三角形封閉盒內之熱質自然對流研究

NATURAL CONVECTION HEAT AND MASS TRANSFER IN A TRIANGULAR ENCLOSURE

陳意欣(Yi-Shin Chen)

指導教授 ： 王立文

元智大學/工程學院/機械工程學系/碩士(2009年)

https://doi.org/10.6838/YZU.2009.00186

摘要

本研究是藉由實驗方式來探討一三角形封閉盒內之熱質自然對流現象。此熱質自然對流現象主要是由於溫度梯度及濃度梯度所引起，再加上幾何形狀為一等腰直角三角形的設計與邊界條件，徹底探討熱質自然對流在其間的變化。
本次實驗中，等腰直角三角形的任兩邊由銅組成，第三邊則為壓克力(視為絕緣、絕熱)，實驗的工作流體為0.05M的硫酸銅水溶液(CuSO4+H2SO4+H2O)。溫度梯度由兩個不同溫度的恆溫水槽來維持，濃度梯度則是以電化學系統來建立。流場的觀察是採以雷射光暗影法後，再以數位相機拍照紀錄。
為了解流場之結構，本研究對流場的溫度及濃度分布做測量，最後再針對質傳遞率Sh值與Grm、Grt之間關係做分析。在固定Grm的情況下，Sh值會隨著Grt的增加而呈現遞增狀態。
最後得到的結論有:當在熱質逆向的cases中，會有鹽手指的產生；此外，在熱質順向的cases中，熱源在冷源上方，此時可觀察到多重渦流的流場型態。在質傳遞率Sh值與Grm、Grt之間關係探討中，實驗得出，當Grt增加Sh值也隨之增加；另外，在熱質順向時的質傳遞率較逆向來得要好。
本實驗中無因次參數研究範圍如下:
Pr=7~8，Sc=1700~2100，Grt =8.75×106，Grm=9.35×107，|N|= 10.69

關鍵字

三角形封閉盒,熱質傳,自然對流

並列摘要

The current study is primarily motivated to gain a better understanding of the flow pattern, the temperature and concentration gradient cause by thermosolutal convection in an electrochemical system with a right triangular enclosure.
The test cell is a right triangular enclosure formed with acrylic, Bakelite and copper plates, which is wrapped with block Bakelite insulator to ensure an adiabatic boundary condition.
In this experiment, the temperature and the concentration differences are made between two copper walls. The research area targets the flow pattern, change of Grt. We use copper sulphate-sulfuric acid solution as the working fluid. Two constant temperature baths sustain the temperature gradient. The concentration gradient is controlled via an electrochemical system. In order to visualize the flow, the shadowgraph technique is used.
To understand the flow structure, the temperature distribution and concentration distribution will be investigated. Finally, the correlations between the Sherwood number, and the thermal Grashof number will also need to be analyzed.
It is demonstrated that multilayer structure and finger type flow are found in the cooperating case and the opposing case, respectively. It is also found that Sh increased with increasing Grt for fixed Grm value and decreased with increasing θ(inclination angle).
The ranges of the parameters in this study are:
Pr=7~8，Sc=1700~2100，Grt =8.75×106，Grm=9.35×107，|N|= 10.69

並列關鍵字

triangular enclosure, heat and mass transfer, natural convection

參考文獻

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