Abstract: De-ionized water, used as working fluid, flows through a staggered micro-cylinders-group, which is made up of micro-cylinders with hydraulic diameter of 500 μm and height of 500 μm, and an experimental study is performed on the influence of tip clearance on heat transfer efficiency in the staggered micro-cylinders-group.Using an electricity heater, the flow rate and the temperature difference between the inlet and the outlet of micro-cylinders-group are measured and the friction factor and Nusselt numbers can be obtained over Reynolds numbers ranging from 8 to 400.The relationship between heat transfer efficiency and Reynolds number is grasped.The experimental results indicate that the tip clearance has a little influence on flow resistance and Nusselt number at low Reynolds number and these influences become apparent with the increase of Reynolds number.The heat transfer efficiency of micro-cylinders-group heat sink increases rapidly with Reynolds number for a start, and it increases slowly with the increase of Reynolds number, even begins to drop with the further increase of Reynolds number.However, the existence of the tip clearance promotes heat transfer efficiency in the micro-cylinders-group heat sink, though it reduces Nusselt number based on the experimental results.

Key words: micro-cylinders-group, tip clearance, heat transfer efficiency, flow resistance, Nusselt number

摘要： 以去离子水为工质，实验研究了直径为500 μm、高度为500 μm以叉排排列的微柱群内顶部缝隙对传热效率的影响规律。采用电加热棒进行加热，测量微柱群板Reynolds数在8～400之间在不同顶部缝隙时的进出口温度与流量，获得微柱群内流动阻力系数及Nusselt数，进而掌握微柱群内传热效率与Re关系。研究结果表明，在较低Re时，顶部缝隙对微柱群内流动阻力和Nu影响较小；随着Re增加，其对流动阻力与Nu的影响越来越显著。微柱群传热效率一开始随着Re增加而快速增加，随着Re进一步增加，其传热效率开始缓慢增加甚至出现下降。根据实验结果，尽管微柱群顶部缝隙存在降低了其内Nu，但提高了微柱群的传热效率。

关键词: 微柱群, 顶部缝隙, 传热效率, 流动阻力, Nusselt数