Frost formation criterion framework for ambient air vaporizers integrating inter-fin mainstream air temperature correction

Ambient Air Vaporizers (AAVs) for Liquefied Natural Gas (LNG) regasification suffer from performance degradation due to frost formation on finned tubes. To address this, a novel frost formation criterion was developed based on phase equilibrium and mass transfer principles. It emphasizes the critical role of the inter-fin mainstream air temperature, a parameter that significantly deviates from ambient conditions. Integrated numerical simulations of the tube bundle were conducted to quantify this deviation. Results show that the inter-fin air can be up to 33 °C colder than ambient air at the bundle center, and reveal a near-linear relationship between the ambient-wall and ambient-mainstream air temperature differences, with a proportionality constant of 4.5∼5.0. An empirical temperature correction formula was derived and experimentally validated. Compared to conventional methods, the new criterion reduces the root-mean-square error (RMSE) in predicting the frost initiation wall temperature from 4.41 °C to 2.28 °C. Furthermore, the analysis proposes practical frost mitigation strategies, such as modifying surface wettability and elevating the LNG inlet temperature. These findings provide fundamental insights for advancing anti-frost technologies and developing more accurate predictive models.