Experimental study on the effect of surface temperature on the frost characteristics of a vertical cold plate under natural convection

Frosting is a common natural phenomenon, and is widely seen in engineering fields. To avoid the drawbacks and take advantage of frost, analyzing the frost characteristics is meaningful. Frosting experiments of a vertical cold plate under natural convection are carried out, with the surface temperature varied at a range of −30 ∼ -10 ℃. The frost characteristics, including the frosting stages, frost layer thickness and surface roughness, dynamic frosting rate, reverse melting and frost density, are analyzed and discussed. Results show that the growth trend of frost thickness at different surface temperatures presents a leaf shape, and the first three frosting stages are within 300 s. Under the surface temperature of −25 ℃, formations of the frost seed, tree and forest advance the time of the branches break and the first reverse melting, thus increase the proportion of the Droplet condensation and coalescence stage to 53.70% and influence the frost layer surface roughness. Periodic reverse melting causes the fluctuations of the frost layer surface roughness and the frost density, and changes the trend of dynamic frosting rate when the first reverse melting occurs. Contributions of this study are expected to provide a more in-depth understanding of frosting and thus provide a reference for frost prediction, suppression and defrosting in engineering applications.