Subtopic: Steady state heat transfer in conduction, convection and radiation
Question Statement:
A steam pipe carrying saturated steam at $120^\circ\text{C}$ is covered with insulation of thermal conductivity $k = 0.08\text{ W/(m}\cdot\text{K)}$. If the surrounding ambient air has a convective heat transfer coefficient $h = 8.0\text{ W/(m}^2\cdot\text{K)}$, calculate the critical radius of insulation in $\text{mm}$.
Answer Key:
10
Step-by-Step Solution & Explanation
Critical radius of insulation for a cylindrical pipe is:
$r_{cr} = \frac{k}{h} = \frac{0.08\text{ W/(m}\cdot\text{K)}}{8.0\text{ W/(m}^2\cdot\text{K)}} = 0.01\text{ m} = 10.0\text{ mm}$