本研究以實驗方法探討噴流於橫風中衝擊平板的壓力分佈及熱傳特性。，於一自製的閉迴路風洞測試段中沿軸向裝設一平板作為噴流衝擊對象；架設一支與平板及橫風垂直不鏽鋼管提供空氣噴流，噴流管出口與平板相距50 mm。噴流管內徑與外徑各為5 mm與6.4 mm。在不同噴流雷諾數Rej (1000、1333、1700)及噴流-橫風速度比Ru (1.2、1.8、2.4、3、3.6、4、4.2、4.8、5、5.4、6、9、12、15、18、21)之下進行實驗。結果顯示，在噴流雷諾數與噴流-橫風速度比介於實驗範圍內時，流場大致可歸納出四種特徵模態。分別為：無衝擊模態、輕微衝擊模態、單渦漩模態及噴流衝擊模態。無衝擊模態時，噴流並未衝擊平板且壓力分布呈現往下游遞減的趨勢；平板熱傳主要受橫風影響，速度比越小熱傳效果越佳，且同速度比時越往下游熱傳效果越差，為溫度邊界層成長所致。輕微衝擊模態時，噴流輕觸平板，壓力分布多為負值，壓力係數於噴流輕觸點附近呈微幅上揚的趨勢；平板熱傳效果於此模態最差，於噴流輕觸點附近觀測到溫度些微降低趨勢。單渦漩模態時，在衝擊點上游觀測到一顆快速旋轉之小渦漩，壓力分佈除了可觀察到因噴流衝擊所造成的峰值外，也可觀察到因小渦漩所產生的負壓；平板散熱效果於此模態隨著速度比增大而明顯增強，熱傳效果最佳處隨速度比提升而移往上游。噴流衝擊模態時，於衝擊點上游觀測到一顆大渦漩，壓力分布在原點附近顯現一個峰值，大渦漩結構範圍內呈現些微負壓；散熱效果最佳處多集中在原點附近，溫度分布以該處為圓心呈現同心圓往外遞增趨勢。若欲使用衝擊噴流進行平板表面散熱，但有橫風影響時，應使噴流-橫風速度比達到噴流衝擊模態，方能獲得較佳熱傳效果。

Impinging jet was conventionally used to enhance heat dissipation performance of a heated surface. In many cases, the impinging jet was easily subjected to the influences of crossflow so that the heat dissipation performance was decreased drastically. The present study investigated the effects of crossflow on the flow characteristics, heat transfer performance, and pressure distribution of a vertical jet impinging on a flat surface. The experiments were conducted in a close-loop wind tunnel by installing a flat plate parallel to the wind direction and a tube vertical to the flat plate. The crossflow was provided by the wind in the test section, while the impinging jet was supplied by the air issuing from the tube tip. The distance between the plate surface and the jet exit was fixed at 50 mm. The physical parameters dominating the flow were jet Reynolds number and jet-to-crossflow velocity ratio. By varying the jet Reynolds number and jet-to-crossflow velocity ratio, the flow patterns in the symmetric plane, pressure distributions on the center line of the flat plate, and the heat transfer characteristics of the flat plate surface were obtained by flow visualization, pressure measurement, and temperature measurement, respectively. Four characteristic flow modes (no impingement, slight impingement, single vortex, and impingement) were observed in the domain of jet Reynolds number and jet-to-crossflow velocity ratio. The pressure distribution profiles of the impingement mode all exhibited a single-peak pattern, demonstrating the strong effect induced by the dynamic pressure asserted by the jet on the flat plate surface. The measured temperature distributions indicated that the impinging jet would present the highest heat transfer performance when the flow pattern exhibited the impingement mode.

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