An electrical transmission lin of 1.2 cm diameter carries a current of 200 Amps and has a resistance of 3 x 10^–4 ohm per meter of length. If the air around this line is at 16°C, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.

GIVEN

• An electrical transmission line on a windy day
• Line outside diameter (D) = 12 cm = 0.012 m
• Current (I) = 200b Amps
• Resistance per unit length (R_e/L) = 3 x 10^–4 ohm/m
• Air temperature (T_b) = 16°C
• Air velocity (V) = 33 km/h = 9.17 m/s

ASSUMPTIONS

• Steady state conditions
• Air flow approaching line has low free-stream turbulence