대한기계학회논문집B (Transactions of the Korean Society of Mechanical Engineers B)

  • 제37권7호
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  • Pages.695-701
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  • 2013
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  • 1226-4881(pISSN)
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  • 2288-5324(eISSN)
대한기계학회 (The Korean Society of Mechanical Engineers)
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증발하는 물방울의 계면활성제에 의한 열모세관 유동 억제

Surfactant-Induced Suppression of the Thermocapillary Flow in Evaporating Water Droplets

  • 윤성찬 (포항공과대학교 기계공학과) ;
  • 김태권 (부산대학교 기계공학부) ;
  • 임희창 (부산대학교 기계공학부) ;
  • 강관형 (포항공과대학교 기계공학과) ;
  • 임근배 (포항공과대학교 기계공학과)
  • Yun, Sungchan (Dept. of Mechanical Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Kim, Tae Kwon (School of Mechanical Engineering, Pusan Nat'l Univ.) ;
  • Lim, Hee Chang (School of Mechanical Engineering, Pusan Nat'l Univ.) ;
  • Kang, Kwan Hyoung (Dept. of Mechanical Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Lim, Geunbae (Dept. of Mechanical Engineering, Pohang University of Science and Technology (POSTECH))
  • 투고 : 2013.01.21
  • 심사 : 2013.05.21
  • 발행 : 2013.07.01
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초록

본 논문은 비이온의 계면 활성제에 의해 증발하는 물방울의 열모세관 유동(마랑고니 유동)이 억제되는 것을 실험적으로 검증한다. 물방울이 소수성 표면 위에서 증발할 때, 액적 내부의 마랑고니 유동을 관찰하였고, 계면 활성제 농도에 따라 이 유동이 억제되는 것을 조사하였다. 초기 계면 활성제 농도가 증가하면, 마랑고니 유동의 속도와 수명이 감소한다. 이 결과는 계면 활성제에 의해 액적 계면에서 점착 경계 조건이 성립됨을 보여주는데, 이것은 계면 점착 현상과 관련된 기존의 모델에 기초하여 설명되었다. 또한 액적의 초기 계면 활성제 농도가 임계 농도 이하일 때, 증발 초기 접촉선 비고정 현상을 발견했는데, 이것은 마랑고니 유동이 접촉각의 이력 현상을 감소시키기 때문이다.

The suppression of a thermocapillary flow (Marangoni flow) by a nonionic surfactant is experimentally investigated for evaporating pure water droplets on hydrophobic substrates. The experiment shows that as the initial concentration of the surfactant increases, the velocity and lifetime of the flow monotonically decrease. The result confirms the no-slip boundary condition at a liquid-air interface, which is explained on the basis of the previous model regarding the effect of surfactants on the no-slip condition. Interestingly, at an initial concentration much less than a critical value, it is found that depinning of the contact line occurs during the early stage of evaporation, which is ascribed to a reduction in the contact angle hysteresis owing to the presence of the Marangoni flow.

키워드

참고문헌

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