三維圓管後附加一矩形鰭片之流場及熱傳現象之研究

A study on 3-D fluid flow and heat transfer in a channel in the presence of a build-in circular tube with an integral wake splitter

陳永全(Yung-Chuang Chen)

指導教授 ： 鄧志浩

中原大學/工學院/土木工程研究所/碩士(2006年)

https://doi.org/10.6840/cycu200600024

摘要

摘 要
本研究利用最小平方有限元素法求解Navier-Stokes equations及熱擴散方程式，模擬三維圓管後附加一矩形鰭片所造成流場及熱傳現象之影響。在本文中考慮不同雷諾數(Re=200、600、1000)及不同鰭片長度(0、2H、3H、4H)，來探討流場的流線、壓力、溫度及紐賽值分佈。
雷諾數大於40，圓柱後方會出現二排渦流，此即為馮．卡曼渦漩，流場中之圓管後加上一鰭片後，使得其渦漩後移甚至削減，隨著鰭片的增長使得其削減效果會更好。對於壓力而言，加裝鰭片後圓管兩側極小值也跟著降低，所以有助於流場的流速增加。因為渦漩會造成圓管後有一高紐賽值區，鰭片的存在會使圓管後部份紐賽值減少，隨著鰭片長度的增加，高熱傳區域也隨之增加。雷諾數越高，鰭片的有無對於流場與熱傳現象有較高的影響。利用最小平方有限元素法所模擬之現象與實驗做比較亦有較佳的結果。

關鍵字

鰭片 ； 最小平方有限元素法 ； 雷諾數 ； 紐賽值 ； 熱傳

並列摘要

ABSTRACT
A numerical calculation procedure based on the least-squares finite element method (LSFEM) is employed to solve the Navier-Stokes equations and energy equation for simulating flow fields and heat transfer in a channel of a build-in circular tube with and without a rectangle splitter plate. For different Reynolds numbers (Re=200,600,1000) and different splitter plate lengths (0.2H,3H,4H) in this paper, the distribution for the streamline, pressure, temperature, and Nusselt number are discussed in detail.
When Reynolds number is greater than 40, the cylinder will present two rows of vortexes at rear of the cylinder, this is called Von Karman shedding cycle. When adding a splitter plate behind the circular tube, it can make vortexes move forward downstream or even cut down the vortexes. It will cut down the vortexes more with the growth of the splitter plate length. For the pressure distribution, the minimum values at both sides of circular tube decrease after installing the splitter plate so that the velocity of flow field increase accordingly. The presence of a splitter plate causes a general decrease in local Nusselt number behind the circular tube. The size of the section of the high heat transfer in the wake increases as the chord length of the splitter plate increases.
The numerical simulation by using the LSFEM is shown in good agreement with the experimental measurement.

並列關鍵字

Nusselt number ； heat transfer ； Least-squares finite element method ； Reynolds number ； splitter plate

參考文獻

19. 李宏文(2004),”橢圓鰭管式空氣冷凝器三維熱液動性能分析”

18. 陳啟宏(2004),”以最小平方有限元素法探討雙橋墩流場變

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