介電液FC-72在傾斜矩形流道之流動沸騰研究

Abstract

本論文以實驗方法探討介電液FC-72以完全發展流，在雷諾數500,1200,2000，次冷度15℃,21℃,28℃條件下，於加熱銅片朝上，工作流體在渠道水平流動(0°)和由下往上流動(45°、90°)以及加熱銅片朝下，工作流體在渠道由下往上流動(135°)之管道方位的沸騰熱傳特性。其中矩形流道之截面積為間隙高度2mm、寬度10mm，水力直徑為3.33mm。 實驗結果發現，在單相熱傳區與部分發展核沸騰區，增加流速與次冷度可降低加熱銅片表面之溫度。在完全發展核沸騰區，流速與次冷度對加熱銅片表面之溫度則逐漸失去影響力。臨界熱通量會隨流速與次冷度的增加而升高。工作流體於渠道水平流動和由下往上流動以及加熱銅片朝上之管道方位，所得到之臨界熱通量近乎相同。至於加熱銅片朝下之管道方位所得到的臨界熱通量則遠小於加熱銅片朝上之管道方位所得到的臨界熱通量。

This thesis describes the experimental investigation of the fully developed flow boiling heat transfer for FC-72 with Reynolds numbers 500,1200,2000 , subcooled temperatures 15℃,21.5℃,28℃,as well as test section orientations of 0°horizontal flow, 45°upflow, 90°upflow with the heated copper block face-up and 135°upflow with the heated copper block face-down. The channel is constructed having a crosssection of 2mm height and 10mm width with a hydraulic diameter of 3.33mm. The results show that increasing both fluid velocity and subcooled temperature would reduce the wall temperature gradually at the regions of single phase heat transfer and partially developed nucleate boiling. At the region of fully developed nucleate boiling, the influences of both fluid velocity and subcooled temperature are reduced gradually. The critical heat flux (CHF) always increases as the values of flow velocity and subcooled temperature rise.The CHF values of 0°,45°,90° with heated surface upward-facing orientations are almost the same. However, the CHF values for upflow with heated surface downward-facing are much smaller than those for upflow with heated surface upward-facing.