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Heat Transfer Analysis of Impinging Flow near Entrance Region in a Serpentine Heat Exchanger
|關鍵字:||蛇行熱交換器;Serpentine heat exchanger;紐塞數;SIMPLE;交錯網格;衝擊熱傳;Nusselt number;SIMPLE;Staggered grid;Impingement heat transfer||出版社:||機械工程學系所||引用:||1. M. Muthtamilselvan, P. Kandaswamy, J. Lee, “Heat transfer enhancement of copper-water nanofluids in a lid-driven enclosure ”, Communications Nonlinear Science and Numerical Simulation, Vol. 15, pp. 1501~1510, 2010. 2. P. Ming, W. Zhang, “Numerical simulation of low Reynolds number fluid-structure interaction with immersed boundary method”, Chinese Journal of Aeronautics, Vol. 22, pp. 480~485, 2009. 3. S. Pretot, B. Zeghmati, J. Bresson, “Numerical and experimental study of free convection above a sinusoidal horizontal plate”, Heat and Mass Transfer, Vol. 39, pp. 183~194, 2003. 4. V. Sivakumar, S. Sivasankaran, P. Prakash, J. Lee, “Effect of heating location and size on mixed convection in lid-driven cavities”, Computer and Mathematics with Applications, Vol. 59, pp. 3053~3065, 2010. 5. M. I. Hasan, A. A. Rageb, M. Yaghoubi, H. Homayoni, “Influence of channel geometry on the performance of a counter flow micro-channel heat exchanger”, International Journal of Thermal Sciences, Vol. 48,pp. 1607~1618, 2009. 6. H. F. Oztop, Z. Zhao, B. Yu, “Fluid flow due to combined convection in lid-driven enclosure having a circular body”, International Journal of Heat and Fluid Flow, Vol. 30, pp. 886~901, 2009. 7. M-S Shin, H-S Kim, D-S Jang, S-N Lee, Y-S Lee, H-G Yoon, “ Numerical and experimental study on the design of a stratified thermal storage system”, Applied Thermal Engineering, Vol. 24, pp. 17~27, 2004. 8. N. Altuntop, M. Arslan, V. Ozceyhan, M. Kanoglu, “Effect of obstacles on thermal stratification in hot water storage tanks”, Applied Thermal Engineering, Vol. 25, pp. 2285~2298, 2005. 9. H. Hadim, M. North,“Forced convection in a sintered porous channel with inlet and outlet slots”, International Journal of Thermal Sciences, Vol. 44, pp. 33~42, 2005. 10. A. W. Date, “Fluid dynamical view of pressure checkerboarding problem and smoothing pressure correction on meshes with colocated variables”, International Journal of Heat and Mass Transfer, Vol. 46, pp. 4885~4898, 2003. 11. Y-T Yang, C-Z Hwang, “Calculation of turbulent flow and heat transfer in a porous-baffled channel”, International Journal of Heat and Mass Transfer, Vol. 46, pp. 771~780, 2003. 12. S. M. Saeidi, J. M. Khodadadi, “Forced convection in a square cavity with inlet and outlet ports”, International Journal of Heat and Mass Transfer, Vol. 49, pp. 1896~1906, 2006. 13. W. Qu, I. Mudawar, “Analysis of three-dimensional heat transfer in micro-channel heat sinks”, International Journal of Heat and Mass Transfer, Vol. 45, pp. 3973~3985, 2002. 14. H. F. Oztop, Z. Zhao, B. Yu, “Conduction-combined forced and natural convection in lid-driven enclosures divided by a vertical solid partition”, International Communications in Heat and Mass Transfer, Vol. 36, pp.661~668, 2009. 15. N. O. Moraga, E. E. Medina, “Conjugate forced convection and heat conduction with freezing of water content in a plate shaped food”, International Journal of Heat and Mass Transfer, Vol. 43, pp. 53~67, 2000. 16. S. V. Patankar, D. B. Spalding,“A calculation procedure for heat, mass and momentum transfer in three-dimensional parabolic flow”, International Journal of Heat and Mass Transfer, Vol. 15, pp. 1787~1806, 1972.||摘要:||
本研究探討一個蛇行管式熱交換器中氣體側前端之熱傳性能，此熱交換器由矩形截面管組合而成，氣體先與管道之側面垂直接觸，然後通過兩個狹小平行管道，最後流出熱交換器外，在進入狹小管距前，氣體會與矩形管之側面進行垂直衝擊之接觸，此研究主要探討此衝擊面處之熱傳性能。本研究首先利用有限差分法將質量平衡、Navier-Stokes與能量平衡等方程式離散成有限差分公式，格點之設計為交錯網格（staggered grid），在將所得之有限差分公式無因次化後，配合SIMPLE 演繹法進行數值分析之運算，電腦程式乃使用Fortran語言編輯。此數值分析中考慮之流體為二維層流，雷諾數(Re)為50與100兩種，流道收縮比亦分為0.25與0.5兩種，流體之普朗特數為0.7，管壁則考慮為等溫之狀態。於流場之分析結果中顯示，在較小之流道收縮比(=0.25)情形下，流體流動方向之改變會較大。於熱傳分析之結果中顯示，在相同流道收縮比之條件下，Re值增加一倍時，局部紐塞數(Nu)會增加，但平均紐塞數( )並未以等倍率增大；在Re值為50時，流道收縮比之變化對 值之影響甚小，而在Re值為100時，當流道收縮比變小時， 值會微略增加。
The heat transfer performance in the front surface of a serpentine heat exchanger was investigated. The heat exchanger is composed of rectangular tubes. During operation, gas vertically contacts with the front surface of the tubes and then it passes through a narrow spacing in between two neighboring tubes. Before the gas flows into the narrow spacing, it would impinge on the lateral side of the tubes. This work focuses on the impingement heat transfer in this region. A staggered-grid finite-difference method was used to discretize the continuity, Navier-Stokes and energy equations into a set of finite difference equations. These equations were converted into a dimensionless form and then solved following the SIMPLE algorithm. The computer program was compiled using Fortran language. In the analysis, the flow was two-dimensional and laminar. Two Reynold numbers (Re=50 and 100), and two flow-field contraction ratios (0.25 and 0.5) were considered respectively. The Prandtl number was 0.7 and the wall was considered to be isothermal. The result of the fluid analysis shows that, the smaller the contraction ratio (= 0.25), the larger the change of the flow direction. The result of the heat transfer analysis shows that, at the same contraction ratio, for an increase of the Re from 50 to 100, the local Nusselt number would increase. But the average Nusselt number does not increase two-folds. At the Re of 50, the contraction ratio almost does not have any effect on the average Nusselt number. At the Re of 100, as the contraction ratio decreases, the average Nusselt number value slightly increases.
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