Page 528 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

How of Fluids 483

Pressure Gradient
zm)
The friction factor for the liquid is first calculated by
(
O.O46/ReE %Re, = L
1,500
2
fw, = (6-1024
[16/Re, if Re, e 1,500
The pressure gradient due to friction in the bubbly flow regime is evaluated from

(6-1 02b)
and the gravitational pressure gradient
(%Ig = -g[HLy, + (1 - HL)yg]sin6 (6-102~)

Correction for Acceleration Effects
The methods used in this section so far neglected the contribution of accelera-
tion effects to the pressure gradient,
The acceleration pressure gradient in pipeline flow is due to the changes in
the fluid properties through the pipe segment. These changes include expansion
of the gas phase, expansion of the liquid phase and the changes in quality (due
to phase behavior).
To account for acceleration effects, the total pressure gradient should be
calculated by:

(6-10%)

where the parameter A is calculated by the method appropriate for each flow
regime as follows:

[= o to neglect acceleration effects
:
(

I
)
[ (3
= (yp, +yLvsL)* x - +(1-X) -
.i
A for bubbly or slug flow regime
(6-1036)

for stratitied or annu~ar flow regime