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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

NUMERICAL STUDY ON THE DETAILED DROPLET SIZE DISTRIBUTIONS IN DROPWISE CONDENSATION WITH THE CONSIDERATION OF DROPLET "OVERLAPPING" AND MULTIPLE RE-NUCLEATION

Get access (open in a dialog) DOI: 10.1615/IHTC16.cod.024152
pages 2299-2306

Sinopsis

Evolution and distribution of condensate droplets were the most important information in dropwise condensation. For surfaces with larger contact angles, the interactions between droplets became more complicated due to their three dimensional profiles, yielding different droplet size distributions. In this study, the detailed droplet evolution and size distributions were analyzed by complete droplet lifecycle simulations with a modified droplet coalescence criterion and the consideration of 3D droplet profile. The results showed that it was possible for two droplets with overlapping projected profiles to be isolated in 3D configurations, which guaranteed that surfaces with larger contact angles can allow small droplets to locate beneath the larger ones and improved the spatial distribution of small droplets. The results also indicated that the coalescence of droplets with significant different sizes were able to realize multiple coalescence and multiple re-nucleation, which ensured that the small droplets can be renewed more frequently. Experimental droplet images obtained by ESEM also showed similar droplet behaviors and supported the above analyses. The multiple re-nucleation and the presence of small droplets underneath larger ones guaranteed that the small droplets can take an more active part in dropwise condensation for surfaces with larger contact angles. Comparative results confirmed that, as the contact angle was increased, the surface coverage was decreased, while the number of small droplets was greatly increased, and the overall effect lead to a improved heat transfer performance. The present simulations presented more detailed droplet information from the perspective of 3D droplet profiles, which provided insight into the better understanding of the droplet size distributions and extended the dropwise condensation theory.