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The effects of non-condensable gas on condensation heat transfer on a super-hydrophobic surface tube

초소수성 코팅 튜브에서의 비응축가스 영향에 대한 응축 열전달 연구

  • Ji, Dae-Yun (School of Mechanical and Control Engineering, Handong Global University) ;
  • Kim, Daeho (School of Mechanical and Control Engineering, Handong Global University) ;
  • Lee, Kwon-Yeong (School of Mechanical and Control Engineering, Handong Global University)
  • 지대윤 (한동대학교 기계제어공학부) ;
  • 김대호 (한동대학교 기계제어공학부) ;
  • 이권영 (한동대학교 기계제어공학부)
  • Received : 2018.01.17
  • Accepted : 2018.04.06
  • Published : 2018.04.30

Abstract

This purpose of this research is to observe the influence of non-condensable gas (NCG) on a horizontal super-hydrophobic aluminum tube and compare it with a bare aluminum tube. To achieve super-hydrophobic characteristics, an aluminum tube was coated with a Self-Assembled Monolayer (SAM). The overall heat transfer coefficient U was used to represent the condensation performance. The NCG mass fraction was the main variable, and its range was 0.08 to 0.45. The condensation performance of the SAM tube and bare tube increased with decreasing mass fraction of NCG. The SAM tube showed 1.9 to 2.5 times larger dropwise condensation performance than the bare tube. When the mass fraction of NCG decreased in the SAM tube, the rate of increase of the SAM tube was lower because flooded condensation occurred. In addition, filmwise condensation occurred in the SAM tube when more active condensation was generated, and its performance was lower than that of the bare aluminum tube. The flooded and filmwise condensation in the SAM tube is explained by the pinning effect. In conclusion, controlling the condition of the condenser is necessary to improve the condensation performance by surface modification a SAM.

Keywords

Condensation heat transfer;Super-hydrophobic surface;Dropwise condensation;Horizontal aluminum tubes;Non-condensable gas

Acknowledgement

Supported by : 한국연구재단

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