A Comparative CFD Study of Mesh Topology, Wall Treatments, and Turbulence Models for Forced Convection in Narrow Tubes

This study presents a systematic CFD investigation of forced convection in a long circular tube representative of heat exchanger channels, with particular emphasis on the coupled effects of mesh topology, turbulence modeling, and near‐wall treatment. The primary objective is to identify the most suitable combination of mesh type, turbulence model, and near‐wall treatment for accurately predicting heat transfer and pressure drop over a wide Reynolds number range (Re = 1573 − 23,592). This assessment is carried out through a comprehensive analysis involving five mesh types, 10 turbulence models, and four wall treatments. Validation against experimental data yielded heat transfer predictions within ±10%, with grid independence achieved at approximately 1.7 million cells. The O‐grid mesh provided the highest accuracy but at the highest computational cost, while hexahedral and prism meshes offered optimal accuracy–efficiency trade‐offs. Turbulence models were systematically evaluated using a MATLAB–Fluent framework. The linear pressure‐strain RSM with EWT performed best for wall‐dominated quantities, while k – ω GEKO with standard wall functions and k – ϵ standard with ML treatment excelled at high and transitional Reynolds numbers, respectively. Velocity‐profile analysis at Re = 23,592 showed weak sensitivity to mesh density and axial resolution, enabling accurate bulk‐flow predictions on relatively coarse structured meshes.