A sphere, (k = 50 W/m.K, α = 1.5 × 10 –6 m 2 /s), 80 mm in diameter is initially at uniform temperature of 800°C. It is suddenly quenched in an oil bath at 50°C with h = 1000 W/ m 2 .K. At a certain...

A sphere, (k = 50 W/m.K, α = 1.5 × 10^–6
m²/s), 80 mm in diameter is initially at uniform temperature of 800°C. It is suddenly quenched in an oil bath at 50°C with h = 1000 W/ m².K. At a certain time, the surface temperature of the sphere is observed to be 150°C. What is the corresponding centre temperature of the sphere ?