During a fire, the trunks of some dry oak trees (k = 0.17 W/m · °C and α = 1.28 × 10-7m2/...

During a fire, the trunks of some dry oak trees (k = 0.17 W/m · °C and α = 1.28 × 10-7m2/s) that are initially at a uniform temperature of 30°C are exposed to hot gases at 520°C for a period of 5 h, with a heat transfer coefficient of 65 W/m2 · °C on the surface. The ignition temperature of the trees is. 410°C. Treating the trunks of the trees as long cylindrical rods of diameter 20 cm, determine if these dry trees will ignite as the fire sweeps through them.

FIGURE P18-97