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Droplet condensation on chemically homogeneous and heterogeneous surfaces

Ashrafi, A ; Sharif University of Technology | 2016

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  1. Type of Document: Article
  2. DOI: 10.1063/1.4962645
  3. Publisher: American Institute of Physics Inc , 2016
  4. Abstract:
  5. Nucleation and growth of condensing droplets on horizontal surfaces are investigated via a 2-D double distribution function thermal lattice Boltzmann method. First, condensation on completely uniform surface is investigated and different mechanisms which cause dropwise and filmwise condensation are studied. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. In the second step, condensation on chemically heterogeneous surfaces is investigated. Moreover, the effect of non-uniformity in the surface temperature is also studied. The results indicate that the vapor layer instability and the nucleation start from the heterogeneities. The effects of different numbers of heterogeneities, their distance, and hydrophobicity on the condensation are also inspected. It is shown that by increasing the hydrophobicity of the heterogeneities and considering an optimum space between the heterogeneities, maximum condensation performance can be achieved. Finally, condensation on wettability gradient surfaces is studied and the effects of the gradient form and contact angle of the core region on the condensation are studied. It is shown that hydrophobicity of the core region plays a key role in increasing the condensation performance. A heat transfer analysis and flow dynamics of dropwise condensation as a function of time is also presented and it is shown that the results are in good agreements with the previous theoretical and experimental results
  6. Keywords:
  7. Atmospheric temperature ; Computational fluid dynamics ; Distribution functions ; Drop formation ; Drops ; Heat transfer ; Hydrophobicity ; Nucleation ; Double distribution functions ; Dropwise condensation ; Filmwise condensation ; Heat transfer analysis ; Heterogeneous surface ; Nucleation and growth ; Thermal lattice-Boltzmann method ; Wettability gradients ; Condensation
  8. Source: Journal of Applied Physics ; Volume 120, Issue 12 , 2016 ; 00218979 (ISSN)
  9. URL: http://aip.scitation.org/doi/10.1063/1.4962645