Chapter 13, Problem 13.68P

Coatings applied to long metallic strips are cured by installing the strips along the walls of a long oven of square cross section.

Thermal conditions in the oven are maintained by a long silicon carbide rod (heating element), which is of diameter $D=20\text{mm}$ and is operated at $T_1=1700\text{K}$ . Each of two strips on one side wall has the same orientation relative to the rod $\left(s_1=60\text{mm},s_2=20\text{mm},L=80\text{mm}\right)$ and is operated at $T_2=600\text{K}$ . All surfaces are diffuse and gray with ${\epsilon }_1=0.9$ and ${\epsilon }_2=0.4$ . Assuming the oven to be well insulated al all but the strip surfaces and neglecting convection effects, determine the heater power requirement per unit length (W/m).