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.

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