Journal
EXPERIMENTAL THERMAL AND FLUID SCIENCE
Volume 35, Issue 1, Pages 211-218Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.expthermflusci.2010.09.003
Keywords
Titanium; Dropwise and film co-existing condensation; Condensation pattern; Heat transfer model
Funding
- Shanghai Leading Academic Discipline Project [B503]
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Visual experiments were employed to investigate heat transfer characteristics of steam on vertical titanium plates with/without surface modifications for different surface energies. Stable dropwise condensation and filmwise condensation were achieved on two surface modification titanium plates, respectively. Dropwise and rivulet filmwise co-existing condensation form of steam was observed on unmodified titanium surfaces. With increase in the surface subcooling, the ratio of area (eta) covered by drops decreased and departure diameter of droplets increased, resulting in a decrease in condensation heat transfer coefficient. Condensation heat transfer coefficient decreased sharply with the values of eta decreasing when the fraction of the surface area covered by drops was greater than that covered by rivulets. Otherwise, the value of eta had little effect on the heat transfer performance. Based on the experimental phenomena observed, the heat flux through the surface was proposed to express as the sum of the heat flux through the dropwise region and rivulet filmwise region. The heat flux through the whole surface was the weighted mean value of the two regions mentioned above. The model presented explains the gradual change of heat transfer coefficient for transition condensation with the ratio of area covered by drops. The simulation results agreed well with the present experimental data when the subcooling temperature is lower than 10 degrees C. (C) 2010 Elsevier Inc. All rights reserved.
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