Thermal performance improvement and entropy generation in a novel complex cavity with influence of multiple finned arrangement: A CFD study with RSM and sensitivity analysis

This study employs the finite element method to enhance the thermal performance in the natural convection (NC) regime within a complex cavity incorporating multiple fins and an inner circular cylinder. The study examines the effects of Rayleigh number (103 ≤ Ra ≤ 106) across four configurations, as well as the influence of fin height (h) and width (w), while Prandtl number, Pr = 0.71, is fixed. A comprehensive validation is performed to confirm the accuracy of the present study. In the absence and presence of an adiabatic inner cylinder, the average Nusselt number (Nu_avg) increases by 36.80% and 38.37%, respectively, as Ra rises from 103 to 106. Concurrently, the entropy generation (E_gen) rises significantly from 9.2496 to 160.70, and from 9.2203 to 159.56, respectively. When incorporating a hot cylinder, the Nu_avg increases by 46.58%, signifying a stronger HT rate, while the E_gen enhances from 10.625 to 191.39 for varying Ra from 103 to 106. However, in the case of a cold cylinder, HT rate is relatively low and Nu_avg enhances approximately 31.60%, while E_gen rises from 9.6097 to 102.08. Additionally, inner heated cylinder shows higher ECOP values compared to other inner configurations highlights the sustainable and efficient configurations. Using response surface methodology, a new correlation for the Nu_avg is introduced. Sensitivity analysis reveals that Ra has the highest impact on HT, whereas height (h) and width (w) of fins exert moderate and minor effects, respectively. This research provides a valuable guideline for optimizing advanced thermal systems such as heat exchangers, CPU, and electric cooling devices.