Question

A bare copper cable 2.5 cm in diameter is situated in still air at 15°C. A current of 800 Amps is passed along the cable. Heat is transferred from the cable to its surroundings by natural convection for which the heat transfer coefficient may be expressed as 2.95025 W/m2 K. Determine whether or not it may be assumed that the temperature across the copper cross section is uniform and what the equilibrium temperature of the cable surface will be. If the current is stopped, neglecting radiation heat transfer, estimate the time for the copper to cool to a temperature of 20°C Is it a good assumption to neglect radiation in this problem and why? Assume the following for copper: density ? = 8950 kg/m3, specific heat capacity c,-380 J/kg K, electrical resistivity p* -17x 10-9 ? m, thermal conductivity k-400 W/m K.

Answer 1

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