Optimizing Convergence Ratio for Improved Heat Transfer Performance in Macro Channels: A Hybrid Approach Using Design, Analysis, and Optimization

ABSTRACT Efficient thermal management is vital for high‐performance systems, where conventional heat sinks often face limitations due to high thermal resistance and excessive pressure drop. Geometric modification of macro‐channels using an optimized convergence ratio (CR) offers a promising approach to simultaneously enhance heat transfer and hydraulic efficiency. This study aims to systematically evaluate and optimize CR in macro rectangular channels to improve thermo‐hydraulic performance for heat exchange applications. A three‐dimensional CFD‐based numerical investigation was conducted using ANSYS Fluent for channels with inlet widths of 7 and 10 mm, lengths of 70–110 mm, and CR values ranging from 1.0 (straight) to 0.4 (highly tapered), under laminar flow conditions (Re = 200–1600). The model was validated against benchmark experimental data, achieving deviations within 6.6% for Nusselt number (Nu) and 2.8% for friction factor, ensuring high fidelity. Reducing CR from 1.0 to 0.4 improved Nu by up to 29% for 10 mm channels and 18% for 7 mm channels at Re = 1600, while Nu nearly doubled across the full Re range. However, this enhancement incurred a hydraulic penalty, with pressure drop increasing by +180% (10 mm) and +204% (7 mm). An optimal CR window of 0.50–0.65 was identified, achieving 8%–12% Nu improvement while limiting ΔP to < 25% of the maximum penalty. The proposed taper geometry provides a simple, manufacturable solution for electronics cooling and industrial heat exchangers, bridging a critical gap in laminar macro‐scale optimization. This work introduces a robust CFD‐based framework that delivers actionable design guidelines and establishes a foundation for future extensions into turbulent regimes, multiphase flows, and techno‐economic assessments.