Suppression of frost layer growth on glass or copper surfaces with micro-scale lattice-patterned grooves

Abstract

The growth of frost crystals and frost layers on solid surfaces causes serious problems, such as poor visibility of traffic lights or convex traffic mirrors and a deterioration of the performance of heat exchangers. Thus, controlling the growth of frost crystals and frost layers is very important for reducing these problems. In this study, the observation of frost growth was carried out for cooling glass or copper plates with micro-scale lattice-grooves. It was found from the captured images that frost crystals were formed from the surfaces of condensation droplets, which appeared on the protrusions of the grooved plates. The frost crystals growing from the surface of a droplet on one of the tops of the protrusions coalesced to those on other tops nearby. The coalescence caused local, gradual growth of a frost layer. It was also found that the droplets on some of the tops of the protrusions of the glass plates rapidly evaporated as a result of the growth of frost crystals near the tops. It was noted that new frost crystals did not appear on the surfaces of evaporating droplets and the dried tops of the protrusions. A further finding was that the porosity of the frost layer increased by coating a silane coupling agent onto the glass surfaces. It can be concluded from these findings that the glass or copper surfaces with micro-scale lattice-patterned grooves coated with the silane coupling agent are effective for attenuating the frost layer growth.