As the core component of aircraft propulsion systems, turbofan engine performance critically governs thrust generation and operational efficiency. Within this framework, heat exchanger effectiveness constitutes a pivotal subsystem for thermal management, where baffle plate design significantly influences shell-side hydrodynamics and heat transfer augmentation. This investigation employs a three-dimensional computational fluid dynamics (CFD) model to systematically analyze the optimization potential of baffle notch geometry on heat exchanger performance. Key findings reveal that baffle notch heights spanning 20–45 mm exhibit peak performance at 20 mm, where enhanced cross-flow mixing mechanisms develop within the shell-side cavity. Velocity vector diagrams and temperature iso-surfaces demonstrate that this optimized configuration reduces flow stagnation regions by 37.2% while attenuating thermal gradients in high-enthalpy zones by 28.5%. Quantitative analysis indicates that the optimized baffle geometry elevates the average shell-side convective heat transfer coefficient (h_{avg}) by 58.9% compared to baseline configurations, concomitant with a 20.0% improvement in overall heat transfer rate (Q_total) based on NTU-effectiveness methodology. Notably, the associated pressure drop penalty (ΔP = 3.7 kPa) remains within acceptable engineering limits, yielding a favorable thermal–hydraulic performance index (THPI) of 1.43. The present work elucidates the interdependent relationships between baffle notch morphology, secondary flow structures, and heat transfer enhancement mechanisms. The experimental validation of optimized baffle geometries provides critical design parameters for developing compact, high-efficiency heat exchangers in aero-engine applications, demonstrating a 19.3% improvement in thermal management efficiency while maintaining system-level energy sustainability.