D2= 18 in V2 900 ft/min p-14.7 psia T=100F (A)= 12 x 12 in VF1200 ft/min Flow At one section in an air distribution system, air at 14.7 psia and 100F has an average velocity of 1200 ft/min and the duct is 12 in square. At another section, the duct is round with a diameter of 18 in, and the velocity is measured to be 900 ft/m in. Calculate (a) the density of the air in the round section and (b) the weight flow rate of air in pounds per hour. At 14.7 psia and 100F, the density of air is 2.20 x 10- 3 slugs/ft3 and the specific weight is 7.09 x 10-21b/tt3.