Annular Flow Research Articles

Assessing the influence of far UV-C (222 nm) and UV-C (254 nm) treatment on the physicochemical and microbial properties of milk in an annular flow reactor

The quest for alternatives to traditional cold chain preservation and heat-based shelf-life extension has become increasingly important in recent years. As a result, investigation into the effects of ultraviolet (UV) radiation on the physicochemical properties of various substances, including milk, has gained significant attention. UV-C light, in particular, is recognized for its effectiveness in inactivating a wide range of bacteria and spores in aqueous solutions. This work aims to design a continuous annular UV reactor for milk treatment to examine the impacts on milk’s microbial and physicochemical characteristics and compare these outcomes to those achieved through conventional pasteurization methods. For the same, a 11 W conventional UV-C lamp (254 nm) and an in house designed 17.5 W far UV-C (222 nm) lamp have been used. The key parameters, such as pH, conductivity, temperature, fat/solid not fat, and microbial load, are assessed. The UV dosage supplied to milk samples is determined using actinometry and measured to be 6.16 J/ml. The methylene blue reduction test of milk increases up to more than 5 h, with just four passes through the UV reactor. Approximately 5 log reductions in the Salmonella typhimurium and Staphylococcus aureus have been achieved in just three passes (residence time 24.3 s) of whole milk. The results obtained are compared to those obtained using the pasteurization technique. We found that the proposed UV reactor has an identical performance in inactivating the micro-organisms compared to pasteurization without altering the physico-chemical properties. This suggests the possibility of utilizing UV sources to improve milk’s safety, quality, and shelf life. This study expands the scope of applications for UV-C irradiation as a feasible non-thermal method in the dairy industry.

Vertical two-phase flow regimes in an annulus image dataset - Texas A&M university.

The Vertical Two-Phase Flow Regimes in an annulus Image Dataset, generated at Texas A&M University, presents an extensive collection of high-resolution images capturing various gas-liquid two-phase flow dynamics within a vertical flow setup. This dataset results from meticulous experimental work in the 140 ft Tower Lab, utilizing a combination of water and air flows to simulate real-world conditions and employing high-quality video recordings to document flow regime transitions. Designed to support research in fluid dynamics, machine vision, and computational modeling, the dataset offers valuable resources for developing machine vision models for accurate regime detection and differentiation, enhancing the fidelity of computational fluid dynamics simulations, and facilitating the estimation of critical flow parameters. Despite its comprehensive nature, the dataset notes limitations such as the absence of annular flow regime images and its exclusive focus on vertical flow conditions.

Numerical study on dense-phase powder conveying in the feeding system of powder fueled ramjets

A better understanding of gas-solid flow in the pneumatic conveying of dense powders is an essential prerequisite for effective design and operation of conveying systems in powder fueled ramjets. This paper presents a resistance modified model applicable to the dense-phase powder conveying in gas-driven piston powder feeding system based on Two-Fluid Model (TFM), and the dynamic grid techniques related to the output powder mass flow rate has been applied on gas-driven piston boundary. The validity of the modified model is confirmed by comparing the predicted powder mass flow rate with data obtained from the experiment. The resistance modified model, which incorporates a comprehensive consideration of gas momentum loss by accounting for local solid fraction, interphase slip velocity, and powder diameter, is proved to significantly improve the accuracy of predicting dense powder conveyance. The features of gas-solid flow evolution in gas-driven piston powder feeding systems are numerical explored. The formation of the fluidizing gas cavity and its radial diffusion characters are studied and the influences of the total pressure of fluidizing gas on mass flow rate of powders are obtained. And choked occurs in gas-powder two-phase conveying to realize a stable propellant feeding under specific pressure ratio conditions. Moreover, pressure ratio determines pressure distribution in nozzle pipe revealing the transition of the flow pattern from core flow to annular flow corresponds directly to the pressure ratio.

Liquid–Liquid Flow and Mass Transfer Enhancement in Tube-in-Tube Millireactors with Structured Inserts and Advanced Inlet Designs

Liquid–liquid mass transfer is crucial in chemical processes like extraction and desulfurization. Traditional tube-in-tube millireactors often overlook internal flow dynamics, focusing instead on entry modifications. This study explores mass transfer enhancement through structured inserts (twisted tapes, multi-blades) and inlet designs (multi-hole injectors, T-mixers). Using high-speed imaging and water–succinic acid–butanol experiments, flow patterns and mass transfer rates were analyzed. Results show annular and dispersion flows dominate under tested conditions with structured inserts lowering the threshold for dispersion flow. Multi-hole injectors improved mass transfer by over 40% compared to T-mixers in plain tubes, while C-tape inserts achieved the highest volumetric mass transfer coefficient (2.43 s−1) due to increased interfacial area and droplet breakup from energy dissipation. This approach offers scalable solutions to enhance tube-in-tube millireactor performance for industrial applications.

Study on Improving Liquid Carrying Performance of Horizontal Wells With Swirl Jet Composite Device

ABSTRACTIn the later stages of horizontal gas well development, due to insufficient formation energy, the stratified flow of gas and liquid in the horizontal section generates a decrease in the well's liquid‐carrying capacity, accumulating liquid in the wellbore. Since the flow pattern of gas–liquid two‐phase flow in horizontal wells is significantly different from that in vertical wells, existing vertical well liquid removal and gas production technologies cannot be directly applied to address the liquid accumulation issues in horizontal wells. This paper presents a swirl jet composite device that, through the combination of a spiral guide belt and an internal flow channel, effectively integrates the jet and vortex effects, capable of transforming the stratified flow in the horizontal section into an annular flow, thereby enhancing the gas well's liquid‐carrying capacity. This study applies a combination of theoretical, experimental, and simulation methods to conduct computational fluid dynamics analysis on the device's ability to improve the gas well's liquid‐carrying capacity. It deeply investigates the flow characteristics of the gas–liquid two‐phase flow within the device. The results indicate that the device can not only achieve gas–liquid separation by transforming the flow regime from laminar to an orderly annular flow but also increase the axial velocity to extend the effective distance of the swirling section. Compared with the case without the device installed, the liquid phase volume fraction at the bottom of the well is reduced by 85.9%, and the liquid holdup is reduced by 38%. This demonstrates that compared to traditional technologies such as gas‐lift dewatering and gas production, the device can enhance the liquid‐carrying capacity of horizontal wells and effectively address the issue of liquid accumulation in horizontal wells. It provides theoretical guidance and a practical basis for future research on applying swirl jet composite devices to improve the liquid‐carrying capacity of horizontal wells.

Lightweight method for injection rate prediction of supersonic gas flow from pintle-type hydrogen injector

Research on hydrogen engines has been actively pursued to achieve carbon neutrality in the transportation sector. To optimize the combustion characteristics of hydrogen engines under various driving conditions, active and precise control of the hydrogen injection flow rate is crucial. Lightweight prediction for hydrogen injection rates from pintle-type injectors, which are widely used in hydrogen engines, is required for the control of the injection rate as well as the model-based engine development. However, lightweight injection rate prediction for gaseous fuel has been conducted solely for hole-type injectors and not for pintle-type injectors that have an annular internal flow path with complex configurations. In this study, a lightweight methodology is introduced to predict the hydrogen injection rate of pintle-type hydrogen injectors based on the compressible flow theory of converging-diverging nozzles with minimum mass flow rate data obtained with a safer surrogate gas. The validity of the method for various injection conditions and gases (nitrogen, helium, and hydrogen) is discussed. The methodology demonstrated prediction accuracy of over 92% for nitrogen and helium injection rates under different injection pressures (1.5–4 MPa) and ambient pressures (0.1–2 MPa). The versatility of the prediction methodology for various gases, including hydrogen, was also confirmed. The error sources were analyzed thoroughly based on the dynamic characteristics of the pintle behavior and differences in gas properties.

Heat transfer in the entrance region of annular laminar flow with constant and different heat flux on two walls

AbstractHeat transfer differs in the regions where the flow is developed and developing thermally. These regions can be differentiated by using the thermal entry length. Many researchers have presented correlations to determine the thermal entry length for natural and forced convection. In this study, heat transfer in the entrance region of a concentric annuli is investigated. It is accepted that beginning from the inlet of annuli the flow is developed hydrodynamically and it is developing thermally. Heat transfer is investigated where the internal or external surfaces of the annuli are at constant but different heat fluxes. The fluid velocity is assumed to be constant or radially variable. Due to thermal boundary conditions, one thermal boundary layer appears on the outer cylinder surface, another on the inner cylinder surface. The edge of two boundary layers will be adiabatic and naturally, the temperature of fluid between the two edges will be equal to free stream temperature. Transformation, Separation of Variables method, eigenvalue problem, Sturm‐Liouville system, Bessel differential equation and properties of orthogonal functions are used in solution of the problem. Exact and analytical solutions of the momentum and energy equations are presented. Velocity and temperature distributions, local Nusselt numbers and convection heat transfer coefficients are calculated for the internal and external surfaces of annuli.

Development and simulation of annular flow photoreactors: integration of light-diffusing fibers as optical diffusers with laser diodes

Laser driven platform for photochemical reactions. Modelling: predictability and optimization.

Annular flow reactor with side-by-side titania-deposited self-luminous textile and glass fiber velvet for efficient aqueous treatment of active pharmaceutical ingredients

Annular flow reactor with side-by-side titania-deposited self-luminous textile and glass fiber velvet for efficient aqueous treatment of active pharmaceutical ingredients

Computational Fluid Dynamics Simulation and Analysis of Non-Newtonian Drilling Fluid Flow and Cuttings Transport in an Eccentric Annulus

This study examines the flow behavior as well as the cuttings transport of non-Newtonian drilling fluid in the geometry of an eccentric annulus, accounting for what impacts drill pipe rotation might have on fluid velocity, as well as annular eccentricity on axial and tangential distributions of velocity. A two-phase Eulerian–Eulerian model was developed by using computational fluid dynamics to simulate drilling fluid flow and cuttings transport. The kinetic theory of granular flow was used to study the dynamics and interactions of cuttings transport. Non-Newtonian fluid properties were modeled using power law and Bingham plastic formulations. The simulation results demonstrated a marked improvement in efficiency, as much as 45%, in transport by increasing the fluid inlet velocity from 0.54 m/s to 2.76 m/s, reducing the amount of particle accumulation and changing axial and tangential velocity profiles dramatically, particularly at narrow annular gaps. At a 300 rpm rotation, the drill pipe brought on a spiral flow pattern, which penetrated tangential velocities in the narrow gap that had increased transport efficiency to almost 30% more. Shear-thinning behavior characterizes fluid of which the viscosity, at nearly 50% that of the central core low-shear regions, was closer to the wall high-shear regions. Fluid velocity and drill pipe rotation play a crucial role in optimizing cuttings transport. Higher fluid velocities with controlled drill pipe rotation enhance cuttings removal and prevent particle build-up, thereby giving very useful guidance on how to clean the wellbore efficiently in drilling operations.

Prediction of Liquid Film Thickness and Pressure Gradient of Swirling Annular Flows in Vertical Pipes Based on One-Dimensional Three-Fluid Model

Prediction of Liquid Film Thickness and Pressure Gradient of Swirling Annular Flows in Vertical Pipes Based on One-Dimensional Three-Fluid Model

Numerical Study on the Effect of the Combined Radial Flow Field on the Performance of Proton Exchange Membrane Fuel Cells

ABSTRACTAs the flow field structure has a crucial influence on the performance of the proton exchange membrane fuel cell, in this research, the radial flow field R‐0 is designed and optimized based on the characteristics of the annular serpentine and annular flow channels to form combined flow field structure (R‐1 to R‐5). Subsequently, a three‐dimensional and two‐phase model is established and the effects of each flow field on the cell performance are numerically investigated. Results indicate that the R‐0 can enhance the gas vertical velocity on the diffusion‐catalyst interface compared to the parallel flow field, which increases the effective concentration of reaction gases within the catalyst layer, thereby accelerating the electrochemical reaction rate, and the performance of the combined flow fields is further improved. In addition, the effect of the percentage of annular serpentine within the combined flow field on the concentration distribution, uniformity, and output performance is analyzed. Results indicate that increasing the percentage of annular serpentine structure can increase the pressure between adjacent channels, and thus the higher pressure and concentration gradient generated can enhance the gas transport and reduce the water accumulation under the ribs thus effectively improving the cell performance.

Entrance Lengths for Fully Developed Laminar Flow in Eccentric Annulus

Abstract We study the entrance length in eccentric annular geometries, where the axes of the inner and outer pipes forming the annulus are offset from each other. Such geometries are considered relevant for several industrial applications, such as drilling of wells for hydrocarbon production or geothermal energy recovery, as well as biomedical research involving annular vessels. Previous studies have shown that eccentricity increases the entrance length in annular geometries, and this has been attributed to azimuthal redistribution of fluid between the wide and narrow sides of the annulus. The present computational study aims to increase the understanding of entrance lengths in eccentric annuli for laminar flow with Reynolds numbers spanning the range from the creep limit and up to intermediate laminar values, below the regime of annular gap instabilities. We find that the entrance lengths in eccentric annuli generally increase for narrower annular gaps (higher aspect ratios). Moreover, the entrance lengths in the annuli with higher aspect ratios are also more sensitive to the degree of eccentricity compared to wider annuli (lower aspect ratios). We report empirical correlations for the dimensionless entrance length using the same form as earlier studies (Le=[C0n+(C1Re)n]1/n). We find that eccentricity, which breaks the axial symmetry of the annulus and causes azimuthal flow in the entrance region, impacts the value of the exponent n, which has been assigned the value of 1.6 in previous studies of axisymmetric conduits.

Heat Transfer Mechanism Study of an Embedded Heat Pipe for New Energy Consumption System Enhancement

Aiming at the demand for new energy consumption and mobile portable heat storage, a gravity heat pipe with embedded structure was designed. In order to explore the two-phase heat transfer mechanism of the embedded heat pipe, CFD numerical simulation technology was used to study the internal two-phase flow state and heat transfer process of the embedded heat pipe under different working conditions. The evolution law of the internal working medium of the heat pipe under different working conditions was obtained. With the increase in heating power, it is easier to form large bubbles and large vapor slugs inside the heat pipe. When the heating power increases to a certain extent, the shape of the vapor slugs can no longer be maintained at the bottom of the adiabatic section, and the vapor slugs begin to break and merge, forming local annular flow. When the filling ratio (FR) is relatively low, the bubble is easy to break through the liquid level and rupture, unable to form a vapor slug. With the increase in FR, the possibility of projectile flow and annular flow in the heat pipe increases. Under the same heating power, the temperature uniformity of the heat pipe becomes stronger with the increase in heating time. The velocity distribution in the heat pipe is affected by the FR. The heating power has almost no effect on the distribution of the velocity field inside the heat pipe, but the maximum velocity is different. At an FR of 30%, there are two typical velocity extremes in the tube near positions of 120 mm and 160 mm, respectively, and the velocity in the tube is basically unchanged above a position of 200 mm. There are also multiple velocity extremes at an FR of 70%, with the maximum velocity occurring near 240 mm.

Flow structure and characteristics of fluid undergoing a sudden contraction to an annular gap under dynamic boundary

Pipeline transport serves as an effective means to alleviate traffic congestion and reduce carbon emissions from transportation. The hydraulic delivery system, which employs pipeline cars as carriers, addresses the limitations of existing systems. However, its transportation efficiency is affected by variations in the flow structure within the pipelines. During the acceleration of the pipeline car, the sudden contraction flow field from circular to annular gap formed in the vicinity of the end face under dynamic boundary conditions. This study utilized particle image velocimetry (PIV) to visualize and measure the sudden contraction flow field. Based on the obtained experimental results, it investigated the impact of dynamic boundary velocity on the flow structure, velocity characteristics, and energy dissipation of the annular gap. The acceleration process of the dynamic boundary is the conversion of flow energy into the kinetic energy of the annular gap flow and the kinetic energy of the pipeline car. This process is accompanied by phenomena of velocity slip and velocity overshoot. As the velocity of the pipeline car increases, the recirculating vortex within the annular gap dissipates and eventually disappears. The velocity slip gradually decreases, the location of the overshoot point shifts radially, and the magnitude of the overshoot diminishes before ultimately vanishing. From static to steady, the probability density distribution of the slipstream face transitions from a distribution with high skewness and low peak value to a normal distribution with high peak value and low skewness. The irreversible losses that arise in a sudden contraction flow field can be quantified by the increase in entropy. Due to the similarity of the solving processes of large Eddy simulation and PIV, a combined sub-grid stress model is used to solve the flow losses in the flow field. The turbulent dissipation occurs mainly in the recirculation region, shear layer, and high-speed shear regions near the wall.

Experimental and numerical investigation of spray characteristics of gas–liquid swirl coaxial injectors

To investigate the velocity distribution and atomization characteristics of gas–liquid swirl coaxial (GLSC) injectors, atomization experiments and simulations were conducted under atmospheric conditions. The velocity distribution and morphology of the spray from GLSC injectors at varying gas–liquid ratios were measured using particle image velocimetry. The gas–liquid interaction, breakup dynamics, and the velocity of liquid sheet were simulated based on the three-dimensional volume of fluid to discrete particle model (VOF-to-DPM) and octree adaptive mesh refinement. Additionally, a method for extracting droplet diameters from high-quality images has been developed and validated. The results indicate that the sprays maintain a stable cone when the gas–liquid ratio is low. As the gas–liquid ratio increases, particularly at larger recess ratios, self-pulsation phenomena occur. During self-pulsation, the spray cone angle is enlarged, and the breakup length shortens. In a stable spray field, the center exhibits a low velocity region (5–10 m/s), while the spray periphery shows a high velocity region (20–25 m/s). Self-pulsation is induced by the “Klystron effect,” which arises from the Kelvin–Helmholtz (K–H) instability at the gas–liquid interface. The center of the self-pulsated spray transitions to a high velocity region due to the accelerated droplet motion driven by the annular gas flow through the spray's center. The radial distribution of mean droplet diameters for both stable and self-pulsated sprays has been summarized. As the gas–liquid ratios and recess ratios increase, the global droplet diameters gradually decrease, with a 75% of droplet diameters falling between 0 and 0.1 mm.

Experimental investigation on transition mechanisms and modal decomposition analysis of gas–liquid flow patterns in horizontal–vertical elbow

A series of experiments are conducted to investigate the transition mechanisms and characteristics of six typical gas–liquid flow patterns in a horizontal–vertical elbow using electrical capacitance tomography and high-speed camera. The dominant modes and corresponding time coefficients are obtained by performing proper orthogonal decomposition on the pulsating gas holdup (GHU) distribution data to explore their physical mechanisms and correlations. Reduced-order descriptions for different flow patterns are discussed. The results show that after passing through the elbow, the horizontal slug or bubble flow turns into vertical bubble flow due to the small gas volume content and the mixing effect of secondary flow, accompanied by a swirl-switching phenomenon. A slug flow forms at the elbow outlet when there is a stratified flow comes from the horizontal pipe, and changes in flow conditions will affect the generation frequency and stability of Taylor bubbles. The horizontal annular or mist flow with high gas volume content will be transformed into churn flow in the vertical pipe. The modal decomposition analysis indicates that, for all the investigated conditions in the present study, mode 1 represents the mean distribution of GHU fluctuations, and there is a pair of modes representing the dominant swirling features. For the slug and churn flows, mode 2 characterizes the features of gas slug or large bubbles, the time coefficient of which is highly connected with that of mode 1. Meanwhile, it is also shown that the obtained low-dimensional descriptions of different flow patterns using the dominant modes are able to reconstruct most of the GHU distribution features in gas–liquid flows with the reconstructive loss less than 3%.

Design and experimental study of a new hydraulic tool for lost-circulation materials (LCM) plugging while drilling

Big Data Analysis from the worldwide field shows that lost circulation is a common phenomenon in drilling and the success ratio of remedial treatment for lost circulation is low. It is not only because of these complexities of the formation, but also because of the poor performances of the lost-circulation materials (LCM) and technologies. This paper proposes a new method in plugging, which is based on a particular physical method for lost circulation controlling and plugging while drilling. This method is different from these traditional treatments, which only use chemical methods. When pore-permeable and fractured leakage formations are encountered while drilling, We can use this new hydraulic tool, the drilling fluid will have a diffluence at a constant rate from the jet of the hydraulic tool which is installed on the drilling pipe and the fluid laden with particles can be injected into the natural or induced fractures of the borehole wall which may lead to lost circulation. Combined with the corresponding drilling fluids which have been tested in the laboratory, the additives such as ground marble, ground nutshells, and graphite in the drilling fluid are quickly pushed into the fractures because of the differential pressure provide by the hydraulic tool, then form a firm seal at the mouth of the fractures which could isolate fluid pressure in the wellbore and prevent effective pressure communication to interfere the extension of the fracture. What’s more, according to the stress cage theory, when these sealing particles which prop the fracture open, act as wedges to compress the rock around the wellbore, the hoop stress could be increased, so that the wellbore pressure containment (WPC) could be improved. Since the annular flow may have some interference with the side nozzle jet, this paper also numerically simulates the flow field of the annular air section through the fluid simulation software Fluent, and the simulation results show that the interference of the annular flow on the jet is very weak and basically has no effect. In addition, through the oilfield field test, it is known that this new physical plugging method has good plugging effect, and it can obviously improve the pressure-bearing capacity of the formation, which has great popularization value.

Study on dynamic mechanical properties and damage characteristics of wollastonite fiber reinforced oil well cement paste

In cement engineering, the cement sheath is not only influenced by elevated temperatures, increased pressure, and the static load confining pressure within the formation but also encounters external impact loads. These loads can rupture the cement paste, compromising the cement sheath’s interlayer sealing capability. Consequently, this can give rise to an annular flow of oil, gas, and water. Hence, this study introduces wollastonite fiber (WF) into the cement slurry to modify the cement paste. The investigation explores the mechanical properties, energy evolution, and damage characteristics of the cement paste with WF under dynamic impact loads. This is achieved by simulating the dynamic impact loads experienced downhole using the separated Hopkinson pressure bar (SHPB) technique. A straightforward SHPB model is constructed using ABAQUS finite element simulation software, and its accuracy is confirmed through experimental validation. The impact test outcomes revealed a notable enhancement in the dynamic load peak strength of the cement paste cured for 14 days. Specifically, there was an increase of 136.75%, 202.10%, and 320.55% compared to the control group at impact speeds of 6 m/s, 8 m/s, and 10 m/s, respectively. The absorption energy increased remarkably, showing 356.03%, 388.61%, and 142.14%, respectively. The simulation findings confirm that the devised simple SHPB model effectively replicates electrical signals aligned with the observed experimental results. The dispersed fibers create a three-dimensional network within the cement paste. This network enhances the impact resistance of the cement paste by leveraging the mechanisms of crack deflection, fiber fracture, and energy dissipation through fiber pull-out.

End of tubing placement optimization for multi-stage fractured horizontal wells by transient multiphase flow simulation

The exploitation of shale gas offers an effective pathway towards mitigating greenhouse gas emissions and promoting a clean and low-carbon energy system. Nonetheless, liquid loading has been commonly observed in the middle and late production stage, leading to sharp decline of shale gas production. How to improve unloading performance is challenging due to limited liquid-loading capacity. The strategic and timely installation of oil tubing serves as an effective means to mitigate wellbore fluid accumulation in the gas field. Thus, this work tries to improve gas recovery factor by optimizing the End of Tubing (EOT) location and the timing of tubing installation in shale gas wells through transient multiphase flow simulation. The transient simulation approach is adopted owing to its capability to accurately characterize the transient unloading process in gas wells and its closer approximation to field operation conditions compared to steady-state simulation methods. The casing production model and tubing production model have been developed to accurately simulate the flow behavior of fracturing fluid in the casing and tubing production, respectively. The annular flow and the coupling of fluid flow between reservoir and wellbore are the primary focuses of the two models aimed at analyzing fluid flow behavior and the total pressure drop (Δptotal). The casing production model is used to optimize the timing of tubing installation by simulating the liquid loading process of gas well including Δptotal and liquid inventory of wellbore. The optimal time of tubing placement is identified as the point when fluid starts to accumulate in the wellbore, as confirmed through the quantifiable analyses of Δptotal and liquid inventory. The tubing production model is further utilized to optimize the EOT location and tubing diameter considering variations in annular flow and the challenges associated with tubing installation. The placement of tubing in up-dip wells is recommended at Point A, which is determined by considering the influence of fluid gravity as a resistive force. Conversely, for down-dip wells, it is advisable to position the tubing between 1/3 of AB and 1/2 of AB as fluid gravity serves as a driving force in these scenarios. This work offers guidance for the optimum EOT location in shale gas reservoirs experiencing severe liquid loading. Consequently, it is essential to establish guidelines for determining the optimal EOT location across various horizontal well configurations and flow conditions.