本實驗為仿生模擬人肺之氣管幾何特徵，藉以提高脈衝流熱傳效能，利用交錯排列之附著菱形柱鰭與分離六角形柱鰭陣列，組成新穎混合式柱鰭陣列，模擬人肺中氣管。實驗控制時間平均雷諾數(Re)為1500、2000、5000、10000、15000和20000，於通道入口處以1/4、1/6和1/12 Hz的頻率局部釋放氣流，形成脈衝流之進口條件，相對之史屈霍數(Sr)介於0.0004-0.017之間。於各組測試Re和Sr數，管道進口之釋放氣流週期分別為1/4、1/2或3/4脈衝週期，藉以改變脈衝波形。實驗結果證明紐塞數與凡寧摩擦係數受到脈衝波形、脈衝頻率、雷諾數影響，並引用一組實驗數據，說明脈衝流對管道全流域紐塞數分佈及凡寧摩擦係數造成之影響。研究結果發現，持續增加Sr，管道端壁面之面積與時間平均紐塞數出現先降後升之變化趨勢，Sr=0.017時，其面積與時間平均紐塞數高於穩流條件量測之面積平均紐塞數。脈衝波形對熱傳係數之個別影響則隨Sr變化而改變。將面積與時間平均紐塞數除以穩流條件量測之紐塞數後，發現Re對此標準化紐塞數影響些微。受到脈衝流引生複雜流場之影響，增加Sr，脈衝流之凡寧摩擦係數亦自穩流基準值先降後升。相對平滑圓管穩流之熱傳性能，本研究柱鰭陣列，產生顯著之熱傳強化增益。考量相對熱傳強化之壓損增益所估算之熱性能因子，於Re>5000之條件均大於1，提供定泵功率條件之高效率熱傳強化。基於本研究建置之時間與面積平均紐塞數和凡寧摩擦係數之數據庫，推導出兩組實驗公式，估算本柱鰭通道於穩流與脈衝流條件之時間與面積平均紐塞數和凡寧摩擦係數，提供相關工程設計應用。

The present experiment study adopts the bionic simulation of the tracheal geometry of the human lung to emulate the flow pathways through a rectangular channel aimed at improving the heat transfer performance of pulsating flow. To formulate the flow pathways similar to the trachea in a human lung, the staggered array of attached rhombic columnar pin-fins and detached hexagonal columnar pin-fin is proposed as a newly hybrid columnar pin-fin array. The average Reynolds numbers (Re) tested are 1500, 2000, 5000, 10000, 15000 and 20000. The flow pulsations are generated by releasing coolant flow prior to the channel entrance at the frequency of 1/4, 1/6 and 1/12 Hz to alter the frequency of flow pulsation. At each set of Re and pulsating frequency, the coolant release over 1/4, 1/2, or 3/4 pulse cycle is tested to modify the waveform of the flow pulsation. The range of Strouhal number (Sr) tested is 0.0004-0.017.
The experimental results confirm that the thermal performance factors evaluated at the constant pumping power consumptions are greater than unity at Re>5000, suggesting the high-efficiency heat transfer enhancements at Re>5000. Based on the databases generated by the present study, two sets of empirical correlations that permit the evaluations of the temporally mean area-averaged Nusselt numbers and Fanning friction factors of the present pin-fin channel under steady-flow and pulsating-flow conditions are proposed for relevant engineering applications.

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