A fundamental understanding of factors affecting frost nucleation

Theoretical analysis of the nucleation process for frost formation on a cold surface shows that the air at the cold surface should be supersaturated in order for frost nucleation to occur. This understanding is new, relative to previously published frost growth models. Further, the supersaturation degree is dependent on the surface energy, which is related to the water contact angle. The theoretical predictions were compared to experimental results, and reasonable agreement was obtained. Qualitatively, a low energy surface (high contact angle) requires higher supersaturation degree for frost nucleation than a high energy surface. Quantitatively, the experimental data shows that the low energy surface requires approximately 10 times higher supersaturation degree than the high energy surface when the contact angle difference is approximately 80degrees at -20 degreesC surface temperature. The factors affecting the surface energy such energy such as temperature, surface roughness, and foreign particles are discussed in this paper. (C) 2003 Elsevier Ltd. All rights reserved.