scholarly journals Dispersed Two-Phase Flow Modelling for Nuclear Safety in the NEPTUNE_CFD Code

2017 ◽  
Vol 2017 ◽  
pp. 1-41
Author(s):  
Stephane Mimouni ◽  
William Benguigui ◽  
Solène Fleau ◽  
Arnaud Foissac ◽  
Mathieu Guingo ◽  
...  
Keyword(s):  
Power Systems ◽  
Nuclear Reactor ◽  
Thermal Power ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Vapor Condensation ◽  
Nuclear Safety ◽  
Two Phase ◽  
Boiling Crisis ◽  
Pressure Profiles

The objective of this paper is to give an overview of the capabilities of Eulerian bifluid approach to meet the needs of studies for nuclear safety regarding hydrogen risk, boiling crisis, and pipes and valves maintenance. The Eulerian bifluid approach has been implemented in a CFD code named NEPTUNE_CFD. NEPTUNE_CFD is a three-dimensional multifluid code developed especially for nuclear reactor applications by EDF, CEA, AREVA, and IRSN. The first set of models is dedicated to wall vapor condensation and spray modelling. Moreover, boiling crisis remains a major limiting phenomenon for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems. The paper aims at presenting the generalization of the previous DNB model and its validation against 1500 validation cases. The modelling and the numerical simulation of cavitation phenomena are of relevant interest in many industrial applications, especially regarding pipes and valves maintenance where cavitating flows are responsible for harmful acoustics effects. In the last section, models are validated against experimental data of pressure profiles and void fraction visualisations obtained downstream of an orifice with the EPOCA facility (EDF R&D). Finally, a multifield approach is presented as an efficient tool to run all models together.

Different Modes of Gas Entrainment Through Bottom Discharge Branch by Using Three Dimensional Particle Image Velocimetry System

2007 ◽  
Author(s):  
Wael Fairouz Saleh ◽  
Ibrahim Galal Hassan
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Structure ◽  
Particle Image ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Particle Image Velocimetry System ◽  
Three Dimension ◽  
Two Phase ◽  
Mean Velocity ◽  
Image Velocimetry

The discharge of two-phase flow from a stratified region through single or multiple branches is an important process in many industrial applications including the pumping of fluid from storage tanks, shell-and-tube heat exchangers, and the fluid flow through small breaks in cooling channels of nuclear reactors during loss-of-coolant accidents (LOCA). Knowledge of the flow phenomena involved along with the quality and mass flow rate of the discharging stream(s) is necessary to adequately predict the different phenomena associated with the process. Particle Image Velocimetry (PIV) in three dimension was used to provide detailed measurements of the flow patterns involving distributions of mean velocity, vorticity field, and flow structure. The experimental investigation was carried out to simulate two phase discharge from a stratified region through branches located on a semi-circular wall configuration during LOCA scenarios. The semi-circular test section is in close dimensional resemblance with that of a CANDU header-feeder system, with branches mounted at orientation angles of zero, 45 and 90 degrees from the horizontal. The experimental data for the phase development (mean velocity, flow structure, etc.) was done during single discharge through the bottom branch from an air/water stratified region over a three selected Froude numbers. These measurements were used to describe the effect of outlet flow conditions on phase redistribution in headers and understand the entrainment phenomena.

scholarly journals CFD Code Validation against Stratified Air-Water Flow Experimental Data

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
F. Terzuoli ◽  
M. C. Galassi ◽  
D. Mazzini ◽  
F. D'Auria
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Water Flow ◽  
Nuclear Reactor ◽  
Cold Water ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Two Phase ◽  
Code Validation

Pressurized thermal shock (PTS) modelling has been identified as one of the most important industrial needs related to nuclear reactor safety. A severe PTS scenario limiting the reactor pressure vessel (RPV) lifetime is the cold water emergency core cooling (ECC) injection into the cold leg during a loss of coolant accident (LOCA). Since it represents a big challenge for numerical simulations, this scenario was selected within the European Platform for Nuclear Reactor Simulations (NURESIM) Integrated Project as a reference two-phase problem for computational fluid dynamics (CFDs) code validation. This paper presents a CFD analysis of a stratified air-water flow experimental investigation performed at the Institut de Mécanique des Fluides de Toulouse in 1985, which shares some common physical features with the ECC injection in PWR cold leg. Numerical simulations have been carried out with two commercial codes (Fluent and Ansys CFX), and a research code (NEPTUNE CFD). The aim of this work, carried out at the University of Pisa within the NURESIM IP, is to validate the free surface flow model implemented in the codes against experimental data, and to perform code-to-code benchmarking. Obtained results suggest the relevance of three-dimensional effects and stress the importance of a suitable interface drag modelling.

A VoF-Based Consistent Mass-Momentum Transport for Two-Phase Flow Simulations

2017 ◽  
Author(s):  
Annagrazia Orazzo ◽  
Isabelle Lagrange ◽  
Jean-Luc Estivalézes ◽  
Davide Zuzio
Keyword(s):  
Density Ratio ◽  
Three Dimensional ◽  
Industrial Applications ◽  
High Density ◽  
Momentum Transport ◽  
Two Phase ◽  
Mass Fluxes ◽  
Numerical Instabilities ◽  
Density Ratios ◽  
Control Volumes

The most part of two-phase flows relevant to industrial applications is characterized by high density ratios that make numerical simulations of such kind of flows still challenging in particular when the interface assumes complex shape and is distorded by high shear. In this paper a new strategy, to overcome the numerical instabilities induced by the large densities/shears at the interface, is described for staggered cartesian grids. It consists in a consistent mass-momentum advection algorithm where mass and momentum transport equations are solved in the same control volumes. The mass fluxes are evaluated through the Volume-of-Fluid color function and directly used to calculate momentum convective term. Two and three-dimensional high-density test cases (the density ratio goes from 103 to 109) are presented. The new algorithm shows signifcantly improvements compared to standard advection methods therefore suggesting the applicability to the complete atomization process simulations.

scholarly journals Three Dimensional Imaging of Structure and Flow—Critical to Advances in Microfluidics

2007 ◽  
Vol 15 (6) ◽  
pp. 18-23
Author(s):  
Carlos Hidrovo ◽  
Terence Lundy
Keyword(s):  
Heat Transfer ◽  
Integrated Circuits ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Pem Fuel Cells ◽  
Industrial Applications ◽  
Two Phase ◽  
Microscale Heat Transfer ◽  
Flow Through ◽  
Micrometer Scale

Microfluidics, the study of fluid flow through structures with micrometer scale dimensions, is an increasingly important discipline within a number of commercial and industrial applications. One focus of active microfluidic research at the Stanford University Microscale Heat Transfer Laboratories (MHTL) is mass and heat transport in two-phase flows, which has applications in the cooling of integrated circuits and the management of water created in PEM fuel cells. At its core, two-phase microfluidics is the study of interactions between moving liquids and/or gases and/or solids (though not necessarily stationary) structures. Advanced confocal microscopy, with its ability to visualize and measure both flow and structure on a single instrumental platform, will certainly play a key role in the continuing development of microfluidic devices.

Using Scenarios to Evaluate Technology Development Options for Power Generation Equipment

2006 ◽  
Author(s):  
Flavio J. Franco
Keyword(s):  
Power Generation ◽  
Power Systems ◽  
Gas Turbines ◽  
Nuclear Reactor ◽  
Technology Development ◽  
Thermal Power ◽  
Primary Energy ◽  
Energy Sources ◽  
Power Generation Equipment

The world of power generation is currently facing a number of challenges and uncertainties, caused by technical, economic, political, geographical and social factors. Manufacturers of power generation equipment have to design their strategies for technology development taking into account these challenges and uncertainties. They have to set goals for the medium and the long term, which involve the commitment of huge amounts of resources. At the same time, given the uncertainty of the future, they have to try to reduce their risks. Scenario-Based Planning is a methodology to deal with uncertainty in making decisions for the long term. It does not tell planners what will probably happen but helps them to understand what may happen through an understanding of the relationships of cause and effect within the environment of interest. Taking gas turbines as an example, this paper shows an application of the method to the evaluation of the markets related to different primary energy sources and different technologies, within power generation scenarios given by the IEA and scenarios proposed in previous papers by the author. Although current power generation gas turbines are predominantly designed to burn natural gas, developments based on other primary energy sources will require gas turbines to run with different fuels (synthetic gas or hydrogen, for example), helium or CO2 (in high temperature nuclear reactor systems) or hot air (in hybrid solar thermal power systems). Wind power may also require backup from gas turbines, probably incorporating significant fuel flexibility. An estimate of the value of the potential markets related to these different applications of gas turbines is made in this paper. Historical and estimated experience curves for the technologies of interest and their dependence relationships are used in this analysis, with a system dynamics model as described in [1].

scholarly journals 3D gas-liquid interfaces and flow characteristics of two-phase flows in horizontal tubes

2021 ◽  
Vol 2116 (1) ◽  
pp. 012072
Author(s):  
Jingzhi Zhang ◽  
Bengt Sunden ◽  
Vishwas Wadekar ◽  
Zan Wu
Keyword(s):  
Flow Pattern ◽  
Void Fraction ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Industrial Applications ◽  
Liquid Interfaces ◽  
Two Phase Flows ◽  
Two Phase ◽  
Void Fractions

Abstract In order to investigate the characteristics of gas-liquid two-phase flows in horizontal mini circular tubes with inner diameters of 3.14 and 6.68 mm, a prism is adopted to improve the light path in the visualization experimental setup. The front and top views of air-water two-phase flow patterns in two tubes are captured synchronously based on the improved method. Three-dimensional gas-liquid interfaces, flow pattern maps, and void fraction are obtained. The experimental results show that tube diameters have significant effects on flow patterns transition lines in the flow pattern maps, but the void fractions are independent on channel sizes. The effect of gravity gradually decreases with decreasing tube diameter, while that of surface tension is enhanced. As a consequence, the proportion of annular flow in flow pattern map increases in mini tubes, while the reverse is true for the stratified flow whose proportion decreases dramatically in mini channels. The void fraction increases with increasing gas quality. Experimental void fractions obtained using the three-dimensional gas-liquid interfaces fit well with correlations in the open literature. The shape of PDF distributions varies with flow patterns, which could be used to identify flow patterns in industrial applications.

Analysis of a PHWR Outlet Feeder Vibration Due to Random Turbulence-Induced Excitation

2007 ◽  
Author(s):  
Y. Han ◽  
V. P. Janzen ◽  
B. A. W. Smith ◽  
T. Godet
Keyword(s):  
Finite Element ◽  
Nuclear Reactor ◽  
Three Dimensional ◽  
Nuclear Industry ◽  
Finite Element Code ◽  
Two Phase ◽  
Accelerated Corrosion ◽  
Beam Elements ◽  
Vibration Tests ◽  
Flow Accelerated Corrosion

A nuclear-reactor feeder pipe has been analyzed to assess its vibration and stresses due to internal coolant random turbulence-induced excitation. The structural models were created from both isoparametric beam elements and continuum elements in the finite-element code H3DMAP, a general three-dimensional mechanics analysis package developed to solve a wide variety of problems encountered in the nuclear industry. The feeder was also modelled with beam elements in VIBIC, a finite-element code designed for the vibration assessment of beam-like structures. The excitation forces were based on recent experimental results obtained from piping-vibration tests that used two-phase air/water flow, performed at E´cole Polytechnique at Montreal. Feeder vibration levels, in terms of normalized response amplitude and velocity, and normalized vibratory stresses along the feeder are predicted for the as-designed feeder and for feeders thinned by flow-accelerated corrosion.

scholarly journals Experimental Test of Properties of KCl–MgCl2 Eutectic Molten Salt for Heat Transfer and Thermal Storage Fluid in Concentrated Solar Power Systems

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Xiankun Xu ◽  
Xiaoxin Wang ◽  
Peiwen Li ◽  
Yuanyuan Li ◽  
Qing Hao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Power Systems ◽  
Molten Salt ◽  
Thermal Power ◽  
Eutectic Mixture ◽  
Thermal Storage ◽  
Strength Loss ◽  
Industrial Applications ◽  
Test Results ◽  
Salt Corrosion

The eutectic mixture of MgCl2–KCl molten salt is a high temperature heat transfer and thermal storage fluid able to be used at temperatures up to 800 °C in concentrating solar thermal power systems. The molten salt thermophysical properties are reported including vapor pressure, heat capacity, density, viscosity, thermal conductivity, and the corrosion behavior of nickel-based alloys in the molten salt corrosion at high temperatures. Correlations of the measured properties as functions of molten salt temperatures are presented for industrial applications. The test results of tensile strength of two nickel-based alloys exposed in the molten salt at a temperature of 800 °C from 1-week length to 16-week length are reported. It was found that the corrosion and strength loss is rather low when the salt is first processed to remove water and oxygen.

FMM/GPU Accelerated BEM Simulations of Emulsion Flow in Microchannels

2013 ◽  
Author(s):  
Olga A. Abramova ◽  
Yulia A. Itkulova ◽  
Nail A. Gumerov
Keyword(s):  
Oil Recovery ◽  
Large Scale ◽  
Heterogeneous Computing ◽  
Three Dimensional ◽  
Industrial Applications ◽  
Computational Techniques ◽  
Graphics Processors ◽  
Two Phase ◽  
Scalable Algorithm ◽  
Wide Range

Modeling of motion of two-phase liquids in microchannels of different shape is needed for a variety of industrial applications, such as enhanced oil recovery, advanced material processing, and biotechnology. Development of efficient computational techniques is required for understanding the mechanisms of many effects in “liquid-liquid” systems, such as the jamming of emulsion flows in microchannels and blood cell motion in capillaries. In the present study, a mathematical model of a three-dimensional flow of a mixture of two Newtonian liquids of a droplet structure in microchannels at low Reynold’s numbers is considered. The computational approach is based on the boundary element method accelerated both via an advanced scalable algorithm (FMM), and via utilization of a heterogeneous computing architecture (multicore CPUs and graphics processors). To solve large scale problems flexible GMRES solver is developed. Example computations are conducted for dynamics of many deformable drops of different sizes in microchannels. The results of simulations and accuracy/performance of the method are discussed. The developed approach can be used for solution of a wide range of problems related to emulsion flows in micro- and nanoscales.

scholarly journals Verification of three-dimensional mathematical modeling when calculating the combustion of hydrocarbon fuel in an experimental cylindrical furnace enriched with a plasma fuel system

2020 ◽  
Vol 4 (315) ◽  
pp. 96-105
Author(s):  
V. E. Messerle ◽  
◽  
S. A. Bolegenova ◽  
M. K. Bodykbayeva ◽  
A. A. Kuykabayeva ◽  
...  
Keyword(s):  
Coal Combustion ◽  
Thermal Power ◽  
Combustion Process ◽  
Three Dimensional ◽  
Thermal Characteristics ◽  
Hydrocarbon Fuel ◽  
Fuel System ◽  
Two Phase ◽  
Coal Particles ◽  
Kinetics Of

In this work, the operation of the boiler in traditional and plasma-activated conditions is investigated. To test the possibility of modeling the Cinar ICE program with an understanding of the physical mechanism of the processes of electrothermochemical fuel preparation (ETCF) and combustion, a study of coal combustion in an experimental furnace with a thermal power of 3 MW equipped with a plasma fuel system was carried out. To study the combustion process of an air mixture that had undergone preliminary plasma preparation for combustion, one-dimensional plasma-coal and three-dimensional computer programs Cinar ICE were used, which study in detail the mechanism of the kinetics of thermochemical exchange in a two-phase flow, where the plasma fuel source is located, and the exact geometry of the furnace, and the kinetics of the process сombustion of coal particles. As a result of calculations, the distribution of temperature, velocity of gas and particles in the process of ETCPT, the concentration of gas-phase mixtures, the concentration of carbon and the degree of gas contamination in the remainder of alloyed coal were determined. It was found that the plasma activation of combustion affects the thermal characteristics of the Torch, the mechanical non-combustible fuel residue and the concentration of nitrogen oxide at the outlet from the furnace. It has been proven that when simulating coal combustion, it is possible to achieve an effective description of the process using the Cinar ICE program.

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