Conjugate Heat Transfer Modeling of Mixed Convection Using an Off-Lattice Boltzmann Method

This study addresses the limitations of isothermal boundary conditions in predicting flow and thermal behaviors in multi-component systems. The study employs a characteristic-based off-lattice Boltzmann method (OLBM) augmented with a source-term-based conjugate heat transfer (CHT) model designed for polar geometries. The present work focuses on examining conjugate mixed convection within two-dimensional annular spaces. The developed CHT-OLBM solver's validity is established using two test cases. The impact of wall conduction on conjugate mixed convection is investigated under varying governing parameters: Rayleigh number = 105, Reynolds number = 0-1,000, dimensionless solid wall thickness (= 0.1, 0.2), and thermal conductivity ratio (=1, 5, 10). Qualitative observations using streamlines and isotherms are presented. Complementing this, a quantitative analysis evaluates the degree of thermal plume shift and the average Nusselt number. It is observed that the optimal choice of Reynolds number for mixed convection scenarios is altered due to the presence of solid walls. The outcomes underscore the effectiveness of incorporating CHT analysis and showcase the effectiveness of the present CHT-OLBM solver in investigating conjugate mixed convection in annular spaces.