Ambient air vaporizer (AAV) utilizes ambient air which belongs to low grade energy to regasify LNG in gas terminals. Study on the heat transfer performance of AAV is the foundation of its optimal design and operation. This paper presents a CFD-based coupled numerical model to investigate the heat transfer performance of AAV. The heat transfer coupling between the LNG boiling phase change and the natural convection of the air is taken into consideration. The mixture model combined with Lee model was used to calculate the heat and mass transfer in the process of LNG boiling. The coupled numerical model was calculated and validated by the operating data of a real-life MV. Based on the simulation results of the coupled model, the influence of the air temperature, the inlet flow of LNG and the location in the fin tube bundle on the heat transfer performance of AAV were analyzed. (C) 2015 Elsevier Ltd. All rights reserved.