Consider a vertical, double-pane window for the conditions prescribed in Problem 9.96. That is, vertical panes at temperatures of T₁ = 22° and T₂ = - 20° C are separated by atmospheric air, and the critical Rayleigh number for the onset of convection is Ra _{L, c} = 2000.

(a) What is the conduction heat flux across the air gap for the optimal spacing Lop between the panes?

(b) If the glass has an emissivity of ε_g = 0.90, what is the total heat flux across the gap?

(c) What is the total heat flux if a special low emissivity coating (ε_c = 0.10) is applied to one of the panes at its air-glass interface? What is the total heat flux if both panes are coated?