%0 Journal Article %A Zhang, Tongxin %A O'Neal, Dennis L. %D 2019 %I Begell House %K hydrophobic coating, empirical correlation, dimensionless freezing time, phase change %N 4 %P 381-397 %R 10.1615/HeatTransRes.2018019776 %T PHASE TRANSITION OF WATER DROPLETS WITH DIFFERENT STATIC CONTACT ANGLES %U https://www.dl.begellhouse.com/journals/46784ef93dddff27,069137575e3e0439,3542c9344568318e.html %V 50 %X The freezing process of water droplets was investigated for an uncoated and two coated aluminum surfaces subjected to the action of a forced convective environment. One of the coatings was a silicon-based conformal polymer and the other was a hydrophobic coating. Static contact angles of the droplets ranged from 74.6 deg for the uncoated aluminum to 127.1 deg for the hydrophobic coating. Air velocities ranged from 0.2 to 1.85 m/s, surface temperatures ranged from –5 to –13°C, air temperatures ranged from 4 to 24°C, and air relative humidities were varied from 24 to 54%. Droplet radii ranged from 0.4 to 1.5 mm. A digital high speed microscopy system was used to visually observe and measure the freezing in individual droplets. Empirical correlations for dimensionless freezing time as a function of three nondimensional variables (Am, Re, and Ste) were developed. These correlations could be used to estimate dimensionless freezing time over a wide range of experimental conditions. Droplets on the hydrophobic surface showed the slowest nondimensional freezing times while those on the silicon-based conformal polymer coating and uncoated surfaces were comparable. The data for the silicon-based conformal polymer coating surface were also compared to the data from a prior researcher. %8 2018-12-12