Research on the viscosity of stabilized emulsions in different pipe diameters using pressure drop and phase inversion

This paper reports experimental research on the flow behavior of oil-water surfactant stabilized emulsions in different pipe diameters along with theoretical and computational fluid dynamics (CFD) modeling of the relative viscosity and inversion properties. The pipe flow of emulsions was studied in turbulent and laminar conditions in four pipe diameters (16, 32, 60, and 90 mm) at different mixture velocities and increasing water fractions. Salt water (3.5% NaCl w/v, pH = 7.3) and a mineral oil premixed with a lipophilic surfactant (Exxsol D80 + 0.25% v/v of Span 80) were used as the test fluids. The formation of water-in-oil emulsions was observed from low water fractions up to the inversion point. After inversion, unstable water-in-oil in water multiple emulsions were observed under different flow regimes. These regimes depend on the mixture velocity and the local water fraction of the water-in-oil emulsion. The eddy turbulent viscosity calculated using an elliptic-blending k-ε model and the relative viscosity in combination act to explain the enhanced pressure drop observed in the experiments. The inversion process occurred at a constant water fraction (90%) and was triggered by an increase of mixture velocity. No drag reduction effect was detected for the water-in-oil emulsions obtained before inversion.

Thermo-Fluid Mechanics of gas-Solid Particle Flows over horizontal Flat Plate

Mathematical model has been developed to protect fluid and solid particle homogeneous mixture velocity concentration and temperature for a heated horizontal flat plate. Conversation equation based on Eulerian scale are approximated for small relaxation times through stream function and similarity transformations. Parametric database generated through computer program for arbitrary constants on comparison with clear fluid reveals the particle concentration has pronounced effect on velocity and temperature profiles.

Flow pattern and pressure drop for oil–water flows in and around 180° bends

Pressure drop and flow pattern of oil–water flows were investigated in a 19-mm ID clear polyvinyl chloride pipe consisting of U-bend with radius of curvature of 100 mm. The range for oil and water superficial velocities tested was $$0.04 \le U_{{{\text{so}}}} \le 0.950 \;{\text{m/s}}$$ 0.04 ≤ U so ≤ 0.950 m/s and $$0.13 \le U_{{{\text{sw}}}} \le 1.10 \;{\text{m/s}}$$ 0.13 ≤ U sw ≤ 1.10 m/s , respectively. Measurements were carried out under different flow conditions in a test section that consisted of four different parts: upstream of the bend, at the bend and at two redeveloping flow locations after the bend. The result indicated that the bend had limited influence on downstream flow patterns. However, the shear forces imposed by the bend caused some shift flow pattern transition and bubble characteristics in the redeveloping flow section after the bend relative to develop flow before the bend. Generally, pressure gradient at all the test sections increased with both oil fraction and water superficial velocity and there was a sharp change of pressure gradient profile during phase inversion. The transition point where phase inversion occurred was always within the range of $$0.4 \le U_{{{\text{sw}}}} \le 0.54 \;{\text{m/s}}$$ 0.4 ≤ U sw ≤ 0.54 m/s . Pressure losses differed at the various test sections, and the difference was strongly linked to the superficial velocity of the phases and the flow pattern. At high mixture velocity, pressure losses at the redeveloping section after the bend were higher than that at the bend and that for fully developed flows. At low mixture velocity, pressure losses at the bend are higher than in the straight sections. Pressure drop generally decreased with level of flow development downstream of the bend.

Flow Pattern and Pressure Drop for Oil-Water Flows in and around 180° Bends

Pressure drop and flow pattern of oil-water flows were investigated in a 19 mm ID clear polyvinyl chloride pipe consisting of U-bend with radius of curvature of 100 mm. The range for oil and water superficial velocities tested were and respectively. Measurements were carried out under different flow conditions in a test section that consisted of four different parts: upstream of the bend, at the bend and at two redeveloping flow locations after the bend. The result indicated that the bend had limited influence on downstream flow patterns. However, the shear forces imposed by the bend caused some shift flow pattern transition and bubble characteristics in the redeveloping flow section after the bend relative to develop flow before the bend. Generally, pressure gradient at all the test sections increased with both oil fraction and water superficial velocity and there was a sharp change of pressure gradient profile during phase inversion. The transition point where phase inversion occurred was always within the range of . Pressure losses differed at the various test sections and the difference was strongly linked to the superficial velocity of the phases and the flow pattern. At high mixture velocity, pressure losses at the redeveloping section after the bend were higher than that at the bend and that for fully developed flows. At low mixture velocity, pressure losses at the bend are higher than in the straight sections. Pressure drop generally decreased with level of flow development downstream of the bend.

Dissipation of Injected Slug in Enlarged Impacting Tee in Single Branch Blocking Configuration

A novel Enlarged Impacting Tee-Junction (EIT), which introduces longer slugs to be dissipated utilizing “Single-Branch-Blocking” is studied experimentally and theoretically under stationary slug-injection conditions to further understand the dissipation mechanism through observation of longer slugs. The EIT test section is designed and constructed, which consists of one inlet pipe connected to a larger, perpendicular pipe allowing flow in both directions. The inlet is 4.6 m of 0.05 m diameter pipe, while the perpendicular “manifold” is 0.074 m in diameter and 5.5 m in length. In order to observe the dissipation of longer slugs, a modification is made to the Normal EIT configuration. The longer slugs in the EIT are generated by blocking one of the EIT branches, allowing flow in only the unblocked branch of the EIT. Thus, the entire injected slug (rather than half in the case of no blocking configuration) dissipates in the branch. For this configuration, stationary slugs are injected into the EIT with lengths of 40d, 50d, 60d, and 70d (with d being the inlet diameter). A total of 64 slug injection tests are conducted utilizing both air-water and air-oil flow. The experimental data show that slug dissipation has a nonlinear increasing relationship with mixture velocity. Furthermore, the data show that higher dissipation length is observed with air-water flow as compared to air-oil flow in the slug injection experiments due to higher shed slug volume of oil. Also, the acquired data are used to validate the EIT slug dissipation model developed by Mohammadikharkeshi (2018). For the Single-Branch-Blocking investigation, comparison between the acquired experimental data and the modified Mohammadikharkeshi (2018) Normal EIT model predictions reveals excellent comparison, with an average discrepancy of 12%.

Effect of Phase Velocities Prediction on Fluidelastic Instability of a Cantilever Pipe Subjected to Gas-Liquid Flow

The effect of the phase velocity models on the prediction of fluidelastic instability of a cantilever pipe subjected to gas-liquid internal flow is studied. According to the accepted fluidelastic formulation, a two-phase flow correlation is needed to relate phase velocities in order to solve the system equation. In this study, seven reported correlations, including the homogeneous no-slip model, are used to study the effect of phase velocities prediction on fluidelastic instability parameters, specifically, critical mixture-velocity and critical frequency. Comparisons between simulations and previously reported experiments are performed. Results show that the correlation selection plays an important role in critical mixture-velocity predictions. On the other hand, the critical frequency is less sensitive to the correlation.

Effect of mixture velocity for given equivalence ratio on flame development in Swiss roll combustor

Small-scale power generation using heat energy from hydrocarbon (HC) fuels is a proven technology. In this study, we analyzed 2D flame development in meso-scale Swiss roll combustor (SW). A mixture of 60% butane and 40 % propane was used (0.25-0.55 l/min). During all the analyses, equivalence ratio (1.1) was kept constant by adjusting air quantity against fuel quantity. The effect of increase in the mixture velocity on the development of flame shapes/patterns was monitored. We found different patterns of flame, e.g., Planar, Concave, conical, with the increase in mixture velocity. Increase in combustion chamber temperature was also noted. No Flashback was observed and blowout was observed with very high mixture velocity. Combustion chamber temperatures were found to be increasing with the increase in mixture velocity at the same equivalence ratio. Elongation of the flame was observed because of the increased flow velocity. Heat recirculation to the reactants enhances flame characteristics.

Experimental Investigation of Gas-Hydrate Formation and Particle Transportability in Fully and Partially Dispersed Multiphase-Flow Systems Using a High-Pressure Flow Loop

Summary As the oil-and-gas industries strive for better gas-hydrate-management methods, there is the need for improved understanding of hydrate formation and plugging tendencies in multiphase flow. In this work, an industrial-scale high-pressure flow loop was used to investigate gas-hydrate formation and hydrate-slurry properties at different flow conditions: fully dispersed and partially dispersed systems. It has been shown that hydrate formation in a partially dispersed system can be more problematic compared with that in a fully dispersed system. For hydrate formation in a partially dispersed system, it was observed that there was a significant increase in pressure drop with increasing hydrate-volume fraction. This is in contrast to a fully dispersed system in which there is gradual increase in the pressure drop of the system. Further, for a partially dispersed system, studies have suggested that there may be hydrate-film growth at the pipe wall. This film growth reduces the pipeline diameter, creating a hydrate bed that then leads to flowline plugging. Because there are different hydrate-formation and -plugging mechanisms for fully and partially dispersed systems, it is necessary to investigate and compare systematically the mechanism for both systems. In this work, all experiments were specifically designed to mimic the flow systems that can be found in actual oil-and-gas flowlines (full and partial dispersion) and to understand the transportability of hydrate particles in both systems. Two variables were investigated in this work: amount of water [water cut (WC)] and pump speed (fluid-mixture velocity). Three different WCs were investigated: 30, 50, and 90 vol%. Similarly, three different pump speeds were investigated: 0.9, 1.9, and 3.0 m/s. The results from these measurements were analyzed in terms of relative pressure drop (ΔPrel) and hydrate-volume fraction (ϕhyd). It was observed that, for all WCs investigated in this work, the ΔPrel decreases with increasing pump speed, at a similar hydrate-volume fraction. Analysis conducted with the partially-visual-microscope (PVM) data collected showed that, at constant WC, the hydrate-particle size at the end of the tests decreases as the mixture velocity increases. This indicates that the hydrate-agglomeration phenomenon is more severe at low mixture velocity. Calculations of the average hydrate-growth rate for all tests conducted show that the growth rate is much lower at a mixture velocity of 3.0 m/s. This is attributed to the heat generated by the pump. At a high mixing speed of 3.0 m/s, the pump generated a significant amount of heat that then increased the temperature of the fluid. Consequently, the hydrate-growth rate decreases. It should be stated that this warming effect should not occur in the field. Flow-loop plugging occurred for tests with 50-vol% WC and pump speeds lower than 1.9 m/s, and for tests with 90-vol% WC at a pump speed of 0.9 m/s. In addition, in all 90-vol%-WC tests, emulsion breaking, where the two phases (oil and water) separated, was observed after hydrate formation. From the results and observations obtained from this investigation, proposed mechanisms are given for hydrate plugging at the different flow conditions. These new findings are important to provide qualitative and quantitative understanding of the key phenomena leading to hydrate plugging in oil/gas flowlines.

The evolution of segregation in dense inclined flows of binary mixtures of spheres

We consider the evolution of particle segregation in collisional flows of two types of spheres down rigid bumpy inclines in the absence of sidewalls. We restrict our analysis to dense flows and use an extension of kinetic theory to predict the concentration of the mixture and the profiles of mixture velocity and granular temperature. A kinetic theory for a binary mixture of nearly elastic spheres that do not differ by much in their size or mass is employed to predict the evolution of the concentration fractions of the two types of spheres. We treat situations in which the flow of the mixture is steady and uniform, but the segregation evolves, either in space or in time. Comparisons of the predictions with the results of discrete numerical simulation and with physical experiments are, in general, good.