A long, cylindrical nickel rod (d 1 = 10 mm) is heated electrically and releases a heat flow per length L of Q˙ 1 /L = 210W/m. The emissivity of nickel can be calculated from ε(T)= XXXXXXXXXXT /K) ....

A long, cylindrical nickel rod (d₁
= 10 mm) is heated electrically and releases a heat flow per length L of Q˙₁/L = 210W/m. The emissivity of nickel can be calculated from

ε(T)=0.050 + 0.000 10 (T /K) .

The rod is surrounded by a concentrically arranged hollow cylinder, d₂
= 25 mm, ε₂
= 0.88. The hollow cylinder is cooled from outside to a temperature of T₂
= 290 K. What surface temperature does the nickel rod reach, if heat is only transferred by radiation?