Frost propagation and distribution on cold plate surface under forced convection

Abstract

The characteristics of frost propagation and distribution on cold plate surfaces under forced convection conditions were studied experimentally. The influence of forced convection on frost propagation was analyzed by comparing it with natural convection. The weakening effect of airflow on the frost suppression of the superhydrophobic and groove-superhydrophobic surfaces was revealed. The results indicate that the superhydrophobic micro-nanostructure increases the required volume of the ice bridge, inhibiting the one-way frost propagation from the sample edge to the center. By evaporating the droplets and forming dry zones in the groove valley, the groove patterns can intercept the generation of the ice bridge, and reduce the frost coverage. Under forced convection, the airflow can continuously provide sufficient water vapor to promote the growth of the droplets and trigger isolated-droplet nucleation, thus accelerating the frost propagation by building ice bridge connections in multiple directions. Moreover, the vapor can deposit in the groove valley to prevent the formation of the dry zone, which causes the anti-frosting function of the groove patterns by regulating the local vapor flux to have a limited effect. With the increase of the airflow velocity, the frost morphology changes from spreading columnar crystals to independent ice blocks covered with a frost layer, and the frost coverage rate increases. The frost propagation time drastically reduces, and then rises slightly due to the change in freezing mode and coalescence of the frozen droplets, which are caused by the intenser convective heat transfer.