臺灣博碩士論文加值系統

摘 要
本研究主要是藉助實驗方法來探討具三圓柱矩形封閉區域中，溫度梯度及濃度梯度所引起的自然對流之流場形態，以及圓柱附近的溫度及濃度分佈情形。
研究動機起因於結晶成長過程中組成不均勻的現象非常嚴重，因此對於過程中熱量及質量的傳遞應作充分了解，並延續學長所做的實驗，探討從雙圓柱至三圓柱的流場型態的不同。
本文所作實驗，將三圓柱擺法成品字形，同時賦予溫度差和濃度差，其它邊界保持絕緣。所以，本研究又分兩部分：
(1) 矩形盒水平放置，圓柱為上冷下熱或上熱下冷之雙擴散對流現象。
(2) 矩形盒垂直放置，圓柱為左冷右熱或左熱右冷之雙擴散對流現象。
工作中工作溶液為硫酸銅水溶液。溫度梯度由兩個不同溫度的恒溫水槽來維持。濃度梯度是由電化學方法造成的，即利用電解方法形成不同濃度的邊界層。對於矩形密閉容器內流場現象，採用雷射光暗影（shadowgraphy）來觀察流場，並以相機拍照記錄以利分析。
順向流場在加入質傳後因為流體堆積的關係，通常會有interface的產生，而逆向流場在溫度傳遞速率與濃度傳遞速率不均勻的情況下通常會有鹽手指的產生。在質傳遞率方面，在固定Gr,m的情況下，當Gr,t增加時，質傳遞率(Sh)會隨之增加，且順向的質傳遞率比逆向的質傳遞率高，而在矩形盒垂直放置時質傳遞率又比矩形盒水平放置時質傳遞率高。
本實驗中無因次參數研究範圍如下：
Ar=0.75 Gr,t=5.9 ×104 ~ 1.18 ×105
Gr,m=3.16 ×105 N=-5.35~5.35
Sc=1700~2300 Pr=6.0~7.0

ABSTRACT
The purpose of present study is to investigate flows pattern, temperature and concentration distributions resulting from buoyancy force due to a combination of temperature and species convection effects in a rectangular enclosure with triple cylinders inside.
In the process of crystal growth, the non-homogeneous phenomenon would become more and more serious. So to know the sufficient understanding of heat and mass transports is indispensable.
In this experiment, the temperature and concentration differences are made between three cylinders and the insulation is kept all over the margin. Cupric Sulphate solution is selected as the working fluid. Two constant temperature baths keep the temperature gradient. Concentration gradient is controlled via electrochemical system. In order to visualize the flow, the shadowgraph technique is used. Electrical measurements will be used to obtain mass transfer rates and to infer a Sherwood number. We can find that in the cooperating case, the interface is shown due to the fluid accumulation after imposing the mass transport. However, in the opposing case, the salt finger is found owing to the difference between the thermal diffusive velocity and mass diffusive velocity.
This study can be divided into two parts:
(1)The enclosure is placed horizontally, and convection is established where one cylinder is inserted right up to the other two.
(2)The enclosure is placed vertically, and convection is established where one cylinder is inserted next to the other two.
The range of the parameters in this study are
Ar=0.75 Gr,t=5.9 ×104 ~ 1.18 ×105 Gr,m=3.16 ×105
N=-5.35~5.35 Sc=1700~2300 Pr=6.0~7.0

目錄
中文摘要------------------------------------------------------I
英文摘要------------------------------------------------------Ⅱ
誌謝----------------------------------------------------------Ⅲ
目錄----------------------------------------------------------Ⅳ
圖目錄--------------------------------------------------------Ⅶ
符號說明------------------------------------------------------Ⅹ
一 前言------------------------------------------------------1
1.1 研究動機----------------------------------------------1
1.2研究文獻探討-------------------------------------------1
二 實驗設計與方法--------------------------------------------3
2.1 溫度梯度的建立----------------------------------------3
2.2 濃度梯度的建立----------------------------------------3
2.3 實驗裝置----------------------------------------------4
2.4 實驗過程----------------------------------------------4
2.5 流場觀察----------------------------------------------5
2.6 雷射光暗影法------------------------------------------5
2.7 溫度量測之方法----------------------------------------5
2.8 濃度量測之方法----------------------------------------6
三 實驗結果與討稐--------------------------------------------7
3.1 純熱傳的流場型態--------------------------------------7
3.2 Case 1的流場型態------------------------------------------8
3.3 Case 2的流場型態------------------------------------------10
3.4 Case 3的流場型態------------------------------------------11
3.5 Case 3的流場型態------------------------------------------14
3.6流場的溫度分佈---------------------------------------------16
Case 1的溫度分佈----------------------------------------------16
Case2的溫度分佈-----------------------------------------------17
Case 3的溫度分佈-----------------------------------------17
Case 4的溫度分佈-------------------------------------------18
3.7流場的濃度分佈---------------------------------------------20
Case 1的濃度分佈----------------------------------------------20
Case2的濃度分佈-----------------------------------------------20
Case 3的濃度分佈-----------------------------------------20
Case 4的濃度分佈----------------------------------------------21
3.8質傳遞率分析-----------------------------------------------21
四 結論------------------------------------------------------23
五 參考文獻--------------------------------------------------24
六 圖表------------------------------------------------------25

參考文獻
1.S. Ostrach, "Natural Convection with Combined Buoyancy Forces", Physico Chem. Hydrodyn, Vol.1, pp.233-247, 1980.
2.鄭偉駿,”密閉矩形盒中具溫差之雙圓柱之自然對流現象”2001私立元智大學碩士論文
3. H. Stommel, A. B. Arons and D. Blanchard, "An Ocean graphical Curiosity the Perpetual Salt Fountain", Deep. Sea Res.15, 275-280, 1956.
4. J. S. Turner, "The Behavior of a Stable Salinity Gradient Heated from Below", J. Fluid Mech. Vol. 33, pp.183-200, 1968.
5. J. Lee, M.T. Hyun and K.W. Kim, "Confined Natural Convection Due to Lateral Heating in a Stably Stratified Solution", Int. J. Heat and Mass Transfer, 31,No.10, 1969-1977, 1990.
6. L.W. Wang, D.J. Sun, "Convection Mass Transfer in Enclosures with Vertical Temperature and Concentration" J. of National Cheng-Kung University, Vol.20,pp.313-322,1985.
7. J. Chang, T.F. Lin and C.H. Chien, "Unsteady Thermosolutal Opposing Convection of A Liquid-Water Mixture in a Square Cavity-I, Flow Formation and Heat and Mass Transfer Characteristics" Int. J. of Heat and Mass Transfer Vol.36, No.5, pp.1315-1331,1993.
8. J.A. Weaver, and R. Viskanta, "Natural Convection in Binary Gases Due to Horizontal Thermal and Solutal Gradients", J. Heat Transfer, Vol.133 pp.141-147,1991.
9. C. Gau and K.H. Wu, "A Non intrusive Technique for Concentration Distribution Measurement in Enclosure", Experiment Heat Transfer , Vol. 2, pp. 215-226,1989.
10.Y. Kamotani, L.W. Wang, S. Ostrach and H.D. Jiang, "Experimental Study of Natural Convection in Shallow Enclosures with Horizontal Temperature and Concentration Gradients", Int. J. Heat Mass Transfer, Vol.28, No.1, pp. 165-173, 1985.
11.C. R. Wilke, M. Eisenberg and C. W. Tobias, "Correlation of Limiting Currents under Free Convection Conditions", J. of the Electrochemical Society, Vol. 100, pp.513-523, 1953.
12.V.G. Levich，Physicochemical Hydrodynamics. Prentice-Hall，1962.
13.T.Mizushina，The Electrochemical Method in Transport Phenomena.Adv.Heat Transfer 7.，pp.87-161,1971.
14.L.W. Wang，C.T. Chen，and J.J. Chen,”Flow-patterns of Convection in Enclosure with Vertical Temperature and Concentration in Gradients” , Presented at the joint ASME/JSME Thermal Engineering Conference,1987.
15.龐立達,”矩形容器內加熱圓柱之雙擴散對流之研究”國立台灣大學碩士論文
16.J.Dosch,H. Beer,”Numerical Simulation and Holographic Visualization of Double Diffusive Convection in a Horizontal Concentric Annulus”,Int.J Heat Mass Transfer. Vol.35.No.9,p1811,1992
17.J.M. Metha,”Dual Wavelength Interferometric Technique for Simultaneous Temperature and Concertration Measurements in Liquids”,App.Optics Vol.29No.13,p1924,1990
18.D.G.Neilson,F.P. Incropera,”Double-diffusive Flow and Heat Transfer for a Cylindrical Source Submerged in a Salt-stratified Solution”, Int.J Heat Mass Transfer. Vol.30.No.12,p2559,1987