Numerical investigation of azimuthal heat conduction effects on CHF phenomenon in rod bundle channel. (November 2018)

• Record Type: Journal Article
• Authors: Dong, Xiaomeng; Duarte, Juliana P.; Liu, Dong; Wang, Jun; Zhang, Zhijian; Tian, Zhaofei
• Is Part Of: Annals of nuclear energy. Volume 121(2018)
• Page Start: 203
• Page End: 209
• Publication Date: 2018-11
• Subjects: Boiling flow -- Azimuthal heat conduction -- CFD simulation -- Rod bundle; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2018.07.033
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: The boiling flow (include subcooled boiling flow and boiling crisis) calculations are investigated in vertical pipe and rod bundle channel by use of CFD simulation. Comparisons are done among different heating methods or boundary condition settings. The effect of solid domain and azimuthal heat conduction should not be neglected in the calculation of boiling flow and CHF phenomenon especially in non-centrosymmetric geometries. The inhomogeneity of velocity distribution leads to the inhomogeneity of heat flux and temperature distribution. The boundary conditions should be set according to the experiment as accurately as possible. Abstract: In CFD simulations of boiling flow and CHF phenomenon, the solid domains are usually neglected to reduce the complexity and computational time. However, based on the simulation of three test sections, the azimuthal heat conduction in the solid domains is found to have a significant influence on the numerical results, especially on the wall temperature distribution. This technical note tries to give the researchers some suggestions about the azimuthal heat conduction effects on boiling flow by CFD simulation of steady state flows in vertical pipes and rod bundle geometry. The CFD modeling methodology was developed using FLUENT. Eulerian two-phase flow is used to model the flow and heat transfer phenomena of boiling flow. Three boundary conditions are tested to investigate the effect of azimuthal heat conduction. The results show that the three boundary conditions are nearly equivalent to each other for subcooled boiling flow in centrosymmetric and non-centrosymmetric geometry, like vertical pipe and rod bundle. But for the CHF phenomenon in rod bundle, the simplified BC overestimates the azimuthal inhomogeneity and the peak temperature of the rod surface. During this process, azimuthal heat conduction plays a key role in this result. The conclusions require researchers should model the entire domain in the CFD simulation and set the heating boundary according to the experiment as accurately as possible to better predict the flow and heat transfer characteristics in the boiling flow.