The most accurate method of determining HL, is using the Darcy-Weisbach's equations.

(1)

Darcy-Weisbach equation (Design Model)

HL = f x L x V2

Where f = Friction factor, dimensionless

64.4 x D

L = Pipe length, feet

V = Velocity, ft/sec

D = Inside diameter, feet

(2)

Darcy-Weisbach equation (Modified Model)

HL= 0.031 x f x L x Q2

Where f = friction factor

d5

L = Pipe length, feet

Q = Flow rate, GPM

d = Inside diameter, in

PROBLEM: Given:

f = 0.035

L = 0.5 mile

V = 300 ft/min

D = 0.5 ft

SG = 0.8260

Determine HL in PSI.

SOLUTION:

L = 0.5 mile x 5280 ft/mile = 2640 ft

V = 300 ft/min x 1min/60sec = 5 ft/sec

V2 = 25 (ft/sec2)

HL = 0.035 x 2640 x 25 = 71.7 FT

64.4 x 0.5

PSI = - HL x SG = 71.7 x 0.8260 = **25.7**

2.31

2.31

PROBLEM: Given:

f = 0.92

L = 2 miles

Q = 300 BPH

d = 8 in LWST

SG = 0.8448

Determine HL in PSI.

QM5203

1-21

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