具階梯之環狀空間的熱質自然對流現象之實驗研究

Natural Convection Heat and Mass Transfer in an Annular Enclosure with Step

許芳晨(Fang-Chen Hsu)

指導教授 ： 王立文

元智大學/工程學院/機械工程學系/碩士(2006年)

https://doi.org/10.6838/YZU.2006.00082

摘要

本研究主要是從實驗方法探討具階梯之環狀空間的封閉盒，由溫度梯度與濃度梯度所引起的熱質自然對流現象。利用幾何形狀與邊界條件的設計，探討具階梯之環狀空間對流場結構之影響。
外圓環及內圓柱由銅所組成，實驗工作流體為濃度0.05M的硫酸銅水溶液( CuS04 + H2SO4+ H2O )。溫度梯度由兩個不同溫度的恆溫水槽維持，濃度梯度利用電化學系統建立。採用雷射光暗影法(shadowgraphy)觀察封閉盒內流場現象，並且以數位相機拍照紀錄。為了瞭解流場結構，對流場的溫度及濃度分佈亦做量測。
在傾斜角度流場，階梯對於流場的效應很明顯，可以清楚的看到流體流經背向階梯所產生的迴流區效應。在相同Grt時，順向流場的無因次質傳遞率較逆向流場的無因次質傳遞率為大，在固定Grm的情況下，當Grt增加時，無因次質傳遞率會隨之增加。

關鍵字

環狀封閉盒 ； 階梯 ； 熱質自然對流

並列摘要

The purpose of the study is to investigate flow patterns, temperature and concentration distributions resulting from buoyancy force due to a combination of temperature and species convection effects in an annular enclosure with step.
In this experiment, the temperature and the concentration differences are made between the inner cylinder and the outer annular. Cupric Sulphate solution is selected as the working fluid. Two constant temperature baths keep the temperature gradient. The concentration gradient is controlled via electrochemical system. The temperature and concentration gradients are imposed in such a way that their effects on the flow were either cooperating or opposing.
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.
To understand the flow structure, the temperature distribution and concentration distribution are investigated. Finally, the correlations between Sherwood number and solutal concentration Grashof number and thermal Grashof number are also needed to be analyzed.

並列關鍵字

Annular Enclosure ； Step ； Natural convection

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