Energy-Efficient Enclosures in Natural Convection Systems Using Partition Control

Improving energy efficiency and thermal management in enclosure-based systems requires an understanding of how internal geometry governs buoyancy-driven flow and heat transfer. This study employs a partition-based control strategy to regulate flow organization and thermal stratification in natural convection enclosures. Numerical simulations are performed in a differentially heated square cavity with a bottom-attached adiabatic partition ($H=0.0L$–$0.9L$) for Rayleigh numbers ($Ra$) ranging from ${10}^3$ to ${10}^6$. The analysis examines how buoyancy–geometry interaction drives vortex suppression, extinction, and regeneration, shaping the thermal performance of energy-efficient enclosures. Flow evolution is characterized using vortex center trajectories, the local Nusselt number difference ($\Delta Nu$), and classification into the Thermal Transition Layer (TTL) and Conduction-Dominated Zone (CDZ). Increasing partition height progressively decouples the upper and lower cavity regions. At low $Ra$, suppression occurs gradually and symmetrically, maintaining a single-vortex structure up to large H. At high $Ra$, strong buoyancy induces nonlinear transitions from dual vortices to regenerated upper vortices. Cold wall circulation is suppressed more strongly than that near the hot wall, producing pronounced thermal asymmetry and reduced heat transfer. At the maximum partition height ($H=0.9L$), the surface-averaged Nusselt number decreases by approximately 75–$92\%$ across all $Ra$, indicating strong cooling suppression due to geometric confinement. TTL/CDZ mapping reveals that rapid CDZ growth and TTL expansion beyond $H\approx 0.4L$ lead to a sharp decline in the average Nusselt number. These findings provide a quantitative framework for predicting suppression-driven transitions and guiding partition-controlled, energy-efficient enclosure design under varying buoyancy conditions.