Consider a person standing in a room maintained at 20°C at all times. The inner surfaces of the walls, floors, and ceiling of the house are observed to be at an average temperature of 12°C in winter and 23°C in summer. Determine the rates of radiation heat transfer between this person and the surrounding surfaces in both summer and winter if the exposed surface area, emissivity, and the average outer surface temperature of the person are 1.6 m2, 0.95, and 32°C, respectively.

2. Consider steady heat transfer between two large parallel plates at constant temperatures of T1 = 295 K and T2 = 155 K that are L = 2 cm apart. Assuming the surfaces to be black, 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,(k = 0.01979 W/m- o C) (b) evacuated,(c) filled with superinsulation having an apparent thermal conductivity of 0.00015 W/m · °C.

The wall of an oven in an industrial plant, made of fire brick (k = 0.71 W/m/K) has thickness of L = 15 cm. The oven is exposed to air at 28oC and the surfaces of the far surroundings are at 20oC. If the temperature of the outer surface of the wall is 92oC and the heat transfer coefficient and emissivity are 20 W/(m^2*K) and 0.8 respectively, determine the temperature of the inner surface of the wall.

Calculate the temperature in an unheated space (Tunc) adjacent to a conditioned room with three (3) common surface areas of 175-ft2, 190-ft2, and 210-ft² with an overall heat transfer coefficient of 0.21, 0.27, and 0.32 Btu/h-Ft2 °F, respectively. The surface areas of the unheated space exposed to the outdoors are 175-ft² and 210-ft² with corresponding overall heat transfer coefficients of 0.21 and 0.40 Btu/h- Ft².°F. The sixth (6th) surface is on the ground and can be neglected for this example as can be the effect of any outdoor air entering the space. Inside & outside design reference temperatures are 70°F & -10°F, respectively. Tunc = 37°F Tunc = 36°F Tunc = 30°F Tunc = 35°F