管道中不連續質源之混合對流實驗研究

Experimental Study of Mixed Convection Mass Transfer from Discrete Sources in a Rectangular Channel

林政宏(Cheng-Hong Lin)

指導教授 ： 王立文

元智大學/工程學院/機械工程學系/碩士(1997年)

摘要

摘要

本實驗研究是將不連續質量傳遞引入方形管道之主流中，在不同的傾斜角度及強制對流效應及改變間隔長度之下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，在速度完全發展之後，與質傳所形成的自然對流合併之流體運動現象；全實驗可分為三部份進行討論，第一部份為傾斜角度等於零，第二部份為傾斜角度大於零，第三部份為傾斜角度小於零之質混合對流研究。
實驗時所使用的工作流體為硫酸銅水溶液（CuSO4＋H2SO4＋H2O），質量傳遞是由電化學系統，上板陽極產生氧化反應而解離出銅離子，下板陰極產生還原反應而析出銅。藉此達成濃度梯度之建立。
流場觀察採用雷射光暗影法（shadowgraph）作觀察及照相記錄。並量測極限電流，以計算質傳遞率。
實驗的無因次參數範為如下：
Ar=1， Sc=1700~2400 ， Pr=5.0~7.0 ，Re=50~300 ，
Gr,m=1.27×106， L/Ls=0.3~2 及 L/H=0.5~1

至於質傳遞率量測方面，質傳遞率Sherwood值在傾斜角度大於零時，因陰極板對流效應增加而增加，而傾斜角度小於零時質傳遞率Sherwood值因陰極板對流效應減弱而變小，而且增加間隔長度會提高對流效應使Sherwood值增加。

關鍵字

傾斜 ； 不連續質源 ； 混合對流

並列摘要

ABSTRACT

An experimental study of mixed convection mass transfer from discrete mass sources flow of a CuSO4＋H2SO4＋H2O solution is carried in an inclined channel with an electrochemical system.
The purpose of the present study is to investigate the laminar fully- developed mixed convection mass transfer for the flow in horizontal ducts and in inclined ducts. The influence of the mass transfer rate and the separation distance between the sources has been investigated. The experiments are divided into three main parts. In the first part, the angle of the channel isθ = 0o. In the second part, the angle of the channel isθ ＞0o. Finally, in the last part, the angle of the channel isθ ＜0o.

To visualize the flow, the shadowgraph technique is used. Electrical measurements are used to obtain mass transfer rates and to infer a Sherwood number. The ranges of the parameters studied in the present work are Ar = 1, Sc = 1700 ~ 2400, Pr = 5.0 ~ 7.0, Re = 50 ~ 300, Gr,m = 1.27’106 , L/Ls=0.3~2 and L/H=0.5~1.

For mass convection, the mass transfer rate for the two types of tests increase with increasing Re for a fixed Ra,m and increase with increasing inclined angle for Re and Ra,m. It is found that for increasing space length configuration, the rate of mass transfer increases when the separation distance between the sources is increased.

並列關鍵字

Mixed Convection ； Inclined Channel ； Discrete Mass Sources

參考文獻

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