Experimental Study of Frost Formation on a Flat Surface Under Nature Convection

Abstract

A series of experiments were conducted to investigate the frost formation and characteristics on a flat surface under natural convections. The process of frost formation and structures is visibly observed and measured by using of a microscope. The temperature distribution of the air around the frost layer is measured by using of the holographic interferometry technique. The influences of the main parameters are analyzed. Especially, the microscopic analysis of frost growth on the surface characteristics on the microscopic characteristics of a frost layer during the early growth period when sub-cooled droplets are formed and changed to the ice. The thickness and mass of frost layer are measured while frost formation is visualized simultaneously. The results show that the frost surface temperatures are much lower than the freezing temperature and close to the cold surface temperature at the early growth period. After the early growth period, the frost surface temperature is dominated by the convective heat transfer between the frost surface and surrounding air.

Analysis of Thermal Conductivity of Frost on Cryogenic Finned-tube Vaporizer Using Fractal Method

“…Liquid nitrogen in cryogenic vessel absorbs heat by convection between the vertical flat plate and indoor humid air, and then gasifies; humid air will form frost on the surface of vertical flat plate. Figure 2 shows the experimental images of frost growth on the cryogenic surface (with cryogenic surface temperature T w = −120℃) at different time, it can be seen from (a) and (b) that many dendritic frost crystals formed on the cryogenic surface, and new dendritic crystals produced with increasing time; as shown in (c), these dendritic frost crystals are characterized with fractal self-similarity to some extent [14,15]. Figure 3 shows the simulated image of frosting on the cryogenic surface of finned-tube vaporizer in MATLAB based on the DLA model of fractal theory.…”

Fractal model for simulation of frost formation and growth

“…[3], the authors pointed out that the full growth frost layer satisfied with the three criterions above and was of fractal characteristics. Besides the distributions of initial frost crystals formed on the copper surface and the random positions where the crystal nucleus formed also show fractal characteristics [2].…”

“…It is very recently that Hao et al [2] pointed out that the sizes and distributions of ice particles formed on the cold surface showed fractal characteristics under critical state conditions. Whereafter Hou et al [3] made a fractal analysis to frost crystal with Box-counting dimension.…”