臺灣博碩士論文加值系統

在對流現象的研究上，自然、混和、強制對流三種機制常為學術研究上的重點，其中以混和對流因兼備其他兩者效應而常被提出來討論。本實驗研究是將多圓柱狀質源之質量傳遞引入矩形管道主流中，在不同的傾斜角度、強制對流效應以及銅板與圓柱間的陰陽極性變化在極限電流的情況下來進行質混合對流研究。由於大多的研究都是在探討群體圓柱間的純流力研究，或是以數值分析來模擬圓柱加熱下的流場現象，對於研究質混合對流的相關實驗是非常少的。
在做相關的研究時，研究群體圓柱間的排列方式與位置是必要的，所以在本實驗中，第三章所探討的是單圓柱與雙圓柱在上下極板間不同距離下的研究，並且觀察圓柱在靠近極板時的流場現象。第四章所要探討的是多圓柱在不同的間距比下的流場研究，並且量測質傳遞率與雷諾數的關係。至於質傳遞率量測方面，固定傾斜角時，在不同邊界條件下，質傳遞率Sherwood數隨Reynolds數的增加而增加。當我們增加間距比(h/l)從0.88到1.5，對於固定雷諾數的情況下，此時所對應的Sherwood值會有反比的趨勢。由此可知在h/l=0.88的時候有最佳的熱傳遞率，也就是說最佳的群體排列方式以正三角形的幾何形狀最好。這個推測與文獻中所探討在熱混合對流的數值模擬研究中有相同的結果。
本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，實驗的無因次參數範圍如下：Pr=5~7, Ar=1, Sc=1700~2400, Re=50~300, Grm = 1.88×105 (Red=7.94 ~ 47.64, Grm* = 4378), h/l=0.88~1.5, l/H=0.4~0.5, d/H=0.125 and d/G=0.45~0.9, θ=0°~15°.

This doctoral thesis is the research on the mixed solutal convection in the duct flow passing through an inclined channel with multiple cylinder sources. Seldom research can be found on this subject. With the mass transport factor on the channel flow, the flow patterns have become more complex. The fluids from the anode or the cathode are denser or less dense so that they do not match the flow patterns in the pure fluid dynamics. In order to observe the cylinders effects inside the channel, a series of the boundary conditions concerning about the cylinders will be involved. Although the Reynolds numbers in this research are from 50 to 300, the complete natural convection, mixed convection and forced convection are presented in the flow patterns. Besides changing the Reynolds numbers, the gap ratio effects of the cylinders on the inclined channel are also investigated.
Some investigations about the mass transfer rate are also clearly found. First, with increasing the Reynolds number, the corresponding Sherwood number is increasing, for the Reynolds number is directly proportional to the Sherwood number. Second, with increasing the height-to-gap ratios (h/l) from 0.88 to 1.5 for the fixed Reynolds number, the corresponding Sherwood number is inversely proportional. It is because the equilateral triangle cylinders arrangement is the best design on the mass transfer. Finally, the Sherwood number is inversely proportional to the electrode area on the cathode. Therefore, the larger the area on the cathode is, the smaller Sherwood number can be.
An experimental study of mixed convection with CuSO4+ H2SO4 + H2O solution in the inclined channel is performed. The shadowgraph technique is used to visualize the flow and to determine the nature and effect of solutal driven secondary flows in the inclined channel with the multiple cylinder sources inside. The ranges of the parameters in the present work are Pr=5~7, Ar=1, Sc=1700~2400, Re=50~300, Grm = 1.88×105 (Red=7.94 ~ 47.64, Grm* = 4378), h/l=0.88~1.5, l/H=0.4~0.5, d/H=0.125 and d/G=0.45~0.9, θ=0°~15°.

Chinese Abstract………………………………….……….....i
English Abstract.………………………………….………....ii
Acknowledgments……………….…………………..…………...iii
Table of Contents..…….………………………..……….…..iv
List of Figures…..………………………………………….…...vi
Nomenclature…………………………...………….…………...xii
Chapter Page
Chapter I Introduction…………………………………….………….1
1.1 Motivation………….…………………………………………......1
1.2 Related Past Work………….…………………….………......2
1.3 Objectives……………………………………..…………………..7
Chapter II Experimental Design……………………..……...……….8
2.1 Coordinate Setup………………………………………….……....8
2.2 Governing Equation………………………………….…….…..….8
2.3 Parameters with Migration Effect……………….……...…....8
2.4 Dimensional Parameters…………………………………..………9
2.5 Fluid Cyclic System…………………………………..….…....10
2.6 Electrochemical System…………………………..…...........11
2.7 Laser Optical System...................................12
2.8 Definition of the Parameters..…………..…………….....12
2.8.1. Definition of the Reynolds Number.…..……….……….12
2.8.2. Definition of the Solutal Grashof Number………………….13
2.8.3. Definition of the Sherwood Number.……....………..13
2.8.4. Definition of the Limiting Current ...……….………...13
2.9 Experimental Procedure…...……………………..……...15
Chapter III The Flow Patterns of Single and Two Cylinders…..16
3.1 The Flow Patterns of Case (A)…………………………..…....16
3.2 The Flow Patterns of Case (B)…………………………..…....19
3.3 The Flow Patterns of Case (C)…………………………..…....23
Chapter IV Results and Discussions of Three Cylinders........28
4.1 Part I-Horizontal Channel θ=0°...................28
4.1.1. The Flow Patterns of Case (A)……………………….28
4.1.2. The Flow Patterns of Case (B)…………………………30
4.1.3. The Flow Patterns of Case (C)…..……..……………....32
4.1.4. The Flow Patterns of Case (D)……...….……………….34
4.2 Part II-Uphill Channel θ=15...........................37
4.2.1 The Flow Patterns of Case (A)……………………37
4.2.2 The Flow Patterns of Case (B)…………………...…39
4.2.3 The Flow Patterns of Case (C)…..……………...…41
4.2.4 The Flow Patterns of Case (D)……………………43
4.3 Part III-Downhill Channel θ=-15..................46
4.3.1 The Flow Patterns of Case (A)…............………...46
4.3.2 The Flow Patterns of Case (B)……………….…….….48
4.3.3 The Flow Patterns of Case (C)….......................50
4.3.4 The Flow Patterns of Case (D)……....................52
4.4 Mass Transfer Rate……………………………………….……..55
4.4.1 The Correlation of the Re and Sh in Case (A)…...…....55
4.4.2 The Correlation of the Re and Sh in Case (B)……….…….55
4.4.3 The Correlation of the Re and Sh in Case (C)……...…..56
4.4.4 The Correlation of the Re and Sh in Case (D).…...…..57
Chapter V Conclusions and Future Works.................58
References……………...………………….…….....60

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