COSINE多相场子通道分析程序的开发与评估

COSINE多相场子通道分析程序基于两流体三相子通道守恒方程，在气液两相的基础上，单独考虑了液滴相的行为，并通过考虑通道间的交混，提高了对压水堆压力容器内的热工水力学现象分析能力及大破口事故的计算能力。本研究介绍了程序的基本模型及求解方法，选取代表性算例及实验工况进行建模计算，验证多相场子通道程序的计算能力。计算结果表明：程序可以对多通道热工水力现象进行模拟计算，计算结果与理论分析相符，程序可以精确模拟堆芯交混及再淹没工况，计算结果与实验数据具有良好的一致性，COSINE多相场子通道程序具备对压力容器内热工水力工况的计算能力。

Development and Assessment of Multiphase Sub-channel Code of COSINE

COSINE software package provides various functions in thermal-hydraulic analysis of pressurized water reactor (PWR) after years of development. In order to meet the engineering design and safety analysis requirements of the advanced passive reactor CAP1400, the multiphase field sub-channel code with higher calculation accuracy was developed based on the homogeneous sub-channel program (cosSUBC) in COSINE software package. The multiphase sub-channel code contained 11 basic equations including the mass conservation equations of the vapor, continuous liquid, and droplet, the axial momentum conservation equations of the gas, continuous liquid phase, droplet phase, the transverse momentum conservation equation of the gas, continuous liquid, and droplet, and the energy conservation equations of the gas and total liquid phases. The continuous liquid and the droplet were in energy equilibrium states in one cell was assumed, therefore the continuous liquid and droplet were merged into total liquid phases in energy conservation equation. The constitutive relation models between different phases were introduced in the code to realize the closure of the basic equations, the staggered discrete format in space and a semi-implicit time discrete format were adopted in multiphase field sub-channel code. The typical test cases and representative experiments were modeled and calculated in this paper to verify the calculation capability of the code. First, the test of droplet behavior was modeled to verify the correctness of droplet model adopted in the code. Then the turbulent mixing experiment was modeled to verify the correctness of turbulent mixing model used in the code. In the end, the wall heat transfer experiment and the reflooding process experiment were modeled to verify the simulation ability in the heat transfer regime especially in the post critical heat flux (post-CHF) condition. The results show that the droplet behaviors including the generation and the flow distribution of droplet phase are in good agreement with the reference code. And the code can well simulate the flow distribution phenomenon according the comparison between the calculation results and experimental data in flow distribution experiment and the turbulent mixing experiment. Besides, the code can well simulate the distribution of the wall temperature and the reflooding process in the post-CHF and heat transfer condition. Therefore, the calculation of the thermal-hydraulic phenomena in the core of reactor by the multiphase field sub-channel code is reasonable and right, and the code has the ability to calculate and simulate the thermal-hydraulic conditions in the core of PWR.