Numerical simulation of frosting behavior and its effect on a direct-contact ambient air vaporizer

• A numerical model for ambient air vaporizer (AAV) is developed.
• Frosting on the wall and vaporization are considered comprehensively.
• Frosting behavior and thermal performance of AAV are investigated.
• Deterioration mechanism of the vaporizer is revealed.

Ambient air-based technology for liquefied natural gas vaporization is an ideal selection for reducing the average cost of terminals and maximizing operating efficiency. Thus, this study presents a numerical model to predict the frosting behavior and thermal performance of a direct-contact ambient air vaporizer. The empirical correlations for predicting some basic properties of the frost layer are used to establish the numerical model. The flow of cryogenic fluid in the vaporizer and the adverse effect of the frost layer are both considered in the model. Numerical results agree with the experimental data in the literature in a wide range of working conditions. The outlet temperature of the vaporizer initially surges because of the frost formation at the early stage. This surge decreases with time and ambient air temperature. The frost behavior on the vaporizer surface is not only related to surrounding conditions but also to the flow state of the fluid in the vaporizer. During operation, the lengths of the liquid-phase and two-phase sections increase, whereas that of the vapor-phase section decreases.