風扇流場之數值模擬與量測

Abstract

本文利用數值方法對一般電腦內常散熱風扇與發熱晶片之搭配進行研究與分析。本文利用有限體積法求得電扇與晶片之間的速度分佈，而流場的模擬則採用紊流K-ε模式。在實驗觀測方面，利用暗房與攝影機，以及閃光燈的準確觸發，將風扇下方流場結構清楚的紀錄下來，並與數值計算所得之結果吻合。結果顯示，一般常用風扇下方中心處會造成流體的滯流，而在四週受到窩流的包圍而使得晶片所發出之熱無法有效的帶走。經過分析發現，此現象乃是風扇葉片之對稱性所造成。根據此一結果，所提出改變葉片對稱性可以有效的縮小晶片中心高溫區以及降低晶片溫度。

This study is to investigate a flow field of common used computer fan. A finite volume method is employed to solve the flow field in the fan. During the computing process, the k-ε turbulent model is used to solve the governing equation of the flow field. In experiment investigation, a dark room and camera is used to film the flow field. However, by using an accurately triggered flashlight, the flow field down below the fan can be clearly recorded. According to the above investigation, the flow is almost stay still in the center below the fan. And there are several vortexes around the center below the fan, which keep the heat generated by the chip from the outgoing flow. After analysing the above phenomenon, to break the geometric symmetry is the most efficient mean to improve the fan efficiency.