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

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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.