高速噴射流衝擊發熱板之流場及熱傳分析

Abstract

本研究應用STAR-CD套裝軟體作為數值分析的工具，來探討衝擊噴射流之熱傳問題。本研究主要分成垂直衝擊噴射流及斜角衝擊噴射流兩部分。影響衝擊噴射流的因素有許多，本文主要針對不同雷諾數及噴管至衝擊盤面之距離做研究。基於有限容積法，探討衝擊噴射流問題，並指出空氣速度、溫度及熱對流係數分佈等結果，以了解噴射衝擊流的熱傳情形。 由研究結果顯示，在垂直衝擊噴射流部分，數值所計算出的熱對流係數與Donaldson等人實驗數據相當的吻合，只是在停滯區的值略低於實驗數據。根據數值模擬所得的結果可歸納出平均紐賽數等於雷諾數的c次方的關係式。不同的雷諾數的情形下，局部紐賽數除以雷諾數的c次方(c為常數)的關係式曲線，在r/D大於等於4的地方相當的一致。 在斜角衝擊噴射流部分，經數值模擬得到之最大熱對流係數並不與衝擊中心一致，而是往上坡方向偏移，其偏移量隨著傾斜角越大而增加。熱對流係數分佈很不均勻，在上坡的熱對流係數較下坡衰減快。

The heat transfer of a turbulent jet impinging on both normal and oblique heating plate had been investigated numerically. The temperature distribution and heat transfer in the flow field and the heating plate are solved simultaneously. The governing equations of this system are solved using the commercial software STAR-CD code. For the normal impinging jet, the local heat transfer coefficient as well as the mean Nusselt number are presented for the Reynolds number ranging 10000 to 110000 for L / D=2、6 and 10. Generally good agreement between the numerical results and experimental data is obtained in the present study. However, the heat transfer coefficient near the stagnation flow region is underestimated. The heat transfer can be well correlated by using Nu / Re^c as r / D greater or equal to 4 . Similar phenomenon is also observed in the experiments. Local heat transfer distributions from an obliquely impinging circular jet to a heating plate were obtained. Distribution of local heat transfer shows a non-symmetric pattern. The point of maximum heat transfer shifts from the geometrical impinging point toward the uphill plate。