【作者】 郭健；

【导师】 贾力；

【作者基本信息】 北京交通大学 ， 工程热物理， 2012， 硕士

【摘要】 随着目前电子芯片的集成度越来越高,传统的散热方式已经逐渐开始无法适应小空间和高热流密度下的散热需求,微通道散热作为一种新型高效的散热方式,目前在国际上具有很高的关注度。本文利用商业软件Ansys-CFX用数值模拟的方法,系统地研究了不同截面尺寸、不同加热功率和不同的入口Re下微通道中液体单相流动和换热特性,热入口段中温度边界层较薄,因而对流换热强度较高,对于微通道中液体流动的入口段分析对于后面微通道的设计具有十分重要的意义。文中重点分析了不同的宽高比、入口Re和加热功率下的流动及热入口段的当量长度。根据对200μm*700μm、200μm*500μm和200μm*200μm的矩形截面长直微通道中水的流动及热入口段的分析,设计了由这三种微通道结构组成的组合型微通道,通道宽度逐级缩小,一方面由于在通道联接处采用通道错位布置的方式,能够使得流体在经过每个通道联接处时破坏边界层,使流动重新发展,充分利用入口效应有效地增大对流换热系数,同时由于沿流动方向上对流换热面积也在逐级增大,因而能有效地改善通道底面上沿流动方向的温度分布不均现象；另一方面虽然由于错位以及流动的入口段所占比例增大会使流动的压降增大,但是由于通道中有较大当量直径的通道,因此系统整体的压降相对较小。设计并搭建了实验台,对三种矩形长直微通道和组合型微通道的流动和传热特性进行了实验研究,分析了入口Re数,加热功率对压降、摩擦阻力系数、对流换热系数、Nu数和固体壁面温度的影响。发现在相同的入口Re数和加热功率下,组合型微通道的换热系数略低于200μm*200μm的矩形长直微通道,但是压降却远远低于长直通道。更多还原

【Abstract】 With the development of IC, it’s very hard for the traditional cooling technology to cool down the element with high heat flux density in narrow space. As a new cooling technology, heat transfer in microchannels gets more international attention.Ansys-CFX is used to simulate the single-phase liquid flow and heat transfer in microchannels with different aspect ratio in the condition of same Rein and heat flux. Because the thermal boundary layer is very thin in the thermal entrance region, the heat transfer coefficient is very high in this region. So the investigation of entrance region is significant. The length of flow and thermal entrance region is investigated in different conditions in this paper.According to the result of entrance region of200μm*700μm,200μm*500μm and200μm*200μm rectangular microchannels, a new structure microchannel which combines three rectangular microchannels is designed. Staggered microchannels destroy the thermal boundary layer and the heat transfer area increase along the flow direction. So the heat transfer is enhanced and the temperature on the heating surface is more uniform. Although the pressure drop is larger in flow entrance region which is longer in this combined microchannel, the total pressure drop is smaller than200μm*200μm rectangular microchannel.The effects of Rein and heat flux on pressure drop, frictional factor, heat transfer coefficient, Nu and the temperature on the heating surface are experimental investigated. The combined microchannel gets very high heat transfer coefficient which is similar to that of200μm*200μm rectangular microchannel with smaller pressure drop.更多还原