搖擺式散熱片之熱傳性能研究

Abstract

振動發熱物體是一個有效地增加熱傳遞率的方法，散熱鰭片擺動速率較大時，會在鰭片上表面與下表面交錯形成回流區和再附著區，並逐漸往下游遷移，使得原本附著在鰭片上之速度和溫度邊界層受到擾動而被破壞和縮小，熱傳效果會提升。 本文即以實驗對自製之搖擺式散熱片進行熱傳分析，此動態散熱鰭片是以厚度15μm之極薄銅片為鰭片的材質，使空氣流經鰭片時能誘導鰭片在流場中振動，並與傳統固定式之散熱片作比較，但因實驗中所有種類的搖擺式散熱片其熱傳效能並未如預期中的理想，故再以數值模擬輔助分析實驗結果，討論動態散熱片效果不理想的可能原因，結果發現實驗中擺動式散熱片的散熱效果反而比傳統固定式散熱片差的原因，是因為非一體成型與鰭片過薄對散熱性能的負面影響，已經蓋過鰭片擺動對散熱性能的正面影響，故熱傳效果無法有效提升。

It is an effective way to enhance the heat transfer rates by oscillating a heat source. For fins swinging in a flow, the velocity and thermal boundary layers may be contracted and disturbed as the fins swing with a large speed, and the heat transfer rates are remarkably affected by the swinging speed and amplitude of the fins. This study investigates the heat transfer ability of heat sinks with swinging fins experimentally, those finned heat sink were made by installing extremely thin copper fins (15μm) in the heat sink, and these fins may swing back and forth in a flow as the fluid flows through them, compared the heat transfer performance with the heat sink with fixed fins. But in the results of the experiments, the heat transfer ability of all kinds of the heat sinks with swinging fins is not as good as expected. So the present study discuss the results of the experiments further by numerical simulations, the results show that the reason of the worse heat transfer ability of heat sink with swinging fins is that the contact resistance between the interfaces of the fins and base of the heat sink, and another reason is that the fins are too thin to transfer enough heat from base to fins. The negative influence of those two reasons on heat transfer covers up the positive one of the swinging fins. So the heat transfer performance of the heat sinks with swinging fins is not better than that of the heat sinks with fixed fins in the experiments.