Experimental Study Of Two-phase Flow Research Articles

Numerical simulation and experimental study of two-phase flow in downhole spiral gas-liquid separator

Gas-liquid separator is an important surface equipment in oilfield development. Improving the separation efficiency of separator is of great significance to the overall economic benefit of oilfield. Spiral separator is a high efficiency separation device that has been widely used, but at present, there are not enough studies on separation efficiency in number of spiral turns and pitches. In view of this problem, this paper analyzed the gas–liquid separation efficiency of spiral separators with different number of spiral turns and pitches via the fluent numerical simulation software and laboratory experiments. The results showed that a greater number of spiral turns and a larger particle diameter could lead to higher separation efficiency. The separation efficiency has an optimum value for the pitch. The performance of the downhole spiral separator was verified by laboratory experiments, and the separation efficiency was above 90% under the conditions where the treatment amount was either unchanged or changed. These results can provide a reference for the application of spiral separators in oil fields.

Experimental study on condensation heat transfer and pressure drop characteristics of R32 flowing inside an alternating cross-section flattened tube

This work presents the experimental study of two-phase flow inside an alternating cross-section flattened (ACF) tube. The ACF tube was made from a copper circular tube with an inner diameter of 4.31 mm. We conducted the test under the following experimental conditions: a mass flux of 280, 430, and 580 kg/m2s; a saturation temperature of 40, 45, and 50 °C; a heat flux of 10, 15, and 20 kW/m2; and an average vapor quality of 0.1–0.8. Compared to the existing flow pattern maps, most fell into the annular and semi-annular flow regimes. However, the results were found in the transition and intermittent flow regions at low vapor quality. The results from the circular and ACF tubes were examined and discussed. We found that the ACF tube revealed a prominent condensation heat transfer coefficient and a reasonable pressure loss penalty. The heat transfer coefficient and frictional pressure drop of the ACF tube were higher than that of the circular tube by approximately 25.6–111.1% and 4.3–39.9%, respectively. New correlations for the Nusselt number and two-phase friction factor were proposed.

Экспериментальное исследование двухфазного течения жидкостей в цилиндрическом капилляре

Экспериментальное исследование двухфазного течения жидкостей в цилиндрическом капилляре

Film flow dominated simultaneous flow of two viscous incompressible fluids through a porous medium

We present an experimental study of two-phase flow in a quasi-two-dimensional porous medium. The two phases, a water-glycerol solution and a commercial food grade rapeseed/canola oil, having an oil to water-glycerol viscosity ratio of 1.3, are injected simultaneously into a Hele-Shaw cell with a mono-layer of randomly distributed glass beads. The two liquids are injected into the model from alternating point inlets. Initially, the porous model is filled with the water-glycerol solution. We observe that after an initial transient state, an overall static cluster configuration is obtained. While the oil is found to create a connected system spanning cluster, a large part of the water-glycerol clusters left behind the initial invasion front is observed to remain immobile throughout the rest of the experiment. This could suggest that the water-glycerol flow-dynamics is largely dominated by film flow. The flow pathways are thus given through the dynamics of the initial invasion. This behavior is quite different from that observed in systems with large viscosity differences between the two fluids, and where compressibility plays an important part of the process.

Experimental study of two-phase flow in a proton exchange membrane fuel cell in short-term microgravity condition

Water management is important for improving the performance and stability of proton exchange membrane fuel cells (PEMFCs) for space applications. An in situ visual observation was conducted on the gas–liquid two-phase flow in the cathode channels of a PEMFC in short-term microgravity condition. The microgravity environment was supplied by a drop tower. A single serpentine flow channel with a depth of 2mm and a width of 2mm was applied as the cathode flow field. A membrane electrode assembly comprising of a Nafion 112 membrane sandwiched between gas diffusion layers was used. The anode and cathode were loaded with 1mgcm−2 platinum. The PEMFC shows a distinct operating behavior in microgravity because of the effect of gravity on the two-phase flow. At a high water production regime, cell performance is enhanced by 4.6% and the accumulated liquid water in the flow channel tends can be removed in microgravity conditions to alleviate flooding. At a low water production regime, cell performance deteriorates by 6.6% and liquid aggregation occurs in the flow channel because of the coalescence of dispersed water droplets in microgravity conditions, thus squeezing the flow channel. The operating behavior of PEMFC in microgravity conditions is different from that in normal gravity conditions. Further studies are needed on PEMFC operating characteristics and liquid management for space applications.

Flow patterns and gas fractions of air–oil and air–water flow in pipe bends

An experimental study of two-phase flow in a 180° pipe bends with 0.016, 0.022 and 0.03m and the curvature radii of 0.11, 0.154, 0.21m, respectively have been carried out. The experiments were conducted under the input superficial phase velocity: air from 0.038 to 5.4ms−1, water from 0.018 to 0.92ms−1 and oil from 0.014 to 0.92ms−1. The conducted research involved the observation of the forming flow patterns and determination of average volumetric in situ gas fraction. On the basis of the results of experimental flow map was created for gas–liquid flow and a method of calculating gas fractions was established.

Dynamics of the gas phase in a fuel-rod assembly simulator with a spacing grid

An experimental study of two-phase flow in a model of assembly of 37 fuel rods in a triangular arrangement was performed. Measurements were performed with local gas supply through a unit nozzle. Distributions of the local void fraction were obtained at various values of angular coordinate and distance from a spacing grid. It was shown that most of the gas phase moves in a space produced by the walls of three nearby rods. A significant increase of gas phase concentration takes place in the flow region just after the grid.

An experimental study of two-phase flow in simulated reduced-gravity condition: dispersed droplet to slug flow transition and slug flow

The results from an experimental study of reduced-gravity two-phase flows are reported in this paper. The experiments were conducted in simulated reduced-gravity conditions in a ground-based test facility with a circular test section of 25 mm inner diameter. The flow conditions for which data were acquired lie in the dispersed droplet to slug flow transition and slug flow regime. Local data were acquired for 17 different flow conditions at three axial locations. The acquired data complement and extend those discussed in an earlier paper by the authors (Vasavada et al. in, Exp Fluids 43: 53–75, 2007). The radial profiles and axial changes in the local data are analyzed and discussed in this paper. The area-averaged data, in conjunction with the local data, are discussed to highlight important interaction mechanisms occurring between fluid particles, i.e., drops. The data clearly show the effect of progressive coalescence leading to formation of slug drops. Furthermore, the shape of slug drops in reduced-gravity conditions was observed to be different from that in normal-gravity case. The analyses presented here show the presence of drop coalescence mechanisms that lead to the formation of slug drops and transition from dispersed droplet flow to the slug flow regime. The most likely causes of the coalescence mechanism are random collision of drops driven by turbulence eddies in the continuous phase and wake entrainment of smaller drops that follow preceding larger drops in the wake region. Data from flow conditions in which the breakup mechanism due to impact of turbulent eddies on drops illustrate the disintegration mechanism.

Regimes of Two-Phase Flow in Short Rectangular Channel

Experimental study of two-phase flow in the short rectangular horizontal channel with height 440 μm has been performed. Characteristics of liquid motion inside the channel have been registered and measured by the Laser Induced Fluorescence technique. New information has allowed determining more precisely the characteristics of churn regime and boundaries between different regimes of two-phase flow. It was shown that formation of some two-phase flow regimes and transitions between them are determined by instability of the flow in the lateral parts of the channel.

Theoretical and experimental study of two-phase flow in micro-channels grooved into horizontal pipes

Theoretical and experimental study of two-phase flow in micro-channels grooved into horizontal pipes

Boiling in capillary tubes

We present here a theoretical and experimental study of two-phase flow in a heated capillary tube. The flow parameters of a single-phase liquid, two-phase liquid-vapor, and single-phase vapor were analyzed in the frame of a one-dimensional model. The pressure, temperature and vapor quality measurements were carried out in a pipe of 1.0 mm inner diameter at various values of heat fluxes and mass flow rates and compared with theoretical predictions. The evolution of the bubble volume was studied both theoretically and experimentally. Using infrared technique, the temperature distribution on the heated tube surface was studied for various flow regimes.

Experimental study of two-phase flow in three sandstones. II. Capillary pressure curve measurement and relative permeability pore space capillary models

By means of the porous plate method and mercury porosimetry intrusion tests, capillary pressure curves of three different sandstones were measured. The testing results have been exploited jointly with three relative permeability models of the pore space capillary type (Burdine’s model type), these models are widely used and in rather distinct fields. To do so, capillary pressure has been correlated to saturation degree using six of the most popular relations encountered in the literature. Model predictions were systematically compared to the experimentally measured relative permeabilities presented in the first part of this work. Comparison indicated that the studied models underestimate the water relative permeability and over-estimate that of the non-wetting phase. Moreover, this modeling proves to be unable to locate the significant points that are the limits of fields of saturation where the variation of the relative permeabilities becomes consequent. We also showed that, if pore structure is modeled as a “bundle of capillary tubes”, model predications are independent of the capillary pressure curve measuring method.

Experimental study of two-phase flow in three sandstones. I. Measuring relative permeabilities during two-phase steady-state experiments

Hysteretic relative permeability curves for three different sandstones were determined during two-phase steady-state experiments. On the one hand, the experimental device designed and developed is inspired, according to the manner in which the end effects are reduced, by the Penn–State method. On the other hand, semi-permeable membranes were used upstream of the flow to separate the two fluids (gas and liquid) injected. Having corrected the gas relative permeability curves for the Klinkenberg effect, our present results were compared to that obtained previously using a modified version of the transient pulse-decay method with two different saturating liquids. Gas relative permeability curves obtained by this method or by steady-state experiments, where both fluids are mobile, have shown good agreement. Thus, one can conclude that gas effective permeability does not depend, neither, on the percolating liquid or on its mobility and that viscous coupling effects are negligible for such type of flows. Saturation history has proved to have more influence on the gas relative permeability than on that of the wetting phase. We finally show that result analysis, along with pore structure information accessible from mercury intrusion tests, would enable the specification of a pore entry radii range, controlling the steep part of the relative permeability curves. For sandstone samples tested here, these pores are of comparable sizes.

Flow Boiling of Refrigerant R141B in Small Tubes

Small circular and non-circular tubes are widely encountered in compact evaporators and condensers. This paper presents an experimental study of two-phase flow and heat transfer of refrigerant R141b, in small tubes. Four circular tubes with diameters of 1.1, 1.8, 2.8, 3.6 mm and one square tube of 2×2mm2 were used in the test programme. The parameter ranges were mass flux 50 ∼ 3500kg m−2 s −1, heat flux 1 ∼ 300kWm−2, and inlet pressure 1 ∼ 3 bar resulting in mean boiling heat transfer coefficients of 0.1 ∼ 10 kW m−2C−1. It was found that local heat transfer coefficients are not only a strong function of heat flux but also a function of vapour quality and a weaker function of mass flux for the all the small tubes tested, showing that both nucleate boiling and convective evaporation occur in small tubes. The mean heat transfer coefficient was found to be is primarily a function of the heat flux, rather than the mass flux. Comparison with data in the literature shows that a general flow map developed from adiabatic two-phase flow tests can provide guidance for prediction of flow regimes in heated tubes. This study provides useful design data for two-phase flow and heat transfer in small tubes and channels.

An experimental study of two phase flow and boiling heat transfer in bi-dispersed porous channels

The results of an experimental study of two-phase flow and boiling heat transfer in channels packed with sintered copper bi-dispersed porous media are presented. For comparison, the same channels were packed with sintered copper mono-dispersed porous media. Experiments were conducted using distilled water as the working fluid. The absolute permeabilities of the sintered copper mono- and bi-dispersed porous media were firstly determined by measuring pressure drops at different inlet velocities of the isothermal flow of subcooled water. Experiments were then carried out to characterize flow boiling of water through both mono- and bi-dispersed porous channels. The pressure drops under the boiling condition were also measured. The results indicated that the porous material has a highly effective two-phase heat sink, especially for bi-dispersed porous materials which have a lower flow resistance than that of the mono-dispersed porous materials having the same pore diameter as the micro-pore diameter of the bi-dispersed porous material.

EXPERIMENTAL AND NUMERICAL INVESTIGATION ON CAVITATING FLOWS IN DIESEL INJECTION SYSTEMS

The present study is concerned with the phase change during rapid depressurization of fluids: the role of vapor bubbles nucleation and growth and the effect on the system fluid dynamics were modeled and experimental measurements were made. Following a control-volume approach, averaged equations governing the motion of a one-dimensional, homogeneous, no-slip two-phase flow were used considering both thermal equilibrium (equal temperature) and non-equilibrium (non-equal temperature) between the liquid and vapor phases. In the non-equilibrium model, the heat transfer from the liquid to the vapor and the corresponding mass transfer velocity were modeled. Model results were compared with experimental data for a loss-of-coolant accident in nuclear power plants: the comparison of numerical vs. experimental data showed the role of nucleation velocity during the earliest phase of rapid depressurization. The experimental study of two-phase flow in a diesel engine injection system has been carried out using a rotative pump which is operated by using a purpose-developed test-bench; pressure measurements inside the system pipes were performed using pressure transducers; moreover, an ultrasonic technique was employed to study phase change phenomena. Several measurements were performed comparing the results obtained by different experimental techniques with the model outputs.

Numerical Simulation and Experimental Study of Two-Phase Flow in a Vertical Pipe

ABSTRACT The fully developed flow of air and solid particles in a vertical pipe was calculated using a modified model for particle-eddy interaction in two-phase turbulent flows, which is developed from the particle-source-in-cell model. This model was proposed to account for the effects of the fluctuation frequency spectrum of turbulent gas flow on the motion of particle phase and the influence of particles on the gas turbulent flow. In order to validate this modified model, the flow characteristics of a turbulent upward gas-solid pipe flow was studied both numerically and experimentally. Various combinations of loading and particle diameter were investigated. Velocities of both phases, turbulence intensities, and volume fraction distributions were obtained. The predictions were compared with experimental data measured by the use of a laser Doppler anemometer showing that the overall agreement is good.

Competition between thermophoretic deposition and erosion leading to appearance of steady coating

A theoretical and experimental study of two-phase flow with bimodal (“coarse” and “fine”) spherical particle distribution was carried out. Deposition of the particles onto a plate inclined at some angle to the flow direction at infinity is considered. The plate temperature being lower than that of the gas at infinity, the fine particles are thermophoretically deposited onto the plate surface and a coating accumulates on it. As the coarse particles impinge inertially upon the coating, the top layer of the latter is eroded and its thickness decreases. It is shown that the competition of these two processes (thermophoretic deposition and growth vs inertial impingement and erosion) may lead to a steady-state situation, which is of practical interest, for example, in creating a self-regulating layer on turbine blades in the polluted gas streams accompanying coal combustion.

An experimental study of two-phase flow in slightly inclined pipes—I. Flow patterns

A series of oil—air two-phase flow experiments were conducted with a 25 m long acrylic pipe installed on an inclinable trestle. Three different pipe diameters (25.8, 51.2 and 76.3 mm) at seven angles (0, ± 1, ±5 and ±9°) were studied. The fluids used were air and a light oil of 858 kg/m 3 density and 7 mPa s viscosity at an average temperature of 23°C and pressure of 230–350 kPa. The data include flow pattern observations and their transitions over a wide range of flow conditions. These data have been analyzed to test existing semi-theoretical models, and new improved models have been proposed.

An experimental study of two-phase flow in slightly inclined pipes—II. Liquid holdup and pressure drop

A series of oil—air two-phase flow experiments were conducted with a 25 m long acrylic pipe (Part I). Pressure drop and liquid holdup were found to be flow pattern dependent. Intermittent flow was the dominant flow regime in upward flow while stratified flow dominated in downward inclined pipes. For Almost all parameters in this model were calculated from first principles and an interfacial shear term was added for the gas film. This model yields excellent results even for the transition region between the intermittent and truly annular flow designated as “proto”-slug flow. A separated model has been proposed for stratified flow and homogeneous models for dispersed bubble and annular flow for predicting pressure drop and liquid holdup in inclined pipes. The results show good agreement with the experimental data.