SA, SherifAlbeshri, Badr2026-05-102026https://hdl.handle.net/20.500.14154/78910Please note that portions of this dissertation contain unpublished research findings that are intended for future journal publication. Therefore, I kindly request that the dissertation not be made publicly accessible for a period of three yearsThis dissertation presents a comprehensive numerical investigation of turbulent forced convection heat transfer in solar air heaters (SAHs) equipped with rotatable turbulators, focusing on three major themes: parametric analysis, geometrical optimization, and nature-inspired design. The research investigates to enhance the thermal performance of SAHs by systematically examining the effects of turbulator angle, solar irradiance, Reynolds number, and geometrical parameters such as turbulator height, spacing, and width. A series of models were developed to predict key performance indicators, including the average absorber temperature, air temperature distribution, velocity field, pressure drop, average and local Nusselt number, and Performance Enhancement Coefficient (PEC). The first part of the study explores the combined effects of turbulator angles and operating conditions, establishing new correlations for the average Nusselt number, pressure drop, and PEC. Results indicate that increasing the turbulator angle and Reynolds number significantly improves convection heat transfer, with the PEC rising above unity at high flow rates due to enhanced turbulence and flow mixing. The second part investigates the influence of geometric configurations across multiple turbulator orientations, demonstrating that specific designs yield superior heat transfer uniformity and reduced pressure drop. Among the examined configurations, those promoting stronger flow disturbance exhibit the highest thermal efficiency. The final part introduces a novel nature-inspired design approach in which rotatable turbulators are equipped according to leaf-vein flow architectures. The biomimetic configuration enhances flow distribution, minimizes temperature gradients, and increases the overall Nusselt number compared to conventional layouts. The analysis confirms that the integration of natural flow principles into engineered absorber geometries leads to higher performance coefficients and improved thermal uniformity. Overall, the outcomes of this research provide new insight into the thermohydraulic behavior of SAHs under varying design and operating parameters. The developed correlations and findings serve as practical tools for optimizing solar air heater designs, contributing to the advancement of efficient, sustainable, and nature-inspired solar thermal systems.167en-USRenewable EnergySustainabilitySolar EnergyPerformance Enhancement CoefficientNatureHeat TransferCorrelationsTurbulentTurbulenceFluidSolar Air HeaterForced ConvectionTurbulatorsPressure DropNusselt NumberThesis