痕量水低温表面结霜及换热性能实验研究

To investigate the effect of trace water frosting on heat transfer over cryogenic surfaces, an experimental platform for visualized frosting and heat transfer on a confined cryogenic surface was developed. Cryogenic liquid nitrogen was used to keep the cold surface within the temperature range of the liquid nitrogen, and on the low-temperature surface where the water vapor content by volume was less than 1 000 × 10^-6, a frosting experiment was carried out. Thereafter, a binary image processing method was employed to extract the growth characteristics of the frost layer thickness along the direction of moist air flow for investigation into the temporal evolution of frost layer thickness, frost mass, frost density, and heat flux, as well as the influence of moist air velocity, temperature, and humidity on frost growth and heat transfer. The results show that the frost layer thickness decreases gradually along the direction of airflow;at the 0 m and 0.1 m positions, the frost layer thickness is significantly different, while relatively small variation in the frost layer thickness is observed from the 0.1 m position onward;relatively high air velocity and humidity, plus low air temperature, correspond to increased frost layer thickness, frost mass, and frost density. In the total heat transfer, sensible heat flux accounts for over 90%. The water vapor content has a primary effect on the latent heat flux but little influence on the total heat transfer. Both sensible and total heat fluxes are positively correlated with the velocity and temperature of the moist air. Furthermore, a dimensionless correlation for frost density on the cryogenic surface within the temperature range of liquid nitrogen was developed based on experimental data, and the overall fitting error was within ± 20%. This study is intended to provide valuable insights for analyzing the frosting and heat transfer performance of cryogenic heat exchangers operating in the temperature regime of liquid nitrogen.