A cryogenic fluid flows through a long tube of 20 mm diameter, the outer surface of which carries the fluid is gray with E₂ = 0.02 and T₂ = 77 K, labelled as Surface 2. This tube is concentric with a larger tube of 50 mm-diameter, where its inner surface (Surface 1) has an 61 = 0.05 and T 1 = 300 K. Estimates all the view factor for both objects and the heat gain by the liquid per square meter.

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