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題名 | Natural Convection in a Porous Enclosure with Water Evaporation and Condensation=在多孔性介質密閉空間中伴隨水膜蒸發與凝結現象之自然對流 |
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作者 | 傅武雄; 柯文旺; | 書刊名 | 中國機械工程學刊 |
卷期 | 20:6 1999.12[民88.12] |
頁次 | 頁563-573 |
分類號 | 446.01 |
關鍵詞 | 多孔性介質密閉空間; 水膜; 蒸發; 凝結; 自然對流; Porous medium; Evaporation; Condensation; Constant heat flux; |
語文 | 英文(English) |
中文摘要 | 本研究以數值方法探討一個充滿多孔性介質密閉空間中向然對流所引發之熱、質 傳現象。為增強熱傳效率,在加熱壁面上加上水膜,並考慮潛熱、顯熱熱傳,面於水膜受熱 蒸發於蒸氣且對流至低溫的右垂壁面進而形成往下流動的水膜。本文應用數值方法 SIMPLEC 法解 Darcy-Brinkman-Forchheimer 的多孔性介質模式,另二組有限差分程式來解水膜蒸發 與右壁的凝結水膜。等熱通量、孔隙率和銅粒粒徑為計算參數。結果顯示左壁面上的蒸發質 通量隨瑞利數增加而增加且熱傳率與孔隙率和銅粒粒徑大小無關。平均紐塞數對參數( Ar. Pr/Ja )可表示為 C ��. ( Ar . Pr/Ja )�@+ C �祖漣峖﹛C 平均紐塞數對瑞利數可表 成 C �窗D (Ra)+C �祖漣峖﹛C |
英文摘要 | A double diffusive natural convection consisting of heat and mass transfer in a rectangular porous enclosure is numerically investigated. The occurrence of mass transfer is induced by water evaporation on the left wall and water film condensation on the right wall, which enhance the natural convection remarkably. The Darcy-Brinkman-Forchheimer and constant porosity models are used, and the factors of constant heat flux, porosity and the size of copper beads are taken into consideration. The SIMPLEC and finite difference methods with iterative processes are adapted to simultaneously solve the governing equations. The results show that the evaporation mass flux increases as the Rayleigh number increases. The effect of water evaporation on heat transfer rate is almost independent of the porosity and the size of bead. The relationship of the average Nusselt number and parameter (Ar . Pr/Ja) can be expressed as the form of C �窗D (Ar . Pr/Ja) �@ + C ��, which is usually adopted in the situation of evaporating mass transfer occurring. Besides, the average Nusselt numbers are well consistent with the form of C �窗D Ra + C ��, which is conveniently used to express the results of experimental conductance on evaporation in porous medium. |
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