The Effects of Nonuniform Cooling on the Heat Transfer From an Insulated Electric Cable

Due to the geometric configurations of convectively cooled underground electric power cable systems, nonuniform cooling of the individual cables can occur. A numerical analysis has been performed on the effects of nonuniform surface cooling on the temperature distribution inside the insulation of a single cable. The results show that with the typical geometries considered, the coolant temperature would have to be lowered significantly in order to maintain a given amount of heat dissipation per unit length in comparison to uniform cooling. It is useful, therefore, to promote uniform cooling around the circumference of each cable by changing the fluid flow pattern and by the use of metal sheathing around the circumference. To evaluate this latter effect, a dimensionless parameter representing the relative magnitudes of heat conduction in the sheathing and in the insulation is proposed.