Computational simulation of natural convection in a square cavity containing a fluid with internal heat generation

Natural convection in cavities containing fluids with internal heat generation has been investigated in nuclear engineering in order to understand the heat transfer mechanisms in light water reactors (LWRs), after severe accidents with core melt- down. This paper reports computational simulation of natural convection in a square cavity containing a fluid with internal heat generation by using a commercial package of Computational Fluid Dynamics (CFD), Ansys CFX 12.0.The work aimed at analyzing the influence of fluid properties and the volumetric heat generation rate in the behavior of the flow regime and heat transfer, based on Prandtl (Pr) and Rayleigh (Ra) numbers. In a square cavity with isothermal vertical and adiabatic horizontal walls, steady laminar, transient laminar and turbulent regimes were identified, for Pr equal to 0.0321, 0.71 and 7.0. The identification of periodic and chaotic transient laminar flow was carried out by spectral analysis of instantaneous velocity and temperature. The critical Rayleigh number.at which transition from steady to transient laminar flow regime occurs was determined. Turbulent natural convection was studied by using Reynolds average Navier-Stokes (RANS) equations with SST model.