A fused-quartz sphere has a thermal diffusivity of 9.5×10−7 m2/s, a diameter of 2.5 cm, and a thermal conductivity of 1.52 W/m· ◦C. The sphere is initially at a uniform temperature of 25◦C and is...

A fused-quartz sphere has a thermal diffusivity of 9.5×10−7 m2/s, a diameter of
2.5 cm, and a thermal conductivity of 1.52 W/m· ◦C. The sphere is initially at a
uniform temperature of 25◦C and is suddenly subjected to a convection environment
at 200◦C. The convection heat-transfer coefficient is 110 W/m2 · ◦C. Calculate the
temperatures at the center and at a radius of 6.4 mm after a time of 3 min.