where K is a constant experimentally determined, and d the internal diameter of the pipe in feet.

If h represents the loss of head in feet, then

E f = W h =
f 2 v ² W L
–––––––––––––––––
gd
 ( 39 )

and h =
f 2 v ² L
––––––––––––
gd
 ( 40 )

If D represents the density of the steam or weight per cubic foot, and p the loss of pressure due to friction in pounds per square inch, then

p =
h D
––––––
144
 ( 41 )

and from equations ( [38] ), ( [40] ) and ( [41] ),