Numerical simulation on the frosting and heat transfer characteristics of plate-fin heat exchanger considering confinement effect

Abstract

In refrigerating industry, frost commonly deposits on the confined cold surfaces of heat exchangers, which affects the heat transfer performance. Along the confined flow path of the heat exchanger, the frosting at downstream is affected by the parameters from the upstream. In this study, a numerical model considering the confinement effect has been proposed to predict frosting characteristics in plate-fin heat exchanger. Convection-diffusion equations for humid air and empirical correlations for local frost density are employed in the numerical prediction. Frosting behavior and heat transfer in the confined channel are investigated with different humid air parameters and cold surface temperatures. The results indicate that frost thickness in the confined channel is thicker than that in open space under the same inlet parameters. The frost layer is thicker and fluffier along the confined channel. In addition, the air temperature difference between inlet and outlet of the confined channel enlarges with frosting. Under the same average temperature of upper and lower surfaces, the heat and mass transfer of frosting are enhanced with diminishing temperature difference of upper and lower surfaces. In such condition, frosting is mainly influenced by the cold surface with the lower temperature.