Question

An absetos insulation having thermal conductivity $0.172W/mK$ surrounding a pipe of 60 mm idameter and exposed to room air at $300K$ with h.t.c fo $2.8W/m^{2}K.$ Calculate the heat loss from the pipe per unit length of pipe if the surface temperature of the pipe is $475K$ when covered with critical radius of insulation

• A. 92.46 W/m
• B. 50.43 W/m
• C. 65.43 W/m
• D. 110.16 W/m

Answer 1

The correct option is D 110.16 W/m

$\text{Critical radius}{r}_c=\frac{k}{h}=\frac{0.172}{2.8}=0.0614m\frac{Q}{L}=\frac{\Delta T}{\frac{\ell n\left(\frac{r_c}{r}\right)}{2\pi k}+\frac{1}{h\left(2\pi r_c\right)}}=\frac{475-300}{\frac{\ell n\left(\frac{0.0614}{0.03}\right)}{2\pi \left(0.172\right)}+\frac{1}{2.8\times 2\pi \times 0.0614}}\frac{Q}{L}=110.172W/m$