Numerical modeling of the hydrodynamic stability in vertical annulus with heat source of different lengths

A numerical investigation of natural convection heat transfer stability in cylindrical annular with discrete isoflux heat source of different lengths is carried out. The adiabatic unheated portions and the discrete heat source are mounted at the inner wall. The top and bottom walls are adiabatic, while the outer wall is maintained at a lower temperature. The governing equations are numerically solved using a finite volume method. SIMPLER algorithm is used for the pressure-velocity coupling in the momentum equation. The numerical results for various governing parameters of the problem are discussed in terms of streamlines, isotherms and Nusselt number in the annulus. The results show that the increase of heat source length ratio decreases the critical Rayleigh number. We can control the flow stability and heat transfer rate in varying of the length of heat source.