启动时间越短,稳定运动时的工作温度越高。更多还原

【Abstract】 Pulsating heat pipe (PHP) is a new type of heat pipe with high efficience of heat transfer performance. The considerable interest in sucha heat pipe is due to its simple structure and high heat transfer performance. It has a promising future for dissipating high grade heat in high power LED field. The inner diameter is small egough so that there are many liquid slugs and vapor plugs in the tube. The temperature difference between the evaporation section and the condensation secetion is the driving force for the movement of the liquid slugs. The two-phase system which embodies multi-disciplinary physics is so complicated that the investigation on pulsating heatpipes is still ata primary stage. Forthis, many scholars made a number of studies in this field. The movement of liquid slug is very important for the heat transfer performance. We can change the movement condition to improve the efficiency of the pulsating heat pipe. Therefore, this dissertation aims to discover the effects of the structure of the pulsating heat pipes.Four kinds of different heat pipes were designed on the basis of an pipe with uniform rectangular channel structure. There were periodic expansion-constriction cross-sections in the channels, and experiments with different charging ratios were conducted. Besides, a new kind of pulsating heat pipe with two sides of channels were designed. The effects of inclination angles for the heat transfer performance and start-up were investigated. These studies can provide experimental support to improve the applicability of pulsating heat transfer performance and different installation environments and the feasibility of the application of high-power LED heat pipe cooling field.A series of experimental studies have shown that because of sharp corners, a rectangular cross-sectional structure of the pulsating heat pipe structure can promote and improve the movement of liquid slugs and the liquid backflow in evaporating section, so it has a better heat transfer propertie. In the periodic expansion-constriction cross-sections in the channels, the forces were different on the both sides. That causes asymmetric vapor-liquid interface and promotes the mixing effect of the liquid inside. Besides, the residual liquid in the evaporator section grooves will reduce dry wall area and promote liquid evaporations, helping improve the pulsating heat transfer performance. Compared with 1# heat pipe, the heat resistance of 3# heat pipe reduced 4%～32%,4%～25% and 6%～18%. However, when the hydraulic diameter is small, the liquid movement is hindered subject to greater resistance, leading to deterioration of the heat transfer performance.In the research for the double-sided rectangular channel heat pipe, the greater the angle, the greater of the gravity on the liquid, and the better the heat transfer performance. The larger heating power, the shorter the start-up time of the pilsating heat pipe and the higher the operating temperature when steady movement occurs.更多还原