Coupled Modeling of CO2 Frosting, Fluid Flow, and Heat Transfer under Cryogenic Conditions Using a Nucleation-Based CFD Framework

Abstract

: A two-dimensional Computational Fluid Dynamics (CFD) model, grounded in classical nucleation theory, is developed to investigate CO 2 frosting and the associated heat transfer under cryogenic conditions. The model integrates gas–solid phase-change kinetics with multiphysics transport equations to capture the coupled phenomena governing frost formation. The Peng–Robinson equation of state is employed to predict CO 2 frost points in binary mixtures, with model predictions validated against experimental data, yielding errors in frost thickness and thermal conductivity below 15%. The results demonstrate that decreasing the cryogenic wall temperature from 160 K to 150 K increases the average frost thickness and density by 57% and 78%, respectively, while advancing the peak in thermal resistance by approximately 5 min. A reduction in CO 2 mol fraction from 10% to 6% leads to an 82% decrease in average frost density. Although inlet velocity exerts a limited influence on frost density, excessively high velocities increase porosity and inhibit densification. Flow field analysis reveals that progressive frost growth constricts the effective channel area, resulting in a local velocity increase of approximately 23%. Moreover, the spatial distributions of supersaturation and nucleation rate exhibit strong consistency. These findings elucidate the complex coupling between CO 2 frosting, fluid flow, and heat transfer in Pressurized Liquefied Natural Gas (PLNG) systems, offering theoretical insights for optimizing low-energy CO 2 cryogenic capture and enhancing natural gas liquefaction processes.