Chapter 4, Problem 173P

A long 18-cm-diameter bar made of hardwood $\text{k = 0}\text{.159 W/m}\text{.K, }\alpha \text{ = 1}\text{.75 }\times {\text{ 10}}^{\text{-7}}{\text{ m}}^{\text{2}}\text{/s)}$ and is exposed to air at 30°C with a heat transfer coefficient of 8.83 W/m² K. If the center temperature of the bar is measured to be 15°C after 3 h. the initial temperature of the bar is

(a) 11.9°C

(b) (4.9°C and (c) 1.7°C

(d) 0°C

(e) -9.2°C