TO-2711 -- The Effect of Air Turbulence on the Rate of Frost Growth on a Horizontal Flat Plate PDF

One factor currently affecting the efficient performance of finned refrigeration coils is frosting. This investigation determined the effect of air turbulence intensity on the growth rate of frost on a chilled flat plate in an effort to reduce the frosting problem.

Air turbulence intensities ranging from 1 to 22 percent were used with air conditions of 7.2°C (45F) dry bulb temperature and 5.1 g/kg (0.0051 lb/lb) humidity ratio and an air velocity of 3 m/s (590 fpm) for the six-hour tests. Additional tests at 7 to 8 percent air turbulence intensity were made for other air and velocity conditions.

The results showed that the effect of air turbulence on frost growth is negligible, if at all existent. However, it was found that increases in air moisture content or velocity, as well as decreases in the test plate surface temperature, all result in increased frost growth. Finally, it was found that the value of the overall heat transfer coefficient decreased as the frost layer grew, indicating that frost performs as an insulator.