暫態液晶量測技術用於入口效應對於旋轉內冷卻通道中熱傳分布之影響

Abstract

本實驗主要研究入口的幾何形狀對旋轉長方型內冷卻通道(寬高比為1：1.5)搭配90度肋條熱傳效果分布之影響，此長方形冷卻通道配合四種不同的入口突縮(contraction)條件，其中包含完全發展型、3比2突縮型、3比1突縮型和3比1突縮型搭配圓形導角。實驗中主要的參數：肋條間距與高度比值(P/e)固定為10，肋條高度與水力直徑比值(e/D_h)為0.125，旋轉數(Ro)為0至0.023，雷諾數(Re)設定為15000、20000、25000和30000。本實驗使用暫態液晶量測技術與閃頻儀造成的視覺暫留搭配CCD攝影機，進而得知目標面各區域的熱傳分布，其結果顯示入口突縮的比例越高其熱傳效果提升的幅度越高。

The effect of entrance geometry and rotation number on the heat transfer in an 1:1.5 rectangular cooling channel with 90º ribs is investigated in this study. The rectangular channel is considered with four different entrance conditions: fully developed, sudden contraction (3:2), sudden contraction (3:1) and sudden contraction (3:1) with circular chamfer. The rib spacing-to-height ratio (P/e) is 10 and rib height-to-hydraulic diameter ratio (e/D_h) is 0.125. The range of rotation number is form 0.0 to 0.023 and Reynolds numbers are 15000, 20000, 25000 and 30000. The contour maps of Nusselt number on roughened walls are obtained by transient thermochromic liquid crystal experiment, using a stroboscopic light and a digital camera. Effect of entrance geometry is tested and it shows that the sudden contraction geometry produces higher heat transfer.