Assessing the Accuracy of Convective Heat Transfer from Overhead Conductor at Low Wind Speed Using Large Eddy Simulations (LES)

Abstract

This project uses Computational Fluid Dynamics (CFD) to assess the accuracy of the forced cooling term for Real Time Thermal Rating (RTTR) of power lines in overhead conductor codes, IEEE 738 and CIGRÉ 207. The analysis is done for low wind speed, corresponding to Reynolds Number of 1,000, and 3,000. The project uses Large Eddy Simulation (LES) in the ANSYS Fluent software. The primary goal is to calculate the convective heat transfer for cylindrical and stranded conductors in non-turbulent flow and for cylindrical conductors with free-stream turbulence. The results showed that the heat transfer correlations used in the codes are accurate for low turbulent flows and that the stranded conductor causes an increase in heat transfer of ~9 % over a cylindrical conductor at low wind speed. The constant heat flux boundary condition experiences ~15 % higher Nusselt Number than uniform temperature boundary condition. The calculated increase in heat transfer due to turbulence was significant; increased heat transfer due to turbulence ~24 % at Reynolds Number of 3,000 at a turbulence intensity of 8% and length scale to diameter ratio of 0.4.