Annular Flow Research Articles

Investigation into the operation of an autothermal two-section subbituminous coal fluidized bed gasifier

Using a newly developed experimental setup, the features and advantages of an autothermal single-casing atmospheric subbituminous coal fluidized bed air-blown gasifier, combining a combustion and gasification section, and mixing the dispersed phase (inert material, char) and heat exchange between them through an annular transfer device, have been revealed. To increase the efficiency of the gasifier, an experimental-computational method was developed find the conditions for optimal operation, combining changing the annular flow’s geometry and regulating the primary air for gasification. A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy. This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants. Syngas with a heating value of 3.6–4.5 MJ/m3 and CGE of 38.2%–42.3% was obtained in the experimental setup without optimizing the primary air flow rate. With optimization, the indicators increased to the heating value of syngas of 5.20–5.34 MJ/m3 and CGE of 42.5%–50.0%. With heat regeneration of 0.8, CGE increases to 70%.

Effect of flow direction on evaporation flow regime of R32/R1234ze(E) mixture inside multiple rectangular minichannels

This study visualized the evaporation flow regime of a non-azeotropic mixture R32/R1234ze(E) inside multiple vertical-upward and horizontal rectangular minichannels with a hydraulic diameter of 2 mm. The effects of the mass flux, vapor quality, heat flux, flow direction, and test refrigerant on the flow regime characteristics were explored. The flow regimes of the mixture were compared to those of R1234ze(E). The effect of flow direction on the flow regime was examined under low mass flux conditions. In the vertical-upward flow, three flow regimes: slug, slug-annular, and annular flow regimes were observed. The flow regime transition boundary of R1234ze(E) shifted to lower mass flux and vapor quality conditions compared to the mixture because of the higher vapor velocity of R1234ze(E). Boiling bubbles were generated in the liquid slug and channel corners around the vapor plug, and the number of boiling bubbles increased with an increasing heat flux. The size of the boiling bubble of the mixture was smaller than that of R1234ze(E), which is attributed to the mass transfer resistance of the non-azeotropic mixture. Only in the vertical-upward flow, the reverse flow was observed in some channels, where the slug flow was observed, because of the effect of gravity. The number of channels with reverse flow decreased with increasing vapor velocity. The annular flow did not appear in the horizontal flow, and the flow regime was observed only in two regimes: slug and slug-annular flow regimes. No difference in flow regime transition boundary between R1234ze(E) and R32/R1234ze(E) was observed.

Computational Fluid Dynamics Simulation of Oil-Water Batch Transport in a Pumpless Virtual Flow Loop

Summary Batch transportation of oil and water is a new transportation method in oil and gas gathering and transportation pipelines. Its corrosion inhibition effect has been preliminarily verified in a horizontal pipe experiment. However, achieving overall visualization in traditional loops is difficult, resulting in limited flow pattern classification and analysis of influencing factors. Combining the advantages of the traditional flow loop and the wheel flow loop, we introduce in this paper a round-head straight pipe loop and analyze the influence of key factors on the evolution of the flow pattern of the oil-water interface and the dimensionless length of the oil-water film (L~o, L~w) on the pipe wall through computational fluid dynamics (CFD) numerical simulation. The results show that the batch transportation of oil and water using the round-head straight pipe loop is more in line with the flow characteristics of oil and water two-phase flow in gathering pipelines. Three distinct three-layered flow patterns were identified, which are Flow Pattern I (oil-in-water in the upper layer, annular flow in the middle layer, and oil as the annular phase, water as the core phase, and oil-in-water in the lower layer, abbreviated as DW/O-AN-DW/O), Flow Pattern II (oil phase in the upper layer, annular flow in the middle layer, water as the annular phase, oil as the core phase, and oil in the lower layer, abbreviated as O-AN-O), and Flow Pattern III (oil phase in the upper layer, water-in-oil dispersion flow in the middle layer, and oil in the lower layer, abbreviated as O-DO/W-O). Additionally, parametric analysis reveals that the velocity of the rigid body (ν) has the greatest influence on the coverage rate of the oil film on the pipe wall, followed by the viscosity of crude oil. The density of crude oil has the least influence. The round-head straight pipe loop model offers an accurate simulation of the process of oil and water batch transportation in actual production pipelines. Therefore, the corrosion mitigation efficiency increases with the increase in oil viscosity when the viscosity of the oil lies within the range of 0.01–1 Pa·s. This increase is due to the formation of a more stable oil film on the pipe wall at higher viscosities. When the speed of the rigid body ranges from 0.5 to 1 m/s, due to the small fluid velocity, the erosion effect on the oil film on the pipe wall is relatively small, and the corrosion mitigation efficiency remains stable within a wide range.

A model for the momentum flux parameters of the 1D Two-Fluid Model in vertical annular flows: Linear stability and numerical analysis

The 1D Two-Fluid model is based on an area average process of the time and phase averaged Two-Fluid conservation equations to render the model tractable for industrial scale problems. Due to the averaging processes, the loss of information renders the standard model ill-posed for certain configurations, i.e., short wavelengths disturbances are amplified at an unbounded rate and unphysical solutions are obtained. Closure relations play a key role in this problem, since they are required to close the 1D system and they reintroduce missing physical parameters that may stabilize the flow and render the model well-posed. Two formulations for the liquid momentum flux parameter (CL) for vertical annular flows are proposed based on local velocities distributions. Differential viscous Kelvin-Helmholtz and von Neumann stability analyses are performed to evaluate the proposed CL formulations and three dynamic pressure models. Results have shown that dynamic pressure closure models introduce a small additional amount of damping into the growth rate curves, without a significant change in the hyperbolicity of the system. On the other hand, the novel CL models can guarantee well posedness of the linear system by introducing a growth rate plateau, blocking the unbounded growth of instabilities. Numerical simulations were also performed, and numerical dispersion relations were extracted from the results showing good agreement against LST data, validating the methodology. The novel CLmodels are evaluated against a large experimental database from the literature, showing that the proposed models outperform the standard constant CL values for both pressure drop and liquid film thickness.

Radial distribution characteristics of droplet size and velocity in annular mist flow around the bluff body

Wet gas is a common gas–liquid flow type in chemical processing. When measuring the gas flow rate and liquid load of wet gas with a vortex flowmeter, the small droplets in the flow can significantly affect the measurement accuracy. The optical shadow method was used to measure the parameters and distribution of droplets around the bluff body in annular mist flow. The experimental results show that the velocity distribution of droplets upstream of the bluff body mainly depends on the gas superficial velocity. After passing through the bluff body, when the liquid loading capacity φl is<0.030, the droplet velocity changes from a concentrated single-peak to an uneven double-peak distribution. However, when φl ≥ 0.041, the droplet velocity distribution recovers to a single-peak distribution. The joint distribution of droplet diameter and velocity indicates that the change in velocity distribution is mainly caused by small droplets within the range of 0 to 20 μm, as large droplets are not easily lifted by vortices but can cause rapid dissipation of vortices. The experimental data quantitatively confirm the momentum transfer and transformation between droplets and the vortex flow field, and describe the motion dynamics of droplets in the flow field through the Stokes number (Stp) to analyze the interaction between droplets and vortices.

Experimental investigation of heat transfer limitations in concentric annular sodium heat pipes and thermosyphon

This paper presents experimental investigations on the heat transfer performance of concentric annular heat pipe (CAHP) and thermosyphon (CATP) using sodium as a working fluid for microreactor applications. CAHP characterized by wicks on the inner and outer walls offers the potential to enhance capillary force and enable more compact microreactor designs. The research aims to understand the implications of structural differences between CAHP, CATP and conventional heat pipe (CHP) and identify favorable conditions for their use in microreactors. The thermal behavior and heat transfer limits of CAHP and CATP were examined under various boundary conditions. The experimental results revealed that CAHP exhibited capillary limits approximately 71.2% higher than cylindrical heat pipes under horizontal conditions. However, the Chi model used for predicting capillary limits showed a difference about 19.7% in horizontal operation and exceeded 44.6% in vertical operation, highlighting the need for considering the effect of non-uniform capillary forces in CAHP. The presence of additional inner wick in CAHP provided large evaporation areas, which facilitated rapid vapor generation and enabled the development of a continuum flow faster than in CHP, by approximately 70 °C. However, in vertical operation, CATP necessitates higher heat fluxes and exhibits notable temperature disparities between the evaporator and condenser regions compared to CAHP. This difference can be explained depend on the vapor generation mechanisms: heat pipes utilize additional wick area to facilitate evaporation, while thermosyphon depend on boiling that the advantages related to the annular flow path in CATP are not clear. Furthermore, the presence of an adiabatic section yields contrasting effects: while it promotes the formation of larger menisci in heat pipes, its presence is unfavorable in thermosyphons as it can elevate boiling temperatures that delayed operations. The findings underscore the advantages of CAHP over CHP, particularly in microreactor applications, provide insights into design optimizations for compact microreactors, and showed gaps in operating prediction models and experimental results.

Analysis of the Total Leakage Characteristics of Finger Seal Considering Fractal Wear and Fractal Porous Media Seepage Effects

As an advanced flexible dynamic sealing technology, the leakage characteristics of a finger seal (FS) is one of the key research areas in this technology field. Based on the fractal theory, this paper establishes a mathematical model of the FS main leakage rate considering the fractal wear effect by taking into account the influence of the wear height on the basis of the eccentric annular gap flow equation. Based on the Hagen-Poiseuille law and the fractal geometry theory of porous media, a mathematical model of the FS side leakage rate considering the fractal porous media seepage effect is developed. Then, a mathematical model of the FS total leakage rate is established. The results show that the mathematical model of the FS total leakage rate is verified with the test results, the maximum error rate is less than 5%, and the mathematical model of the FS total leakage rate is feasible. With the gradual increase in working conditions and eccentricity, the FS main leakage rate gradually increases. In addition, the effects of the fractal dimension, fractal roughness parameters and porosity after loading on the FS main leakage rate are negligible. As the fractal dimension of tortuosity after loading gradually decreases, the fractal dimension of porosity after loading gradually increases, and the FS side leakage rate gradually increases. As the porosity after loading gradually increases, the FS side leakage rate gradually increases. Under different working conditions, different fractal characteristic parameters and different porosities after loading, the weight of the FS main leakage rate is much greater than that of the FS side leakage rate by more than 95%.

Heat generation and transfer simulation of a high temperature heat pipe under induction heating based on a coupled model

High temperature heat pipes are highly efficient heat transfer devices, and induction heating is often utilized in their performance tests. However, issues exist in evaluating the equivalence between induction heating and surface heating encountered in typical application scenarios, and in quantifying the accurate input heat flux of induction heating. In order to identify the key influencing factors and investigate their effects on heat generation and transfer within high temperature heat pipes under induction heating, a finite element thermal-electrical coupled model is developed based on the pseudo wick thermal conductivity model and electromagnetic theory. The effects of frequency (10 kHz, 100 kHz, 300 kHz), loaded current (10 ∼ 890A), cooling coefficient (10 ∼ 250Wm-2K−1) and temperature (300 ∼ 1000 K) are investigated. Over 98% of the induction heat is found to be generated in the evaporator section, with a considerable proportion generated in the annular channel (38 ∼ 52%) and the capillary wick (23 ∼ 26%) at low frequency (10 kHz). The wall temperature of the evaporator section is slightly lower than the temperature of the annular flow channel or even the capillary wick at weak cooling boundary conditions (<130Wm-2K−1@10 kHz, <50Wm-2K−1@100 kHz, <30Wm-2K−1@300 kHz). Quantitative calibration formulas of induction heat are established in relation to frequency, current, and temperature via two sets of quadratic polynomial fitting. The results can be used as reference for design and evaluation of transient and steady-state tests of heat pipes under induction heating.

Mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device

Mass transfer performance of gas–liquid two-phase flow at microscale is the basis of application of microreactor in gas–liquid reaction systems. At present, few researches on the mass transfer property of annular flow have been reported. Therefore, the mass transfer mechanism and relationship of gas–liquid annular flow in a microfluidic cross-junction device are studied in the present study. We find that the main factors, i.e., flow pattern, liquid film thickness, liquid hydraulic retention time, phase interface fluctuation, and gas flow vorticity, which influence the flow mass transfer property, are directly affected both by gas and liquid flow velocities. But the influences of gas and liquid velocities on different mass transfer influencing factors are different. Thereout, the fitting relationships between gas and liquid flow velocities and mass transfer influencing factors are established. By comparing the results from calculations using fitting equations and simulations, it shows that the fitting equations have relatively high degrees of accuracy. Finally, the Pareto front, namely the Pareto optimal solution set, of gas and liquid velocity conditions for the best flow mass transfer property is obtained using the method of multi-objective particle swarm optimization. It is proved that the mass transfer property of the gas–liquid two-phase flow can be obviously enhanced under the guidance of the obtained Pareto optimal solution set through experimental verification.

Magneto-bioconvection flow in a porous annulus between circular cylinders containing oxytactic microorganisms and NEPCM

PurposeThis paper aims to investigate magnetic impacts on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders. The annulus is filled by oxytactic microorganisms and nano-encapsulated phase change materials.Design/methodology/approachThe modified ISPH method based on the time-fractional derivative is applied to solve the regulating equations in Lagrangian dimensionless forms. The pertinent factors are bioconvection Rayleigh number Rab (1–100), circular cylinder’s radius Rc (0.1–0.3), fractional time derivative α (0.95–1), Darcy parameter Da (10−5–10−2), nanoparticle parameter ϕ (0–0.1), Hartmann number Ha (0–50), Lewis number Le (1–20), Peclet number Pe (0.1–0.75), s (0.1–0.9), number of cylinders NCylinders (1–4), Rayleigh number Ra (103–106) and fusion temperature θf (0.005–0.9).FindingsThe simulations revealed that there is a strong enhancement in the velocity field according to an increase in Rab. The intensity and location of the phase zone change in response to changes in θf. The time-fractional derivative a acting on a nanofluid velocity and flow characteristics in an annulus. The number of embedded cylinders NCylinders is playing a significant role in the cooling processes and as NCylinders increases from 1 to 4, the velocity field’s maximum reduces by almost 33.3%.Originality/valueThe novelty of this study is examining the impacts of the magnetic field and the presence of several numbers of embedded cylinders on bioconvection flow within a porous annulus between an outer cylinder and five inner cylinders.

Study of Hydrodnamic Pumping Effects of Fixed Axis Rotation in Eccentric Annular Flow Field

Hydrodynamic effect is one of the key phenomena in journal bearing lubrication. Many researches have been carried out on the supporting force of journal bearing, the motion of suspension shaft and the lubrication effect. This paper studies the hydrodynamic effect from another point of view, that is, the pumping effect caused by the rotation of the eccentric shaft with fixed axis. The clearance between the rotor and the stator is divided into two sections by the inlet port and the outlet port. Their mathematical models are established and studied in polar coordinates. The pressure distribution and pumping flowrate in the flow field are studied theoretically. Under the conditions analyzed in this paper, an output flow larger than 90 ml/s could be generated, overcoming a load pressure of 0.5 MPa. In addition, the pressure distribution and pumping flowrate of the mechanism are affected by the pumping outlet orientation. According to the analysis results of the output angle range from π/8 to 3π/4, when the pump outlet angle is set near 3π/8 to π/2, the pumping flowrate reaches the maximum value of 91.83 ml/s, and nearly half 48% of the inflow liquid can be pumped out to the outlet.

A Machine Learning Approach for Gas Kick Identification

Summary Warning signs of a possible kick during drilling operations can either be primary (flow rate increase and pit gain) or secondary (drilling break and pump pressure decrease). Drillers rely on pressure data at the surface to determine in-situ downhole conditions while drilling. The surface pressure reading is always available and accessible. However, understanding or interpretation of this data is often ambiguous. This study analyzes significant kick symptoms in the wellbore annulus both under static (shut in) and dynamic (drilling/circulating) conditions. We used both supervised and unsupervised learning techniques for flow regime identification and kick prognosis. These include an artificial neural network (ANN), support vector machine (SVM), K-nearest neighbor (KNN), decision trees, K-means clustering, and agglomerative clustering. We trained these machine learning models to detect kick symptoms from the gas evolution data collected between the point of kick initiation and the wellhead. All the machine learning techniques used in this work made excellent predictions with accuracy greater than or equal to 90%. For the supervised learning, the decision tree gave the overall best results, with an accuracy of 96% for air influx cases and 98% for carbon dioxide influx cases in both static and dynamic scenarios. For unsupervised learning, K-means clustering was the best, with Silhouette scores ranging from about 0.4 to 0.8. The mass rate per hydraulic diameter and the mixture viscosity yielded the best types of clusters. This is because they account for the fluid properties, flow rate, and flow geometry. Although computationally demanding, the machine learning models can use the surface/downhole pressure data to relay annular flow patterns while drilling. There have been several recent advances in drilling automation. However, this is still limited to gas kick identification and handling. This work provides an alternative and easily accessible primary kick detection tool for drillers based on data at the surface. It also relates this surface data to certain annular flow regime patterns to better tell the downhole story while drilling.

The Dynamic Characteristics of a Piped Capsule Moving in a Straight Pipeline

The hydraulic transportation of piped capsules is a new and energy-saving transportation mode, which is especially suitable for the long-distance and high-stability requirements of material transportation. In this paper, the COMSOL Multiphysics software was used to construct a mathematical model of the dynamic characteristics of a piped capsule moving in a straight pipeline, in which the boundary conditions were redeveloped, the inlet velocity distribution function was defined, and the physical experiment was carried out for verification. The dynamic characteristics were analyzed, and through the calculation of the energy consumption, the optimal piped capsule under the research conditions was obtained. The results show that the simulation results and experimental results for the piped capsule’s average moving velocity, axial velocity, and wall shear stress along the cylinder wall were basically consistent, with a maximum error of 14.22%, 2.62%, and 20.13%, respectively. With a decrease in the diameter-to-length ratio of the piped capsule, the axial velocity of the concentric annular gap flow decreased gradually. The area with a large shear stress was mainly concentrated at the front and rear ends of the cylinder wall, especially the rear area of the support feet of the piped capsule. With the increase in the diameter of the piped capsule, the wall shear stress of the capsule increased. Finally, the superior diameter-to-length ratio for the piped capsule under the research conditions was obtained and shown to be ε = 0.4. The research in this paper will provide a theoretical reference for the structural design and dynamic mechanism analysis of the piped capsule.

Research on the measurement method of gas-water two-phase flow based on dual-sensor system

Realizing the online accurate measurement of gas-water two-phase flow is of great significance for the natural gas industry. In this paper, a dual-sensor with the microwave resonant cavity sensor embedded in the throat of Venturi is proposed and both of the water volume fraction (WVF) and the separated flowrates of the two phases is attained by the method. To further improve the performance and the measurement accuracy of the sensor, a swirler is fixed inside the contraction section of the precession Venturi, which can regularize all flow patterns into spiral annular flow and reduce the influence caused by the nonuniform distribution of air and water. The microwave sensor response characteristics with WVF and Venturi over-reading (OR) characteristics have been researched through dynamic experiments, and the iteration method of OR model obtained by the precession Venturi and WVF model obtained by the microwave sensor is used to solve the gas and water flowrates respectively. The results show that gas phase flowrate relative error band of ±5% at a confidence probability of 86.08%, and Root Mean Square Error (RMSE) is 3.349%; while water flowrate relative error band of ±10% at a confidence probability of 87.70%, and RMSE is 9.680%, which suggests that the multi-sensor fusion technology provides a powerful solution for the measurement of separated flowrates of gas-water two-phase flow.

Experimental investigation on the condensation of R32 flowing inside alternating cross-section flattened tubes with different aspect ratios

In this experiment, we investigated the condensation of R32 flowing inside alternating cross-section flattened (ACF) tubes with various aspect ratios. ACF tubes were made from a copper circular tube with a 4.31-mm inner diameter. Three ACF tubes with aspect ratios of 5.82 (ACF1), 4.11 (ACF2), and 3.23 (ACF3) were used as test tubes. The experimental conditions covered a mass flux of 280–580 kg/m2s, a heat flux of 10–20 kW/m2, a saturation temperature of 40 °C, and a vapor quality of 0.1–0.8. The results revealed that most experimental data fell into the annular flow regime when using existing flow patterns. In comparison, the ACF1 tube obtained the highest heat transfer coefficient (HTC) and pressure drop (ΔP). The HTC of ACF tubes outperformed those of the circular tube by about 1.7–6.9 (for ACF1), 1.1–2.8 (for ACF2), and 1.2–2.1 (for ACF3) times. In addition, ACF tubes provided a greater frictional pressure drop than circular tubes, around 1.0–2.3 (for ACF1), 1.2–1.9 (for ACF2), and 1.0–1.4 (for ACF3) times. However, the ACF1 achieved the best overall performance by approximately 2.1 times, superior to the circular tube. Since the existing correlations failed to predict the Nusselt number and two-phase friction factor, we propose new correlations for the ACF tube with mean deviations of 14.9% and 7.3%, respectively.

Effects of Salty Additives in Drilling Fluids on Hydrate Formation Dynamics and Phase Equilibrium

In the drilling process for deepwater and hydrate formations, adding salty components to drilling fluids is an important way to avoid secondary generation of hydrates in the annulus, and the effect of salt solutions on the hydrate generation lays a basis for drilling fluid design. In this study, an evaluation device for the effect of drilling fluid additives on hydrate formation and phase equilibrium is designed based on their interaction characteristics. In addition, hydrate generation experiments were carried out for pure water and three commonly used salty additives for drilling fluids. As such, the hydrate phase equilibrium equations under different conditions are established, and the hydrate phase change latent heat is further calculated. The results show that hydrate formation can be divided into four stages, i.e., gas dissolution, hydrate crystal nucleation, hydrate particle mass aggregation, and stabilization. Compared with pure water, sodium chloride and potassium formate solutions can effectively inhibit hydrate formation. At lower ambient temperature, the higher the concentration of potassium formate, the lower the phase equilibrium pressure. On the contrary, at higher ambient temperature, the higher the concentration of potassium formate, the higher the phase equilibrium pressure. The incomplete presence of sodium silicate in water in the form of ions is found to promote methane hydrate formation. Based on the experimental results of methane hydrate generation in potassium formate and sodium silicate solutions with different mass concentrations, the phase equilibrium calculation models for methane hydrate in both salt solutions were finally established. The latent heat of the phase change distribution of hydrate under different conditions was further calculated. The results of this paper can provide a theoretical basis for the study of deepwater drilling fluid systems and multicomponent annular flow.

On parabolic instability regions for inviscid incompressible annular flows

On parabolic instability regions for inviscid incompressible annular flows

Mass transfer and modeling of deformed bubbles in square microchannel

Understanding of mass transfer in gas-liquid slug flow is imperative to design and optimize micro-reactors. There exist extensive studies on symmetric bubbles by the phase volume monitor technique, whereas deformed bubbles are rarely studied due to the limitation of volume calculation methods. In this work, CO2-water and N2-water two-phase flows were investigated in a square microchannel, obtaining annular flow, slug flow, and bubbly flow. A flow pattern map was then proposed and compared with the literature. A 3D slicing technique was developed to measure the volume and interfacial area of bubble, including symmetric bubbles and deformed bubbles, by slicing the bubble along the streamwise direction. Scaling laws of the important parameters that characterize the micro-reactors were proposed. Mass transfer coefficients kLa were quantified from the time-changing volume. The empirical correlation involving dimensionless numbers were fitted, which shows accurate predictive performance for mass transfer coefficients in this study and literatures. The bigger index of Reynolds number ReG indicated that gas flow condition is the main influencing factor during mass transfer process. To have a better universality, a new semi-theoretical model involving the ratio of the size of the liquid and gas phases LL/LG was developed based on the Pigford and Higbie penetration theory because experimental data confirms that the degree of bubble deformation is related to LL/LG. The semi-theoretical model shows a satisfactory agreement over the whole range of slug flow in this study.

Flow Activation Energy Estimation by Thermo‐Rheological Method

AbstractPolymer and many other flows exhibit non‐Newtonian rheological behavior. For some materials, the thermal dependence of viscosity is also essential to be established. It can be described by considering an activation energy, estimated by using the viscosity measurements at different temperatures. Nevertheless, the test temperatures must be reliable and accurate. An annular measuring device (TRAC: Thermo‐Rheo Annular Cell) is previously proposed for highly robust temperature measurement and viscosity identification by inverse method, which exploits the viscous dissipation in the flow. This work explains how critical viscosity points, identified thanks to the TRAC, can be used to estimate the activation energy with different approaches involving the principle of time‐temperature superposition. Thanks to the thermal characteristics of the annular flow, the thermal dependence of viscosity can also be estimated from direct temperature measurements to perform fast analysis, without using inverse method.

Computational fluid dynamics approach for energy savings evaluation in core annular flow of a horizontal T-pipe

The application of core annular flow (CAF) has become an interesting solution in transporting heavy oil through pipeline because of its energy reduction and cost efficiency. At the same time, the CAF in pipe with hydraulic fittings and the problem of unstable CAF are the part of some big issues in using CAF techniques. This study intended to investigate the energy saving of CAF in horizontal T-pipe with symmetrical flow and diameter of 50 mm for oil and water system using CFD approach. Pressure reduction and power consumption were computed as the parameters to measure the energy saving of the flow system. The result of this study showed significant energy reduction of CAF with 94% of pressure drop reduction, for transporting the same amount of oil, when comparing to the traditional single phase oil flow. On the other hand, the intersection of the T-pipe was considered as critical region that promoting the change of flow direction and disturbing the existing CAF pattern. Thus, this study also proposed the strategy for returning the CAF during the process of oil transportation without stopping or restarting the flow operation. The geometry of the T-pipe was modified to facilitate the additional water injection at the intersection as a strategy to get back the CAF pattern. Consequently, the modified T-pipe with certain velocity of additional water injection was recorded to give important improvement of CAF application in terms of more stable CAF and higher pressure drop reduction (98%) compared to oil transportation without lubrication. This study also recorded the values of power reduction factor that indicating the cost of power consumption to transport the oil could be saved more than 80% than single phase oil transportation.