Development of a Measurement Method for Evaporation Coefficient under Non-equilibrium Conditions based on Acoustic Resonance Tube Experiment and Molecular Gas Dynamics

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04202
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Nara National College of Technology
• Principal Investigator: Nakamura Shigeto 奈良工業高等専門学校, 電子制御工学科, 准教授 (80619867)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 蒸発係数 / 凝縮係数 / 相変化 / 音波 / 共鳴

Outline of Final Research Achievements

The objective of this research is to extend the measurement method based on resonant acoustic waves to accommodate non-equilibrium conditions. The evaporation coefficient is an unknown parameter within the boundary conditions of molecular gas dynamics, and precise determination of the evaporation coefficient can directly contribute to engineering fields such as heat exchangers, as well as indirectly contribute to addressing abnormal weather phenomena and environmental issues.
In order to reduce the various errors that have occurred in previous experimental methods, we focused on improving the experimental apparatus and precisely measuring the acoustic field within the resonance tube. However, due to changes in the measurement method and delays in procuring pressure sensors, the progress of the research has significantly lagged behind, and the objective of measuring the evaporation coefficient under non-equilibrium conditions, which was the aim of this project, could not be achieved.

Free Research Field

分子気体力学

Academic Significance and Societal Importance of the Research Achievements

本研究で取り組む、蒸発係数の測定は古くから様々な研究者らによって試みられているが、正確な測定結果はこれまで得られていない。研究代表者らによって開発された共鳴音波を用いた蒸発係数測定法においても、測定結果において同一の液膜温度に対して、蒸発係数にばらつきが見られることが確認されており、この誤差は実験系の非平衡に起因していると考えられる。蒸発係数が正確に決定されれば、蒸発、凝縮が関わる技術において、より効率的な制御が可能となり、加えて異常気象、地球温暖化などに対しても、より正確な現象の予測が可能となる。このように本研究成果による効果は極めて広範囲にわたるものであり、また普遍的なものである。