氣冷式冰水機冷凝盤管配置最佳化之氣流模擬

CFD Simulation for Optimum Coil Configuration on Air-Cooled Chiller

周群傑(Qun-Jie Chou)

指導教授 ： 李宗興

國立臺北科技大學/機電學院/冷凍空調工程系所/碩士(2006年)

摘要

大型氣冷式冰水機之冷凝器通常係由多組鰭管式冷凝盤管所組成，由於受到機組外型尺寸之限制，使得冷凝盤管組之配置常有許多種不同之設計考量。然而，盤管之配置會影響經過冷凝盤管之氣流分佈，造成盤管表面風速不均勻，進而影響冷凝盤管散熱效率以及機組能源效率。因此尋找最佳之冷凝盤管配置，藉以改善氣流分佈與與提高熱傳性能之相關研究，就此成為此類設備性能提升之重要課題。有鑑於此，本研究主要的目的在於：利用CFD氣流模擬與熱交換器熱傳分析，再配合大型氣冷式冰水機組之實驗驗證的方法，比較在相同機組外型尺寸與風機性能之限制與不同外型尺寸相同風機性能條件下，進行不同盤管配置共十四種設計案例之氣流模擬與熱傳分析，藉由探討各個案例冷凝盤管的氣流分佈與熱傳性能之差異，尋找最佳之冷凝盤管的配置方式。
研究結果發現：在相同機型尺寸條件下僅改變盤管角度上的配置，並不能使內外盤管有均勻的分佈，對於平均風速與熱傳的改善也只有小幅度的變化，以案例5為最佳，分別改善7.19%與5.39%。A型式與B型式則分別為案例3A與3B，盤管總平均風速改善為29.01%與30.09%；總熱傳量則增加19.40%與20.74%。若以C型式的擺設，則盤管總平均風速改善為5.7%；總熱傳量則改善3.7%。盤管的配置以案例D為最佳。若以案例1為基準，則總平均風速可以改善達47.14%，熱傳則約有43.51%的改善空間。

關鍵字

氣冷式冰水機 ； 鰭管式熱交換器 ； 計算流體力學

並列摘要

The main purpose of this study is to find out the optimum coil configuration. Air-cooled liquid chiller coil configuration could strongly affect the condensing coil heat transfer. The coil configuration could affect the face velocity of condensing coil. CFD software-Airpak 2.1 is employed to simulate air flow field of the coils configuration. The numerical result was used to calculate the heat transfer of each coil. Compare with the baseline case 1. Case 5 could raise the average velocity nearly 7.19% and the heat transfer about 5.39%. Model A type, case 3A could raise the average velocity 29.01% and the heat transfer 19.40%. The optimum case of Model B type is case 3B, the average velocity could raise 30.09%, and heat transfer could raise 20.74%. When coil is Model C type, could raise the average velocity 5.7% and the heat transfer 3.7%. The optimum case of all cases is the case D, the average velocity could raise 47.14%, and heat transfer could raise 43.51%.

並列關鍵字

Air-cooled liquid chiller ； finned-tubes heat exchanger ； CFD

參考文獻

[1] Wang, C.C., Chang, Y.J., Hsieh, Y.C., Lin, Y.T., 1996, “Sensible heat and friction characteristics of plate fin-and-tube heat exchangers having plane fins” Int. J. of Refrigeration, Vol.19, pp.223-230.

[2] Jang, J.H., Chen L.K., 1996, “Numerical analysis of heat transfer and fluid flow in a three-dimensional wavy-fin and tube heat exchanger” Int. J. of Heat mass transfer, Vol.40, pp.3981-3990.

[3] Chang, Y.J., Wang, C.C., 1996, “A generalized heat transfer correlation for louver fin geometry” Int. J. of Heat Mass transfer, Vol. 40, pp.533-544.

[4] Wang, C.C., Tao, W.H., Chang, C.J., 1999, “An investigation of airside performance of slit fin-and-tube heat exchangers”, Int. J. of Refrigeration, Vol.22, pp.595-603.

[5] Lozza G., Merlo, U., 2001, “An experimental investigation of heat transfer and friction losses of interrupted and wavy fins for fin-and-tube heat exchangers”, Int. J. of Refrigeration, Vol.24, pp.409-416.