Study on Frost Layer Growth Characteristics of Finned Tube Evaporator Under Forced Convection Conditions

Frosting is one main adverse factor hindering the application of finned tube evaporators in refrigeration systems. To accurately predict the growth characteristics of the frost layer, its growth behavior on the surface of a three-dimensional finned tube under forced convection conditions was numerically simulated based on the coupled VOF (volume of fluid) multiphase flow and phase change mass transfer rate model method. The maximum difference between the simulated frost layer thickness and the experimental results was within 15%. The estimated value of the frost layer density was within a confidence interval of up to 90%; this is in good agreement. By building a visualization experimental platform for frosting on the surface of the finned tube of the evaporator, the influences of ambient temperature, relative humidity, and frontal wind speed on frost growth characteristics under single-factor changes were analyzed. The results showed that the thickness of the frost layer gradually decreased from front to back in the direction of the airflow. The lower the air temperature, the greater the wind speed, the higher the relative humidity, the larger the thickness of the frost layer, the more frost, and the larger the thermal resistance of the frost layer. The thickness of the frost layer reached its highest value of 2.344 mm at 85% relative humidity. According to the Morris sensitivity analysis, the relative humidity had the greatest influence on the frost layer thermal resistance, and the sensitivity coefficient reached 2.41. The correlation of the frost layer thermal resistance with different environmental parameters was obtained using the least squares regression method.