Asolid steel disc has an outer diameter of 500mm and a constant thickness of 25mm. the disc has 110 steel blades equi-spaced around its outer edge. each blade has a cross-sectional area of 60mm2. the disc is rotating at 1200rpm and the average radial stress is 150mpa. the density of steel is 7480 kg/m3. how long are the blades to the nearest mm?

Along 8-cm diameter steam pipe whose external surface temperature is 900c connects two buildings. the pipe is exposed to ambient air at 70c with a wind speed of 50 km/hr blowing across the pipe. determine the heat loss from the pipe per unit length. (b) air at 500c enters a section of a rectangular duct (15 cm x 20 cm) at an average velocity of 7 m/s. if the walls of the duct are maintained at 100c. a) the length of the tube for an exit temperature of the air to be 40 0c. b)the rate of heat transfer from the air. c) the fan power needed to overcome the pressure drop in this section of the duct.