215 litres of gasoline (specific gravity 0.82) flow per second through an inclined venturimeter fitted to a 300 mm dia pipe. The venturimeter is inclined at an angle of 600 to the vertical and its 150 mm dia. throat is 1.2 m from the entrance along its length. Pressure at throat =0.077 N/mm2 , calculate Cd. If instead of pressure gauges the entrance and throat of the venturimeter are connected to the two limbs of a U=tube manometer. Determine its reading in mm of differential mercury column.

 215 litres of gasoline (specific gravity 0.82) flow per second through an inclined venturimeter fitted to a 300 mm dia pipe. The venturimeter is inclined at an angle of 600 to the vertical and its 150 mm dia. throat is 1.2 m from the entrance along its length. Pressure at throat =0.077 N/mm2 , calculate Cd. 

 If instead of pressure gauges the entrance and throat of the venturimeter are connected to the two limbs of a U=tube manometer. Determine its reading in mm of differential mercury column. 

Solution: 

Discharge, 

Q=Cd((a1a2)/(√a1 2 -a2 2 ))*√(2gh) = 215*10-3 = 0.215 m3 /s 

a1 = (π/4)*(300/1000)2 = 0.0707 m2

 a2 = (π/4)*(150/1000)2 = 0.0177 m2 

h = ((p1/w) +z1) - ((p2/w) +z2) 

p1/w = (0.141 *106 )/(9810*0.82) = 17.528 m of gasoline 

p2/w = (0.077 *106 )/(9810*0.82) = 9.572 m of gasoline 

z1 = 0, z2 = (1.2 sin 30) = 0.66m 

h = (17.528 + 0) – (9.572 + 0.66) = 7.356 m 

0.215 = Cd((0.0707*0.0177)/(√0.07072 -0.01772 ))*√(2*9.81*7.356) 

Cd = 0.979

 When a U-tube manometer is connected,

 h = x((sm/so)-1) 7.356 = x((13.6/0.82)-1) 

 x = 0.472 m

 x = 472 mm