Mean Liquid Flow Research Articles

The Effect of Crude Oil Stripped by Surfactant Action and Fluid Free Motion Characteristics in Porous Medium.

The surfactant solution is crucial in facilitating the spontaneous imbibition process for the recovery of oil in tight reservoirs. Further investigation is required to examine the fluid flow in porous mediums and the process of crude oil stripping by a surfactant solution during spontaneous imbibition. Hence, this study aims to determine the free motion properties of oil and water in porous mediums using the finite-element approach to solve the multiphase flow differential equation, taking into account the capillary pressure. An investigation was conducted to examine the impact of oil viscosity and interfacial tension on the mean liquid flow rate and oil volume fraction. An experimental study was conducted to investigate the impact of surface tension, interfacial tension, and wetting angle on crude-oil-stripping efficiency. The findings indicate that the stripped crude oil migrated through porous mediums as individual oil droplets, exhibiting a degree of stochasticity in its motion. When the interfacial tension is reduced, the average velocity of the fluid in the system decreases. The crude oil exhibited a low viscosity, high flow capacity, and a high average flow rate within the system. Once the concentration of the surfactant solution surpasses a specific threshold, it binds with the oil to create colloidal aggregates, resulting in the formation of micelles and influencing the efficiency of the stripping process. As the temperature rises, the oil-stripping efficiency also increases. Simultaneously, an optimal range of wetting angle, surface tension, and interfacial tension could enhance the effectiveness of removing oil using surfactant solutions. The research results of this paper enrich the enhanced oil recovery mechanism of surfactant and are of great significance to the development of tight reservoirs.

Horizontal Injection of Gas–Liquid Mixtures in a Water Tank

Experiments were carried out to investigate the behavior of horizontal gas–liquid injection in a water tank. Measurements of bubble properties and mean liquid flow structure were obtained. The turbulence in the liquid phase appears to help generating bubbles with relatively uniform diameters of 1–4 mm . Both bubble properties and mean liquid flow structure depended on the gas volume fraction and the densimetric Froude number at the nozzle exit. It was found that the bubbles strongly affected the trajectory of the water jet, which behaved similarly to single-phase buoyant jets. However, at gas volume fractions smaller than about 0.15, the water jet completely separated from the bubble core. Bubble slip velocity was also found to be higher than the terminal velocity for isolated bubbles reported in the literature. Dimensionless correlations were proposed to describe bubble characteristics and the trajectory of the bubble plumes and water jets as a function of the gas volume fraction and the densimetric Frou...

Bubbly jets in stagnant water

Air–water bubbly jets are studied experimentally in a relatively large water tank with a gas volume fraction, C o, of up to 80% and nozzle Reynolds number, Re, ranging from 3500 to 17,700. Measurements of bubble properties and mean axial water velocity are obtained and two groups of experiments are identified, one with relatively uniform bubble sizes and another with large and irregular bubbles. For the first group, dimensionless relationships are obtained to describe bubble properties and mean liquid flow structure as functions of C o and Re. Measurements of bubble slip velocity and estimates of the drag coefficient are also provided and compared to those for isolated bubbles from the literature. The study confirms the importance of bubble interactions to the dynamics of bubbly flows. Bubble breakup processes are also investigated for bubbly jets. It was found that a nozzle Reynolds number larger than 8000 is needed to cause breakup of larger bubbles into smaller bubbles and to produce a more uniform bubble size distribution. Moreover, the Weber number based on the mean water velocity appears to be a better criteria than the Weber number based on the bubble slip velocity to describe the onset of bubble breakup away from the nozzle, which occurs at a Weber number larger than 25.

Modeling of Gas−Liquid Mass-Transfer Limitations in Slurry Olefin Polymerization

A model of gas to liquid mass transfer in a stirred laboratory reactor was developed with the purpose of controlling mass-transfer limitations in kinetic studies of olefin polymerizations. Renewing the liquid surface is controlling the mass transfer. Generally, two different scales of eddies can be envisaged to be responsible for the renewal: at low stirring rates, the mean liquid flow is the controlling mechanism; at high stirring rates, small-scale turbulence provides the renewal. The change is at a specified turbulent Reynolds number. The model for the high Reynolds number region is based on an established mass-transfer relationship from the literature. For low Reynolds numbers, a new correlation is developed based on literature studies of the liquid circulation velocity at the gas−liquid interface. The model predictions are compared with experimental data for propene polymerization in decane. It was found that the small-scale turbulence model was most appropriate, and fitted the data within a factor ...

Treatment of Domestic Sewage in Horizontal-Flow Anaerobic Immobilized Biomass (HAIB) Reactor

This paper focuses on the evaluation of the start-up period and the performance of a pilot-scale horizontal-flow anaerobic immobilized biomass (HAIB) reactor treating pre-screened domestic sewage. The pilot-scale HAIB reactor comprises a 14.5 cm internal diameter PVC tube 14.4 m long divided into five stages of 2.88 m each. Polyurethane foam cubic matrices with 1 cm sides were used as support for biomass immobilization. The reactor was operated at the mean hydraulic detention time of 4.3 hours and the experimental results presented refer to 15 weeks of operation at mean sewage temperature of 25°C and mean liquid flow rate of 20 l h−1. The mean chemical oxygen demand (COD) of the sewage, based on composed samples, was found to be 350 mg l−1. A short start-up period lasting nearly 8 weeks was observed by monitoring several parameters such as COD, biogas composition, methane concentration and total volatile acid (TVA) concentration. By the end of the start-up period onward, the effluent COD attained approximately constant values of 100 mg l−1 and 75 mg l−1 for non-filtered and filtered samples.

A mathematical model and criteria for designing horizontal-flow anaerobic immobilized biomass reactors for wastewater treatment

The development and the preliminary evaluation of a mathematical model used to design a horizontal-flow anaerobic immobilized biomass (HAIB) reactor applied to domestic sewage treatment is presented. The influences of both the liquid superficial velocity and the bioparticle size on the overall reaction rate were examined. The size of the particle used as biomass support was found to affect strongly the total volume of the designed unit since the effectiveness factor decreased as the bioparticle size increased. On the contrary, the overall organic matter conversion rate was not substantially influenced by the liquid velocity. Based on these data obtained from the mathematical model, a pilot-scale HAIB reactor was constructed adopting some design parameters and following the design criteria established. The HAIB reactor comprised a 14.5 cm internal diameter PVC tube with length of 14.4 m divided in to five stages of 2.88 m each. Polyurethane foam cubic matrices with 1 cm side were used as support for biomass immobilization. The reactor was operated at a mean hydraulic retention time of 4.3 h at mean sewage temperature of 25 ± 1°C and mean liquid flow rate of 20 L h −1. A preliminary evaluation of the mathematical model proposed to design the HAIB reactor was performed based on data of chemical oxygen demand (COD) profiles along the reactor length. Although deviations were observed between experimental and theoretical data, the proposed model was found to be suitable for predicting the overall behavior of the reactor.

Aspects of Electrokinetic Charging in Liquid Microjets

We have investigated the physicochemical basis of electrokinetic charge separation in methanol using micron-sized channel diameters under both turbulent and laminar flow conditions. Turbulent flow studies were conducted using a 40 μm diameter stainless steel aperture which had a channel length of 0.5 mm. Under these conditions, electrokinetic streaming currents arose from a charge stripping process in the region close to the aperture channel wall. The moving liquid removed the relatively weakly held charges from the outer portion of the electrical double layer formed at the solid−liquid interface. Streaming currents were simultaneously measured at both the conducting aperture and a downstream copper plate. The magnitudes of the streaming currents were shown to be equal at the aperture and the plate; however, the sign of the current at each measurement location was opposite. The magnitude of the streaming currents varied quadratically with mean liquid flow velocity. Studies under laminar flow conditions we...

Measurement and modeling of turbulence in the gas/liquid two-phase zone during gas injection

Averaged and turbulent fluctuating liquid velocities in the gas/liquid plume zone of a gas-stirred water model ladle were measured with a combined laser Doppler anemometer (LDA) and elec-trical probe technique. The measured turbulence fields, void fraction distribution, and gas and liquid velocities in the plume zone were used for evaluation of various turbulence models. It was found that, among all of the turbulence models tested, only a modified k-e model, with extra source terms to take into account the generation and dissipation resulting from the inter-action of the bubbles with the liquid, yielded good agreement with both the mean liquid flow field and the turbulent kinetic energy distribution. However, the values of the coefficients orig-inally proposed by their authors were found inapplicable to the bubbly plume situation; more appropriate values of the coefficients were determined based on comparison with experimental measurement.

Mechanism of the disturbance wave generation in a vertical up- and down-ward gas-liquid two-phase annular flow.

The generation of a disturbance wave on a liquid film flowing concurrently with an up-or a down-wards gas flow in a vertical circular pipe is investigated both theoretically and experimentally and compared with that in a horizontal duct. It is made clear that the disturbance wave is generated when the velocity of liquid particles exceeds that of interfacial waves. This is similar to the case of a horizontal duct. The boundary of the existence of the disturbance wave, however, depends strongly on the gravitational force, i.e., the orientation of the pipe line and the direction of the flow in a low gas flow rate region. This is because the gravitational force affects the wave velocity but not the mean liquid flow in a horizontal line, and vice versa in a vertical line ; and also because an annular film cannot be formed in the vertical upward flow if the gas velocity is low, i.e., the interfacial shear force is small.

Recirculating turbulent flow of liquid in gas-liquid-solid fluidized bed.

Axial and radial distributions of gas holdup and liquid velocity were studied in a gas-liquid-solid fluidized bed of 0.12 m i.d. Air, water and glass beads (0.58, 1.2 and 2.2 mm in diameter) were used as gas, liquid and solid particle phases, respectively. Local gas holdup was meaured by using an electric conductivity probe, and local liquid velocity was obtained by the electrolyte tracer method. The value of local gas holdup was in proportion to the square of the distance from the column wall. The liquid flow pattern was similar to that of the bubble column, showing an up-flow in the central region and a down-flow in the peripheral region with respect to the interstitial mean liquid flow. Liquid velocity at the central axis increased with increasing superficial gas velocity and with decreasing particle diameter. The results were analyzed on the basis of the circulating flow model, where a constant turbulent viscosity and a constant composition of the liquid-solid mixtures were assumed. The turbulent viscosity for fully developed fluidization was correlated as a function of particle diameter and superficial gas velocity, and was compared to that of the bubble column.

Methods for measuring the properties of the turbulence in bubble flow

A constant temperature hot film anemometer has been used to evaluate mean liquid flow velocity, bubble frequency, turbulence scale and intensity, and the rate of energy dissipation by liquid phase bubble flow.