The Use of Flow Improvers to Decrease Pressure Drop in Multiphase Pipelines

2002 ◽  
Author(s):  
C. Kang ◽  
W. P. Jepson
Keyword(s):  
Carbon Dioxide ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Large Decrease ◽  
Upward Flow ◽  
Flow Loop ◽  
Downward Flow ◽  
Water Cut ◽  
Flow Improver

Experiments were performed in a 10-cm diameter, 44 m long Plexiglas pipes, multiphase flow loop to examine the effect of flow improver in slug flow at inclinations of ±5degrees. Superficial liquid velocities between 0.5 and 1.5 m/s and superficial gas velocities between 2 and 6 m/s were studied. A 2.5 cP oil at 25 °C was used and water cut was 10%. The experiments were undertaken at a pressure of 0.13 MPa and a temperature of 25 °C with carbon dioxide as the gas. The effectiveness of flow improver on pressure drop and slug frequency was examined for concentrations ranging from 0 ppm to 50 ppm. The results showed that the flow improver was effective in reducing the pressure drop significantly at all superficial liquid and gas velocities. The flow improver concentration of 50 ppm was more effective than 25 ppm for all cases. At superficial gas velocities of less than 4 m/s and all liquid velocities with 50 ppm flow improver, the effectiveness of flow improver in upward flow was around 30%. At superficial liquid and gas velocities of 1.0 and 2 m/s with 50 ppm flow improver concentration, the effectiveness of up to 64% was achieved in downward flow. The slug frequency in both upward and downward flows decreased significantly in all cases with addition of flow improver. For example, at superficial liquid and gas velocities of 1.5 and 2 m/s, the slug frequency in downward flow decreased from 43 to 14 slugs/min. when 50 ppm of chemical was added. The flow pattern in downward flow was changed from slug flow to stratified flow at several velocities, which led to a large decrease in the pressure drop.

A Flow Model for Two-Phase Slug Flow in Horizontal Tubes

1961 ◽  
Vol 83 (4) ◽  
pp. 613-618 ◽  
Author(s):  
E. S. Kordyban
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Flow Model ◽  
Simplified Model ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Horizontal Tubes

The paper presents a construction of a simplified model approximating the actual observed flow pattern. The resulting expressions for frictional pressure drop are found to agree fairly well with the author’s data for steam and water and the data for air and water of other investigators. The similarity with a portion of the Chenoweth-Martin correlation appears to present a logical explanation for the applicability of that correlation to slug flow.

Flow Boiling of Carbon Dioxide in Horizontal Mini-Channel and Pattern Dynamics Approach to Study Flow Pattern

2009 ◽  
Author(s):  
Mamoru Ozawa
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Instability ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Bond Number ◽  
Pattern Dynamics ◽  
Mini Channels

This paper provides a brief review on experimental and numerical investigations of flow patterns, pressure drop, and heat transfer including critical heat flux (CHF) of flow boiling carbon-dioxide (CO2) at high pressure in mini-channels ranging 0.5mm to 3.0mm in diameter. The flow patterns of CO2 at high pressure with small density difference between vapor and liquid and low surface tension show a slightly different structure from so far observed in mini-channels with air and water. The phase mal-distribution, similar to conventional tubes, in the cross-section becomes rather significant beyond the critical Bond number, which leads to the intermittent dryout at the upper wall of the tube. So far proposed flow pattern transition criteria are ineffective there, and newly developed discrete bubble model demonstrates its high potential in predicting flow patterns. Conventional homogeneous flow model is still available in predicting pressure drop. Based on this fact, flow instability problems, which significantly affect CHF, is discussed focusing on high-pressure CO2 flow.

scholarly journals Gas–Liquid Slug Flow Studies in Microreactors: Effect of Nanoparticle Addition on Flow Pattern and Pressure Drop

2022 ◽  
Vol 3 ◽  
Author(s):  
Jie Zong ◽  
Jun Yue
Keyword(s):  
Pressure Drop ◽  
Liquid Film ◽  
Flow Pattern ◽  
Slug Flow ◽  
Base Fluid ◽  
Rational Design ◽  
Colloidal Suspensions ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Nanoparticle Suspension

Colloidal suspensions of nanoparticles (e.g., metals and oxides) have been considered as a promising working fluid in microreactors for achieving significant process intensification. Existing examples include their uses in microflow as catalysts for enhancing the reaction efficiency, or as additives to mix with the base fluid (i.e., to form the so-called nanofluids) for heat/mass transfer intensification. Thus, hydrodynamic characterization of such suspension flow in microreactors is of high importance for a rational design and operation of the system. In this work, experiments have been conducted to investigate the flow pattern and pressure drop characteristics under slug flow between N2 gas and colloidal suspensions in the presence of TiO2 or Al2O3 nanoparticles through polytetrafluoroethylene (PTFE) capillary microreactors. The base fluid consisted of water or its mixture with ethylene glycol. The slug flow pattern with nanoparticle addition was characterized by the presence of a lubricating liquid film around N2 bubbles, in contrast to the absence of liquid film in the case of N2-water slug flow. This shows that the addition of nanoparticles has changed the wall wetting property to be more hydrophilic. Furthermore, the measured pressure drop under N2-nanoparticle suspension slug flow is well described by the model of Kreutzer et al. (AIChE J 51(9):2428–2440, 2005) at the mixture Reynolds numbers ca. above 100 and is better predicted by the model of Warnier et al. (Microfluidics and Nanofluidics 8(1):33–45, 2010) at lower Reynolds numbers given a better consideration of the effect of film thickness and bubble velocity under such conditions in the latter model. Therefore, the employed nanoparticle suspension can be considered as a stable and pseudo single phase with proper fluid properties (e.g., viscosity and density) when it comes to the pressure drop estimation.

Variation of Flow Regimes in +2 Degree Inclined Wet Gas Environments and Drag Reduction

2006 ◽  
Author(s):  
Cheolho Kang ◽  
Parimal More
Keyword(s):  
Pressure Gradient ◽  
Gas Phase ◽  
Slug Flow ◽  
Flow Characteristics ◽  
Phase Variation ◽  
Flow Patterns ◽  
Upward Flow ◽  
Wet Gas ◽  
Wave Forms ◽  
Flow Improver

Experiments were carried out to examine the study of flow patterns and the performance of drag reducing agents in a 40 m long, 10.16 cm diameter, + 2 degree inclined wet gas pipeline environments. Superficial liquid velocities ranging from 0.03 to 0.1 m/s and gas velocities from 2 to 10 m/s were investigated with the commercial DRA concentration of 0, 25 and 50 ppm. Light viscosity oil was used as the liquid phase and carbon dioxide was used as the gas phase. Variation of flow patterns in horizontal and +2 degree pipes are reported in this paper. The effect of inclinations on the pressure gradient is also presented. The stratified flow was dominant flow pattern in horizontal wet gas pipelines. However, for certain conditions, slug flow along with big wave forms was observed in 2 degree upward flow. The pressure gradient for 2 degree upward flow was higher than horizontal flow since the height of the liquid film was higher in case of upward flow. The pressure gradient decreased significantly as drag reducing agent was added in the pipeline. For slug flow in + 2 degree inclination, the pressure gradient reduction of 19 % was achieved for superficial liquid and gas velocities of 0.03 and 2 m/s at a flow improver concentration of 50 ppm. This was because the flow characteristics such as slug frequency and wave activity were changed with the addition of DRA.

Numerical Simulation of Condensation of Upward Flow in a Vertical Pipe

2014 ◽  
Author(s):  
Guodong Qiu ◽  
Zhiyong Wu ◽  
Yiqiang Jiang ◽  
Shulei Li ◽  
Weihua Cai
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Pattern ◽  
Slug Flow ◽  
Upward Flow ◽  
Vapor Quality ◽  
Vertical Pipe ◽  
Transfer Coefficients ◽  
Good Agreement

A transient three-dimensional volume of fluid (VOF) simulation on condensation of upward flow of wet steam inside a 12 mm i.d. vertical pipe is presented. The effect of gravity and surface tension are taken into account. A uniform wall heat flux have been fixed as boundary conditions. The mass flux is m=130∼6000 kg m−2 s−1 and the turbulence inside the vapor phase and liquid phase have been handled by Reynolds Stress (RS) model. The vapor quality of fluid x=0∼0.4. The numerical simulation results show that in all the simulated conditions only the bubbly flow, slug flow, churn flow and annular flow are observed, in addition the results of flow pattern are in good agreement with the regime map from Hewitt and Roberts. The typical velocity field characteristic of each flow pattern and the effect of velocity field on heat transfer of condensation are analyzed. It can be found that only slug flow has an obvious local eddy around the slug gas in all simulated flow patterns. The trend of heat transfer coefficients rises throughout with the increase of vapor quality for all simulated conditions, which is good agreement with the correlation from Boyko and Kruzhilin.

Void Fraction, Pressure Drop, and Flow Pattern Behavior for Two-Phase Non-Newtonian Slug Flow

2021 ◽  
Author(s):  
Faraj Ben Rajeb ◽  
Syed Imtiaz ◽  
Yan Zhang ◽  
Amer Aborig ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Regime ◽  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase

Abstract Slug flow is one of the most common flow patterns in non-Newtonian two-phase flow in pipes. It is a very common occurrence in gas-liquid two-phase flow in the pipe. Usually, it is an unfavorable flow pattern due to its unsteady nature, intermittency as well as high pressure drop. The differences between slug flow and elongated bubble flow are not clear because usually these two types of flow combined under one flow category. In general, these two-phase flow regimes are commonly defined as intermittent flow. In the present study, pressure gradient, and wave behavior in slug flow have been investigated depending on experimental work. In addition, void fraction has been estimated regarding available superficial liquid and gas velocities. The experimental records of superficial velocities of gas and liquid for slug flow and other flow patterns is used to create flow regime map for the gas non-Newtonian flow system. The effect of investigated flow regime velocities for non-Newtonian/gas flow on pressure drop and void fraction is reported. Pressure drop has been discovered to be reduced in slug flow more than other flow patterns due to high shear thinning behavior.

Numerical Investigation on Flow Pattern and Pressure Drop Characteristics of Slug Flow in a Micro Tube

2008 ◽  
Author(s):  
Qunwe He ◽  
Nobuhide Kasagi
Keyword(s):  
Surface Tension ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Thin Liquid Film ◽  
Surface Tension Force ◽  
Tension Force ◽  
Flow Profile ◽  
Liquid Slug ◽  
Two Phase

In the present study, numerical simulation of adiabatic air-water slug flow in a micro tube is carried out. The focus is laid upon the pressure drop characteristics and its modeling. The Phase-Field method is employed to capture the interface between the phases, while the surface tension force is represented by the chemical potential formulation. The numerical results agree fairly well with available experimental results in terms of bubble shape and flow pattern. Simulation is repeated under different conditions of pressure gradient, void fraction and bubble frequency. It is found that the total pressure drop of a slug flow can be decomposed into two parts, i.e., the frictional pressure drop associated with a liquid slug sandwiched by bubbles, and the pressure drop over a bubble itself. For the former, when the liquid slug is longer than one tube diameter, the cross-sectional velocity distribution resembles a Poiseuille flow profile, so that the corresponding pressure drop can be predicted by the theoretical solution of single-phase liquid flow, i.e., fReTP = 64. For the latter, if it is assumed that the surface tension force is strong enough to sustain a thin liquid film between the interface and the tube wall, the pressure drop in this region is negligible. The pressure drop over a bubble is solely dependent on the two-phase superficial Reynolds number ReTP, which can be correlated as: Δpbubb′ = 0.07 + 42.4 / ReTP. This correlation predicts well the two-phase pressure drop in the form of the two-phase multiplier correlation as a function of the Lockhart-Martinelli parameter.

scholarly journals The Performance of Drag Reducing Agent in Three Phase Slug Flow and Annular Flow

2000 ◽  
Author(s):  
C. Kang ◽  
D. Vedapuri ◽  
W. P. Jepson
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Annular Flow ◽  
Maximum Pressure ◽  
Average Pressure ◽  
Effective Height ◽  
Pressure Drops ◽  
Three Phase ◽  
Water Cut ◽  
Maximum Pressure Drop

Experiments have been carried out in a 36-m long, 10-cm diameter multiphase horizontal flow system to examine the effect of drag reducing agents (DRA) on average pressure drop, maximum pressure drop and slug characteristics with the presence of water. Superficial liquid velocities between 0.5 and 1.5 m/s and superficial gas velocities between 2 and 14 m/s were investigated. Oil with a viscosity of 2.5 cP at 25 °C was used for the study. ASTM salt was used as a substitute for seawater and carbon dioxide was used as the gas. Water cut was 50%. Temperature and pressure were maintained at 25 °C and 0.13 MPa. The DRA concentrations of 0, 20 and 50 ppm were used in this study. The results show that the average pressure drop in both slug flow and annular flow decreased significantly with addition of DRA. Under special conditions, it was found that DRA changed the flow pattern from pseudo-slug to annular resulting in a 74% reduction in pressure drop. For annular flow, the average pressure drop reduction of up to 53% was achieved. The maximum pressure drop across the slug also decreased with the presence of DRA. The average and maximum pressure drops at a DRA concentration of 50 ppm were more effective than 20 ppm for all cases. The slug frequency and effective height of the liquid film decreased significantly when DRA concentrations were added. This led to a decrease in the average pressure drop. However, the slug translational velocity did not change significantly with addition of DRA.

Adiabatic Air-Water Two-Phase Flow in Circular Microchannels

2011 ◽  
Author(s):  
Aritra Sur ◽  
Dong Liu
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Phase Pressure ◽  
Circular Microchannels

Gas-liquid two-phase flow in microchannels with hydraulic diameters of 100–500 μm exhibits drastically different flow behaviors from its counterpart in conventional macroscopic channels. Two particular issues are how to determine the two-phase flow patterns and how to predict the two-phase pressure drop at given flow conditions in these microchannels. This paper presents an experimental study of adiabatic two-phase flow of air-water mixture in circular microchannels with inner diameters of 100, 180 and 324 μm, respectively, to investigate the effects of channel size and phase velocity on the two-phase flow pattern and pressure drop. The air and water superficial velocities were in the range of 0.01–120 m/s and 0.005–5 m/s. Two-phase flow patterns were visualized using highspeed photographic technique. Four basic flow patterns, namely, bubbly flow, slug flow, ring flow and annular flow, were observed. The two-phase flow maps were then constructed and the transition boundaries between different flow regimes were identified. It was found that the slug flow is the dominant two-phase flow pattern in microchannels, and the transition boundaries generally shift to regions of higher gas superficial velocities as the channel dimension decreases. The experimental measurements of two-phase pressure drop were compared to the predictions from the available two-phase models in the literature. Results show that the flow pattern-based models provide the best prediction of two-phase pressure drop in microchannels.

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