Influence of wall microstructure on turbulent heat transfer and thermo-hydraulic performance in heat exchange pipes

Abstract

The design of wall structures in heat-exchange pipelines is a key enabling technology for achieving high-efficiency and low-resistance heat-transfer performance. In this study, numerical simulations based on the open-source CFD code OpenFOAM are performed to systematically compare flow and heat-transfer characteristics of three wall configurations: square-toothed, arc-transition, and smooth surfaces. Using a refined diagnostic approach, we extract and analyse the spatial distribution and evolution of multiple parameters, including turbulent kinetic energy, turbulent dissipation rate, vorticity, velocity fields, and temperature fields. The results indicate that the geometric sharpness of the wall surface is positively correlated with turbulence intensity. Among the tested configurations, the square-toothed wall delivers the highest area-averaged Nusselt number (strongest heat-transfer enhancement) but incurs the largest friction penalty. The smooth wall produces the most stable flow field yet limited heat-transfer capacity. Under the present operating conditions, the arc-transition wall achieves favourable flow-heat-transfer synergy through moderate-disturbance effects. It provides a desirable comprehensive thermo-hydraulic balance specifically for pressure-drop-constrained scenarios, with a temperature-drop gradient enhanced by a factor of 2.5–8 relative to the smooth-wall baseline and a Nusselt-number enhancement factor of approximately 3.5, which agrees well with published literature. This study reveals the full coupling mechanism among turbulent kinetic energy, flow field, and temperature field modulated by wall geometry, identifies a moderate-disturbance tendency for the tested geometries, and supplies a quantitative basis and theoretical reference for the topological optimisation of heat-transfer wall surfaces.