Question

3. Water flows through 80 ft of a 4” cast iron pipe. The head loss through the pipe is 0.27 ft. What is the volume flow rate of water through the pipe, in cfs? [Type II]

Answer 1

Due to friction in pipe, a major head loss is seen which is calculated by Darcy-Weisbach equation.

Head loss due to friction=Hf=fLV²/2Dg

where, f is friction factor

L is length of pipe

V is velocity of flow

g is acceleration due to gravity

D is diameter of pipe

where, Q is volume flow rate

A is area of flow

According to the question data,

L=80 ft

D= 0.3333 ft

Hf= 0.27 ft

g= 32.174 ft/s²

f= 0.00085..............{for cast iron pipe}

Q= ?

Solving the above expression, we get

Q= 0.805 ft³/s or. Q= 0.805 cfs