Heat, fluid and substance transfer mechanism of boiling phenomenon in cryogenic fluid during functional cooling of living cell

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K03995
• 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: Akita National College of Technology
• Principal Investigator: NOZAWA Masakazu 秋田工業高等専門学校, その他部局等, 准教授 (60447183)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 沸騰制御 / 熱工学 / 凍結保存 / 伝熱促進

Outline of Final Research Achievements

Recently, ES/iPS cells have attracted attention in the field of regenerative medicine. However, there is a problem that the survival rate after freezing and thawing is low. It is known that the survival rate is improved in the high cooling rate. Therefore, high speed cooling by liquid nitrogen is necessary. However, the film boiling occurs when the cooling object is immersed directly in liquid nitrogen, and as a result, the cooling rate is suppressed. It was found in our past research that the cooling rate is increased by covering the cooling object by a stainless steel mesh. However, it was not clarified how the mesh could suppress film boiling. In order to investigate the boiling state, visualization of film boiling on the surface of cooling object was performed using a high-speed camera and a cryostat. It was confirmed from the image analysis for results of the film boiling that the size and frequency of the vapor bubble were changed with the surface condition.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

本研究課題の成果により、液体窒素浸漬冷却のような高冷却速度の凍結保存において、容器表面の形状を微細な凹凸のある構造にすることで、現状よりも高い冷却速度を得るための方法の1つになることが確認できた。また、表面形状の変化による、外部の伝熱特性の変化が内部への伝熱に及ぼす影響も計測することができたため、これらの知見は、凍結保存用の容器の設計に役立てることができると言える。