15) Radiation to a Tube from a Large Enclosure. A small oxidized horizontal metal tube with an OD of 0.0254 m (1-inch), 0.61 m (2 ft) long, and with a surface temperature at 472 K (390 F) is in a very large furnace enclosure with firebrick walls and the surrounding air at 1088 K (1500 F). The emissivity of the metal tube is 0.94 at 1088 K and 0.79 at 472 K. Calculate the heat transfer to the tube by radiation using SI and English units.