Development of Cooling Technology by Using a Very Minute Pin-Fin and a Micro-Channel

本研究有两个方面。一种是改进传统的空气冷却技术，使用极小的针翅，尽管这种技术存在热接触阻力。二是利用微通道开发下一代冷却技术。这种技术的优点是排除了热接触电阻。在翅片式换热器实验中，采用刻蚀工艺，以不锈钢片为材料制作测试芯。每个大头针有一个正方形的横截面，其边长为50至200mm。采用改进的单吹瞬态测试方法对其换热性能进行了测试。换热结果表明，由于流动显示实验观察到的振荡流动行为，特定引脚布置的换热性能有所提高。在微通道实验中，一束非常小的管子被用作测试核心。我们使用了直径分别为135mum和4mum的不锈钢管和玻璃管两种类型的测试芯。压降实验在滑移流（0.01<Kn<0.1）和过渡流（0.1<Kn<10）范围内进行。实测压降与经验关系吻合较好。在换热实验中，采用了一种新的稳态方法。为了计算换热系数，采用控制容积法进行了二维热传导分析，在计算中寻求满足实测温度的换热系数。进风口和出风口温度对换热系数的变化没有明显的影响，因为目前的微型管的换热系数很高。数值分析表明，采用等通量加热条件可以改善实验结果。

This study has two aspects. One is to improve the conventional air-cooling technology by using very minute pin-fins although this technique suffers from thermal contact resistance. The other is to develop the next generation cooling technology by using a micro-channel. This technique has the advantage of exclusion of the thermal contact resistance.In the pin-fin heat exchanger experiments, the test core was manufactured from stainless sheet by using the etching technology. Each pin had a square cross section of which side length was 50 to 200mum. The heat transfer performance was measured by using the modified single-blow transient testing method. The heat transfer results showed the increased performance for the specific pin arrangement because of the oscillating flow behavior which was observed by the flow visualization experiments.For the micro-channel experiments, a bundle of very minute tubes was used as a test core. We used the two types of test cores made of stainless and glass tubes of which diameters were 135mum and 4mum, respectively. The pressure drop experiment was performed within the regime of the slip flow (0.01<Kn<0.1) and the transition flow (0.1<Kn<10). The measured pressure drop showed good agreement with the empirical correlation. In the heat transfer experiment, a new steady-state method setup was used. In order to calculate the heat transfer coefficient, the two-dimensional heat conduction analysis was performed by using the control volume method and the heat transfer coefficient satisfying the measured temperatures was sought in the computation. The inlet and outlet air temperatures did not give a discernible difference for the change of heat transfer coefficient because the heat transfer coefficient was very high for the present minute tubes. The numerical analysis suggested the improvement in experiment by adopting the isoflux heating condition.