A sprinkler system uses an outdoor reservoir at El 50. A fire pump moves Q = 3 ft^3/sec through a 1.0’ dia pipe 300’ long to an 8” dia main at El 200. To distribute water to sprinklers, a pressure head at the pipe junction hp =100’ is required. The equation for friction loss is hl = (fl/d) x (v^2/2g). With new pipe, the friction coefficient “f” = 0.02.
a. Find the required energy input Ep and ?p to be supplied by the pump. Assume the electric motors are set to turn the centrifugal pump impeller at ? = 4000 rpm
b. Find the power delivered (WHP- don’t worry about BHP) by the pump
c. Derive the expression for the hydraulic radius Rh of a pipe
d. Find the shear ? on the 12” pipe walls
e. Iron precipitates on the pipe walls, forming projections e = 0.001”. Estimate the new coefficient “f” by Moody diagram (60 F ) and required increase in Ep to supply Q and the same hp. Rather than replace or re-line the 12” dia, what can you do to the pump motor to keep the Q = 3 ft^3/sec and hp = 100’ spec.