A numerical study on frosting and its early stage under forced convection conditions with surface and environmental factors considered

To accurately control the frosting process, analyzing the influence of different factors on frosting is meaningful and challengeable, especially in the early frosting stage. According to the sensitivity analysis, the influence of different surface wettability and environmental factors on the growth of frost layer were quantitatively analyzed. Based on the experimental data on cold plate surface under forced convection conditions, new models with emphasis on the initial conditions of the frosting process are developed. Results show that supersaturation degree, supercooling degree and cold plate temperature are the key factors on the growth of frost layer, but their specific influence varies in the early frosting stage. And proportions of these three factors reach 39.42%, 35.58% and 21.15%, respectively. The coincidence rates of the new models with an error of 15% reach>90% for the whole frosting process, and 83% for the early frosting stage. Compared with previous models, the coincidence rates of the new models for the whole frosting process and the early frosting stage are increased by at least 8.86% and 15.28%, respectively. Contributions of this study are expected to predict the growth of frost layer in the early frosting stage and provide a reference for the optimal defrosting control of air source heat pumps.