Abstract: The closure equations of the two-fluid model for heat and mass transfers between liquid phase and vapor phase during boiling flow of liquid nitrogen were developed.The formulas of the interfacial area concentration and the bubble departure diameter were modified for accurate prediction.The equations were incorporated into the two-fluid model and the commercial CFD code CFX-4.3.Two-dimensional numerical simulations of subcooled boiling flow of nitrogen in a vertical tube were performed by using the modified CFD code.The numerical results showed encouraging agreement with the experimental data available in the literature.Detailed distributions of the void fraction, heat transfer coefficient and liquid temperature difference were obtained, leading to better understanding of the basic mechanisms of boiling flow and related cooling systems.