Numerical and experimental investigation of heat transfer augmentation in roughened pipes

Introduction. In many technical applications, such as thermal energy systems, chemical processing, power production, and HVAC, efficient heat transfer (HT) is essential. Research on improving HT performance in circular pipes is still crucial, especially when it comes to changes that cause thermal boundary layers to be disrupted and turbulence to grow. Purpose of the work: The purpose of this work is to thoroughly examine how convective heat transfer can be improved in circular pipes with purposefully roughened surfaces. It focuses on how surface roughness, flow pulsations, Reynolds number (Re), and heat flow rate (Q) affect thermal performance. Methods of investigation. A combination of experimental and numerical methods is employed to assess the thermo-fluid dynamics inside the pipe. Lab-scale experiments and computational fluid dynamics (CFD) simulations are used to investigate temperature distribution, velocity and pressure fields, turbulent kinetic energy (TKE), vorticity, eddy viscosity, local heat transfer coefficient (h), and Nusselt number (Nu). Additionally, sinusoidal pulsations are introduced at the inlet and the outlet, with regular oscillations in frequency (f) and amplitude (A), over a turbulent flow range (6,753 ≤ Re ≤ 31,000). Results and discussion. The results show that surface roughness enhances HT by significantly increasing turbulence and disrupting the thermal boundary layer. TKE becomes a significant factor when there is a strong correlation between higher HT coefficients and rising turbulence intensity. HT performance is further improved by introducing flow pulsations; downstream pulsation increases Nu by 20–22% and upstream pulsing by 16–19%. The outcomes demonstrate how effectively controlled flow pulsations and surface roughness combine to optimize heat transfer. This collaborative approach holds great potential for compact and highly efficient thermal system designs in industrial environments.