Chapter 13, Problem 13.79P

A solar collector consists of a long duct through which air is blown; its cross section forms an equilateral triangle 1 in on a side. One side consists of a glass cover of emissivity ${\epsilon }_1=0.9$ , while the other two sides are absorber plates with ${\epsilon }_2={\epsilon }_3=1.0$ .

During operation the surface temperatures are known to be $T_1=25°\text{C}$ , $T_2=60°\text{C}$ , and $T_3=70°\text{C}$ . What is the net rate at which radiation is transferred to the cover due to exchange with the absorber plates?