scholarly journals Pressure Drop and Void Fraction in Horizontal Air–Water Stratified Flows with Smooth Interface at Atmospheric Pressure

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 101
Author(s):  
Igor Matteo Carraretto ◽  
Luigi Pietro Maria Colombo ◽  
Damiano Fasani ◽  
Manfredo Guilizzoni ◽  
Andrea Lucchini
Keyword(s):  
Pressure Gradient ◽  
Void Fraction ◽  
Fluid Model ◽  
Interfacial Shear Stress ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Two Fluid Model ◽  
Two Fluid

This work presents and analyses the results of an experimental activity aimed at the characterization of stratified air–water flow conditions, which have been poorly analyzed in previous studies although they are significant for industrial applications. Tests were performed in a 24 m long, 60 mm inner diameter PMMA pipe; the superficial velocities ranged between 0.03 m/s and 0.06 m/s for the water and between 0.41 m/s and 2.31 m/s for air. The pressure gradient along the pipeline was determined and compared to the one obtained implementing two-fluid models available in the literature. Fair agreement with the models was found only at high values of the superficial gas velocities, i.e., above 1.31 m/s. Moreover, the void fraction was measured through a resistive probe and compared with the values predicted by available models. Since none of them was able to satisfactorily predict the void fraction in the whole range of superficial velocities, a drift flux model was successfully implemented. Eventually, with both the measured pressure gradient and the void fraction, a two-fluid model was implemented in order to determine the interfacial shear stress and to compare the outcome with the literature, emphasizing the influence of the operating conditions on the prediction performance.

Two-group drift-flux model for closure of the modified two-fluid model

2012 ◽  
Vol 37 ◽  
pp. 196-208 ◽  
Author(s):  
Caleb S. Brooks ◽  
Sidharth S. Paranjape ◽  
Basar Ozar ◽  
Takashi Hibiki ◽  
Mamoru Ishii
Keyword(s):  
Fluid Model ◽  
Drift Flux Model ◽  
Drift Flux ◽  
Flux Model ◽  
Two Fluid Model ◽  
Two Fluid

Numerical Simulation of Boiling Two-Phase Flow in Tight-Lattice Rod Bundle by 3-Dimensional Two-Fluid Model Code ACE-3D

2008 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Takeharu Misawa ◽  
Kazuyuki Takase
Keyword(s):  
Void Fraction ◽  
Lift Force ◽  
Fluid Model ◽  
Phase Flow ◽  
Two Phase ◽  
Rod Bundle ◽  
Fraction Distribution ◽  
Two Fluid Model ◽  
Tight Lattice ◽  
Two Fluid

Two-fluid model can simulate two phase flow less computational cost than inter-face tracking method and particle interaction method. Therefore, two-fluid model is useful for thermal hydraulic analysis in large-scale domain such as a rod bundle. Japan Atomic Energy Agency (JAEA) develops three dimensional two-fluid model analysis code ACE-3D, which adopts boundary fitted coordinate system in order to simulate complex shape channel flow. In this paper, boiling two-phase flow analysis in a tight lattice rod bundle is performed by ACE-3D code. The parallel computation using 126CPUs is applied to this analysis. In the results, the void fraction, which distributes in outermost region of rod bundle, is lower than that in center region of rod bundle. At height z = 0.5 m, void fraction in the gap region is higher in comparison with that in center region of the subchannel. However, at height of z = 1.1m, higher void fraction distribution exists in center region of the subchannel in comparison with the gap region. The tendency of void fraction to concentrate in the gap region at vicinity of boiling starting point, and to move into subchannel as water goes through rod bundle, is qualitatively agreement with the measurement results by neutron radiography. To evaluate effects of two-phase flow model used in ACE-3D code, numerical simulation of boiling two-phase in tight lattice rod bundle with no lift force model (neglecting lift force acting on bubbles) is also performed. From the comparison of numerical results, it is concluded that the effects of lift force model are not so large on overall void fraction distribution in tight lattice rod bundle. However, higher void fraction distribution in center region of the subchannel was not observed in this simulation. It is concluded that the lift force model is important for local void fraction distribution in rod bundles.

Prediction of Parameters Distribution of Upward Boiling Two-Phase Flow With Two-Fluid Models

2002 ◽  
Author(s):  
Wei Yao ◽  
Christophe Morel
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Constitutive Relations ◽  
Turbulent Dispersion ◽  
Dispersion Force ◽  
Liquid Temperature ◽  
Two Phase ◽  
Radial Profiles ◽  
Two Fluid Model ◽  
Two Fluid

In this paper, a multidimensional two-fluid model with additional turbulence k–ε equations is used to predict the two-phase parameters distribution in freon R12 boiling flow. The 3D module of the CATHARE code is used for numerical calculation. The DEBORA experiment has been chosen to evaluate our models. The radial profiles of the outlet parameters were measured by means of an optical probe. The comparison of the radial profiles of void fraction, liquid temperature, gas velocity and volumetric interfacial area at the end of the heated section shows that the multidimensional two-fluid model with proper constitutive relations can yield reasonably predicted results in boiling conditions. Sensitivity tests show that the turbulent dispersion force, which involves the void fraction gradient, plays an important role in determining the void fraction distribution; and the turbulence eddy viscosity is a significant factor to influence the liquid temperature distribution.

CFD Simulation of PWR Subchannel Void Distribution Benchmark

2010 ◽  
Author(s):  
Wang-Kee In ◽  
Chang-Hwan Shin ◽  
Tae-Hyun Chun
Keyword(s):  
Void Fraction ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Small Diameter ◽  
Operating Conditions ◽  
Heated Wall ◽  
Bubble Generation ◽  
Void Distribution ◽  
Wide Range ◽  
Two Fluid Model

A CFD study was performed to simulate the steady-state void distribution benchmark based on the NUPEC PWR Subchannel and Bundle Tests (PSBT). The void distribution benchmark provides measured void fraction data over a wide range of geometrical and operating conditions in a single subchannel and fuel bundle. This CFD study simulated the boiling flow in a single subchannel. A CFD code was used to predict the void distribution inside the single subchannel. The multiphase flow model used in this CFD analysis was a two-fluid model in which liquid (water) and vapor (steam) were considered as continuous and dispersed fluids, respectively. A wall boiling model was also employed to simulate bubble generation on a heated wall surface. The CFD prediction with a small diameter of vapor bubble shows a higher void fraction near the heated wall and a migration of void in the subchannel gap region. A measured CT image of void distribution indicated a locally higher void fraction near the heated wall for the test conditions of a subchannel averaged void fraction of less than about 20%. The CFD simulation predicted a subchannel averaged void fraction and fluid density which agree well with the measured ones for a low void condition.

Effect of void fraction covariance on two-fluid model based code calculation in pipe flow

2018 ◽  
Vol 108 ◽  
pp. 319-333 ◽  
Author(s):  
Tetsuhiro Ozaki ◽  
Takashi Hibiki ◽  
Shuichiro Miwa ◽  
Michitsugu Mori
Keyword(s):  
Void Fraction ◽  
Pipe Flow ◽  
Fluid Model ◽  
Model Based ◽  
Two Fluid Model ◽  
Two Fluid

Simulation Study of Gas-Solid Macro-Mixing Characterization in Small Fixed-Fluidized Bed Reactor

2011 ◽  
Vol 236-238 ◽  
pp. 1537-1545
Author(s):  
Wen Jing Liu ◽  
Hui Zhao ◽  
Chao He Yang ◽  
Hong Hong Shan
Keyword(s):  
Fluidized Bed ◽  
Raw Materials ◽  
Fluid Model ◽  
Structural Parameters ◽  
Flow Behavior ◽  
Fluidized Bed Reactor ◽  
Operating Conditions ◽  
Laboratory Evaluation ◽  
Two Fluid Model ◽  
Two Fluid

In fixed-fluidized bed reactor, laboratory evaluation of different catalyst, raw materials and process parameters can be implemented, so it has wide applications in the refining process. In this study, we focused on small fixed-fluidized bed reactor, using Eulerian-Eulerian two-fluid model, simulated the gas-solid flow behavior in it. Gas residence time distribution was measured in order to characterize macro-mixing. At the same time, by changing the reactor structure and operating conditions, we studied their effects on gas-solid macro-mixing characterization. The results show that the effects of structural parameters are larger than operating conditions, and different parameters have different effects. Different parameters can be adjusted to change the gas-solid macro-mixing characterization in small fixed-fluidized bed reactor. Therefore, the small fixed-fluidized bed reactor can provide better results in more application areas.

An Investigation of the Propagation of Pressure Perturbations in Bubbly Air/Water Flows

1988 ◽  
Vol 110 (2) ◽  
pp. 494-499 ◽  
Author(s):  
A. E. Ruggles ◽  
R. T. Lahey ◽  
D. A. Drew ◽  
H. A. Scarton
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Propagation Speed ◽  
Water Mixture ◽  
Volume Coefficient ◽  
Two Fluid Model ◽  
Pressure Perturbations ◽  
Dispersion And Attenuation ◽  
Range Of Values ◽  
Two Fluid

Dispersion and attenuation was measured for standing waves in a vertical waveguide filled with a bubbly air/water mixture. The propagation speed of pressure pulses was also measured. The data were compared with a two-fluid model for a range of values of the virtual volume coefficient, CVM. The experimentally determined CVM was found to be a function of global void fraction (〈α〉). Moreover it was noted that this CVM was less strongly related to void fraction than those proposed by Zuber (1964) and Van Wijngaarden (1976).

Sign in / Sign up

Export Citation Format

Share Document