A thin sheet of glass is used on the roof of a greenhouse and is irradiated as shown. The irradiation comprises the total solar flux GS, the flux G aim due to atmospheric emission (sky radiation), and the flux Gi due to emission from interior surfaces. The fluxes G aim and G; are concentrated in the far IR region (? > 8?m). The glass may also exchange energy by convection with the outside and inside atmospheres. The glass may be assumed to be totally transparent for ? 1?m.

(a) Assuming steady-state conditions, with all radiative fluxes uniformly distributed over the surfaces and the glass characterized by a uniform temperature Tg, write an appropriate energy balance for a unit area of the glass.

(b) For Tg = 27°C, hi = 10 W/m2 ? K, GS = 1100 W/m2, T?,o = 24°C, ho = 55 W/m2 ? K, G aim = 250 W/m2, and G; = 440 W/m2, calculate the temperature of the greenhouse ambient air, T?,i.

Transcribed Image Text:

Gs Outside ambient Greenhouse interior