Internal mass flux through frost

Abstract

An experimental method is de®eloped for determining the internal mass flux through frost with a dendrite structure. The theory and experimental procedures of the measurements using water slightly concentrated with deuterium are described. The internal mass flux determined from ®ariations in the deuterium concentration in frost with time shows an almost linear decrease in the frost depth direction from the surface. The profile of the local frost density is almost flat in the depth direction. The frost uniformity is kept independent of the cooled-plate temperature and the total pressure in the container unless part of the frost melts. The cause for the uniformity of frost density is discussed in terms of the frost temperature profile and microscopic crystal growth.

Analysis of the frost growth on a flat plate by simple models of saturation and supersaturation

“…Initial porosity seems to have close relation with the characteristic of the ice crystal growth. Fukuda and Inoue [6] and Miller and Young [22] found that the sublimation density of ice crystal increases as the crystal formation temperatures increase. Moreover, according to the S ßahinÕs results [7], the initial value of the volumetric ratio of the ice columns in the frost layer is a function of environmental parameters.…”

“…Both of them reduce the mass diffusivity of the water-vapor and affect the growth of the frost layer. Fukada and Inoue [6] suggested that the water-vapor in the frost layer is supersaturated in their experimental research. Epstein and Rosner [23] concluded that the vapor being transported across the thermal boundary layer is observed to undergo homogeneous nucleation to the liquid phase, and vapor pressure is larger than saturated value.…”

“…Studies agree that frost has a flat density profile in the y direction [6,12], and this means that does not vary in the y direction and the porosity of the frost layer is uniform in the frost layer. The second term of Eq.…”

“…They used correction factors to match the experimental data. Fukada and Inoue [6] developed an experimental method for determining the internal mass flux through frost layer and found that the profile of the local frost density is almost flat in the direction of depth, regardless of the cooling wall temperature and the total pressure. S ßahin [7] found that the effective thermal conductivity of the frost layer was not the only parameter related to frost density.…”