應用漸擴型鰭片陣列於飽和狀態HFE-7100的池沸騰熱傳改善

Abstract

本研究於尺寸為 67 mm × 67 mm 之加熱表面上，使用光化學金屬蝕刻方式製作出兩種鰭片布局方式：一致型及漸擴型，並搭配兩種鰭片形狀：圓柱狀及魚鱗狀，形成共四種鰭片陣列設計之加熱表面，探討其對於常壓飽和狀態下之HFE-7100池沸騰熱傳效能的影響。 由實驗結果可知，使用漸擴型之鰭片設計於高熱通量時可有效提升沸騰熱傳性能，這是因為漸擴流道能有效降低氣泡往上排除之流阻。漸擴型魚鱗鰭片陣列於熱通量 14 W cm-2 至熱通量 21 W cm-2 時，沸騰熱傳係數相較於一致型魚鱗鰭片陣列提升 9.8% 至 16.5%；漸擴型圓柱鰭片陣列於熱通量 17 W cm-2 至熱通量 20 W cm-2 時，沸騰熱傳係數相較於一致型圓柱鰭片陣列提升 11.5% 至 15.3%。 此外，與光滑表面比較，使用任一種鰭片陣列表面，皆具有提升沸騰熱傳性能表現之效果，這是因為鰭片陣列設計能夠有效增加表面上形成之氣泡數量。鰭片陣列表面於熱通量 0.9 W cm-2 至 2 W cm-2 時之沸騰熱傳係數增強效果最明顯，相較於光滑表面提升約 51.1% 至 72.4%。其中在熱通量 2 W cm-2 時，鰭片陣列表面之壁面過熱度相較於光滑表面下降約 34.9% 至 36.9%。在熱通量 3 W cm-2 至 6 W cm-2 之範圍內，鰭片陣列表面的氣泡移除頻率相較於光滑表面改善 4.5% 至 66.0%，使沸騰熱傳係數於此區間中有 31.8% 至 54.0% 之增強效果。鰭片陣列表面之臨界熱通量相對光滑表面能夠提升約 17.6% 至 23.5%。

This study focuses on the pool boiling of HFE-7100 for a vertical surface with various designs of pin-fin arrays at atmospheric pressure. Two types of designs, diverging and uniform, and two pin-fin shapes, cylindrical and fish scale, are implemented so that four variations are etched by photochemical method onto the heated surfaces. The experimental results show that the diverging design can effectively improve the heat transfer at high heat flux because the diverging arrangement of pin-fins reduces the flow resistance for bubble removal. For the fish scale array, the heat transfer coefficient of the diverging design is 9.8% to 16.5% more than that of the uniform design for a heat flux between 14 W cm-2 and 21 W cm-2. For the cylindrical array, the heat transfer coefficient of the diverging design is 11.5% to 15.3% more than that of the uniform design when heat flux varies from 17 W cm-2 to 20 W cm-2. Comparing to smooth surface, heat transfer enhancement is found by utilizing the pin-fin arrays. This is attributed to the increase in the number of nucleation sites on the pin-fin arrays. For heat flux varies between 0.9 W cm-2 and 2 W cm-2 , the heat transfer coefficient is increased by approximately 51.1% to 72.4%. Moreover, the critical heat flux of pin-finned surface is 17.6% to 23.5% higher than that of the smooth surface. In addition, the bubble removal frequency of pin-fin array surface is 4.5% to 66.0% higher, resulting in 31.8% to 54.0% increase of the boiling heat transfer coefficient for heat flux varying from 3 W cm-2 to 6 W cm-2.