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Effect of Spiral-Direction Solid Heat Conduction on the Heat Transfer Performance of a Spiral Heat Exchanger
|關鍵字:||渦捲式熱交換器;Spiral Heat Exchanger;比爾數;熱效率;熱傳單位數;熱傳導;Biot number;Heat transfer effectiveness;the number of transfer units;heat conduction||出版社:||機械工程學系所||引用:||1.M. Sterger, S. Churchill and W. Retallik, “Operational characteristics of a double-spiral heat exchanger for the catalytic incineration of contaminated air”, Industrial and Engineering Chemistry Research, Vol. 29 (9), pp. 1977–1984, 1990. 2.M.J. Targett, W.B. Retallick, and S.W Churchill, “Solutions in closed form for a double-spiral heat exchanger”, Industrial and Engineering Chemistry Research, Vol. 31, pp. 658-669, 1992. 3.T. Bes and W. Roetzel, “Thermal theory of the spiral heat exchanger”, International Journal of Heat and Mass Transfer, Vol. 36, pp. 765–773, 1993. 4.W.D. Wu, “Geometric calculations of the spiral heat exchanger”, Chemical Engineering Technology, Vol. 26, pp. 592–598, 2003. 5.L.C. Burmeister, “Effectiveness of a spiral-plate heat exchanger with equal capacitance rates”, Journal of Heat Transfer, Vol. 128, pp. 295-301, 2006. 6.J.Y. San, G.S. Lin and K.L. Pai, “Performance of serpentine heat exchanger: Part I－Effectiveness and heat transfer characteristics”, Applied Thermal Engineering, Vol. 29, pp. 3081-3087, 2009. 7.J.Y. San, C.H. Hsu, S.H. Chen, “Heat transfer characteristics of a helical heat exchanger”, Apllied Thermal Engineering, Vol. 39, pp. 114-120, 2012. 8.D.K. Nguyen, “Heat transfer effectiveness and exergy recovery effectiveness of a spiral heat exchanger”, Master Thesis, National Chung Hsing University. 9.M. Picon-Nunez, L. Canizalez-Davalos, G. Martinez-Rodriguez, and G.T. Polley, “Shortcut design approach for spiral heat exchangers”, Food and Bioproducts Processing, Vol. 85 (4), pp. 322-327, 2007. 10.M. Picon-Nunez, L. Canizalez-Davalos and J.M. Medina-Flores, “Alternative sizing methodology for compact heat exchangers of the spiral type”, Heat Transfer Engineering, Vol. 30 (9), pp. 744–750, 2009. 11.M. Adamski, “Heat transfer correlations and NTU number for the longitudinal flow spiral recuperators”, Applied Thermal Engineering, Vol. 29, pp. 591–596, 2009. 12.S. Sathiyan, M. Rangarajan, S. Ramachandran, “Studies of heat transfer for water-diesel two-phase system in a spiral heat exchanger”, Chemical and Biochemical Engineering Quarterly. Vol. 25(2), pp. 198-201, 2011. 13.S.P. Narayanan, G. Venkatarathnam, “Performance degradation due to longitudinal heat conduction in very high NTU counterflow heat exchangers”, Cryogenics, Vol. 38( 9), pp 927-930, 1998. 14.G. Venkatarathnam, S.P. Narayanan, “Performance of a counter flow heat exchanger with longitudinal heat conduction through the wall separating the fluid streams from the environment”, Cryogenics, Vol. 39(10), pp. 811-819, 1999. 15.P. Gupta, M.D Atrey, “Performance evaluation of counter flow heat exchangers considering the effect of heat in leak and longitudinal conduction for low-temperature applications”, Cryogenics, Vol. 40(7), pp. 469-474, 2000. 16.P.I. Frank, P.D. David, L.B. Theodore and S.L. Adrienne, “Introduction To Heat Transfer”, edition, John Wiley & Sons, 2007. 17.M. Necati Ozisik. “Heat Conduction” edition, 虹橋出版社,1980.||摘要:||
本研究進行一個渦捲式熱交換器之模擬分析，主要探討兩流體間管壁中沿渦線方向之熱傳導對熱交換器之熱傳性能之影響。此熱交換器之幾何結構由四條渦捲線於同一中心點出發，分別組成管壁與冷熱流道，其中冷熱流道中之流體考慮為逆向流，而冷熱流體之比爾數為相同，同時管壁最外層之半圈與位於中心處冷熱流體間之隔板假設為絕熱之情形，經能量平衡公式之推導與數值方法之解析，並利用電腦計算出流道中流體之無因次出口溫度，即可獲得熱交換器之熱效率。分析之結果顯示，在一個固定之熱傳單位數(NTU)下，當冷熱流體之比爾數值逐漸減小時，或無因次化管壁厚度增加時，亦即管壁之熱傳導增加時，熱效率會隨之減小。在NTU小於10以下，此研究所獲得之熱效率與不考慮渦線方向熱傳導所獲得之熱效率經比較後發現，熱效率之下降值會隨著NTU之增加而變大，在 為0.01、0.1與1.0時且 值為0.01， 之最大值分別為0.015、0.095與0.22。
The effect of spiral-direction heat conduction in solid wall on the heat transfer performance of a spiral heat exchanger was numerically analysed. The heat exchanger is composed of four spirals which form two solid walls, hot-flow channel and cold-flow channel. In the analysis, the flows were considered to be counter-current. The Biot number of the cold flow was the same as that of the hot flow. The outer-most half turns of the walls and the partition between the hot flow and cold flow in the center were assumed to be insulated. The result shows that, at a fixed NTU value, the heat transfer effectiveness decreases with the Biot number of the cold flow and hot flow value, and it decrease with an increase of the ratio of wall value. At NTU 10, the present acquired data were compared to those solved using a model without considering the solid heat conduction effect. The result shows that, the degradation of the heat transfer effectiveness value tends to increase with the NTU value. At the Biot number of the cold flow and hot flow value of 0.01, the maximum degradation of the heat transfer effectiveness values for the ratio of wall values of 0.01, 0.1 and 1 are 0.015, 0.095 and 0.22 respectively.
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