A long steel bar 5 by 10 cm is initially maintained at a uniform temperature of 250C.

Question:

A long steel bar 5 by 10 cm is initially maintained at a uniform temperature of 250ºC. It is suddenly subjected to a change such that the environment temperature is lowered to 35ºC. Assuming a heat-transfer coefficient of 23 W/m2 · ºC, use a numerical method to estimate the time required for the center temperature to reach 90ºC. Check this result with a calculation using the Heisler charts.