Chapter 1, Problem 153P

Steady heat conduction occurs through a $\text{0}\text{.3-m-thick, 9-m×3-m}$ composite wall at a rate of 1.2 kW. If the inner and outer surface temperature of wall are ${15}^{\text{o}}\text{C}$ and $7^{\text{o}}\text{C,}$ the effective thermal conductivity of the wall is

1. $\text{0}{\text{.61 W/m}}^{\text{.}}\text{K}$
2. $\text{0}{\text{.83 W/m}}^{\text{.}}\text{K}$
3. $\text{1}{\text{.7 W/m}}^{\text{.}}\text{K}$
4. $\text{2}{\text{.2 W/m}}^{\text{.}}\text{K}$
5. $\text{5}{\text{.1 W/m}}^{\text{.}}\text{K}$