An aluminum transmission line with a diameter of 20 mm has

Chapter , Problem 7.66

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An aluminum transmission line with a diameter of 20 mm has an electrical resistance of and carries a current of 700 A. The line is subjected to frequent and severe cross winds, increasing the probability of contact between adjacent lines, thereby causing sparks and creating a potential fire hazard for nearby vegetation. The remedy is to insulate the line, but with the adverse effect of increasing the conductor operating temperature. (a) Calculate the conductor temperature when the air temperature is 20 C and the line is subjected to cross flow with a velocity of 10 m/s. (b) Calculate the conductor temperature for the same conditions, but with a 2-mm-thick insulation having a thermal conductivity of 0.15 W/m K (c) Calculate and plot the temperatures of the bare and insulated conductors for wind velocities in the range from 2 to 20 m/s. Comment on features of the curves and the effect of the wind velocity on the conductor temperatures.