Simulating the evaporation of pinned water microdroplets with implementation of a surface concentration distribution

Numerical and experimental investigations of water microdroplet evaporation on polymer substrates are reported. The study is focused on validating numerical models with experimental data. The experimentally measured evaporation rates are compared to the predictions of a commonly reported model based on a solution of the Laplace equation, providing the local evaporation flux along the droplets liquid-vapor interface. The model consistently overpredicts the evaporation rate, which is presumable due to the models constant saturated vapor concentration along the droplets liquid-vapor interface. In result, a modified version of the model is implemented to account for variations in temperature along the droplets liquid-vapor interface. A vapor concentration distribution is then imposed using this temperature distribution, increasing the accuracy in predicted evaporation rate by ~ 7.7% and ~ 9.9% for heated polymer substrates at T_s = 50°C and 65°C, respectively.