Gas-Liquid Two-Phase Research Articles

English

The small or mini channel is widely adopted in compact heat exchanger in particular. In present study, the values of velocity and gas void fraction in two-phase gas-liquid flow in mini-channels were experimentally determined. The depth and width of the rectangular cross-section of the channel were 3 mm x 3 mm and 3 mm x 6 mm. The investigated flow and channel size to be applied in measurements of velocity and gas void fraction, a method based on the digital image analysis was applied. The value of gas phase velocity was defined by the values of distribution parameter C0. The relation describing the value of gas void fraction depended on the Bankoff coefficient and gas input volume fraction.

414 High-Speed Gas-Liquid Two-Phase Nozzle Flow for Carbon Dioxide

414 High-Speed Gas-Liquid Two-Phase Nozzle Flow for Carbon Dioxide

415 High-Speed Gas-Liquid Two-Phase Nozzle Flow for Carbon Dioxide

415 High-Speed Gas-Liquid Two-Phase Nozzle Flow for Carbon Dioxide

Visualization Test for Flow Field of Gas-liquid Two-phase in the Entrance of Rotodynamic Multiphase Pump

Visualization Test for Flow Field of Gas-liquid Two-phase in the Entrance of Rotodynamic Multiphase Pump

K08100 相変化を伴う気液二相流現象

K08100 相変化を伴う気液二相流現象

Application of gamma densitometry and statistical signal analysis to gas phase velocity measurements in pipeline hydrotransport

The work presents selected methods of signal analysis used in the processing of data obtained from radiometric probes. The used data came from an exemplary study of a two-phase liquid-gas flow at the laboratory installation. In such rigs many possible transport types may be observed, i.e. slug, plug and bubble flow, and each of them gives different signal-to-noise ratio of recorded data. Therefore, available radiometric methods of gas phase velocity measurements give diverse accuracies. Authors consider several improvements of data acquisition and processing which increase possibility of the flow type recognition and higher accuracy of the gas phase velocity estimation.

Two-Phase Gas-Liquid Flow Structure Characteristics under Periodic Cross Forces Action

Two-Phase Gas-Liquid Flow Structure Characteristics under Periodic Cross Forces Action

Influence of solid inclusions in liquid drops moving through a high-temperature gaseous medium on their evaporation

The influence of solid inclusions (nonmetallic particles from several tens of micrometers to several hundred micrometers in size) in liquid drops moving through hot gases on the integral characteristics of their evaporation is studied experimentally with optical techniques for diagnosing two-phase gas-liquid and vapor-liquid flows. It is found that when liquid drops less than 1 mm in size move through a hot gas flow, solid inclusions intensify the liquid evaporation.

Measurement of gas-liquid two-phase flow in micro-pipes by a capacitance sensor.

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes.

Gas–Liquid Two-Phase Flow in a Mini-Channel with Water Infiltration Continuously Along the Flow Direction

Characteristics of air–water two-phase flow pattern in a square-mini-channel were investigated experimentally. One sidewall of the flow channel was made of a permeable porous media. Air was fed into the channel from its inlet, while liquid water was injected uniformly into the channel along the permeable sidewall. Based on the results of visualization, the typical flow patterns encountered in the conventional co-current gas–liquid two-phase flow were not observed in the present work. Flow patterns of this special gas–liquid two-phase flow were catalogued, and the influence of gas flow rate and liquid infiltration rate on flow patterns was also analyzed. The results also indicate that the channel differential pressure on both sides brings obvious fluctuations when the liquid is infiltrated. The frequency of this fluctuation depends not only on the amount of liquid infiltration but also relies on the gas flow rate significantly. However, the amount of liquid infiltration barely affects the fluctuation in the amplitude of the pressure differential.

Gas–Liquid Two-Phase Flow Correction Method for Digital CMF

There are large measurement errors in Coriolis mass flowmeter (CMF) when it is used to measure gas-liquid two-phase flow without compensation. In particular, the flowtube of CMF may stall when using analog transmitters and CMF cannot operate normally because of the high damping caused by gas-liquid two-phase. To solve above problems, a gas-liquid two-phase flow rig is developed to perform the two-phase flow experiments. A digital drive method using multiplying digital-to-analog converter and direct digital synthesizer is applied to CMF to maintain the flowtube oscillation under two-phase flow condition. A digital zero-crossing detection method based on Lagrange interpolation is adopted to calculate the frequency and phase difference of the sensor output signals in order to synthesize the digital drive signal and realize the flow measurement. The artificial neural network using back propagation algorithm is applied to correct measurement errors. A digital Coriolis mass flow transmitter is developed with a digital signal processor to control the digital drive, and realize the two-phase flow measurement and correction. By connecting the developed transmitter with a CMF025 type primary instrument, the gas-liquid two-phase flow experiments are conducted to validate the performance of the transmitter. The testing results show that the transmitter can maintain the flowtube oscillation and reduce the metering errors.

Discussion: “Correlations for Prediction of Pressure Gradient of Liquid–Liquid Flow Through a Circular Horizontal Pipe” [Dasari, A., Desamala, A. B., Ghosh, U. K., Dasmahapatra, A. K., and Mandal, T. K., 2014, ASME J. Fluids Eng., 136(7), p. 071302

The comments present an assessment of formulations for frictional pressure gradient correlation of moderately viscous lubricating oil–water two-phase flow through a horizontal pipe of 0.025 m internal diameter, which was obtained by Dasari et al. [1]. Their modified Lockhart–Martinelli correlation was(1)φW2=0.019X3+0.06X2-0.006X+1.397Recently, Muzychka and Awad [2] developed an alternative approach for predicting two-phase frictional pressure gradients using superposition of three pressure gradients: single-phase liquid, single-phase gas, and interfacial pressure gradient. Muzychka and Awad [2] obtained an expression for the two-phase frictional interfacial multiplier for the liquid phase (ϕl,i2) as follows:(2)φl,i2=φl2-1-1X2From Eq. (2), it is clear that ϕl,i2 cannot be negative because their minimum values are zero, which correspond to the case of no contribution to the pressure gradient through phase interaction (i.e., (dp/dx)f,i = 0).It should be noted that the relations of two-phase frictional multiplier for liquid with higher density (water in these comments) and liquid with lower density (lubricating oil in these comments) in two-phase liquid–liquid flow are similar to the relations of two-phase frictional multiplier for liquid and gas in two-phase gas–liquid flow. The two-phase frictional multiplier concept that was introduced by Lockhart and Martinelli [3] for the case of two-phase gas–liquid flow can be used to model the flow of two immiscible liquids such as oil and water. For example, Awad and Butt [4] presented a simple semitheoretical method for calculating the two-phase frictional pressure gradient for liquid–liquid flow in pipes using asymptotic analysis. In their analysis, Awad and Butt [4] used the two-phase frictional multiplier concept that was introduced by Lockhart and Martinelli [3] for the case of two-phase gas–liquid flow to model the flow of two immiscible liquids such as oil and water.Substituting the Dasari et al. [1] correlation, Eq. (1), into the expression of for the two-phase frictional interfacial multiplier, Eq. (2), we obtain(3)φW,i2=0.019X3-0.94X2-0.006X+0.397From Eq. (3), it is clear that the Dasari et al. [1] correlation results in negative values of the two-phase frictional interfacial multiplier in the range of the Lockhart–Martinelli parameter (X) = 0.03–1. This is impossible because its minimum value is zero.Finally, it should be noted that the empirical correlation, i.e., Eq. (1), was developed by Dasari et al. [1] for the range of the Lockhart–Martinelli parameter (X) = 0.1–20, but would not be valid for X < 0.1 as shown by the authors' Eq. (2).

Investigation of Grinding Fluid Supply Parameters on Workpiece Surface Integrity

The grinding heat directly affected workpiece surface in the grinding process and it might produce some defects such as crack and burn. Meanwhile wear debris generated in the grinding process could easily embed grinding wheel blowhole and caused clogging and passivation. So it was particular important to avoid defects and improve the grinding workpiece surface integrity effectively. This paper established an incompressible turbulent fluid spray model based on the study of the existing airflow and the grinding fluid distribution in the grinding zone. Then according to different grinding fluid supply parameters established the two-phase gas liquid spray flow model by using CFD(computational fluid dynamics), simulated and calculated the model, compared the mass flow rate of the grinding fluid flow field with different spray distances, heights, speeds and spray angles in the grinding zone and determined the most reasonable spraying jet position. At the last, through researching on the workpiece surface integrity experiment, it provided an experimental basis to determine the most suitable spray jet position and verify the rationality of supply parameters selection.

Velocity measurement of two-phase liquid-gas flow in a horizontal pipeline using gamma densitometry

This paper presents application of gamma-ray absorption method to liquid-gas flow investigation in a pipeline. In the described measurement two sealed 241Am radioactive sources and probes with NaI(Tl) scintillation crystals have been used. For the analysis of digital signals provided by detectors, a traditional cross-correlation function (CCF), and modified correlation methods based on the quotient of CCF and average magnitude difference function (AMDF), as well as the quotient of CCF, and average square difference function (ASDF) have been proposed. Exemplary results of the mean velocity determination of the gaseous phase transported by a liquid in the water-air mixture flow were demonstrated and the evaluation of its uncertainty have been presented.

Void fraction prediction in two-phase flows independent of the liquid phase density changes

Gamma-ray densitometry is a frequently used non-invasive method to determine void fraction in two-phase gas liquid pipe flows. Performance of flow meters using gamma-ray attenuation depends strongly on the fluid properties. Variations of the fluid properties such as density in situations where temperature and pressure fluctuate would cause significant errors in determination of the void fraction in two-phase flows. A conventional solution overcoming such an obstacle is periodical recalibration which is a difficult task. This paper presents a method based on dual modality densitometry using Artificial Neural Network (ANN), which offers the advantage of measuring the void fraction independent of the liquid phase changes. An experimental setup was implemented to generate the required input data for training the network.ANNs were trained on the registered counts of the transmission and scattering detectors in different liquid phase densities and void fractions. Void fractions were predicted by ANNs with mean relative error of less than 0.45% in density variations range of 0.735 up to 0.98 gcm−3. Applying this method would improve the performance of two-phase flow meters and eliminates the necessity of periodical recalibration.

Influence of the initial parameters of spray water on its motion through a counter flow of high-temperature gases

The motion of spray water through a counter flow of high-temperature gases is experimentally studied on a macroscopic level using optical techniques for diagnostics of two-phase liquid-gas and vapor-liquid flows. It is found that the initial temperature, concentration of typical impurities, and dispersity of water influence the component composition of the forming gas-vapor-droplet mixture. The integral characteristics of evaporation of solitary droplets with initial sizes (conditional characteristic radii) of 3–5 mm and a spray water flow with droplets less than 0.5 mm across through a high-temperature gaseous medium are compared.

Gas-Liquid Two-Phase Flow Detection Techniques Based on Internal and External Tube Differential Pressure Flowmeter

The gas-liquid two-phase flow exists widely in nature and in our daily life, to realize the phase flow does not separate online measurement has become an important subject in the study. Through CFD simulation experiment, the optimal structure of inner and outer tube differential pressure flowmeter prototype. Through the analysis of the experimental data, comparison of the classical theoretical models found high Chishlom prediction model error is minimum. Moisture the modified model, the relative error of measurement is better than in the range of experiment 5%.

A new method for ultrasound detection of interfacial position in gas-liquid two-phase flow.

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe.

A Mathematical Model to Predict the Liquid Holdup in Vertical Slug Two-Phase Flow in Pipes

In the present work, a model to predict the liquid holdup in slug, two-phase gas-liquid, upwardly flow has been developed. This model has compared with nine published methods by using experimental tests for two types of flow systems available in the literature. The comparison achieved using the relative performance factor (FPR) which is representing an equivalent result of the most statistical tools as: error, average error and standard deviation. The results showed the best performance of the present model than the others for each system of flow separately.

Study on Flow Measurement Model of Gas-Liquid Two-Phase at Inlet of Wellhead for the Exploitation of Natural Gas Hydrate

CO2 injection is an effective method for exploitation of natural gas hydrate. The injected CO2 flow measurement at inlet of wellhead is a gas-liquid two-phase flow for the exploitation of natural gas hydrate. The numerical simulation of gas-liquid two-phase flow is carried by FLUENT software in combination with a V-cone flowmeter. The rate of flow of fluid and the turbulent kinetic energy were analyzed for V-cone flowmeter. The efflux coefficients of V-cone flowmeter are calculated for the different equivalent diameter ratio. Based on homogeneous flow model, thoughts of James and the curves of volume flow, the lasted modified model of gas-liquid two-phase flow is obtained. The relative error is only 0.35%. It is feasible to measure the flow of gas-liquid two-phase flow by the lasted modified model, which will improve the exploitation of natural gas hydrate.