An Investigation of Heat and Fluid Flow for Overhead Conductor Cables
Date
2021-09-15
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Abstract
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.
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Keywords
Turbulence, Forced Convection, Stranded Cable, Circular Cylinder, Thermal Boundary Conditions, Wake Dynmics, Turbulent Flow
Citation
Abdelhady, M. (2021). An Investigation of Heat and Fluid Flow for Overhead Conductor Cables (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.