ABSTRACT
The scope of this work was to make detailed analysis of phase
distribution in a horizontal pipe. This detailed analysis has been
successfully carried out. Data obtained from wire mesh sensor (WMS) were
used for the analyses. The operating fluid considered was an
air/silicone oil mixture within a 6 m horizontal pipe with internal
diameter of 0.067 m. The gas superficial velocities considered spans
from 0.047 to 4.727 m/s, whilst liquid superficial velocities ranged
from 0.047 to 0.4727 m/s. The wire mesh sensor (WMS) data obtained
consist of the average cross-sectional and time average radial void
fraction sensor with an acquisition frequency of 1000 Hz over an
interval of 60 s. For the range of flow conditions studied, the average
void fraction was observed to vary between 0.38 and 0.85. An analysis of
the results shows that the major flow patterns observed in this study
were found to be in slug and smooth stratified flow regime with the slug
flow been the dominant one. At constant liquid superficial velocity,
the void fraction increases with an increase in the gas superficial
velocity. This observed trend in the horizontal void fraction is
consistent with the observations made by (Abdulkadir et al., 2014) and
(Abdulkadir et al., 2010) which were all in the vertical orientation.
The performance of the void fraction correlations and their accuracies
were judged in terms of percentage error and RMS error. Nicklin et al.
(1962), Hassan (1995) and Kokal and Stanislav (1989) were judged as the
best performing correlations and Greskovich and Cooper (1975) as the
least. A cubic profile which was dependent on the gas superficial
velocity was observed as the radial void fraction increases with gas
superficial velocity. It was also observed that for a given liquid
superficial velocity, the frictional pressure drop increases with
increase in both gas and mixture superficial velocities. Another finding
made was that, even though Wu et al. (2001)’s model was proposed for
vertical orientation with air and water used as the operating fluid, it
could as well replicate the observed radial void fraction in the
horizontal orientation. The experimental frequency was seen to increase
with liquid superficial velocity but followed a sinusoidal trend with
increase in gas superficial velocity.
CHAPTER 1
INTRODUCTION
1.1 Problem Definition
In this world system you would realize that as human as we are, we
are not complex to understand as single units. For example, let us take
the male species, you would realize that he is kind of burden free when
he is single but as soon as he marries then he brings a burden of the
wife and the children if he has one on himself, in the sense that he now
has a lot of responsibilities relative to the time he was single. These
increases in responsibilities are not peculiar to the man alone but
also to the woman as well. There are therefore a lot of problems that
arise as a result of the union between the man and the woman. If today
they are not figurehting and threatening to divorce each other, tomorrow
they may be quarrelling and insulting each other as to why they made
such a wrong choice. Today, marriage has become like a besieged city,
all those in it want to come out and all those who are out want to go
in. It is amazing, isn’t it?
These complex phenomenon that exist between a man and a woman
co-existing in a marriage is the same complex phenomenon that can be
observed from oil and gas which is transported together in a single
pipe. Initially when an oil well is been produced, at a pressure at or
above the bubble point pressure only oil is been produced which can be
likened to a bachelor who is burden free but immediately the well is
produced below bubble point pressure, gas begin to come out of solution,
hence multiphase phenomenon and therefore the need to transport both
oil and gas through the pipes.
The onshore and offshore production and transportation of oil and gas
resources has always been a challenge within the energy industry, with
engineers having to deal with the various technical and environmental
challenges associated with multiphase flows. For example, in an offshore
environment, it is economically preferable to transport gas and liquid
mixtures through a single flow line and separate them onshore
(Abdulkadir et al., 2010). However, two-phase flow is an extremely
complicated physical phenomenon occurring particularly in the petroleum
industry during the production and the transportation of oil and gas due
to its unsteady nature and high attendant pressure drop. This may
eventually damage the pipe system, therefore the complexity of the
potential flow regimes present within these pipelines has attracted
considerable research interest to improve our understanding of two-phase
flow phase distribution in a pipe system under various processing
conditions. The spatial distribution of the phases inside the pipe and
the pipe geometry play an extremely important role in the accurate
determination of pressure gradient and flow hydrodynamic
characteristics. The flow patterns and the void fraction are one of the
key parameters in two phase flow. The two phase flow in vertical pipes
is symmetrical about the pipe axis and is governed by the interaction
between the liquid inertia, buoyancy, gravity and surface tension
forces. However flow patterns and the void fraction in horizontal pipes
is governed by the density segregation (Bhagwat and Ghajar, 2012).
A vital characteristic of two-phase flow is the presence of moving
interfaces and the turbulent nature of the flow that make theoretical
predictions of flow parameters greatly more difficult than in
single-phase flow. Thus, experimental measurements play an important
role in providing information for design, and supporting analysis of
system behavior. Because of this, there is a real need to make certain
measurements of void fraction distribution for model development and
testing.