A drainpipe 30 cm diameter lies beneath an earth dam. The pipe was partially clogged with sand. The discharge of the pipe was 300 lit/day when the difference between the dam's upstream and downstream water levels was 20 m. Calculate the clogged length, if the permeability of the sand was estimated to be 0.01 cm/sec.

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.