Three dimensional reconstruction of frost structure by replica method

Abstract

To predict and control frosting phenomenon, three-dimensional structure of frost should be quantified in different environmental conditions. This paper experimentally studied frost structure using replica fabrication method. Supplying Formvar solution by a syringe pump under dry air, a plastic shell was successfully fabricated on the frost surface. The voids on the plastic shell were filled with a light-curing resin, from which a replica of frost was obtained. The three dimensional structures frost under different environmental conditions were reconstructed by μX-ray CT. The effects of environmental conditions on the local frost crystal shape, density and tortuosity factor distributions were quantitatively investigated. Frost shape was largely affected by the air relative humidity and temperature. A sheath-like crystal was observed at cooling plate temperature of -15 °C, while dendrite crystal formed at -25 °C. These results are consistent with the knowledge of snow crystal morphologies. The frost density and pore tortuosity factor increased with air velocity and relative humidity.