Studies on unique characteristics of liquid-vapor behaviors and mechanism of CHF enhancement during boiling of aqueous binary mixtures

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K06103
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: Hokkaido University
• Principal Investigator: SAKASHITA Hiroto 北海道大学, 工学研究院, 准教授 (00142696)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 二成分水溶液 / 限界熱流束 / 可視化測定 / 沸騰 / ドライアウト

Outline of Final Research Achievements

The CHF of the mixtures considerably increases when small amount of alcohols are added to water. To examine the mechanism of CHF enhancement, this research visualized the boiling behaviors of water, binary aqueous mixtures of alcohols (2-propanol, butanol, pentanol), and surfactant (Triton-X) using a transparent heating surface. It was found that the dryout expansion on the heating surface was significantly suppressed in the alcohol aqueous solution compared to water, and there was almost no difference between the Triton-X aqueous solution and water.
These results clarified that the CHF enhancement in the binary aqueous mixtures is due to the suppression of surface dryout caused by non-uniform distribution of alcohol concentration formed near the heating surface.

Free Research Field

伝熱工学

Academic Significance and Societal Importance of the Research Achievements

沸騰の除熱限界である限界熱流束(CHF)は，微量のアルコールを添加することで大きく促進されるため，高熱流束機器の沸騰除熱媒体として利用できる可能性がある．しかし， CHF促進機構は明らかになっていなかった．本研究では，透明伝熱面を用いた可視化測定により，伝熱面上の乾燥領域の拡大がアルコールの添加により大幅に抑制されることがCHF促進をもたらしていることを明らかにした．また，炭素数4以上のアルコール水溶液は極めて低濃度でCHFの大幅な促進をもたらす，効率的なCHF促進媒体であることを明らかにした．