Liquid Flow Characteristics Research Articles

Numerical Simulation of Liquid Flow Characteristics on a Single Spherical Particle for Trickle Bed Reactor

Numerical Simulation of Liquid Flow Characteristics on a Single Spherical Particle for Trickle Bed Reactor

Numerical Investigation of the Water-Drop Impact on Low-Drag Airfoil Using the Euler–Euler Approach and Eulerian Wall Film Model

The Eulerian Wall Film (EWF) model is a mathematical model employed to analyze the behavior of fluid films on a surface. The model has been widely adopted in various engineering applications due to its accuracy and efficiency. However, it is rarely applied in the aerospace field. The solution of the water-drop impact constitutes an indispensable prerequisite for the computation of ice accretion on the exterior of aircraft wings. In this study, we propose a novel approach for the estimation of water-drop impact on wing surfaces by integrating the Euler–Euler approach and EWF model. This approach is capable of furnishing a point of reference and a theoretical foundation for prospective water-drop impact experiments. Through comparison with pertinent experimental findings, the precision of the numerical simulation approach utilized in this paper is substantiated. Specifically, the research object is the NACA653-218 airfoil of the C-919 transport aircraft, for which the aerodynamic properties, water-drop collision, and liquid film flow characteristics during steady flight were simulated.

Gas Hydrate Formation and Slurry Flow Characteristics of Gas–Liquid–Solid Multiphase Systems

Hydrate formation, aggregation, and deposition have become major hazards for the safe transportation of oil and gas pipelines. Although there has been a great deal of research into the behavior of particles during hydrate formation and transport, there is less research into the multiphase generation and flow characteristics of hydrate gas and liquids. In this paper, the flow characteristics of hydrate slurry and the flow pattern transition in gas–liquid multiphase system were studied, and the generations of it were compared between a gas–liquid multiphase system and oil–water emulsion system. The results showed that the flow parameters such as pressure, pressure drop, and density fluctuated more drastically in the gas–liquid system than that in the emulsion system, the higher fluctuation meant a higher risk of pipe plugging. At the same time, the influence of pressure and dosage on multiphase flow pattern transformation and boundary change conditions were studied. A gas-slurry flow pattern transformation diagram was drawn based on the defined transformation conditions between flow patterns. The results also indicated that, with the increase of pressure from 5 to 6 MPa, the boundary of slug flow and air mass flow changed to the direction of higher gas and liquid flow velocity. While the boundary of slug flow and wave flow, stratified flow and wave flow changed to the direction of higher gas flow velocity. The boundary of slug flow and air mass flow changed to the direction of lower liquid flow velocity. In contrast, the boundary of slug flow and wave flow, stratified flow and wave flow, slug flow and stratified flow changed to the direction of higher gas flow velocity and lower liquid flow velocity in the 1% inhibitor period compared with that without the inhibitor. This study will provide theoretical references and technological supports for the safety of multiphase transportation pipelines and the safety of deep water production.

Experimental investigation of oil film flow and droplets behavior in the annular channel of a cyclone separator

The separation of the gas and liquid in the gas-liquid cyclone separator is achieved through the swirling flow. The liquid film flow characteristics and the dynamics of droplets impacting the liquid film are very important for the separation performance, but these phenomena have not been well understood in the swirling flow. In this work, an experiment was conducted to investigate the liquid film flow and droplet impingement in the annular channel of the gas-liquid cyclone separator. Three regions of the annular channel could be divided based on the film flow patterns, which were the inlet region, the annular region, and the outlet region; and four typical droplet impact outcomes could be observed, which were splashing, coalescence, bouncing, and jet breakup. According to the characteristics of the liquid film and the outcome of droplet liquid film impingement, if the droplet splashing in the inlet region could be weakened and the length of the annular region was lengthened, it would be beneficial for gas-liquid separation. The impact outcomes were shown to undergo a transition from bouncing to coalescence as the droplet Weber number increased. Droplet coalescence was affected by the disturbance of gas flow and the evenness of the liquid film, so when the superficial velocity of the gas flow was fixed, the transition boundary was constant whatever the liquid volume fraction in the channel, and when the Reynolds number of the gas flow increased, the transition boundary of droplet Weber number increased first and then decreased. This work may provide a basis for a comprehensive understanding of the liquid film flow pattern and droplet behavior in the cyclone separator, and the results have the potential to be applied in other multiphase studies.

Numerical investigation of gas–liquid two-phase performance in a mixed-flow pump by using a modified drag force model

As key devices to lift deep-sea oil and gas, mixed-flow pumps can transport multiphase flow with high inlet gas volume fraction (IGVF). Performance parameters of mixed-flow pumps may be disturbed by the complex flow and gas–liquid distribution under various conditions that need an accurate two-phase flow numerical methodology for prediction. In this work, the gas–liquid mixed flow performance of a mixed-flow pump is investigated based on the modified drag force model, which considers the bubble deformation at high IGVF. The effects of the IGVF on pressure increment and gas phase distribution are explored. The influences of flow rate and rotational speed are studied as well. Experiments are conducted to obtain performance parameters and gas–liquid distribution images. The results show that performance parameters and gas–liquid distribution predicted in simulations are consistent with those obtained in experiments. The pressure increment of the mixed-flow pump is decreased as the IGVF and flow rate increase. Especially when IGVF increases from 5% to 15%, the pressure increment drops sharply, which is the surging phenomenon. The increased speed may improve the performance. The evolution of gas phase distribution is deeply analyzed to improve the understanding of gas–liquid flow characteristics in mixed-flow pumps.

Heat and mass transfer of micropolar liquid flow due to porous stretching/shrinking surface with ternary nanoparticles

The present investigation is carried out to predict the flow characteristics of a micropolar liquid that is infused with ternary nanoparticles across a stretching/shrinking surface under the impact of chemical reactions and radiation. Here, three dissimilarly shaped nanoparticles (copper oxide, graphene and copper nanotubes) are suspended in H2O to analyse the characteristics of flow, heat and mass transfer. The flow is analysed using the inverse Darcy model, while the thermal analysis is based on the thermal radiation. Furthermore, the mass transfer is examined in light of the impact of first order chemically reactive species. The considered flow problem is modelled resulting with the governing equations. These governing equations are highly non linear partial differential equations. Adopting suitable similarity transformations partial differential equations are reduced to ordinary differential equations. The thermal and mass transfer analysis comprises two cases: PST/PSC and PHF/PMF. The analytical solution for energy and mass characteristics is extracted in terms of an incomplete gamma function. The characteristics of a micropolar liquid are analysed for various parameters and presented through graphs. The impact of skin friction is also considered in this analysis. The stretching and rate of mass transfer have a large influence on the microstructure of a product manufactured in the industries. The analytical results produced in the current study seem to be helpful in the polymer industry for manufacturing stretched plastic sheets.

Flow electrification characteristics of liquid hydrogen in pipe flow

Flow electrification occurs when a dielectric liquid flows along the wall surface, and it may cause electrostatic hazards such as spark discharges. Flow electrification issues of liquid hydrogen should be carefully treated since its low electrical conductivity and dangerous flammability. In this study, flow electrification characteristics of liquid hydrogen in pipe flow are numerically investigated. A theoretical model coupling the electric field and the flow field is introduced to govern the behaviour and distribution of charges, and an interface discharge model is adopted to describe the charge transfer boundary condition. The theoretical model is validated by comparing the simulation with experiment data, and the results show a good agreement with the averaged related deviation below 10%. The result of a common case, with flow velocity u of 1 m/s, pipe radius a 0.01 m, and length L 1 m, shows that the charge density, streaming current, and the electric potential of liquid hydrogen flow are in the magnitude of 10−12 C·m−3, 10−16 A and 10−2 V, respectively. Flow parameters, including flow velocity and pipe size, have a certain effect on the flow electrification characteristics of liquid hydrogen flow. By dimensionless parameterization, it is found that Reynolds numbers (Re), r/a, and x/a are exactly three orthogonal parameters determining the charge density distribution. Furthermore, the effects of electrical conductivity on the distribution of charges and charge dissipation have also been discussed. Finally, the safety assessment of the liquid hydrogen transportation system has been discussed, with extra consideration of the impurities and gas-liquid two-phase flow regime. To sum up, this work presents an in-depth and comprehensive insight into the flow electrification of liquid hydrogen flow, which is of great significance to the transportation safety of liquid hydrogen.

Design of nozzle diverter channel system based on uniform distribution performance

Aiming at the nozzle-diverted channel system, two diverted channels with different configurations were designed and optimized, and the liquid flow characteristics in the diverted channel were studied. A finite element simulation model was established to analyze the influence of different diverted channel systems on the uniform distribution performance of the liquid, and the two diverted channels were tested for the uniform distribution of liquid flow. The results show that the diverting effect of the two kinds of diverting disk channels is relatively uniform. However, the distribution performance of the four-bifurcated diverting disk channel is better than that of the double-bifurcated diverting disk channel. The pressure loss is relatively less; the energy consumption is less, so the four-bifurcated diverting disk channel system is selected as the optimal design. The experimental results are consistent with the simulation results.

Numerical study on conjugate heat transfer in a liquid-metal-cooled pipe based on a four-equation turbulent heat transfer model

Conjugate heat transfer between liquid metal and solid is a common phenomenon in a liquid-metal-cooled fast reactor's fuel assembly and heat exchanger, dramatically affecting the reactor’s safety and economy. Therefore, comprehensively studying the sophisticated conjugate heat transfer in a liquid-metal-cooled fast reactor is profound. However, it has been evidenced that the traditional Simple Gradient Diffusion Hypothesis (SGDH), assuming a constant turbulent Prandtl number (Prt, usually 0.85 - 1.0), is inappropriate in the Computational Fluid Dynamics (CFD) simulations of liquid metal. In recent decades, numerous studies have been performed on the four-equation model, which is expected to improve the precision of liquid metal’s CFD simulations but has not been introduced into the conjugate heat transfer calculation between liquid metal and solid. Consequently, a four-equation model, consisting of the Abe k−ε turbulence model and the Manservisi kθ−εθ heat transfer model, is applied to study the conjugate heat transfer concerning liquid metal in the present work. To verify the numerical validity of the four-equation model used in the conjugate heat transfer simulations, we reproduce Johnson’s experiments of the liquid lead-bismuth-cooled turbulent pipe flow using the four-equation model and the traditional SGDH model. The simulation results obtained with different models are compared with the available experimental data, revealing that the relative errors of the local Nusselt number and mean heat transfer coefficient obtained with the four-equation model are considerably reduced compared with the SGDH model. Then, the thermal-hydraulic characteristics of liquid metal turbulent pipe flow obtained with the four-equation model are analyzed. Moreover, the impact of the turbulence model used in the four-equation model on overall simulation performance is investigated. At last, the effectiveness of the four-equation model in the CFD simulations of liquid sodium conjugate heat transfer is assessed. This paper mainly proves that it is feasible to use the four-equation model in the study of liquid metal conjugate heat transfer and provides a reference for the research of conjugate heat transfer in a liquid-metal-cooled fast reactor.

The Capacitive Sensing of the Pulsatile Liquid Flow—Investigation on a Physical Vascular Model

This article investigates a prospective capacitive sensing method for the measurement of physical characteristics of a pulsatile liquid flow. It was tested on a physical vascular model. The volume pulse wave sensor holds a high sensitivity and thus great potential in the field of industrial applications and also in biomedical applications where we also encounter a pulsating flow of blood. Two types of capacity sensors were developed and tested on our blood vessel model, currently used for the simulation of pulse wave propagation with the possibility of changes in vessel properties and many setups are reached for testing different pulse wave propagations. The newly developed capacitive sensor detects the capacity change of pulsating liquid flow in the vascular model. Data from the capacitive sensor are compared with two reference sensors, one for direct pressure sensing and the second for noncontact optical sensing of changes in diameter. The signal processing is used for all three types of sensors and analysis in the time and frequency domain to determine the accuracy. The use of capacitive sensors is promising since it can measure a negligible change in the diameter of the vessel in the range of tens of femtofarads (fF). We can confirm that the high precision measurement is dependent on the environment, which can cause the capacity change, but with proper shielding it can be eliminated.

Experimental study on the passive regulation of a CO2 two-phase thermosyphon loop

• The passive regulation mechanism of CO 2 TPTL was revealed. • Three typical operation states of the TPTL occurred as the heat load increased. • Each operation state showed different characteristics as the filling ratio changed. • The largest normal operation heat load range was found under 45% filling ratio. Vapor–liquid distribution and flow characteristics in a two-phase thermosyphon loop usually exhibit regular variation under varying working conditions, which can be referred to as passive regulation. Currently, the passive regulation law of a CO 2 two-phase thermosyphon loop has not been well understood. In this study, experiments were performed to examine the passive regulation mechanism of a CO 2 two-phase thermosyphon loop under different heat loads and filling ratios. Local flow visualization was adopted, combined with the measurement of operating parameters. The CO 2 two-phase thermosyphon loop entered the pre-start, oscillatory, and stable operation stages successively with the increase in heat load. Vapor–liquid counterflow was observed in the downcomer in the pre-start stage. Temperature change due to thermal unbalance between the vapor and liquid can be observed along the riser or the downcomer. In the oscillatory stage, different types of oscillation were observed under different filling ratios. In the stable stage, the two-phase thermosyphon loop worked under good conditions until the heat transfer limit was reached. The two-phase thermosyphon loop reached its maximum heat transfer limit of 1200 W at a filling ratio of 45%. The normal operation heat load range of the two-phase thermosyphon loop was 380–650 W, 320–770 W, 700–1100 W, 600–1200 W, and 400–630 W for filling ratios of 20%, 25%, 40%, 45%, and 50%, respectively.

전기차 배터리 냉각을 위한 3차원 진동형 히트파이프의 패턴에 따른 유동 가시화 연구

Heat pipes using oscillating characteristics of vapor or liquid flow in a tube called an oscillating heat pipe (OHP) have been visualized and presented. Unlike ordinary planar type oscillating heat pipes, in the present study, 3-D oscillating heat pipes was designed, and tried to shape and verify the operability of upper heating OHP rather than lower heating OHP. Unlike the lower heating method, since the motion of the internal working fluid is directly affected by gravity, structural characteristics were studied to overcome gravity and create oscillation characteristics. In this study, it was observed that the supplied heat to the upper evaporator created the pressure difference as the internal space of the upper region was heated, and then eventually, internal working fluid was circulated by creating a pressure difference in the OHP, which was one of the anti-gravity heat pipes. It was observed that the internal working fluid is heated in the internal space of the upper part according to the heating in the evaporator, creating a pressure difference between the liquid and the lower part, and thus oscillating normally. In this study, the operating conditions of OHP using non-traditional heating and cooling modes were experimentally verified. Future electric vehicles are also suggested to use OHP in a few promising and innovative ways. The fundamental OHP operating mechanism for non-uniform working conditions are planned to be presented in this study.

Extraordinary Solidification Mechanism of Liquid Alloys Under Acoustic Levitation State.

The acoustic levitation of various materials can be realized by highly intensive ultrasound, which provides a free surface and containerless state for materials processing under space simulation conditions. The nonlinear effects such as acoustic radiation pressure, acoustic streaming, and ultrasonic cavitation open up special access to modulate the fluid dynamics and solidification mechanisms of liquid materials. Here, the physical characteristics of liquid flow, undercooling capability, phase separation, and crystal nucleation and growth within acoustically levitated droplets are explored comprehensively to reveal the extraordinary solidification kinetics of liquid alloys. The sectorial shape oscillations of the 2nd to 10th order modes accompanying internal potential flow are observed for water droplets with modulated ultrasound amplitudes, while the enhanced ultrasound intensity promotes ice nucleation and thus reduces water undercooling. The migration of Sn-rich globules during phase separation of immiscible Al-Cu-Sn alloy is dominated by the droplet deformation and rotation related to acoustic levitation. The high undercooling states of liquid Ag-Cu-Ge and Ni-Sn alloys during acoustic levitation result in the refinement of (Ag) dendrites and the formation of anomalous (Ni+Ni3 Sn) eutectics. The ultrasound-liquid interaction also induces surface waves during the containerless solidification of Ag-Cu and Ni-Sn eutectic alloys.

Annular liquid film thermohydraulic and intermittent dryout in microchannel flow boiling

The annular flow regime in microchannels is commonly described as the steady flow of a vapor core with a surrounding liquid film along the channel length. However, limited studies have suggested temporal discontinuity in the liquid film coverage of the microchannel wall. The lack of experimental tools to directly interrogate the liquid flow characteristics and the local surface heat flux has resulted in proliferation of different hypotheses concerning the physics of this process. Surface de-wetting due to high shear stresses at the vapor–liquid interface and liquid film instability and rupture due to perturbation growth at the vapor–liquid interface have been suggested as the underlaying causes of this phenomenon. In this study, a recently developed microsensor array capable of measuring the surface local heat flux and liquid film thickness and velocity is utilized to decipher thermohydraulic characteristics of the annular flow regime and intermittent dryout with unprecedented details. The studies are conducted in a 600 μm square cross-section microchannel using FC-72 as the test fluid at 70–80% exit vapor quality. The results show that liquid film thinning because of evaporation rather than de-wetting and film rupture is responsible for intermittent surface dryout. Studies at different mass and heat fluxes suggest that for a given surface heat flux, there is a mass flux threshold above which intermittent surface dryout vanishes. Furthermore, the experimental liquid and vapor flow velocities and liquid film thickness are used to calculate the liquid–vapor interfacial shear stress. The results suggest that under the studied conditions, the liquid–vapor interfacial shear stress has little impact on the surface intermittent dryout. This study enhances predictable and reliable design and operation of two-phase heat sinks at high exit vapor qualities.

Flow characteristics simulation of concave pipe with zero net liquid flow

Liquid accumulation often occurs during gas transmission through underwater pipeline, which affects the operation of the underwater compressed air energy storage system. To study the liquid accumulation flow characteristics in the concave pipe with zero net liquid flow, a simulation model was established in FLUENT to analyze the flow process. By analyzing the slugging distance and liquid slug frequency, the multiphase flow model, the turbulence model, and the simulation time step are determined. In the simulation, the height of the liquid accumulation is 10.4 mm and the gas velocity is 5 m/s, a series of interface waves are generated at the entrance of the pipe. However, an unstable interface causes waves to grow rapidly and merge. Also, when the wave crest of the interface wave reaches the upper part of the pipeline, it is blocked. In conclusion, the characteristics of the concave pipe with zero net liquid flow are reflected by the model.

Theoretical and experimental research on valve-less piezoelectric pump with arc-shaped tubes

In order to apply a valve-less piezoelectric pump in navigation equipment, this work first revealed a valve-less piezoelectric pump with arc-shaped tubes and then researched the relationship between the main structural parameters of arc-shaped tubes and the output flow rate. According to the velocity difference between clockwise and counterclockwise directions of liquid in circular arc-shaped tubes, the flow characteristics of liquid in circular arc-shaped tubes are analyzed in this paper, and the velocity difference model and flow equation of a piezoelectric pump are established. By using three-dimensional printing technology, five types of prototypes with different parameters were made, and the experimental research was carried out. The results show that at the optimal frequency, the pump output flow is the largest. The output flow is proportional to the driving voltage, the base circle radius, and the cross section area of the pipe. The low-cost and miniaturized navigation equipment made by using the piezoelectric pump has potential application value in unmanned aerial vehicle and intelligent vehicle navigation.

Numerical investigation on heat transfer characteristics of liquid metal cross flow over tube bundles

Helical tube Once Through Steam Generator (OTSG) could further improve the compactness of liquid metal cooled reactors. The heat transfer characteristics of liquid metal cross flow over inline tube bundles is important for the design of helical tube OTSG. In order to consider the low molecular Prandtl number (Pr) effects on turbulent heat flux, different turbulent Prandtl number (Prt) models are validated by a Direct Numerical Simulation (DNS) database for convective Poiseuille flow. Applicability of the Prt and turbulence models for convection with flow separation or adverse pressure gradients is further assessed by DNS results of backward-facing step convection with a fluid Prandtl number of 0.025. Heat transfer of liquid metal cross flow over tube bundle is simulated with k-ω SST turbulence model and the selected Prt model. Heat transfer performances of cross flow over tube bundles with different Pr, Reynolds number (Re) and geometry parameters are simulated. The very large molecular thermal diffusivity (a) of liquid metal results in different temperature distributions and heat transfer characteristics in tube bundles compared with conventional fluids (Pr around and higher than 1). The normalized heat transfer coefficients of liquid metal are enhanced on the upwind side of the tubes and are weaken on the rear side of the tubes compared with conventional fluids. The increments of Pr and Re both weaken the low Pr effect of liquid metal and lead to circumferential heat transfer characteristic more similar to that of conventional fluids. Geometry parameters have little impact on the time and area averaged Nu of liquid metal cross flow over tube bundles. A new Nusselt (Nu) number correlation with wide applicable ranges is proposed based on the numerical results.

Liquid flow behavior in the concentric mesh packing with novel fiber cross-sectional shape in a rotating packed bed

Mesh packing has been widely exploited in rotating packed beds (RPBs). Fiber cross-sectional shape (CSS) of mesh has exhibited significant influence on liquid flow behavior. The concentric mesh packing outperforms conventional coiled mesh packing in mass transfer. However, in-depth insights into liquid flow characteristics in concentric mesh packing, especially with novel fiber CSS, which is indispensable for mass transfer modelling, are scarce. Herein, the liquid flow behavior in concentric mesh packing composed of vertical quadrangular fibers and horizontal elliptical fibers (VQHE) and the packing composed of circular fibers (VCHC) were investigated via high-speed photography technology in an RPB. Typical liquid flow patterns and their transition in packings were illuminated. The liquid film covered wider regions in VQHE than that in VCHC. The transition criteria for flow patterns has been proposed. The VQHE reduced the average droplet diameter by 19%, enhanced the uniformity of droplet size distribution, and decreased average droplet velocity by 15%, compared to VCHC. Furthermore, correlations to predict the average droplet diameter and velocity were developed with deviations of ±15% and ±20%, respectively.

Geometry dimension optimization of a liquid–gas vacuum ejector for MED-TVC system

• Establishing the 3D model for the design and optimization of liquid–gas ejector. • The internal fluid flow characteristics of liquid–gas ejector was investigated. • The optimal NXP, area ratio and the length of mixing chamber were obtained. • A correlation between geometric parameters and ejector performance is developed. A liquid–gas ejector is designed to entrain the non-condensable gas accumulating in the condenser without power consumption in the multi-effect distillation with a thermal vapor compression desalination system and the geometry dimensions are optimized by the optimization method provided in this paper for their vital influence on liquid–gas ejector performance. In this paper, the effects of nozzle exit position, area ratio, and the mixing chamber length on liquid–gas ejector are investigated simultaneously using numerical simulations. The results show that: the mass flow rate ratio and efficiency increase within a certain range and then decrease while the nozzle exit position increases; the mass flow rate ratio increases with the increasing of area ratio, meanwhile, the efficiency increases until reaching a maximum value and then decreases; there is no obvious effect on system vacuum degree as the mixing chamber length increases. Following this, the optimal geometry parameters including nozzle exit position, area ratio, and mixing chamber length are determined. When NXP is 16.95 mm, the area ratio is 4.45 and the length of the mixing chamber is 92.5 mm, the liquid–gas ejector has the best performance with the efficiency, mass flow rate ratio, and vacuum degree of 0.5, 2.02, and 0.18 atm, which satisfies the design requirements. Through the geometry optimization method, the liquid–gas ejector can effectively remove the non-condensable gas from the condenser instead of the mechanical pump in the vacuum system under a typical working condition of the multi-effect distillation with thermal vapor compression desalination system.

Analysis and optimization of feed liquid flow characteristics of distributor in scraping film molecular distillation equipment

Abstract The initial liquid film is the basis of material evaporation during distillation, so it is of great significance to study the distribution of the initial liquid film of distributor in the process of scraping film molecular distillation. In this paper, CFD is used to study the distribution of distributor liquid film, and the mathematical model of the triangular tooth distributor and its peripheral cylinder is established, and the effects of the triangular tooth distributor’s speed, feed rate, and feed position on initial liquid film uniformity are investigated. And the reliability of the numerical simulation model is verified by experiments. In this paper, a new feed structure that includes an intermediate feed device and inclined tooth distributor is proposed and researched by numerical simulation. And compared with the previous structure, the liquid film distribution is more uniform. This has important guiding significance to the optimization of equipment in production.