矽微米線陣列上之池沸騰臨界熱通量

Abstract

本研究以去離子水為工作流體，探討加熱器尺寸和矽微米線陣列密度對池沸騰臨界熱通量(Critical Heat Flux, CHF)的影響，本研究共探討5種不同加熱器尺寸 (0.5 x 0.5, 0.75 x 0.75, 1 x 1, 1.5 x 1.5 和 2 x 2 cm2)及3種微米線補釘大小(73 μm (pa73), 158 μm (pa158)和341 μm (pa341))。在補釘大小為pa158，加熱器尺寸為1 x 1 cm2時，得到最高之CHF為212.7 +- 4.1 W/cm2，其為目前沸騰熱傳界所得之最高臨界熱通量之一。所得結果顯示當加熱器尺寸大於1 x 1 cm2時，CHF隨著加熱器尺寸減小而增加，且所得之CHF與經由流體不穩定性理論所計算出來的值接近吻合，此驗證了我們之前所提出的假說。但當加熱器尺寸小於1 x 1 cm2時，CHF不再隨著加熱器尺寸改變，這可能是由於當加熱器尺寸越小，其表面張力影響越大，造成蒸汽氣泡難以脫離加熱表面，而造成CHF無法隨著加熱器尺寸縮小而更加上升。

In this work, pool boiling of de-ionized (DI) water on the micropillar array-coated surfaces having five different heater sizes (i.e., 0.2 x 0.2, 0.5 x 0.5, 1 x 1, 1.5 x 1.5 and 2 x 2 cm2) and three different patch sizes (i.e., 73 μm (pa73), 158 μm (pa158), and 341 μm (pa341)) were studied. The highest CHF of approximately 212.7 W/cm2 was obtained on the pa73 surface with a heater of 1 x 1 cm2 in size. This value of CHF is one of the highest CHFs obtained in the field of boiling heat transfer. The CHF increases as the heater size reduces when heater size is larger than 1 x 1 cm2. The experimental CHF values qualitatively agreed with the predictions of the modified hydrodynamic model. This suggests that the CHFs on these surfaces were due to hydrodynamic limit. On the other hand, there is no apparently size-dependent-CHF observed when the heater size is smaller than 1 x 1cm2. This might be due to that the hydrodynamic theory is not suitable for very small heaters on which the surface tension force is too large for bubble releasing.