An experimental study on the effect of horizontal cold plate surface temperature on frosting characteristics under natural convection

Frosting is widely seen in nature and many industry fields, and always plays negative effect. To accurately predict and control frosting process on cold plate surface, an experimental study on the frosting characteristics on the surface of horizontal cold plate is carried out, with the surface temperature varied at a range of −30 ∼ -10 °C under natural convection. Based on the experimental results, series of frosting characteristics are analyzed. As reported, the first three stages of frosting are short and account small proportion, within 160 s in the 1,200 s frosting process. The growth trend of frost thickness shows a leaf-shaped area, which could be used for predicting the frost thickness under different conditions. The surface temperature effect on the frosting rate is obvious, and directly influences the surface roughness. For a surface with temperature at −27.5 °C, the peak of frosting rate is 9.59 × 10^-6 m/s, the peak and fluctuation amplitudes of roughness at 90 × 10^-6 m and 57.57 × 10^-6 m, respectively. The periodic reverse melting directly influences the frost layer thickness and dynamic frosting density. On the −27.5 °C surface, the lowest and highest densities are 22.08 kg/m³ and 65 kg/m³ at 368 s and 1229 s into frosting, respectively. Results of this study could be used for the control strategy optimization of anti-frosting and defrosting for energy equipment, such as air source heat pump.