On the Application of the Method of Landau and Lifshitz to Sonic Velocities in Homogeneous Two-Phase Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 186-188 ◽  
Author(s):  
Joseph C. Leung
Keyword(s):  
Thermal Equilibrium ◽  
Mass Fraction ◽  
Sonic Velocity ◽  
Simple Correlation ◽  
Velocity Correlation ◽  
Two Phase ◽  
Fluid Properties ◽  
Vapor Mass

A theoretical sonic velocity correlation for homogeneous two-phase mixtures under thermal equilibrium is proposed. By application of the method of Landau and Lifshitz, a dimensionless correlating parameter ω is found whereby different fluid properties and vapor mass fraction (quality) can be adequately accounted for by the simple correlation.

Numerical Modeling and Validation of Supersonic Two-Phase Flow of CO2 in Converging-Diverging Nozzles

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Miad Yazdani ◽  
Abbas A. Alahyari ◽  
Thomas D. Radcliff
Keyword(s):  
Phase Change ◽  
Velocity Model ◽  
Attractive Alternative ◽  
Sonic Velocity ◽  
Shock Train ◽  
Alternative Refrigerants ◽  
Two Phase ◽  
Expansion Waves ◽  
Fluid Properties ◽  
Layer Flow

Carbon dioxide is an attractive alternative to conventional refrigerants due to its low direct global warming effects. Unfortunately, CO2 and many alternative refrigerants have lower thermodynamic performance resulting in larger indirect emissions. The effective use of ejectors to recover part of the lost expansion work, which occurs in throttling devices, can close this performance gap and enable the use of CO2. In an ejector, the pressure of the motive fluid is converted into momentum through a choked converging-diverging nozzle, which then entrains and raises the energy of a lower-momentum suction flow. In a two-phase ejector, the motive nozzle flow is complicated by the nonequilibrium phase change affecting local sonic velocity and leading to various types of shockwaves, pseudo shocks, and expansion waves inside or outside the exit of the nozzle. Since the characteristics of the jet leaving the motive nozzle greatly affect the performance of the ejector, this paper focuses on the details of flow development and shockwave interaction within and just outside the nozzle. The analysis is based on a high-fidelity model that incorporates real-fluid properties of CO2, local mass and energy transfer between phases, and a two-phase sonic velocity model in the presence of finite-rate phase change. The model has been validated against the literature data for two-phase supersonic nozzles and overall ejector performance data. The results show that due to nonequilibrium effects and delayed phase change, the flow can choke well downstream of the minimum-area throat. In addition, Mach number profiles show that, although phase change is at a maximum near the boundaries, the flow first becomes supersonic in the interior of the flow where sound speed is lowest. Shock waves occurring within the nozzle can interact with the boundary layer flow and result in a ‘shock train’ and a sequence of subsonic and supersonic flow previously observed in single-phase nozzles. In cases with lower nozzle back pressure, the flow continues to accelerate through the nozzle and the exit pressure adjusts in a series of supersonic expansion waves.

Effect of Fluid Properties on Two-Phase Froth Characteristics

1999 ◽  
Vol 38 (10) ◽  
pp. 4110-4112 ◽  
Author(s):  
Dingwu Feng ◽  
Chris Aldrich
Keyword(s):  
Two Phase ◽  
Fluid Properties

Modeling Gas-Liquid Head Performance of Electrical Submersible Pumps

2004 ◽  
Author(s):  
Datong Sun ◽  
Mauricio Prado
Keyword(s):  
Petroleum Industry ◽  
Nuclear Industry ◽  
Two Phase ◽  
Liquid Model ◽  
Electrical Submersible Pumps ◽  
Pump Head ◽  
Fluid Properties ◽  
Interfacial Characteristic ◽  
Model Equations ◽  
Shock Loss

This study presents a new gas-liquid model to predict Electrical Submersible Pumps (ESP) head performance. The newly derived approach based on gas-liquid momentum equations along pump channels has improved the Sachdeva model [1, 2] in the petroleum industry and generalized the Minemura model [3] in the nuclear industry. The new two-phase model includes novel approaches for wall frictional losses for each phase using a gas-liquid stratified assumption and existing correlations, a new shock loss model incorporating rotational speeds, a new correlation for drag coefficient and interfacial characteristic length effects by fitting the model results with experimental data, and an algorithm to solve the model equations. The model can predict pressure and void fraction distributions along impellers and diffusers in addition to the pump head performance curve under different fluid properties, pump intake conditions, and rotational speeds.

scholarly journals A theoretical analysis of local thermal equilibrium in fibrous materials

2015 ◽  
Vol 19 (1) ◽  
pp. 69-82
Author(s):  
Mingwei Tian ◽  
Ning Pan ◽  
Lijun Qu ◽  
Xiaoqing Guo ◽  
Guangting Han
Keyword(s):  
Thermal Equilibrium ◽  
Internal Heat ◽  
Constant Heat Flux ◽  
Local Thermal Equilibrium ◽  
Transfer Model ◽  
Fibrous Materials ◽  
Two Phase ◽  
Convective Boundary ◽  
Boundary Problems ◽  
Criterion System

The internal heat exchange between each phase and the Local Thermal Equilibrium (LTE) scenarios in multi-phase fibrous materials are considered in this paper. Based on the two-phase heat transfer model, a criterion is proposed to evaluate the LTE condition, using derived characteristic parameters. Furthermore, the LTE situations in isothermal/adiabatic boundary cases with two different heat sources (constant heat flux and constant temperature) are assessed as special transient cases to test the proposed criterion system, and the influence of such different cases on their LTE status are elucidated. In addition, it is demonstrated that even the convective boundary problems can be generally estimated using this approach. Finally, effects on LTE of the material properties (thermal conductivity, volumetric heat capacity of each phase, sample porosity and pore hydraulic radius) are investigated, illustrated and discussed in our study.

Numerical Investigation on the Effect of Advanced Breakup Model on Spray Simulation of a Multi-Hole Injector

2018 ◽  
Author(s):  
Srinibas Tripathy ◽  
Sridhar Sahoo ◽  
Dhananjay Kumar Srivastava
Keyword(s):  
Mass Fraction ◽  
Gas Pressure ◽  
Gas Jet ◽  
Computational Time ◽  
Fuel Vapor ◽  
Computational Domain ◽  
Penetration Length ◽  
Spray Penetration ◽  
Ambient Gas ◽  
Vapor Mass

Computational fluid dynamics (CFD) plays a tremendous role in evaluating and visualizing the spray breakup, atomization and vaporization process. In this study, ANSYS Forte CFD tool was used to simulate the spray penetration length and spray morphology in a constant volume chamber at different grid size of a multi-hole injector. An unsteady gas jet model was coupled with Kelvin-Helmholtz (KH) and Rayleigh-Taylor (RT) model for multi-hole spray simulation. The effect of CFD cell size and ambient gas pressure on spray penetration length and spray morphology of fuel vapor mass fraction were investigated for both KH-RT and KH-RT with the unsteady gas jet model. It is found that KH-RT with the unsteady gas jet model shows mesh independent spray penetration length and spray morphology of fuel vapor mass fraction as compared to KH-RT model. This can be explained by the Lagrangian-Eulerian coupling of axial droplet-gas relative velocity is modeled on the principle of unsteady gas jet theory instead of discretizing very fine grid to the computational domain. This reduces the requirement of fine mesh near the nozzle and allows larger time step during spray injection. It is also observed that at higher ambient gas pressure, an aerodynamic force between the droplet and gas intensifies which reduces the overall spray penetration length and fuel vapor mass. The distorted spray morphology of fuel vapor mass fraction was accurately predicted at high ambient gas pressure using the KH-RT with an unsteady gas jet model which results in mesh independent drag predictions. The use of advanced spray model results in the mesh size dependency reduction and accurate drag prediction with less computational time and faster accurate solutions over all conventional spray breakup models.

scholarly journals Simulation of Surfactant Oil Recovery Processes and the Role of Phase Behaviour Parameters

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 983 ◽  
Author(s):  
Pablo Druetta ◽  
Francesco Picchioni
Keyword(s):  
Oil Recovery ◽  
Phase Behaviour ◽  
Residual Oil ◽  
Two Phase ◽  
Oil Saturation ◽  
Recovery Processes ◽  
Fluid Properties ◽  
Injection Water ◽  
Finitedifference Method

Chemical Enhanced Oil Recovery (cEOR) processes comprise a number of techniques whichmodify the rock/fluid properties in order to mobilize the remaining oil. Among these, surfactantflooding is one of the most used and well-known processes; it is mainly used to decrease the interfacialenergy between the phases and thus lowering the residual oil saturation. A novel two-dimensionalflooding simulator is presented for a four-component (water, petroleum, surfactant, salt), two-phase(aqueous, oleous) model in porous media. The system is then solved using a second-order finitedifference method with the IMPEC (IMplicit Pressure and Explicit Concentration) scheme. The oilrecovery efficiency evidenced a strong dependency on the chemical component properties and itsphase behaviour. In order to accurately model the latter, the simulator uses and improves a simplifiedternary diagram, introducing the dependence of the partition coefficient on the salt concentration.Results showed that the surfactant partitioning between the phases is the most important parameterduring the EOR process. Moreover, the presence of salt affects this partitioning coefficient, modifyingconsiderably the sweeping efficiency. Therefore, the control of the salinity in the injection water isdeemed fundamental for the success of EOR operations with surfactants.

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