矩形管中流體經鄰近壁面之雙圓柱狀質源之混合對流研究

A Study Duct Flow Passing in A Channel with Tandem Cylinder Sources Adjacent to Planar Boundary

蘇耕同(K.T. Su)

指導教授 ： 王立文

元智大學/工程學院/機械工程學系/碩士(2004年)

摘要

在熱流現象的研究上，自然、混合、強制對流三種機制常為學術研究上的重點，其中以混合對流因兼具其他兩者效應而常被提出來討論。本實驗研究是將鄰近壁面之雙圓柱狀質源的質量傳遞引入矩形管道主流中，在不同的傾斜角度、強制對流效應與改變銅板質源位置以及銅板與圓柱間的陰陽極性變化來進行質混合對流研究。在此，混合對流係指利用幫浦所造成的強制對流（forced convection），在速度完全發展之後，再與不連續之對稱質源傳遞所形成的自然對流（natural convection）合併之流體運動現象。
實驗使用的工作流體為硫酸銅水溶液（CuSO4 + H2SO4 + H2O），藉由電化學系統於測試區（test section）之銅板與水道中鄰近壁面之銅柱加上端電壓，使其成為電極，達成濃度梯度之建立。
本實驗採用雷射光暗影法（shadowgraph）作流場結構觀察及照相記錄，並作質量傳遞率的量測。實驗的無因次參數範圍如下：Ar=1 ，Sc=1700~2400，Re=50~300，Gr,m=9.45×105，θ=-15°~15°，d / H = 0.25 ( 圓柱直徑與管道高度比 ) ，s/d = 2(雙圓柱圓心間距與圓柱直徑比)。
至於質傳遞率量測方面，Sherwood值皆隨Re的增加而變大，而在陰陽極板面積相同的條件下，分別是Case (C)與Case (D)，但是其Sh值卻有極大的差異， Case(C)為前圓柱陰極，後圓柱為陽極，在此一邊界條件下，前圓柱陰極產生較輕次流體，受到慣性力影響，有足夠的空間往下游移動，增加雙圓柱對流效應；當雙圓柱為陽極，上板為陰極Case(B)，與其他Case相比，Sh值顯著較低，此種極性擺設不利於質量傳遞，若要增大Sh值，可以將流道傾斜來增加質傳遞率。

關鍵字

混合對流 ； 圓柱狀質源 ； 鄰近壁面

並列摘要

An experimental investigation of mixed convection mass transfer from only two tandem cylinders or two tandem cylinders and a plate, the flow of a CuSO4＋H2SO4＋H2O solution will be carried in an inclined rectangular channel with an electrochemical system .
The purpose of the present study is to investigate laminar fully developed flow in inclined rectangular channels with the types of the boundary of test section are: (A) two cylinders are cathode and top plate is anode (B) two cylinders are anode and top plate is cathode (C) the left cylinder is cathode and the right cylinder is anode (D) the left cylinder is anode and the right cylinder is cathode. The influence of the mass transfer rate and the boundary types between the sources has been investigated. The experiments would include three parts : (1)inclined angle θ= 0°(2)inclined angle θ> 0° (3)inclined angle θ< 0°.
To visualize the flow, the shadowgraph technique will be used. Electrical measurements will be used to obtain mass transfer rates and to infer a Sherwood number. The ranges of the parameters in the work are Ar=1, Sc=1700~2400, Re=50~300, Gr,m = 9.45×105 ,θ= -15°~ 15°, d / H = 0.25, s /d=2

並列關鍵字

Cylinder Sources ； Adjacent to Planar Boundary ； Mixed convection

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