Abstract:
The thin liquid film near the contact line is important for
droplet evaporation on a heated surface, however, it remains a
challenge for modeling and simulation since it operates from
macroscale down to nanoscale. The nanoscale thin film profile
has long been unknown; besides in CFD simulations the
meshing work for the thin film could be extremely consuming
therefore a truncation is needed to disregard the very thin part
of the thin film region. The present study is an attempt to
simplify the thin film modeling for partially wetting liquids,
based on a recent Atomic Force microscope (AFM)
experiments that suggested the partially wetting nanoscale thin
film are closely following the macroscale profiles. We conduct
a theoretical study on an evaporating sessile droplet and
evaluate the effect of thin film truncation size on the overall
heat transfer. A small spherical droplet with less than 1mm
diameter is investigated and the wall superheat is 1 C°. The
contact angles are ranged from 5o to 85o. We evaluate the effect
of the dimensionless truncation ratio, i.e. the ratio of the
truncation size and droplet height on the overall heat transfer
underestimation. The results show that the dimensionless
truncation ratio has a critical effect on the heat transfer
calculation while the contact angle and the droplet size have
relatively weaker influences. It is due to the fact that the
variation of truncation ratio has much more effect on the size of
the neglecting thin film region.
Description:
Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .
