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Article

Optimizing Passive Thermal Enhancement via Embedded Fins: A Multi-Parametric Study of Natural Convection in Square Cavities

by
Saleh A. Bawazeer
Department of Mechanical Engineering, College of Engineering and Architecture, Umm Al-Qura University, Makkah 21955, Saudi Arabia
Energies 2025, 18(15), 4098; https://doi.org/10.3390/en18154098 (registering DOI)
Submission received: 10 July 2025 / Revised: 28 July 2025 / Accepted: 30 July 2025 / Published: 1 August 2025

Abstract

Internal fins are commonly utilized as a passive technique to enhance natural convection, but their efficiency depends on complex interplay between fin design, material properties, and convective strength. This study presents an extensive numerical analysis of buoyancy-driven flow in square cavities containing a single horizontal fin on the hot wall. Over 9000 simulations were conducted, methodically varying the Rayleigh number (Ra = 10 to 105), Prandtl number (Pr = 0.1 to 10), and fin characteristics, such as length, vertical position, thickness, and the thermal conductivity ratio (up to 1000), to assess their overall impact on thermal efficiency. Thermal enhancements compared to scenarios without fins are quantified using local and average Nusselt numbers, as well as a Nusselt number ratio (NNR). The results reveal that, contrary to conventional beliefs, long fins positioned centrally can actually decrease heat transfer by up to 11.8% at high Ra and Pr due to the disruption of thermal plumes and diminished circulation. Conversely, shorter fins located near the cavity’s top and bottom wall edges can enhance the Nusselt numbers for the hot wall by up to 8.4%, thereby positively affecting the development of thermal boundary layers. A U-shaped Nusselt number distribution related to fin placement appears at Ra ≥ 103, where edge-aligned fins consistently outperform those positioned mid-height. The benefits of high-conductivity fins become increasingly nonlinear at larger Ra, with advantages limited to designs that minimally disrupt core convective patterns. These findings challenge established notions regarding passive thermal enhancement and provide a predictive thermogeometric framework for designing enclosures. The results can be directly applied to passive cooling systems in electronics, battery packs, solar thermal collectors, and energy-efficient buildings, where optimizing heat transfer is vital without employing active control methods.
Keywords: natural convection; Nusselt number; fin geometry optimization; Rayleigh and Prandtl number effects; thermal conductivity ratio; passive heat transfer enhancement; enclosure heat transfer natural convection; Nusselt number; fin geometry optimization; Rayleigh and Prandtl number effects; thermal conductivity ratio; passive heat transfer enhancement; enclosure heat transfer

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MDPI and ACS Style

Bawazeer, S.A. Optimizing Passive Thermal Enhancement via Embedded Fins: A Multi-Parametric Study of Natural Convection in Square Cavities. Energies 2025, 18, 4098. https://doi.org/10.3390/en18154098

AMA Style

Bawazeer SA. Optimizing Passive Thermal Enhancement via Embedded Fins: A Multi-Parametric Study of Natural Convection in Square Cavities. Energies. 2025; 18(15):4098. https://doi.org/10.3390/en18154098

Chicago/Turabian Style

Bawazeer, Saleh A. 2025. "Optimizing Passive Thermal Enhancement via Embedded Fins: A Multi-Parametric Study of Natural Convection in Square Cavities" Energies 18, no. 15: 4098. https://doi.org/10.3390/en18154098

APA Style

Bawazeer, S. A. (2025). Optimizing Passive Thermal Enhancement via Embedded Fins: A Multi-Parametric Study of Natural Convection in Square Cavities. Energies, 18(15), 4098. https://doi.org/10.3390/en18154098

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