臺灣博碩士論文加值系統

本研究以實驗方法探討改變熱輻射效果是否會影響到自然對流為主軸，利用鰭片主面積相等，但改變灰體視因子之值，以求增強熱輻射效果，分別採用矩形、直角三角形、鈍角三角形(120。)，三種形狀來進行，排列形式有交錯和平行排列兩種；在粗度真空狀態下，可觀察熱沉之熱輻射能力，隨著壓力增加，熱輻射能力也隨之減弱，當壓力增加至約為100mm-Hg，自然對流效果會明顯出現。實驗結果發現，改善灰體視因子可以有效改善熱輻射效果；主面積為(2000mm2)時，在粗度真空狀態下量測熱輻射效果，相較於矩形鰭片，各樣式鰭片可使熱沉熱對流係數增加1.5%~11.89%，在自然對流(760mm-Hg)時，相對於矩形，效果可增加1.7%~12.69%；主面積為(3000mm2)時，效果增加3.5%~26.5%，自然對流時為 -0.6%~15%。根據本研究指出交錯排列形式之鳍片及鈍角三角形形狀可以改善自然對流之效果。

The present thesis is aimed to investigate natural convection heat sink performance by thermal radiation enhancement. The experiments use different kinds fin but same heat transfer area to change gray view factor. There are three different fin shapes including rectangular-fin, right-triangular-fin and obtuse-triangular-fin with two different arrangements, parallel and staggered. To measure thermal performance of heat sink, the chamber was kept in low vacuum state. As pressure increased, we can observe that natural convection gradually dominate heat transfer mechanisms. The experiment result shows that both radiation and natural convection thermal performance was improved by increasing gray view factor. Obtuse-triangular-fin can improve thermal efficiency effectively. Besides, staggered arrangement is better than parallel arrangement.

圖目錄 I
表目錄 IV
符號說明 V
第一章 緒論 1
1-1 前言 1
1-2 常見的散熱方式介紹 2
1-2-1 強制對流(氣冷散熱) 3
1-2-2 強制對流(水冷散熱)： 3
1-2-3 自然對流 4
1-3 自然對流介紹 5
1-3-1 自然對流原理 5
1-3-2 自然對流常用的無因次參數 5
1-4 熱輻射介紹 7
1-4-1 熱輻射原理 7
1-4-2 熱輻射性質 7
1-4-3 輻射視因子 (Radiation view factor)： 8
1-4-4 表面間的輻射交換 8
1-5 灰體視因子 10
1-6 文獻回顧 10
第二章 實驗設備與方法 16
2-1實驗設備： 16
2-2儀器校正： 17
2-3實驗方法及步驟： 18
2-4資料簡化： 19
第三章 結果與討論 34
3-1 灰體視因子計算 34
3-2 粗度真空與中度真空測試 34
3-3 不同壓力下熱沉散熱之性能 35
3-4 模擬不同角度三角形鰭片(交錯排列)於自然對流之性能 38
3-5 模擬熱沉於不同壓力下之熱輻射與對熱對流性能 40
第四章 結論 60
第五章 參考文獻 62
附錄A：灰體視因子(Gray view factor)計算 64
附錄B：誤差分析 66

[1] M. Reynell, Advanced thermal analysis of packaged electronic systems using computational fluid dynamics techniques, Computer-Aided Engineering Journal 7(4) (1990),104-106

[2]G.N. Ellison, Generalized Computations of the Gray Body Shape Factor for Thermal Radiation from a Rectangular U-Channel, IEEE Transaction On Component, Hybrid, And Manufacturing Technology 2(4), December (1979), 517-522.

[3]Y. Shabany, Radiation Heat Transfer from Plate-Fin Heat Sinks, 24th IEEE SEMI-THERM Symposium (2008).

[4] Y. K. Khor, Y. M. Hung, B. K. Lim, On the role of radiation view factor in thermal performance of straight-fin heat sinks, International Communications in Heat and Mass Transfer 37 (2010) 1087-1095.

[5] D. Sahray, H. Shmueli, G. Ziskind and R. Letan, Study and Optimization of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection and Radiation, Journal of Heat Transfer 132(2010) 012503,1-12.

[6] E. M. Sparrow and S. B. Vemuri, Orientation Effects on Natural Convection/Radiation Heat Transfer From Pin-Fin Arrays, Int. J. Heat Mass Transfer 29(1986), 359-368.

[7] S.H. Yu, D. Jang, K.S. Lee, Effect of radiation in a radial heat sink under natural convection, International Journal of Heat and Mass Transfer 55 (2012) 505–509.

[8] D. Jang, S. Yu, K. Lee, Multidisciplinary optimization of a pin-fin radial heat sink for LED lighting applications, International Journal of Heat and Mass Transfer 55 (2012) 515–521

[9] M. Dogan, M. Sivrioglu, O. Yılmaz, Numerical analysis of natural convection and radiation heat transfer from various shaped thin fin-arrays placed on a horizontal plate-a conjugate analysis, Energy Conversion and Management 77 (2014) 78–88.

[10] R. Hosseini, M. Saidi, Experimental study of air pressure effects on natural convection from a horizontal cylinder, Heat Transfer Enginerring, 33(10) (2012) 878-884.

[11] H. Hirano, H. Ozoe, N. Okamoto, Experimental study of natural convection heat transfer of air in a cube below atmospheric pressure, Internaltional Journal of Heat and Mass Transfer, 46 (2003) 4483-4488.

[12] J. R. Howell, A Catalog of Radiation Configuration Factors, McGraw-Hill, New York, 1982.