Question

A solid slab of thickness $H1$ is initially at a uniform temperature $T0$. At time $t = 0$, the temperature of the top surface at $y = H1$ is increased to $T1$, while the bottom surface at $y = 0$ is maintained at $T0$ for $t \geq 0$. Assume heat transfer occurs only in the $y$-direction, and all thermal properties of the slab are constant. The time required for the temperature at $y = \frac{H1}{2}$ to reach 99% of its final steady value is $T1$. If the thickness of the slab is doubled to $H2 = 2H1$, and the time required for the temperature at $y = \frac{H2}{2}$ to reach 99% of its final steady value is $T2$, then $\frac{T2}{T1}$ is .

• A. 2
• B. $\frac14$
• C. 4
• D. $\frac12$

Answer 1

Answer: (C)

4

Answer 2

The correct option is (C) :4