氣冷式冰水機創新冷凝盤管設計之氣流模擬

CFD Simulation for Innovative Condensing Coil Design of Air-Cooled Chillers

王聖凱(Sheng-Kai Wang)

指導教授 ： 李宗興

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00231

摘要

氣冷式冰水機冷凝器多採用鰭管式熱交換器，以V型擺設配合頂部風機抽吸而成，雖提高整體風速，但冷凝盤管表面出口速度分布上下不均、內外不一致的現象尚在，使得冷凝盤管之熱傳性能與原設計值產生差異，導致冷凝溫度升高，進而降低冰水機組之性能效率。有鑑於此，本研究主要目的為：利用CFD氣流模擬與熱交換器熱傳分析，針對傳統氣冷式冰水機冷凝盤管氣流分佈大小不均且內外不一致之缺點，設計七種創新冷凝盤管，探討創新冷凝盤管對於氣冷式冰水主機冷凝器氣流分佈之影響，試圖找出最佳設計配置，達到改善冷凝器熱傳性能與提升機組能源效率之目的。
研究結果發現，改變盤管鰭片間距，僅能降低成本並不能提升熱傳量，且無法使內外盤管有較一致的平均風速，且熱傳量僅有小幅度變化，改變盤管鰭片間距分佈以案例D2為最佳，以案例A為基準，平均風速與熱傳分別提升13.51%與3.23%，較案例C提升3.86%與-0.51%。改變盤管管排數排列，能使內外盤管有較均勻的氣流分佈，案例F為最佳之設計方式，可改善風速分布不均，且內外盤管平均風速較為一致性，較案例A改善為20.42%，總熱傳量則為10.28%；較案例C改善為9.59%與4.9%。

關鍵字

氣冷式冰水機 ； 鰭管式熱交換器 ； 鰭片間距 ； 管排數 ； 計算流體力學

並列摘要

The primary purpose of this research is as follows: Utilizing the CFD simulation and heat exchange conducting analysis, in lieu of traditional condensing coil of air-cooled liquid chiller distributes air flow unevenly and unsteadily, to devise seven innovative coils and to discuss the influence of such inventions on the flow circulation in the air-cooled liquid chiller, in order to find the best configuration which would lead to improved heat transfer efficiency of the condenser and in turn increase the machine's overall efficiency.
Research results show that by changing the fin pitch on the tube plate, it can only lower total cost, but it does not increase volume of heat transferred, nor does it stabilize face velocity inside and outside of the tube plate. The change in heat transfer is also neglectable. Changing fin pitch of coil arrangement best results in case D2. Compared to those of case A, the average velocity and heat transfer increased by 13.51% and 3.23% respectively; and 3.86% increase in average velocity but 0.51% decrease in heat transfer compared to results in case C. By changing the tube row arrangement of coil, it helps distribute face velocity of the condensing coil more evenly among the inside and outside of the condensing coil. Case F appears to be the best configuration. It improves face velocity distribution and stabilizes average face velocity on the inside and outside of the condensing coil. The results of this case show an increase in average face velocity of 20.42% and a 10.28% increase in total heat transfer compared to those in case A; and a 9.59% and 4.9% respective improvement compared to case C.

並列關鍵字

Air-cooled liquid chiller ； finned-tubes heat exchanger ； fin pitch ； tube row arrangement ； CFD

參考文獻

[2] 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.

[3] 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.

[4] Colburn, A.P., 1933, “A method of correlating forced convection heat transfer data and comparison with fluid friction” Transaction of the AlChe, Vol. 29, pp.174-2.

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

[6] Mcquiston F.C., J.D. Parker, J.D. Spitler, “Heating, Ventilating, and Air Conditioning Analysis & Design, 2000.