Study on fundamental heat transfer processes in boiling heat transfer

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01265
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 19020:Thermal engineering-related
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: Yabuki Tomohide 九州工業大学, 大学院工学研究院, 教授 (70734143)
• Co-Investigator(Kenkyū-buntansha): Shen Biao 筑波大学, システム情報系, 助教 (80730811)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 沸騰熱伝達 / 高速度赤外線カメラ / 人工発泡点 / ミクロ液膜 / 対流熱伝達

Outline of Final Research Achievements

Water saturated pool experiments using a high-speed infrared camera and artificial nucleation sites revealed that convective heat transfer with a large area occupancy dominates wall heat transfer in a wide range of nucleation site density conditions. At least for the surfactant type and concentration tested in this study, the enhancement of heat transfer by surfactant addition was found to be due to an increase in microlayer area, and the increase in microlayer area was attributed to bubble softening (decrease in surface tension), bubble coalescence suppression, and bubble sliding motion. Using a newly developed thin-film stacked heat flux sensor with a spatial resolution of 2 microns, we measured the heat flux near the three-phase contact line in FC-72 boiling. A high local evaporative heat flux exceeding 0.6 MW/m2 was measured as the three-phase contact line passed over the sensor.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

本研究で明らかにした各種伝熱素過程の総熱輸送量への寄与は，電子機器の冷却などに用いられる沸騰伝熱面の開発において有用な知見である．例えば，ミクロ液膜蒸発が極めて高い局所熱伝達率をもつ一方で面積占有率が小さいために総熱輸送量への寄与が小さかったことを踏まえると，表面の微細構造化や濡れの制御等でミクロ液膜蒸発を促進して全体の熱伝達率を向上させるアイデアが生まれる．界面活性剤水溶液に対する試験では，界面活性剤の添加がミクロ液膜面積を増大させ，それが熱伝達促進につながっていることが明らかになった．