Consider a long, insulated cable supplying power to a community. It is elevated in the air by using poles. The ambient air temperature is 20oC and the convective heat transfer coefficient is h = 20 W/m2.K. Radiation exchange between the cable surface and the environment can be neglected. Make your calculations considering per meter-length. The wire carries 500 Amp current and has a resistance of 0.0001 Ohm/m. The diameter of the solid core wire is 1.0 cm and has a thermal conductivity of k = 20 W/m.K The electrically insulating material covering the wire-core has a thickness of 0.5 cm with a thermal conductivity of k = 0.01 W/m.K a) What is the rate of heat loss from the cable to the environment in kW/meter? b) What is the outside surface (exposed to air) temperature of the cable? c) What is the temperature of the interface between the insulation sleeve and the core-wire carrying the electric power? If the sleeve material has to remain below 100 oC for the long term, would this operation be safe? d) What and where is the maximum temperature in the conductive core?
Consider a long, insulated cable supplying power to a community. It is elevated in the air by using poles. The ambient air temperature is 20oC and the convective heat transfer coefficient is h = 20 W/m2.K. Radiation exchange between the cable surface and the environment can be neglected. Make your calculations considering per meter-length. The wire carries 500 Amp current and has a resistance of 0.0001 Ohm/m. The diameter of the solid core wire is 1.0 cm and has a thermal conductivity of k = 20 W/m.K The electrically insulating material covering the wire-core has a thickness of 0.5 cm with a thermal conductivity of k = 0.01 W/m.K
a) What is the rate of heat loss from the cable to the environment in kW/meter?
b) What is the outside surface (exposed to air) temperature of the cable?
c) What is the temperature of the interface between the insulation sleeve and the core-wire carrying the electric power? If the sleeve material has to remain below 100 oC for the long term, would this operation be safe?
d) What and where is the maximum temperature in the conductive core?
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