Browsing by Author "Abdelhady, Mohamed"
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- ItemOpen AccessAssessing the Accuracy of Convective Heat Transfer from Overhead Conductor at Low Wind Speed Using Large Eddy Simulations (LES)(2017-12-22) Abdelhady, Mohamed; Wood, David; Morton, Christopher; Ware, AntonyThis 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.
- ItemOpen AccessAn Investigation of Heat and Fluid Flow for Overhead Conductor Cables(2021-09-15) Abdelhady, Mohamed; Wood, David H.; Martinuzzi, Robert; Morton, Christopher; Zhou, Qi; Sullivan, Pierre E.The flow dynamics and forced convective heat transfer of stranded cables and circular cylinders were studied, numerically and experimentally, for Reynolds number, Re, of up to 3,900. The effects of Constant Temperature (CT) and Constant Heat Flux (CHF) thermal boundary conditions on forced convection were assessed for circular cylinders. In addition, particle image velocimetry and Large Eddy Simulations (LES) were used to investigate in detail the heat and fluid flow of stranded cables and how they differ from circular cylinders. Besides, the effects of free-stream turbulence on a circular cylinder placed close to a turbulence grid was investigated using LES. The results showed that the thermal boundary condition significantly affects forced convection, contrary to the common assumption; the overall Nusselt number is ~15% higher for CHF boundary condition than the CT. In addition, the results revealed that stranded cable wakes are dominated by alternatively shed Kármán vortices, at a frequency similar to the cylinder. However, the Reynolds stresses, shape factor, and the details of vortex shedding showed substantial alterations associated with the cable strands. Proper orthogonal decomposition and phase averaging were used to triply decompose into mean, coherent, and incoherent components. It is shown that stranded cable coherent fields are different from the cylinder; and that the strands of the cable affect the transport and production of turbulent kinetic energy for the total, coherent, and incoherent fields. The stranded cable surface parameters, like Nusselt number, surface pressure, and skin friction, are altered significantly by the cable strands which are associated with three-dimensional mean flow and heat transfer. The cable gaps have near-stagnant flow, which decreases the local heat transfer rate between the strands, but the overall Nusselt number is only slightly lower than for the cylinder. The cable coherent vorticity and temperature fields were noticeably different from the cylinder. Besides, the coherent and incoherent heat energy transport of the cylinder and stranded cables, showed that, in general, the highest heat energy transport takes place close to the cable rear side. Finally, the cylinder experiencing free-stream turbulence had 43% higher convective cooling relative to non-turbulent free-stream.