太陽能真空管流場與熱質對流之研究

Study on the flow field with heat and mass convection of an evacuated tubular solar collector

廖坤聰(kun-Tsung Liao)

指導教授 ： 蘇艾

元智大學/工程學院/機械工程學系/碩士(2012年)

https://doi.org/10.6838/YZU.2012.00024

摘要

本研究是以實驗的方法探討具隔板傾斜矩形盒之熱質自然對流現象，針對固定浮力比（N值）、隔板位置所展現的流場型態，傾斜盒內溶液溫度及濃度的變化情形均是研究的對象。
實驗裝置為展弦比等於2之矩形盒，以銅板及壓克力板構成，在盒內放置隔板，並變化矩形盒傾斜角度。工作溶液為硫酸銅水溶液，溫度梯度是由兩個不同溫度的恆溫水槽來維持。而濃度梯度乃使用電化學方法造成的，即利用電解方法在兩邊銅板附近形成不同濃度的邊界層。對於盒內流場現象以採用雷射光暗影法來觀察流場，並且以相機拍照記錄。以便瞭解流場結構，對流場的溫度及濃度和質傳遞率作量測分析。
實驗結果顯示，傾斜角度對流場結構和質傳遞率有顯著的影響。對於大傾斜角度而言，質邊界層化流動會造成堆積和降低質傳遞率。而小傾斜角度時，由於產生之質柱狀流及鹽手指現象會造成濃度變動和強化質的傳遞。

關鍵字

集熱器 ； 流場 ； 溫度 ； 濃度 ； 鹽手指

並列摘要

The current study is primarily motivated to gain better understanding of the flow pattern, the temperature distribution and concentration distribution caused by thermosolutal convection in an electrochemical system with a partially divided enclosure.
The test cell is an inclined rectangular enclosure formed with acrylic and copper plates, which is wrapped with foam insulator to ensure an adiabatic boundary condition, and its aspect ratio is 2. The temperature is maintained uniform and controlled by two separated constant temperature baths, which circulate heated or cooled water through the heat exchanger. The working solution used is aqueous copper sulphate. An electrochemical method based on a diffusion-controlled electrode reaction will be employed in this work for creating the concentration gradient.
To visualize the flow, the shadowgraph technique is used. To understand the flow structure, the temperature distribution and concentration distribution are investigated.
Finally, the correlations between Sherwood number and solutal Grashof number, thermal Grashof number and angle inclination varied are also need to be analyzed.
It was found that the inclination have a significant effect on the flow structure and mass transfer. For a large angle of inclination, the accumulation of solutal boundary layer leads to stratification of the flow and reduction of the mass transfer. For a small inclination, generation both protrusion of solutal and finfer flow leads to oscillation of concentration and enhancement of mass transfer.

並列關鍵字

Salt fingers ； Collector ； Flow ； Temperature ； Concentration

參考文獻

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