3. (25 points) A horizontal semitransparent plate is uniformly irradiated from above and below, while air at T = 25C flows over the top and bottom surfaces, providing a uniform convection heat transfer coefficient of 55 W/ mK. The absorptivity of the plate to the irradiation is 0.45. Under steady-state conditions measurements made with a radiation detector above the top surface indicate a radiosity of 4500 W/m, while the plate is at a uniform temperature 7 = 75C. Analyze the system at steady state Air Toooh Plate Air Too, h (a) Write the energy balance expression for the plate accounting for both surfaces of the plate. (b) Using the energy balance in (a), determine the irradiation (G) of the plate. (c) Now calculate the emissivity of the plate. (d) Is the plate a gray body for these conditions? Note, by definition, a "grey body" has: = a