p =
D v ² L
–––––––––––
72 gd
 × K(1 +
3
–––––––
10 d
) ( 42 )

To convert the velocity term and to reduce to units ordinarily used, let d 1 the diameter of pipe in inches = 12 d , and w = the flow in pounds per minute; then

w = 60 v ×
π
––
4
(
d1
––––
12
 ) ²D
and v =
9.6 w
–––––––––––
π d1 ² D

[Pg 318]

Substituting this value and that of d in formula ( [42] )

p = 0.04839 K(1 +
3.6
–––––
d1
)
w ² L
––––––––
D d15
 ( 43 )

Some of the experimental determinations for the value of K are:

K = .005 for water (Unwin).
K = .005 for air (Arson).
K = .0028 for air (St. Gothard tunnel experiments).
K = .0026 for steam (Carpenter at Oriskany).
K = .0027 for steam (G. H. Babcock).