側向開口端部封閉管流紊流器熱傳及流場效應探討

Turbulator Effects on Heat Transfer and Flow Characteristics in Side-open End-sealed Duct Flows

郭哲翔(Zhe-Shaun Kuo)

指導教授 ： 陳增源

淡江大學/工學院/航空太空工程學系碩士班/碩士(2006年)

https://doi.org/10.6846/TKU.2006.00243

摘要

本研究以實驗量測方式利用側向開口端部封閉管道，探討流體側向溢流以及紊流產生器對流場結構與熱傳之關連性，並探討在邊界層內流場對流、二次流及紊流特性影響。本實驗使用一小型風洞系統用來產生均勻流之空氣，流入側向開口端部封閉管道之入口，將紊流產生器置於管道入口，且流場雷諾數介於1500至15000之間。在管道壁面設置一9 × 12 cm*cm 之銅熱傳板當作量測面。在流場量測方面，以都卜勒雷射測速儀(LDV)量測管道斷面、邊界層內三維向穩態之平均速度與擾動速度，並藉以獲得近熱傳表面之對流速度、二次流速度及紊流動能。而在熱傳板之溫度，則以T型之熱電偶線(type T thermocople)量測，藉以獲得Nusselt number。研究結果顯示，管道中央斷面流場有一般衝擊流特性；而靠近管道壁面之流體，受到端板所造成逆向壓力與壁面摩擦力雙重影響，導致逆向流產生，且雷諾數愈小，逆向流較早發生。加裝紊流產生器能提升熱傳效應，且增加近熱傳面之二次流速度及紊流動能。

關鍵字

側向開口端部封閉管流 ； 熱傳 ； 紊流產生器

並列摘要

The research experimentally investigate the turbulator effects on heat transfer and flow characteristics in a side-open, end-sealed duct, which simulates the cooling passages in the fin-type heat sinks of electronic equipments. Specifically, this research investigates the effects of fluid side-leakage and turbulator on the flow structures and near-wall flow characteristics, such as the convective mean velocity, the secondary flow and the turbulent kinetic energy. A wind tunnel system is used to generate a uniform flow at the inlet of the side-open, end-sealed duct. The Reynolds number is between 1500 and 15000. The turbulator have three type, such as a 45?? delta-wing turbulator, a 10?? delta-wing turbulator and a 90?? rectangular-wing turbulator. The turbulator is placed at the inlet of the duct for the turbulator-effect study. The measurements include three-component mean and fluctuating velocities at duct cross-sections and near the duct wall. Results of this study indicate that the flow in the central plane of the duct is similar to an impinging flow. Due to the reverse pressure by the end wall and the friction force by the duct wall, the flow reversal occurs near the duct wall. The reversal flow occurs earlier for smaller Reynolds number than that for larger Reynolds because of the smaller flow kinetic energy. The effects of the turbulator causes lager dead water flow region and, thus, results in worse convective effect. However, the turbulator causes the larger secondary velocity and turbulent kinetic energy and, thus, results in better secondary and turbulent effects on the near-wall flow characteristics.

並列關鍵字

Side-open end-sealed duct flow ； Heat transfer ； Turbulator

參考文獻

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