The radial temperature distribution and effective radial thermal conductivity in bare solid and stranded conductors

The radial temperature distribution in monometallic and bimetallic, solid and stranded circular cylindrical conductors is calculated for uniform circumferential temperature, uniform current density, and uniform radial thermal conductivity. An analysis of the radial heat flow in concentric-lay stranded conductors is presented. Parallel heat paths are formed by the asperities and the air gaps at the contacts between crossing wires, and the air voids between wires in adjacent layers. Most of the heat is transferred by conduction through the air gaps and the air voids; there is negligible heat transfer by radiation and convection. It is shown that the temperature difference between layers depends on the number of contacts per unit length and the area of each contact. The latter depends on the radial force, and hence on the tension. The calculated effective radial thermal conductivity for a 61/3.5 mm AAC conductor falls within the range of experimental values. Tests were performed on pairs of crossing, 3.5 mm, hard-drawn aluminum wires to determine the relationships between the radial force per contact, the crossing angle, the apparent area of contact, and the loading duration