A 1/10th scale model of an airplane is tested in a wind tunnel. The Reynolds number of the model is the same as that of the full scale airplane in air. The velocity in the wind tunnel is then .
O 1/10th that of the full scale airplane.
O the same as that of the full scale airplane.
O 10 times that of the full scale airplane.
O 100 times that of the full scale airplane.

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.