Investigation of solid-liquid interfacial heat transfer influenced by the complex mobility of colloidal particles in the vicinity of a solid wall

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04223
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19020:Thermal engineering-related
• Research Institution: Shibaura Institute of Technology
• Principal Investigator: Shirai Katsuaki 芝浦工業大学, 工学部, 准教授 (00634916)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: コロイド / 電気運動学 / 固液境界 / ブラウン運動 / マイクロ・ナノスケール / ナノ流体 / 計測 / 近接場光

Outline of Final Research Achievements

Motions of small particles dispersed in liquid were investigated in the interfacial boundary region between solid and liquid related to heat transferring colloids including nanofluids. For the measurement of particle velocities, two different optical systems were built based on evanescent waves penetrating from a solid wall to test colloid. In the experiment, test colloid with dispersed particles was flown into square-shaped test section and the measurement was accomplished in the region within about 200 nanometers from the solid wall beyond the diffraction limit. From the results, the particles seem to flow with the average velocity of the surrounding fluid exhibiting fluctuating velocities based on Brownian motion. The average velocities exceeded the prediction based on the linear regression of the fluorescence irradiance of the particles, which indicates the signals came from the region deeper into the test liquid than it was expected originally.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

電子機器では回路集積化により発熱密度が増加し、高効率な冷却が求められる。微粒子を添加したコロイドは単層液体のみと比べ伝熱性能の向上が期待され、流動性を有するため、熱輸送媒体として注目される。しかし伝熱に関わる領域は壁面から粒径程度の極薄い領域で計測は容易ではない。本研究では壁面からコロイドへ僅かに浸透するエバネッセント波に基づく2種類の光学計測を構築し、壁面から約200 nm程度の領域で粒子速度計測を実現した。計測結果から、粒子速度が周囲流体の平均的な流れに追従しブラウン運動の影響を確認し、本手法を用いた現象の計測に加え、理論やモデル構築に繋がる基礎データ取得に活用可能なことを示唆した。