Development of Two-Dimensional Heat Conduction Model in Subchannel Code Based on OpenFOAM

Abstract Subchannel codes play an important role in the thermal-hydraulic analysis of reactor cores. Based on the open-source CFD software OpenFOAM, the research team developed CorTAF, a finite volume method-based thermal-hydraulic analysis code for the core subchannel level. All the CorTAF codes are done on OpenFOAM, which has the function of calculating different phenomena in different reactor types. Compared with the traditional subchannel codes, CorTAF utilizes the advanced discrete algorithm of OpenFOAM to distinguish different plane directions on the flow, and implants more advanced models to calculate the phenomena in the reactor core, which has many advantages such as higher computational accuracy, faster computational efficiency, and better developability. Most of the subchannel codes ignore the axial heat transfer when calculating the temperature of the fuel rod, and the corresponding error is introduced here. In this paper, the axial heat conduction of fuel rods is further studied on the basis of CorTAF thermal-hydraulic model. On the basis of the previous model which only considers the heat conduction of radial nodes, the axial heat conduction is considered, the construction and solution of two-dimensional heat conduction matrix is realized, and the two-dimensional unsteady heat conduction model of fuel rod is developed. The developed two-dimensional unsteady heat conduction model is used to calculate the normal and blocking conditions respectively, and compared with the previous node heat conduction model, it is found that: Under normal operating conditions, there is little difference between them, and the maximum error is less than 0.5K. Under the condition of blocking accident, the overall temperature distribution trends of the two models are basically the same, but the temperature distribution of the two-dimensional heat conduction model is more uniform, and the maximum temperature of the fuel pellet is smaller. In a word, the upgrade of CorTAF fuel rod heat conduction model further improves the accuracy of core thermal-hydraulic calculation, and provides support for its calculation of special working conditions such as blockage accident, which can be used for reference in similar program development.