Numerical simulation of heat transfer coefficient around different immersed bodies in a fluidized bed containing Geldart B particles

•CFD study of a fluidized bed with two shape of immersed bodies as thermal sources.•A comparison between hydrodynamic of the 3D, 2D planar and axisymmetric models.•Testing two methods to calculate surface-to-bed HTC for 2D and axisymmetric models.•Studying Archimedes number on the surface to bed HTC for a circular internal shape. Using the Eulerian-Eulerian two-fluid model (TFM) the hydrodynamics and heat transfer around different immersed bodies in a fluidized bed were analyzed. The kinetic theory of granular flow (KTGF) was used to simulate the solid phase. For hydrodynamic simulations, 3D, 2D Cartesian and 2D axisymmetric frameworks were examined and the differences in the results of these simulations were discussed. For the heat transfer analysis, due to the high computational demand of 3D simulations, the analyses were performed using 2D Cartesian and axisymmetric frameworks. For studying the effect of shape on the CFD results, two cases of spherical and cylindrical immersed bodies were simulated. In addition, two methods for calculating the surface-to-bed heat transfer coefficient (HTC) for 2D Cartesian and axisymmetric models were examined. The first (method I) is based on constant heat flux boundary condition, while the second one (method II) is based on the isothermal wall boundary condition. It was found that method I outperforms the second one for both 2D Cartesian and axisymmetric configurations in prediction of average HTC. It was shown that the simulation results were in closed agreement with the corresponding measured data. The findings revealed that the spherical immersed body, which has a better aerodynamic shape, produced higher HTC in bubbling fluidized bed with Geldart B particles. Finally, the impact of Archimedes number (Ar) on the surface-to-bed HTC was studied.