The improvement of thermal-hydraulic analysis techniques is essential to ensure the safety and reliability of nuclear power plants. The one-dimensional two-fluid model has been adopted in state-of-the-art thermal-hydraulic system codes. Current constitutive equations used in the system codes reach a mature level. Some exceptions are the partition method of wall friction in the momentum equation of the two-fluid model and the interfacial drag force model for a horizontal two-phase flow. This study is focused on deriving the partition method of wall friction in the momentum equation of the two-fluid model and modeling the interfacial drag force model for a horizontal bubbly flow. The one-dimensional momentum equation in the two-fluid model is derived from the local momentum equation. The derived one-dimensional momentum equation demonstrates that total wall friction should be apportioned to gas and liquid phases based on the phasic volume fraction, which is the same as that used in the SPACE code. The constitutive equations for the interfacial drag force are also identified. Based on the assessments, the Rassame-Hibiki correlation, Hibiki-Ishii correlation, Ishii-Zuber correlation, and Rassame-Hibiki correlation are recommended for computing the distribution parameter, interfacial area concentration, drag coefficient, and relative velocity covariance of a horizontal bubbly flow, respectively.

热工水力分析技术的改进对于确保核电站的安全性和可靠性至关重要。一维二维流体模型已在最先进的热工水力系统代码中采用。目前系统代码中使用的本构方程已达到成熟水平。一些例外是两流体模型的动量方程中的壁摩擦分区方法和水平两相流的界面阻力模型。本研究的重点是推导两流体模型动量方程中壁面摩擦的划分方法，并模拟水平气泡流动的界面阻力模型。二流体模型中的一维动量方程是从局部动量方程推导出来的。推导出的一维动量方程表明，总壁面摩擦应根据相体积分数分配给气相和液相，这与 SPACE 代码中使用的相同。还确定了界面阻力的本构方程。根据评估，推荐使用 Rassame-Hibiki 相关性、Hibiki-Ishii 相关性、Ishii-Zuber 相关性和 Rassame-Hibiki 相关性来计算水平气泡流的分布参数、界面面积浓度、阻力系数和相对速度协方差， 分别。