Internal flow in freezing and non-freezing water droplets at freezing temperatures

Abstract

By comparing freezing and non-freezing water droplets with Particle Image Velocimetry (PIV), this paper aims to further advance the knowledge of the internal movement in deposited water droplets. The experiments are carried out at substrate temperatures below 0 °C, and the onset of the freezing process is controlled by the structure of the plate. Results show similar flow patterns for the freezing and non-freezing case, indicating that the phase change is not the initial driving force of the internal movement or the directional change phenomena. The phase change will, however, decrease the volume of the liquid and generate a difference in heat transfer and temperature, hence introducing a faster decrease in velocity and sooner directional velocity change. In the non-freezing case, a stagnated period at the beginning of the internal movement is observed before the decrease in velocity. • Influence of the freezing process on the internal flow in water droplets is studied • Freezing and non-freezing water droplets show similar trends regarding flow field • A short steady state phase is observed only for non-freezing droplets • The directional change of the internal velocity occurs earlier for freezing droplets

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