Verification of wave hypothesis for critical heat flux in nucleate boiling heat transfer

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03169
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Hirosaki University
• Principal Investigator: Shirota Minori 弘前大学, 理工学研究科, 准教授 (40423537)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 沸騰 / 液滴衝突 / 臨界熱流束 / マイクロレイヤー / 蒸発 / 凝縮

Outline of Final Research Achievements

Drop impact on a hot surface causes a sub-cooled boiling wave with violent bubble volume oscillations. The sub-cooled wave covers all the contact area between the drop and the surface in several milliseconds of drop impact event. We call the unique boiling phenomena in an impacting drop as impact drop boiling.In the present research, we captured in detail the dynamics of vapor bubbles in impact drop boiling with a high-speed camera and a long-distance microscope. We also developed an analytical model to describe the bubble dynamics based on the spherical bubble model. By comparing the model with experimental results on the time variations of bubble radius, we evaluated the validity of our model.
As a result, we clarified that the thermal boundary layer developed on a heated surface and the microlayer formed in between the bubble and the surface play dominant roles in the bubble dynamics in impact drop boiling.

Free Research Field

流体工学，熱工学

Academic Significance and Societal Importance of the Research Achievements

情報技術の高度化や，半導体デバイスの高集積・大型化に伴う半導体チップ冷却技術の向上が求められる中，噴霧冷却が有力視されている。従来の噴霧冷却では，加熱面上に液膜が形成されるほどに，液滴を大量に吹き付けてきた。対して申請者は，本研究において，衝突液滴が急加熱されることで生成される蒸気気泡が，液滴の衝突変形過程において，激しく凝縮するいわゆるサブクール流動沸騰領域が高温領域へ自発的に広がって行く現象に着目し，数理モデルを構築した。
本研究成果によって，より最適な噴霧冷却手法が今後見出され，それにより現代科学を象徴する高度技術の飛躍的な性能向上や高効率化へとつながることが期待される。