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.

Flow Pattern, Void Fraction and Pressure Drop During Adiabatic Two-Phase Gas-Liquid Flow in Vertical Micro-Channel

2012 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Void Fraction ◽  
Test Section ◽  
Annular Flow ◽  
Fused Silica ◽  
Working Fluid ◽  
Micro Channel ◽  
Two Phase ◽  
Churn Flow

The experimental investigation is performed to study two-phase flow pattern, void fraction and pressure drop characteristics in a vertical micro-channel. The test section is a fused silica tube with a diameter of 0.53 mm and a length of 320 mm. Air and water are used as working fluid which is introduced to the test section in vertical upward direction. The test runs are done at superficial velocities of gas and liquid ranging respectively from 0.375 to 21.187 m/s and 0.004 to 2.436 m/s. Stereozoom microscope mounted together with camera are employed to conduct flow visualization from which slug flow, throat-annular flow, churn flow, annular flow and annular-rivulet flow are observed. Based on image analysis, void fraction data are obtained and found to be linear relationship with volumetric quality. The frictional pressure drop is relatively high when the formation of churn flow is established. Besides, the two-phase frictional multiplier is found to be strongly dependent on both mass flux and flow pattern.

Effect of Thin Film Condensation on Thermal Performance of Oscillating Heat Pipes

2006 ◽  
Author(s):  
S. B. Liang ◽  
G. P. Xu
Keyword(s):  
Thin Film ◽  
Liquid Film ◽  
Heat Pipe ◽  
Heat Transport ◽  
Slug Flow ◽  
Thin Liquid Film ◽  
Experimental Studies ◽  
Heat Pipes ◽  
Film Condensation ◽  
Working Fluid

Self-sustainable motions of the slug flow in oscillating heat pipes have been investigated in the paper. Thin film condensation in the capillary channels of the condenser of the oscillating heat pipes was studied. Instability of the thin liquid film on the characteristics of heat pipes was analysed. The extra thermal resistance caused by the thickness of the thin liquid film was taken into account for the numerical simulation of the oscillatory motions of the slug flow in the heat pipes. Saturated temperatures and pressures of the working fluid in the condenser were obtained. Thermoacoustic theory was applied to calculate heat transport through the adiabatic section of the heat pipes. Experimental studies were carried out to understand the heat transfer behaviours of heat pipes. One heat pipe with the working fluid of HFC-134a was evaluated. The heat pipe is made of aluminium plate and has the width of 50 mm and thickness of 1.9 mm. Numerical and experimental results relevant to the heat transport capability of the heat pipe were analysed and compared.

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.

A Numerical Study on Motion of a Sphere Coated With a Thin Liquid Film at Intermediate Reynolds Numbers

1997 ◽  
Vol 119 (2) ◽  
pp. 397-403 ◽  
Author(s):  
S. Kawano ◽  
H. Hashimoto
Keyword(s):  
Reynolds Number ◽  
Liquid Film ◽  
Drag Coefficient ◽  
Flow Pattern ◽  
Numerical Study ◽  
Thin Liquid Film ◽  
Strong Dependence ◽  
Reynolds Numbers ◽  
Rigid Sphere ◽  
Flow Past A Sphere

The steady viscous flow past a sphere coated with a thin liquid film at low and intermediate Reynolds numbers (Re ≤ 200) was investigated numerically. The influences of fluid physical properties, film thickness, and Reynolds number on the flow pattern were clarified. Temperature field around the compound drop was also analyzed. The strong dependence of flow pattern on the characteristics of heat transfer was recognized. The empirical equation of the drag coefficient for the compound drop was proposed. Furthermore, the explicit adaptability of the drag coefficient equation for a gas bubble, a liquid drop, and a rigid, sphere in the range of Reynolds number Re ≤ 1000 was confirmed.

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.

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.

scholarly journals Computational simulation of laminar heat convection of nanofluids in a circular tube and squared duct

DYNA ◽  
2016 ◽  
Vol 83 (196) ◽  
pp. 113-118
Author(s):  
Diego Andrés Vasco Calle ◽  
Daming Chen ◽  
Jorge Acevedo Cabello
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Base Fluid ◽  
Circular Tube ◽  
Computational Simulation ◽  
Colloidal Suspensions ◽  
Reynolds Numbers ◽  
Ansys Fluent ◽  
Metallic Oxides ◽  
Friction Temperature

<p>Nanofluids are colloidal suspensions of nanometer-sized particles (metals, metallic oxides or carbon nanotubes) in a base fluid (polar or non-polar). Nanofluids have interesting properties that make them useful especially in the design of compact heat transfer equipment. Laminar convective heat transfer of nanofluids (water, Al<sub>2</sub>O<sub>3</sub>) in a square and circular ducts has been studied numerically using the software ANSYS/FLUENT 12.1. Results for the Nusselt number, skin coefficient friction, temperature and velocity profiles are presented for four nanoparticle volume fractions (<span style="font-family: Symbol;">j</span> = 0 - 20%) and Reynolds numbers (Re = 800, 1300 and 2000). For the studied Re numbers, Nu is decreased by 12% and 10%, when <span style="font-family: Symbol;">j</span> is increased from 0% to 10% and from 10% to 20%, respectively. Regard to the skin friction factor, the obtained value is increased around a 30% when <span style="font-family: Symbol;">j</span> is increased 10%.</p>

Computational Fluid Dynamic Modeling to Determine the Resistance Coefficient of a Saturated Steam Flow in 90 Degree Elbows for High Reynolds Number

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Juan C. López-López ◽  
Martín Salinas-Vázquez ◽  
Mahendra P. Verma ◽  
William Vicente ◽  
Iván F. Galindo-García
Keyword(s):  
Pressure Drop ◽  
Reynolds Numbers ◽  
Resistance Coefficient ◽  
Operating Conditions ◽  
Steam Flow ◽  
Saturated Steam ◽  
Working Fluid ◽  
High Reynolds Numbers ◽  
Geothermal Power ◽  
High Reynolds

The pressure drop in 90 deg elbows under the operating conditions of geothermal power plants in Mexico is studied using the computational fluid dynamics model. The elbow resistance coefficient was calculated for a steam flow with high Reynolds numbers (1.66–5.81 × 106) and different curvature ratios (1, 1.5, and 2). The simulations were carried out with the commercial software ANSYScfx, which considered the Reynolds-averaged Navier–Stokes (RANS) compressible equations and the renormalization group (RNG) k–ε turbulence model. First, the methodology was validated by comparing the numerical results (velocity and pressure) with published data of airflow (25 °C, 0.1 MPa) with high Reynolds numbers. Then, scenarios with different diameters (0.3–1.0 m) and conditions of the working fluid (0.8–1.2 MPa) were simulated to obtain velocity, pressure, density, and temperature profiles along the pipeline. The temperature and density gradients combined with the compressible effects achieved in the 90 deg elbows modified the flow separation, pressure drop, and resistance coefficient. Based on the resistance coefficient, factors were generated for a new equation, which was integrated into Geosteam.Net to calculate the pressure drop in a pipeline at the Los Azufres geothermal power plant. The difference with the data measured by a pressure transducer was 7.59%, while the equations developed for water or air showed differences between 11.23% and 45.22%.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document