this presentation described the pipeline hydraulic.

this presentation described the pipeline hydraulic.
These include water lines, refined petroleum products and crude oil
pipelines. This course will prove to be a refresher in fluid mechanics as it is applied to real
world pipeline design. Although many formulas and equations are introduced, we will
concentrate on how these are applied to the solution of actual pipeline transportation
problems First, the liquid properties are discussed, and how they vary with temperature and pressure
are analyzed. The pressures in a liquid and liquid head are explained next. Then the
classical method of determining pressure drop due to friction in liquid flow is introduced and
a modified more practical versions are explained. Common forms of equations relating to
flow versus pressure drop due to friction are introduced, and applications are illustrated by
example problems. In a long distance pipeline, the need for multiple pump stations and
hydraulic pressure gradient is discussed.

1. Pipeline hydraulics
Andrew Palmer

2. single-phase horizontal steady flow
pressure p p+dp
x x+dx
direction of flow
mean velocity U,
density
D
resultant force on fluid element must be
zero
pD pdpD Ddx
dp
dx D
fU
dp
dx
fU
D
( /)( )(/)( )
(/)
  

 

2 2
2
2
4 4
4
12
2
 





3. for Newtonian fluids (shear rate proportional to shear
stress, viscosity ), f is a function of Reynolds number
Re=


UD
and dimensionless roughness k/D
f
10
3
10
4
10
5
10
6
laminarturbulent
smooth
increasing
roughness
Re

4. dp
dx
fU
D
q D U
dp
dx
fq
D



2
4
32
2
2
2
2
5




volumetric flow rate
so
( /)
which implies that dp/dx is very sensitive to D
a 10 per cent reduction in D increases dp/dx by
69 per cent

5. 1
datum
z
1
z
2
lin
e
p
r
o
f
ile
no flow pp unitweightzz
12 12 ( )( )

6. single-phase steady flow
mean velocity U,
density
ds
dz
g
D
Uf
ds
dp
Uf)/(
ds
dz
g
Dds
dp
ds
dz
ds)/D(g)Dds(
)/D)(dpp()/D(p












2
2
2
22
2
21
4
4
44pressure p p+dp
s
s+ds
D 
z
z+dz
resultant force parallel to axis = 0
flow
g(D
2
/4)ds

7. )differenceheight(g)length(
D
Uf
pp 


2
12
2
if - but only if - f  U and D are all constant along the
length of the line
1
s+ds
s
2
integrate from 1 to 2
dp
ds
fU
D
g
dz
ds
 
2
2



8. usually f  U and D are not constant along the length
of the line, because
1 in oil lines, the temperature changes, which
affects  and therefore f
2 in gas lines, the pressure changes, and
therefore since gas is compressible  and U change
3 in gas lines, Joule-Thomson cooling reduces
the temperature, and therefore affects  and U

9. the gases engineering is generally concerned with can be
idealised as perfect gases:
Boyle’s law: for a fixed mass of gas at a fixed
temperature, volume is inversely proportional to
pressure
Charles’ law: for a fixed mass of gas at a fixed pressure,
volume is proportional to absolute temperature
p
1 p
2,T
2,T
1 perfect insulation
ppbutTT
1 2 21
  from steady flow energy equation

10. petroleum gases (methane, ethane, propane, etc., ethylene...)
usually cannot be idealised as perfect gases: they are real gases
Boyle’s law and Charles’ law are not obeyed
p
1 p
2,T
2,T
1 perfect insulation
ppandTT
1 2 21  Joule-Thomson cooling
pV
RT
ZpTcompressibility factor (.)

11. sea
temperature
gas
platform
compressors
distance

12. integrate step by step, from upstream to
downstream, taking account of:
changes of properties
height profile
heat flows into and out of pipe, by coupled heat-
flow model
dp
ds
fU
D
g
dz
ds
 
2
2



13. hydrates
at low temperatures and high pressures
water + hydrocarbon combine to form solid hydrate (like
wet snow)

14. 10
100
1000
0 10 20 30
temperature (degC)
p
r
e
s
s
u
r
e

(
b
a
r
s
)
methane/water
95% methane,
5%ethane / water
methane/methanol
20% w/w in water

15. hydrates
options
remove water
keep temperature high (insulation, heat tracing)
add hydrate inhibitor
thermodynamic (glycol, methanol) shifts
equilibrium to lower temperatures
kinetic (alters crystals so they don’t
agglomerate)

16. wax
collects on wall, reduces diameter
options
keep temperature high
remove by pigging
remove by solvent

17. multi-phase flow
gas
oil
(water)
(sand)
first difficulty is number of different flow regimes
that can occur
in single-phase flow, describe by mean velocity U
in multi-phase, we need to describe the velocities of
more than one phase
superficial velocity of a phase is mean velocity of
that phase if other phases were absent

18. gas superficial velocity Ug
liquid
superficial
velocity Ul
lg
l
g
l
g
annular-mist
mist
bubble
slug
stratified
wavy-stratified
l
l
g

19. different correlations have been proposed to decide which flow
regime occurs
caution is needed: some correlations have been developed for
air/water systems at atmospheric pressure in small diameter
pipes
in a typical laboratory experiment, diameter is 2 inches (50
mm), and density ratio is 800 (water/air at atmospheric
pressure)
in a typical application, diameter is 10 inches, and density ratio
is 8 (oil/gas at pipeline pressure)

20. effect of gradient
gas
oil

21. effect of gradient
gas
oil
oil only continues to flow uphill if drag force of gas
moving over the upper surface more than balances the
gravity force tending to make the oil flow the other
way

22. riser slugging
stratified
gas
oil
g
a
s

23. riser slugging
stratified
gas
oil
g
a
s

24. riser slugging
stratified
gas
oil
g
a
s
slug

25. riser slugging
stratified
gas
oil
g
a
s

26. Italy Germany
flow direction
flow
rate
time
Italy
Germany
2 hours