Question

A steam pipe $(\epsilon =0.9)$ of 0.4m diameter has a surface temp of 500 K. The pipe is located in room at ${27}^{o}C$, and the convection heat transfer coefficient is $25W/m^{2}K.$. The rate of heat loss from the pipe if the combined heat transfer coefficient by radiation and convection is $39W/m^{2}K$

• A. 9.8 kW/m
• B. 13.5 kW/m
• C. 11.5 kW/m
• D. 3.5 kW/m

Answer 1

The correct option is A 9.8 kW/m

Diameter = 0.4 m
$T_s=500K$
$T_{\infty }={27}^{o}C=300K$
Combined heat transfer
$\left(Q\right)=(h{)}_{combined}.A\times (T_s-T_{\infty })$

$=39\times \pi \times d\times L\times (500-300)$

$\frac{Q}{L}=39\times \pi \times 0.4\times 200=9.8kW$

Combined heat transfer = 9.8 kW/m