Numerical simulation and experimental investigation of heat transfer and flow structures around heated spherical bluff bodies

The objective of this work is to evaluate the influence of vortices on heat transfer behaviour and a flow structure around a heated sphere. Numerical simulation and experimental verification are performed using a stationary copper sphere located inside a cylindrical channel with a constant channel-to-sphere diameter ratio. Numerical simulation is done for three-dimensional steady-state flow using ANSYS-FLUENT by solving the Reynolds-averaged Navier Stokes (RANS) equations. Over the test range of Reynolds numbers (2500-55000), CFD simulation results are in reasonable agreement with experimental data. The importance of vortices on heat transfer behaviour was investigated by taking the surface temperature and heat transfer coefficient (HTC) measurements around the sphere surface as a function of a zenith angle. The CFD simulation results confirmed that the impact of vortices on heat transfer behavior occurred in a lower-rear area of the sphere with a zenith angle (from 120 degrees to 180 degrees).