Growth and behavior characteristics of frost crystals on a single micro-sized frozen droplet at different surface temperatures

Condensation frosting is widespread in many engineering fields and usually brings serious harm. Given that a frost layer is comprised of interactional frost crystals that grow on many micro-sized frozen droplets, research on the frosting characteristics on a single micro-sized frozen droplet may help to better reveal the frosting mechanism. In this study, a series of frosting experiments on a single micro-sized frozen droplet in the surface temperature range of −30 to −10 °C are conducted. The results show that as the surface temperature decreases, the duration of the crystal rapid growth stage shows a decreasing trend while that of the crystal growth and collapse stage increases first and then decreases. The frequency of crystal collapse in the crystal growth and collapse stages for −10, −15, −20, −25, and − 30 °C are 0.182, 0.078, 0.079, 0.190, and 0.259 Hz, respectively, decreasing first and then increasing. Three frost crystal growth patterns on frozen droplets are concluded, including the wrap-around, spike, and hybrid growth patterns, which significantly impact the variation trends of the average crystal height and roughness. The results are meaningful to understanding the frost crystal growth and behavior mechanisms, and further provide a reference for frost prediction and defrosting strategy.