隨著電子產品尺寸愈來愈小，強化散熱能力為目前重要趨勢。本研究探討鋸齒狀表面迷你流道熱沉之沸騰熱傳的強化。本研究在熱沉上設計迷你尺寸的鋸齒狀表面結構，熱沉共含有四條水力直徑為0.8 mm之迷你流道，材料以無氧銅作為流道基底。熱沉底面面積為90 mm × 5 mm。鋸齒狀結構以線切割方式加工。鋸齒狀結構尖端間隔1 mm。為了環境之永續發展，本研究以低全球暖化潛勢的HFE-7100為工作流體分別探討三種表面結構(平流道、順齒狀流道、逆齒狀流道)、三種尖端角度(30、45及60 度)及兩種齒狀高度(0.5與0.75 mm)在質量通率為63 kg/m^2s至285 kg/m^2s情況下的沸騰熱傳現象。
實驗結果顯示臨界熱通率隨著質量通率的增加而上升，且齒狀結構有助於臨界熱通率的提升。在低質量通率，齒狀結構尖端角度45 ∘與高度0.5 mm的情況之下，順齒及逆齒流道的臨界熱通率與平流道相比，分別提升46.7 %及40.2 %。此結果指出低質量通率時，齒狀結構可顯著提高臨界熱通率。而在高質量通率時，相對於平流道，順齒及逆齒流道的臨界熱通率分別增加1 % 及17.1 %。由此可知，在高質量通率時，逆齒狀結構有助於臨界熱通率的強化。除此之外，逆齒流道齒狀尖端角度60度及高度0.5 mm時，臨界熱通率具最大值，為本研究之最佳設計。

The dimension of electronic devices become smaller and smaller and it is of significant importance to enhance the heat dissipation from such tiny devices. The present study investigates the boiling heat transfer in a minichannel heat sink with saw-tooth structure on channel surface. The heat sink is comprised of four minichannels with hydraulic diameter of 0.8 mm and made of copper. The dimensions of the base area of the heat sink are 90 mm × 5 mm. The saw-tooth topology on the bottom of minichannel was manufactured by wire-cut EDM. The saw-tooth structure is with a pitch of 1 mm and three different tip angles ( 30 ∘,45 ∘, and 60 ∘) and two different tooth heights (0.5 and 0.75 mm). This study employs HFE-7100 refrigerant, which is of low GWP, as the working fluid to investigate the boiling heat transfer in three kinds of surface structures (plain, parallel saw-tooth and counter saw-tooth). The mass flux ranges from 63 kg/m^2s to 285 kg/m^2s.
The experimental results show that the critical heat flux increases with increasing mass flux and enhancement of critical heat flux due to saw-tooth structure. For the structure with a tip angle of 45 ∘and tooth height of 0.5 mm. The critical heat flux in the parallel and counter saw-tooth minichannel are greater than that of the plain minichannel by 46.7 % and 40.2 % for a low mass flux of 127 kg/m2s. This indicates that the critical heat flux is significantly enhanced by the saw-tooth structure with either parallel or counter flow design for low mass flux. On the other hand, compared to the plain minichannel, the critical heat flux of the parallel and counter saw-tooth minichannel are increased by 1 % and 17.1 % , respectively, for a large mass flux of 285 kg/m2s. A saw-tooth structure with counter flow design may significantly enhance the critical heat flux. Furthermore, a tip angle of 60 ∘and height 0.5 mm in minichannel with counter flow is found to perform best.

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