FANS AND BLOWERS 153 



Weight of water = 62.4 Ib. per cu. ft. at 62 deg. F. 

 Weight of column of water 1 ft. sq., 1 in. high, 5.20 

 Ib. at 62 deg. F. 



Weight of cu. ft. of air at 30 in. Bar., 70 deg. F., 70 per 

 cent humidity = 0.07465 Ib. 



This is taken as "Standard Air." 



Weight of air under other conditions, neglecting 

 humidity = 



0.07465 XBX 530, , 



30(460 + f r Fahrenheit ' 

 or 



0.07465X5X2941, 

 030(273+0 - f 



V = Velocity of air in feet per minute. 

 v = Velocity of air in feet per second. 

 Q = Volume in cubic feet per minute. 

 P = Pressure of air in Ib. per sq. ft. 

 p = Pressure of air in ounces per sq. in. 



. 



/" = Loss of head in inches due to friction in pipes 



>X47 



L = Length of pipe between the fan and the Pitot 



tube. 

 D = Diameter of pipe, if it is round ; or = the 



average of the width and depth, if it is 



square or nearly square. 

 P =5.20X/* = 9 p. 

 A =Area of pipe in sq. ft. A e = Effective area 



of 



H = 5.20X- = 69.73X/* for standard air. 

 w 



v 



w 



ruT*' 



V = 481. 2V / #"' = 1097V 



V w 



