Consider a vertical, double-pane window for the conditions prescribed in Problem 9.94. That is, vertical panes at temperature of T₁ = 22°C 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 L_op 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, lowemissivity 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?