Numerical studies of temperature fields in cable lines to analyze the possibility of compacting a cable channel

Abstract

This paper proposes a two-dimensional mathematical model of the nonstationary processes of complex convective heat transfer in a rectangular duct buried in the ground at a depth of 1 m taking into account radiative heat transfer under natural convection. Mathematical description of convective processes is based on the laws of conservation of energy, mass, and momentum. The complex problem of convective heat transfer of air flow in the duct is solved together with the heat-conduction problem in the structural elements of the power cables, cable channel, and ground. A system of differential equations describing thermal processes in the cable channel that is complemented by appropriate initial and boundary conditions is solved by the finite-element method in the ANSYS Fluent software package. The viability of the proposed mathematical model of thermal processes is confirmed by the convergence of the numerical method. The dependences of the maximum temperature on the surface of the power-cable insulation as a function of the number of nodes are obtained for the steady-state operating regime of cable lines. The temperature fields in the cable channel are calculated in dependence on the position and number of power cables. It is concluded that, with decreasing geometrical dimensions of a cable channel and retention of the initial number of power cables, the maximum temperature on the insulation surface is kept constant. The nonstationary problem of determining the time of cable-line heating up to the limiting values is solved. Curves of cable-line heating are obtained in the unsteady operation regime.