The closed tank of a fire engine is partly filled with water, the air space above being under pressure. a 6 cm bore connected to the tank discharges on the roof of a building 2.5 m above the level of water in the tank. the friction losses are of 45 cm of water. determine the air pressure which must be maintained in the tank to deliver 20 litres/sec on the roof.

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.