A 0.2 m × 0.2 m street sign surface has an absorptivity of 0.6 and an emissivity of 0.7, while the street sign is subjected to a cross flow wind at 20°C with a velocity of 1 m/s. Solar radiation is incident on the street sign at a rate of 1100 W/m², and the surrounding temperature is 20°C. Determine the surface temperature of the street sign. Evaluate the air properties at 30°C. Treat the sign surface as a vertical plate in cross flow.

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8=0.7 α = 0.6 as Wind, 20°C