Chapter 13, Problem 13.114P

A flat-plate solar collector, consisting of an absorber plate and single cover plate, is inclined at an angle of $\tau =60°$ relative to the horizontal.

Consider conditions for which the incident solar radiation is collimated at an angle of 60° relative to the horizontal and the solar flux is $900{\text{W/m}}^2$ . The cover plate is perfectly transparent to solar radiation $\left(\lambda \le 3\mu \text{m}\right)$ and is opaque to radiation of larger wave lengths. The cover and absorber plates are diffuse surfaces having the spectral absorptivities shown.

The length and width of the absorber and cover plates are much larger than the plate spacing L. What is the rate at which solar radiation is absorbed per unit area of the absorber plate? With the absorber plate well insulated from below and absorber and cover plate temperatures T_aand T_cof 70°C and 27°C, respectively, what is the heat loss per unit area of the absorber plate?