7 = 300 K -L=1 cm 17-200 K Consider steady heat transfer between two large parallel plates at constant = temperatures of T = 300 K and T2 = 200 K that are L 1 cm apart, as shown. Assuming the surfaces to be black (emissivity = 1), determine the rate of heat transfer between the plates per unit surface area assuming the gap between the plates is (a) filled with atmospheric air, (b) evacuated, (c) filled with urethane insulation, and (d) filled with superinsulation that has an apparent thermal conductivity of 0.00002 W/mC.