A study on thermo-fluid behavior under natural convection flow inside a staggered cavity with differently heated octagonal obstacles

In this study, the effects of natural convection, heat transfer, and entropy generation within a staggered cavity filled with differently heated octagonal obstacles for the Rayleigh number regime of 10² ≤ Ra ≤ 10⁶ and Pr = 0.70 are numerically investigated. The study considers two configurations comprising cavities with non-heated octagonal obstacles (Case I) and cavities with heated octagonal obstacles (Case II). The governing equations are numerically solved within the Boussinesq approximation through the finite element method. The analysis reveals that the average Nusselt number (Nu avg ) and the average entropy generation (E avg ) are increased by 51.75% and 32.49%, respectively, due to the heated obstacles as compared to non-heated obstacles. As convection increases, the Bejan number decreases monotonically with increasing Ra, thus indicating the heat-transfer dominated regime to the friction-dominated regime of irreversibility. Heated obstacles also produce higher, more sustainable, Ecological Coefficients of Performance (ECOP). The results obtained from the Response Surface Methodology (RSM) and sensitivity analysis show that the radius of the obstacles and Prandtl number are comparatively small influence parameters during the heat transfer process, and Ra is the most influential parameter. The novelty of this work is the integrated analysis of entropy generation, ECOP, and RSM-based optimization for a staggered cavity with octagonal obstacles. Results are relevant to the electronics cooling, building insulation, and compact heat exchanger design applications.