Significance of Thermal Conductivity of Molten Polyethylene in Cable Extrusion Process

The dominating parameter for heat transfer during continuous curing of extruded high voltage cables is the thermal conductivity of molten polyethylene. Literature on thermal conductivity has been reviewed, and it is found that there are differences of order 50% between different investigations. From numerical simulations it is found that 20% increase in thermal conductivity corresponds to 8 °C increase in maximum conductor temperature for constant line speed or 16% increase in line speed for optimized crosslinking. The calculated conductor temperature profile is compared with experimental data from the cable manufacturing. The conductor temperature was measured continuously, using an optical fiber embedded in the outer layer of the conductor, while the conductor passed through the extrusion line. The comparison between measured and simulated conductor temperature profiles show good agreement provided that an appropriate value of the thermal conductivity is chosen.