Oostrom, M.; Zhong, L.; Wietsma, T.; Covert, M.
2007-12-01
Multifluid relative permeability - saturation - capillary pressure (k-S-P) empirical constitutive models are components of numerical simulators that are used to predict fluid distributions following a nonaqueous phase liquid (NAPL) contamination event or during remediation. The S-P parameter values for these empirical models are either obtained from the literature or determined experimentally by fitting the models to measured data. Most of the experimental emphasis so far has been on testing the S-P component of the k-S-P constitutive relations. Due to the difficulties in obtaining quality relative permeability laboratory data for multiphase systems, testing of the k-S models that are used in multifluid flow simulators has been virtually non-existent. A new tool, the Multiple Location Saturation Pressure Apparatus (MLSPA), located in PNNL's EMSL Subsurface Flow and Transport Laboratory, has been developed to obtain data sets that can be used to test both S-P and k-S relationships for two-phase NAPL-water systems. The MLSPA is a long column (~1 m) equipped with several hydrophilic and hydrophobic pressure transducers. Fluid saturations are determined along the length of a column using a dual-energy gamma radiation system. Although the MLSPA is limited to porous media with a relatively small entry pressure and fairly homogeneous pore-size distributions, it offers the distinct advantage of obtaining S-P data at multiple locations. Besides for static determinations of S-P relations, the MLSPA offers the benefit that it can be used for more dynamic experiments where fluid pressures are changed more rapidly. The data sets produced by the dynamic experiments can be used in relative permeability models. Results of several experiments with crude-oil brine systems will be presented.
International Nuclear Information System (INIS)
Chu, W.; Dhir, V.K.; Marshall, J.
1983-01-01
An experimental investigation of two phase flow through porous layers formed of non-heated glass particles (nominal diameter 1 to 6 mm) has been made. Particulate bed depths of 30 cm and 70 cm were used. The effect of particle size, particle size distribution and bed porosity on void fraction and pressure drop through a particulate bed formed in a cylindrical test section has been investigated. The superficial velocity of liquid (water) is varied from 1.83 to 18.3 mm/s while the superficial velocity of gas (air) is varied from 0 to 68.4 mm/s. These superficial velocities were chosen so that pressure drop and void fraction measurement could be made for the porous layer in fixed and fluidized states. A model based on drift flux approach has been developed for the void fraction. Using the two phase friction pressure drop data, the relative permeabilities of the two phases have been concluded with void fraction. The void fraction and two phase friction pressure gradient in beds composed of mixtures of spherical particles as well as sharps of different nominal sizes have also been examined. It is found that the models for single size particles are also applicable to mixtures of particles if a mean particle diameter for the mixture is defined
Some issues in the simulation of two-phase flows: The relative velocity
International Nuclear Information System (INIS)
Gräbel, J.; Hensel, S.; Ueberholz, P.; Farber, P.; Zeidan, D.
2016-01-01
In this paper we compare numerical approximations for solving the Riemann problem for a hyperbolic two-phase flow model in two-dimensional space. The model is based on mixture parameters of state where the relative velocity between the two-phase systems is taken into account. This relative velocity appears as a main discontinuous flow variable through the complete wave structure and cannot be recovered correctly by some numerical techniques when simulating the associated Riemann problem. Simulations are validated by comparing the results of the numerical calculation qualitatively with OpenFOAM software. Simulations also indicate that OpenFOAM is unable to resolve the relative velocity associated with the Riemann problem.
Some issues in the simulation of two-phase flows: The relative velocity
Energy Technology Data Exchange (ETDEWEB)
Gräbel, J.; Hensel, S.; Ueberholz, P.; Farber, P. [Niederrhein University of Applied Sciences, Institute for Modelling and High Performance Computing, Reinarzstraße 49, 47805 Krefeld (Germany); Zeidan, D. [School of Basic Sciences and Humanities, German Jordanian University, Amman (Jordan)
2016-06-08
In this paper we compare numerical approximations for solving the Riemann problem for a hyperbolic two-phase flow model in two-dimensional space. The model is based on mixture parameters of state where the relative velocity between the two-phase systems is taken into account. This relative velocity appears as a main discontinuous flow variable through the complete wave structure and cannot be recovered correctly by some numerical techniques when simulating the associated Riemann problem. Simulations are validated by comparing the results of the numerical calculation qualitatively with OpenFOAM software. Simulations also indicate that OpenFOAM is unable to resolve the relative velocity associated with the Riemann problem.
Measurement of average density and relative volumes in a dispersed two-phase fluid
Sreepada, Sastry R.; Rippel, Robert R.
1992-01-01
An apparatus and a method are disclosed for measuring the average density and relative volumes in an essentially transparent, dispersed two-phase fluid. A laser beam with a diameter no greater than 1% of the diameter of the bubbles, droplets, or particles of the dispersed phase is directed onto a diffraction grating. A single-order component of the diffracted beam is directed through the two-phase fluid and its refraction is measured. Preferably, the refracted beam exiting the fluid is incident upon a optical filter with linearly varing optical density and the intensity of the filtered beam is measured. The invention can be combined with other laser-based measurement systems, e.g., laser doppler anemometry.
Models for assessing the relative phase velocity in a two-phase flow. Status report
International Nuclear Information System (INIS)
Schaffrath, A.; Ringel, H.
2000-06-01
The knowledge of slip or drift flux in two phase flow is necessary for several technical processes (e.g. two phase pressure losses, heat and mass transfer in steam generators and condensers, dwell period in chemical reactors, moderation effectiveness of two phase coolant in BWR). In the following the most important models for two phase flow with different phase velocities (e.g. slip or drift models, analogy between pressure loss and steam quality, ε - ε models and models for the calculation of void distribution in reposing fluids) are classified, described and worked up for a further comparison with own experimental data. (orig.)
Relations between the kinetic equation and the Langevin models in two-phase flow modelling
International Nuclear Information System (INIS)
Minier, J.P.; Pozorski, J.
1997-05-01
The purpose of this paper is to discuss PDF and stochastic models which are used in two-phase flow modelling. The aim of the present analysis is essentially to try to determine relations and consistency between different models. It is first recalled that different approaches actually correspond to PDF models written either in terms of the process trajectories or in terms of the PDF itself. The main difference lies in the choice of the independent variables which are retained. Two particular models are studied, the Kinetic Equation and the Langevin Equation model. The latter uses a Langevin equation to model the fluid velocities seen along particle trajectories. The Langevin model is more general since it contains an additional variable. It is shown that, in certain cases, this variable can be summed up exactly to retrieve the Kinetic Equation model as a marginal PDF. A joint fluid and solid particle PDF which includes the characteristics of both phases is proposed at the end of the paper. (author)
International Nuclear Information System (INIS)
Hsu, Y.Y.
1974-01-01
The following papers related to two-phase flow are summarized: current assumptions made in two-phase flow modeling; two-phase unsteady blowdown from pipes, flow pattern in Laval nozzle and two-phase flow dynamics; dependence of radial heat and momentum diffusion; transient behavior of the liquid film around the expanding gas slug in a vertical tube; flooding phenomena in BWR fuel bundles; and transient effects in bubble two-phase flow. (U.S.)
Zhao, Jianlin; Kang, Qinjun; Yao, Jun; Viswanathan, Hari; Pawar, Rajesh; Zhang, Lei; Sun, Hai
2018-02-01
Relative permeability is a critical parameter characterizing multiphase flow in porous media and it is strongly dependent on the wettability. In many situations, the porous media are nonuniformly wet. To investigate the effect of wettability heterogeneity on relative permeability of two-phase flow in porous media, a multi-relaxation-time color-gradient lattice Boltzmann model is adopted to simulate oil/water two-phase flow in porous media with different oil-wet solid fractions. For the water phase, when the water saturation is high, the relative permeability of water increases with the increase of oil-wet solid fraction under a constant water saturation. However, as the water saturation decreases to an intermediate value (about 0.4-0.7), the relative permeability of water in fractionally wet porous media could be lower than that in purely water-wet porous media, meaning additional flow resistance exists in the fractionally wet porous media. For the oil phase, similar phenomenon is observed. This phenomenon is mainly caused by the wettability-related microscale fluid distribution. According to both our simulation results and theoretical analysis, it is found that the relative permeability of two-phase flow in porous media is strongly related to three parameters: the fluid saturation, the specific interfacial length of fluid, and the fluid tortuosity in the flow direction. The relationship between the relative permeability and these parameters under different capillary numbers is explored in this paper.
Generalized nonequilibrium capillary relations for two-phase flow through heterogeneous media.
Amaziane, Brahim; Milišić, Josipa Pina; Panfilov, Mikhail; Pankratov, Leonid
2012-01-01
For two-phase flow in porous media, the natural medium heterogeneity necessarily gives rise to capillary nonequilibrium effects. The relaxation to the equilibrium is a slow process which should be introduced in macroscopic flow models. Many nonequilibrium models are based on a phenomenological approach. At the same time there exists a rigorous mathematical way to develop the nonequilibrium equations. Its formalism, developed by Bourgeat and Panfilov [Computational Geosciences 2, 191 (1998)], is based on the homogenization of the microscale flow equations over medium heterogeneities. In contrast with the mentioned paper, in which the case of a sufficiently fast relaxation was analyzed, we consider the case of long relaxation, which leads to the appearance of long-term memory on the macroscale. Due to coupling between the nonlinearity and nonlocality in time, the macroscopic model remains, however, incompletely homogenized, in the general case. At the same time, frequently only the relationship for the nonequilibrium capillary pressure is of interest for applications. In the present paper, we obtain such an exact relationship in two different independent forms for the case of long-term memory. This relationship is more general than that obtained by Bourgeat and Panfilov. In addition, we prove the comparison theorem which determines the upper and lower bounds for the macroscopic model. These bounds represent linear flow models, which are completely homogenized. The results obtained are illustrated by numerical simulations.
Rand, Miya K; Shimansky, Yury P
2013-09-01
In the companion paper utilizing a quantitative model of optimal motor coordination (Part I, Rand and Shimansky, in Exp Brain Res 225:55-73, 2013), we examined coordination between X and Y movement directions (XYC) during reaching movements performed under three prescribed speeds, two movement amplitudes, and two target sizes. The obtained results indicated that the central nervous system (CNS) utilizes a two-phase strategy, where the initial and the final phases correspond to lower and higher precision of information processing, respectively, for controlling goal-directed reach-type movements to optimize the total cost of task performance including the cost of neural computations. The present study investigates how two different well-known concepts used for describing movement performance relate to the concepts of optimal XYC and two-phase control strategy. First, it is examined to what extent XYC is equivalent to movement trajectory straightness. The data analysis results show that the variability, the movement trajectory's deviation from the straight line, increases with an increase in prescribed movement speed. In contrast, the dependence of XYC strength on movement speed is opposite (in total agreement with an assumption of task performance optimality), suggesting that XYC is a feature of much higher level of generality than trajectory straightness. Second, it is tested how well the ballistic and the corrective components described in the traditional concept of two-component model of movement performance match with the initial and the final phase of the two-phase control strategy, respectively. In fast reaching movements, the percentage of trials with secondary corrective submovement was smaller under larger-target shorter-distance conditions. In slower reaching movements, meaningful parsing was impossible due to massive fluctuations in the kinematic profile throughout the movement. Thus, the parsing points determined by the conventional submovement analysis
Bianchi Janetti, Emanuela; Riva, Monica; Guadagnini, Alberto
2017-04-01
We study the relative role of the complex pore space geometry and wettability of the solid matrix on the quantification of relative permeabilities characterizing steady state immiscible two-phase flow in porous media. We do so by considering elementary cells, which are typically employed in upscaling frameworks based on, e.g., homogenization or volume averaging. In this context one typically relies on the solution of pore-scale physics at a scale which is much smaller than that of an investigated porous system. Pressure-driven two-phase flow following simultaneous co-current injection of water and oil is numerically solved for a suite of regular and stochastically generated two-dimensional explicit elementary cells with fixed porosity and sharing main topological/morphological features. We show that relative permeabilities of the randomly generated elementary cells are significantly influenced by the formation of preferential percolation paths (principal pathways), giving rise to a strongly nonuniform distribution of fluid fluxes. These pathways are a result of the spatially variable resistance that the random pore structures exert on the fluid. The overall effect on relative permeabilities of the diverse organization of principal pathways, as driven by a given random realization at the scale of the unit cell, is significantly larger than that of the wettability of the host rock. In contrast to what can be observed for the random cells analyzed, relative permeabilities of regular cells display a clear trend with contact angle at the investigated scale. Our findings suggest the need to perform systematic upscaling studies in a stochastic context, to propagate the effects of uncertain pore space geometries to a probabilistic description of relative permeability curves at the continuum scale.
International Nuclear Information System (INIS)
Shin, Y.W.; Wiedermann, A.H.
1984-02-01
A method was published, based on the integral method of characteristics, by which the junction and boundary conditions needed in computation of a flow in a piping network can be accurately formulated. The method for the junction and boundary conditions formulation together with the two-step Lax-Wendroff scheme are used in a computer program; the program in turn, is used here in calculating sample problems related to the blowdown transient of a two-phase flow in the piping network downstream of a PWR pressurizer. Independent, nearly exact analytical solutions also are obtained for the sample problems. Comparison of the results obtained by the hybrid numerical technique with the analytical solutions showed generally good agreement. The good numerical accuracy shown by the results of our scheme suggest that the hybrid numerical technique is suitable for both benchmark and design calculations of PWR pressurizer blowdown transients
Xie, Jian.-Fei.; He, S.; Zu, Y. Q.; Lamy-Chappuis, B.; Yardley, B. W. D.
2017-08-01
In this paper, the migration of supercritical carbon dioxide (CO2) in realistic sandstone rocks under conditions of saline aquifers, with applications to the carbon geological storage, has been investigated by a two-phase lattice Boltzmann method (LBM). Firstly the digital images of sandstone rocks were reproduced utilizing the X-ray computed microtomography (micro-CT), and high resolutions (up to 2.5 μm) were applied to the pore-scale LBM simulations. For the sake of numerical stability, the digital images were "cleaned" by closing the dead holes and removing the suspended particles in sandstone rocks. In addition, the effect of chemical reactions occurred in the carbonation process on the permeability was taken into account. For the wetting brine and non-wetting supercritical CO2 flows, they were treated as the immiscible fluids and were driven by pressure gradients in sandstone rocks. Relative permeabilities of brine and supercritical CO2 in sandstone rocks were estimated. Particularly the dynamic saturation was applied to improve the reliability of the calculations of the relative permeabilities. Moreover, the effects of the viscosity ratio of the two immiscible fluids and the resolution of digital images on the relative permeability were systematically investigated.
Varseev, E.
2017-11-01
The present work is dedicated to verification of numerical model in standard solver of open-source CFD code OpenFOAM for two-phase flow simulation and to determination of so-called “baseline” model parameters. Investigation of heterogeneous coolant flow parameters, which leads to abnormal friction increase of channel in two-phase adiabatic “water-gas” flows with low void fractions, presented.
International Nuclear Information System (INIS)
Olive, J.
1990-01-01
The design, operation and safety of nuclear components requires increasingly accurate knowledge of two-phase flows. This knowledge is also necessary for some studies related to electricity applications. The author presents some concrete examples showing the range of problems and the complexity of the phenomena involved in these types of flows. Then, the basic principles of their numerical modelling are explained, as well as the new tendency to use increasingly local and refined models. The newest computer codes developed at EDF are briefly presented. Experimental studies dealing with twophase flow are also referred to, and their connections to numerical modelling are explained. Emphasis is placed on the major efforts devoted to the development of new test rigs and instrumentation [fr
Ahmad, Zahoor; Hanif, Muhammad
2013-01-01
The development of estimators of population parameters based on two-phase sampling schemes has seen a dramatic increase in the past decade. Various authors have developed estimators of population using either one or two auxiliary variables. The present volume is a comprehensive collection of estimators available in single and two phase sampling. The book covers estimators which utilize information on single, two and multiple auxiliary variables of both quantitative and qualitative nature. Th...
International Nuclear Information System (INIS)
Botelho, David A.; Faccini, Jose L.H.
2002-01-01
The main topic in this paper is a new device being considered to improve nuclear reactor safety employing the natural circulation. A scaled experiment used to demonstrate the performance of the device is also described. We also applied a similarity analysis method for single and two-phase natural convection loop flow to the IEN CCN experiment and to an APEX like experiment to verify the degree of similarity relative to a full-scale prototype like the AP600. Most of the CCN similarity numbers that represent important single and two-phase similarity conditions are comparable to the APEX like loop non-dimensional numbers calculated employing the same methodology. Despite the much smaller geometric, pressure, and power scales, we conclude that the IEN CCN has single and two-phase natural circulation similarity numbers that represent fairly well the full-scale prototype. even lacking most complementary primary and safety systems, this IEN circuit provided a much valid experience to develop human, experimental, and analytical resources, besides its utilization as a training tool. (author)
Sample problem calculations related to two-phase flow transients in a PWR relief-piping network
International Nuclear Information System (INIS)
Shin, Y.W.; Wiedermann, A.H.
1981-03-01
Two sample problems related with the fast transients of water/steam flow in the relief line of a PWR pressurizer were calculated with a network-flow analysis computer code STAC (System Transient-Flow Analysis Code). The sample problems were supplied by EPRI and are designed to test computer codes or computational methods to determine whether they have the basic capability to handle the important flow features present in a typical relief line of a PWR pressurizer. It was found necessary to implement into the STAC code a number of additional boundary conditions in order to calculate the sample problems. This includes the dynamics of the fluid interface that is treated as a moving boundary. This report describes the methodologies adopted for handling the newly implemented boundary conditions and the computational results of the two sample problems. In order to demonstrate the accuracies achieved in the STAC code results, analytical solutions are also obtained and used as a basis for comparison
Karlsson, Oskar; Colombo, Giancarlo
2015-01-01
Background There is a growing consensus that similar neural mechanisms are involved in the reinforcing properties of natural rewards, like food and sex, and drugs of abuse. Rat lines selectively bred for high and low oral alcohol intake and preference have been useful for understanding factors contributing to excessive alcohol intake and may constitute proper animal models for investigating the neurobiological basis of natural rewarding stimuli. Methods The present study evaluated copulatory behavior in alcohol and sexually naïve Sardinian alcohol-preferring (sP) and -nonpreferring (sNP) male rats in three consecutive copulatory behavior tests. Results The main finding was that, under the conditions used in this study, sNP rats were sexually inactive relative to sP rats. To gain more information about the sexual behavior in sP rats, Wistar rats were included as an external reference strain. Only minor differences between sP and Wistar rats were revealed. Conclusions The reason behind the low copulatory activity of sNP rats remains to be elucidated, but may in part be mediated by innate differences in brain transmitter systems. The comparison between sP and Wistar rats may also suggest that the inherent proclivity to excessive alcohol drinking in sP rats may mainly be dependent on its anxiolytic properties, as previously proposed, and not changes in the reward system. PMID:25728453
Indian Academy of Sciences (India)
Home; Journals; Bulletin of Materials Science. S P Sen Gupta. Articles written in Bulletin of Materials Science. Volume 24 Issue 2 April 2001 pp 173-180. Particle fracture and plastic deformation in vanadium pentoxide powders induced by high energy vibrational ball-mill · Partha Chatterjee S P Sen Gupta Suchitra Sen.
Indian Academy of Sciences (India)
Home; Journals; Sadhana. S P Panda. Articles written in Sadhana. Volume 40 Issue 1 February 2015 pp 89-106 Electrical and Computer Sciences. Experimental validation of waveform relaxation technique for power system controller testing · S P Panda K A Salunkhe A M Kulkarni · More Details Abstract Fulltext PDF.
International Nuclear Information System (INIS)
Delaje, Dzh.
1984-01-01
General hypothesis used to simplify the equations, describing two-phase flows, are considered. Two-component and one-component models of two-phase flow, as well as Zuber and Findlay model for actual volumetric steam content, and Wallis model, describing the given phase rates, are presented. The conclusion is made, that the two-component model, in which values averaged in time are included, is applicable for the solving of three-dimensional tasks for unsteady two-phase flow. At the same time, using the two-component model, including values, averaged in space only one-dimensional tasks for unsteady two-phase flow can be solved
Rand, Miya K; Shimansky, Yury P
2013-03-01
A quantitative model of optimal transport-aperture coordination (TAC) during reach-to-grasp movements has been developed in our previous studies. The utilization of that model for data analysis allowed, for the first time, to examine the phase dependence of the precision demand specified by the CNS for neurocomputational information processing during an ongoing movement. It was shown that the CNS utilizes a two-phase strategy for movement control. That strategy consists of reducing the precision demand for neural computations during the initial phase, which decreases the cost of information processing at the expense of lower extent of control optimality. To successfully grasp the target object, the CNS increases precision demand during the final phase, resulting in higher extent of control optimality. In the present study, we generalized the model of optimal TAC to a model of optimal coordination between X and Y components of point-to-point planar movements (XYC). We investigated whether the CNS uses the two-phase control strategy for controlling those movements, and how the strategy parameters depend on the prescribed movement speed, movement amplitude and the size of the target area. The results indeed revealed a substantial similarity between the CNS's regulation of TAC and XYC. First, the variability of XYC within individual trials was minimal, meaning that execution noise during the movement was insignificant. Second, the inter-trial variability of XYC was considerable during the majority of the movement time, meaning that the precision demand for information processing was lowered, which is characteristic for the initial phase. That variability significantly decreased, indicating higher extent of control optimality, during the shorter final movement phase. The final phase was the longest (shortest) under the most (least) challenging combination of speed and accuracy requirements, fully consistent with the concept of the two-phase control strategy. This paper
Thermo-fluid dynamics of two-phase flow
Ishii, Mamoru; Ishii, Mamoru; Ishii, M
2006-01-01
Provides a very systematic treatment of two phase flow problems from a theoretical perspectiveProvides an easy to follow treatment of modeling and code devlopemnt of two phase flow related phenomenaCovers new results of two phase flow research such as coverage of fuel cells technology.
Song, Jinxi; Yang, Xiaogang; Zhang, Junlong; Long, Yongqing; Zhang, Yan; Zhang, Taifan
2015-01-01
Accurate estimation of the variability of heavy metals in river water and the hyporheic zone is crucial for pollution control and environmental management. The biotoxicities and potential ecological risks of heavy metals (Cu, Zn, Pb, Cd) in a solid-liquid two-phase system were estimated using the Geo-accumulation Index, Potential Ecological Risk Assessment and Quality Standard Index methods in the Weihe River of Shaanxi Province, China. Water and sediment samples were collected from five study sites during spring, summer and winter, 2013. The dominant species in the streambed sediments were chironomids and flutter earthworm, whose bioturbation mainly ranged from 0 to 20 cm. The concentrations of heavy metals in surface water and pore water varied obviously in spring and summer. The degrees of concentration of Cu and Cd in spring and summer were higher than the U.S. water quality Criteria Maximum Concentrations. Furthermore, the biotoxicities of Pb and Zn demonstrated season-spatial variations. The concentrations of Cu, Zn, Pb and Cd in spring and winter were significantly higher than those in summer, and the pollution levels also varied obviously in different layers of the sediments. Moreover, the pollution level of Cd was the most serious, as estimated by all three assessment methods. PMID:26193293
Nonlinear dynamics of two-phase flow
International Nuclear Information System (INIS)
Rizwan-uddin
1986-01-01
Unstable flow conditions can occur in a wide variety of laboratory and industry equipment that involve two-phase flow. Instabilities in industrial equipment, which include boiling water reactor (BWR) cores, steam generators, heated channels, cryogenic fluid heaters, heat exchangers, etc., are related to their nonlinear dynamics. These instabilities can be of static (Ledinegg instability) or dynamic (density wave oscillations) type. Determination of regions in parameters space where these instabilities can occur and knowledge of system dynamics in or near these regions is essential for the safe operation of such equipment. Many two-phase flow engineering components can be modeled as heated channels. The set of partial differential equations that describes the dynamics of single- and two-phase flow, for the special case of uniform heat flux along the length of the channel, can be reduced to a set of two coupled ordinary differential equations [in inlet velocity v/sub i/(t) and two-phase residence time tau(t)] involving history integrals: a nonlinear ordinary functional differential equation and an integral equation. Hence, to solve these equations, the dependent variables must be specified for -(nu + tau) ≤ t ≤ 0, where nu is the single-phase residence time. This system of nonlinear equations has been solved analytically using asymptotic expansion series for finite but small perturbations and numerically using finite difference techniques
Two-phase flow in fractured rock
International Nuclear Information System (INIS)
Davies, P.; Long, J.; Zuidema, P.
1993-11-01
This report gives the results of a three-day workshop on two-phase flow in fractured rock. The workshop focused on two-phase flow processes that are important in geologic disposal of nuclear waste as experienced in a variety of repository settings. The goals and objectives of the workshop were threefold: exchange information; describe the current state of understanding; and identify research needs. The participants were divided into four subgroups. Each group was asked to address a series of two-phase flow processes. The following groups were defined to address these processes: basic flow processes; fracture/matrix interactions; complex flow processes; and coupled processes. For each process, the groups were asked to address these four issues: (1) describe the two-phase flow processes that are important with respect to repository performance; (2) describe how this process relates to the specific driving programmatic issues given above for nuclear waste storage; (3) evaluate the state of understanding for these processes; and (4) suggest additional research to address poorly understood processes relevant to repository performance. The reports from each of the four working groups are given here
International Nuclear Information System (INIS)
Boure, J.A.
1974-12-01
Two-phase flow instabilities are classified according to three criteria: the static or dynamic nature of the phenomenon, the necessity or not of a triggering phenomenon, and the pure or compound character of the phenomenon. Tables give the elementary instability phenomena, and the practical types of instability. Flow oscillations (or dynamic instabilities) share a number of characteristics which are dealt with, they are caused by the dynamic interactions between the flow parameters (flow rate, density, pressure, enthalpy and their distributions). Oscillation types are discussed: pure oscillations are density wave oscillations, acoustic oscillations may also occur, various compound oscillations involve either the density wave or the acoustic wave mechanism, interacting with some of the boundary conditions in the device. The analysis of slow oscillations has been made either by means of a simplified model (prediction of the thresholds) or of computer codes. Numerous computer codes are available [fr
Two phase titanium aluminide alloy
Deevi, Seetharama C.; Liu, C. T.
2001-01-01
A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.
Apparatus for monitoring two-phase flow
Sheppard, John D.; Tong, Long S.
1977-03-01
A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.
Apparatus for monitoring two-phase flow
International Nuclear Information System (INIS)
Sheppard, J.D.; Tong, L.S.
1977-01-01
A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods. 3 claims, 9 figures
Review of two-phase instabilities
Energy Technology Data Exchange (ETDEWEB)
Kang, Han Ok; Seo, Han Ok; Kang, Hyung Suk; Cho, Bong Hyun; Lee, Doo Jeong
1997-06-01
KAERI is carrying out a development of the design for a new type of integral reactors. The once-through helical steam generator is important design features. The study on designs and operating conditions which prevent flow instability should precede the introduction of one-through steam generator. Experiments are currently scheduled to understand two-phase instability, evaluate the effect of each design parameter on the critical point, and determine proper inlet throttling for the prevention of instability. This report covers general two-phase instability with review of existing studies on this topics. The general classification of two phase flow instability and the characteristics of each type of instability are first described. Special attention is paid to BWR core flow instability and once-through steam generator instability. The reactivity feedback and the effect of system parameters are treated mainly for BWR. With relation to once-through steam generators, the characteristics of convective heating and dryout point oscillation are first investigated and then the existing experimental studies are summarized. Finally chapter summarized the proposed correlations for instability boundary conditions. (author). 231 refs., 5 tabs., 47 figs
A review of damping of two-phase flows
International Nuclear Information System (INIS)
Hara, Fumio
1993-01-01
Damping of two-phase flows has been recognized as one of the most unknown parameters in analyzing vibrational characteristics of structures subjected to two-phase flows since it seems to be influenced by many physical parameters involved in the physics of dynamic energy dissipation of a vibrating structure, for example, liquid viscosity, surface tension, flow velocity, mass ratio, frequency, void fraction, flow regime and so forth. This paper deals with a review of scientific works done to date on the damping of two phase flows and discussions about what has been clarified and what has not been known to us, or what kinds of research are needed about two-phase flow damping. The emphasis is put on the definition of two-phase fluid damping, damping measurement techniques, damping characteristics in relation to two phase flow configurations, and damping generation mechanisms
Energy Technology Data Exchange (ETDEWEB)
Mori, Shoji [Yokohama National University, Yokohama 240-8501 (Japan)]. E-mail: morisho@ynu.ac.jp; Fukano, Tohru [Kurume Institute of University, Fukuoka 830-0052 (Japan)]. E-mail: fukanot@cc.kurume-it.ac.jp
2006-05-15
If a flow obstacle such as a spacer is placed in a boiling two-phase flow within a channel, the temperature on the surface of the heating tube is severely affected by the existence of the spacer. Under certain conditions the spacer has a cooling effect, and under other conditions the spacer causes dryout of the cooling water film on the heating surface, resulting in burnout of the tube. The burnout mechanism near the spacer, however, remains unclear. In a previous paper (Fukano, T., Mori, S., Akamatsu, S., Baba, A., 2002. Relation between temperature fluctuation of a heating surface and generation of drypatch caused by a cylindrical spacer in a vertical boiling two-phase upward flow in a narrow annular channel. Nucl. Eng. Des. 217, 81-90), we reported that the disturbance wave has a significant effect on dryout occurrence. Therefore, in the present paper, the relation between dryout, burnout occurrence, and interval between two successive disturbance waves obtained from the differential pressure fluctuation caused by the disturbance waves passing by a spacer, is further discussed in detail.
International Nuclear Information System (INIS)
Mori, Shoji; Fukano, Tohru
2006-01-01
If a flow obstacle such as a spacer is placed in a boiling two-phase flow within a channel, the temperature on the surface of the heating tube is severely affected by the existence of the spacer. Under certain conditions the spacer has a cooling effect, and under other conditions the spacer causes dryout of the cooling water film on the heating surface, resulting in burnout of the tube. The burnout mechanism near the spacer, however, remains unclear. In a previous paper (Fukano, T., Mori, S., Akamatsu, S., Baba, A., 2002. Relation between temperature fluctuation of a heating surface and generation of drypatch caused by a cylindrical spacer in a vertical boiling two-phase upward flow in a narrow annular channel. Nucl. Eng. Des. 217, 81-90), we reported that the disturbance wave has a significant effect on dryout occurrence. Therefore, in the present paper, the relation between dryout, burnout occurrence, and interval between two successive disturbance waves obtained from the differential pressure fluctuation caused by the disturbance waves passing by a spacer, is further discussed in detail
Microgravity Two-Phase Flow Transition
Parang, M.; Chao, D.
1999-01-01
Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.
Two Phase Flow Simulation Using Cellular Automata
International Nuclear Information System (INIS)
Marcel, C.P.
2002-01-01
The classical mathematical treatment of two-phase flows is based on the average of the conservation equations for each phase.In this work, a complementary approach to the modeling of these systems based on statistical population balances of aut omata sets is presented.Automata are entities defined by mathematical states that change following iterative rules representing interactions with the neighborhood.A model of automata for two-phase flow simulation is presented.This model consists of fie lds of virtual spheres that change their volumes and move around a certain environment.The model is more general than the classical cellular automata in two respects: the grid of cellular automata is dismissed in favor of a trajectory generator, and the rules of interaction involve parameters representing the actual physical interactions between phases.Automata simulation was used to study unsolved two-phase flow problems involving high heat flux rates. One system described in this work consists of a vertical channel with saturated water at normal pressure heated from the lower surface.The heater causes water to boil and starts the bubble production.We used cellular automata to describe two-phase flows and the interaction with the heater.General rule s for such cellular automata representing bubbles moving in stagnant liquid were used, with special attention to correct modeling of different mechanisms of heat transfer.The results of the model were compared to previous experiments and correlations finding good agreement.One of the most important findings is the confirmation of Kutateladze's idea about a close relation between the start of critical heat flux and a change in the flow's topology.This was analyzed using a control volume located in the upper surface of the heater.A strong decrease in the interfacial surface just before the CHF start was encountered.The automata describe quite well some characteristic parameters such as the shape of the local void fraction in the
State of the art: two-phase flow calibration techniques
International Nuclear Information System (INIS)
Stanley, M.L.
1977-01-01
The nuclear community faces a particularly difficult problem relating to the calibration of instrumentation in a two-phase flow steam/water environment. The rationale of the approach to water reactor safety questions in the United States demands that accurate measurements of mass flows in a decompressing two-phase flow be made. An accurate measurement dictates an accurate calibration. This paper addresses three questions relating to the state of the art in two-phase calibration: (1) What do we mean by calibration. (2) What is done now. (3) What should be done
International Nuclear Information System (INIS)
Mori, Shoji; Fukano, Tohru
2003-01-01
If a flow obstacle such as a spacer is set in a boiling two-phase flow within an annular channel, where the inner tube is used as a heater, the temperature on the surface of the heater tube is severely affected by the existence of the spacer. In some case the spacer has a cooling effect, and in the other case it causes the dryout of the cooling liquid film on the heating surface resulting in the burnout of the tube. The burnout mechanism near the spacer, however, is not still clear. In the present paper we focus our attention on the occurrence of the burnout near a spacer, and discuss the occurrence location of dryout and burnout and the relation between the occurrence of burnout and differential-pressure fluctuation characteristics caused by the disturbance waves passing by a spacer. (author)
Modeling two-phase flow in PEM fuel cell channels
Energy Technology Data Exchange (ETDEWEB)
Wang, Yun; Basu, Suman; Wang, Chao-Yang [Electrochemical Engine Center (ECEC), and Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)
2008-05-01
This paper is concerned with the simultaneous flow of liquid water and gaseous reactants in mini-channels of a proton exchange membrane (PEM) fuel cell. Envisaging the mini-channels as structured and ordered porous media, we develop a continuum model of two-phase channel flow based on two-phase Darcy's law and the M{sup 2} formalism, which allow estimate of the parameters key to fuel cell operation such as overall pressure drop and liquid saturation profiles along the axial flow direction. Analytical solutions of liquid water saturation and species concentrations along the channel are derived to explore the dependences of these physical variables vital to cell performance on operating parameters such as flow stoichiometric ratio and relative humility. The two-phase channel model is further implemented for three-dimensional numerical simulations of two-phase, multi-component transport in a single fuel-cell channel. Three issues critical to optimizing channel design and mitigating channel flooding in PEM fuel cells are fully discussed: liquid water buildup towards the fuel cell outlet, saturation spike in the vicinity of flow cross-sectional heterogeneity, and two-phase pressure drop. Both the two-phase model and analytical solutions presented in this paper may be applicable to more general two-phase flow phenomena through mini- and micro-channels. (author)
Two-phase flow characteristics in BWRs
International Nuclear Information System (INIS)
Katono, Kenichi; Aoyama, Goro; Nagayoshi, Takuji; Yasuda, Kenichi; Nishida, Koji
2014-01-01
Reliable prediction of two-phase flow characteristics is important for safety and economy improvements of BWR plants. We have been developing two-phase flow measurement tools and techniques for BWR thermal hydraulic conditions, such as a 3D time-averaged X-ray CT system, an ultrasonic liquid film sensor and a wire-mesh sensor. We applied the developed items in experiments using the multi-purpose steam-water test facility known as HUSTLE, which can simulate two-phase thermal-hydraulic conditions in a BWR reactor pressure vessel, and we constructed a detailed instrumentation database. We validated a 3D two-phase flow simulator using the database and developed the reactor internal two-phase flow analysis system. (author)
Two-phase flow in refrigeration systems
Gu, Junjie; Gan, Zhongxue
2013-01-01
Two-Phase Flow in Refrigeration Systems presents recent developments from the authors' extensive research programs on two-phase flow in refrigeration systems. This book covers advanced mass and heat transfer and vapor compression refrigeration systems and shows how the performance of an automotive air-conditioning system is affected through results obtained experimentally and theoretically, specifically with consideration of two-phase flow and oil concentration. The book is ideal for university postgraduate students as a textbook, researchers and professors as an academic reference book, and b
Two-phased flow component loss data
International Nuclear Information System (INIS)
Fairhurst, C.P.
1983-01-01
Pressure loss measurements were made for valves and orifice plates under horizontal and vertical two-phase, air/water flow. The results displayed similar trends and were successfully correlated using a semi-empirical approach. (author)
Condensation in a two-phase pool
International Nuclear Information System (INIS)
Duffey, R.B.; Hughes, E.D.
1991-01-01
We consider the case of vapor condensation in a liquid pool, when the heat transfer is controlled by heat losses through the walls. The analysis is based on drift flux theory for phase separation in the pool, and determines the two-phase mixture height for the pool. To our knowledge this is the first analytical treatment of this classic problem that gives an explicit result, previous work having established the result for the evaporative case. From conservation of mass and energy in a one-dimensional steady flow, together with a void relation between the liquid and vapor fluxes, we determine the increase in the mixture level from the base level of the pool. It can be seen that the thermal and hydrodynamic influences are separable. Thus, the thermal influence of the wall heat transfer appears through its effect on the condensing length L*, so that at high condensation rates the pool is all liquid, and at low rates overflows (the level swell or foaming effect). Similarly, the phase separation effect hydrodynamically determines the height via the relative velocity of the mixture to the entering flux. We examine some practical applications of this result to level swell in condensing flows, and also examine some limits in ideal cases
Two-phase flux simulations by robots
International Nuclear Information System (INIS)
Barrera, F.D.
1997-01-01
Two-Phase flow systems are studied following the statistical formulation, which takes into account the bubble population balances. This is done by means of automata simulation. Geometrical automata are associated to the dispersed phase, and are represented by discs on the plane, resembling bubbles moving in a fluid environment. Following pre-determined rules, the automata evolve, and useful statistical information about their interaction is obtained. This information is applied in the present work to study the mechanisms that induce bubble coalescence. Models for one and two sized automata are presented. It was found that in the case of the model for one size, the probability of interaction among bubbles and the pair correlation function depends not only on the void fraction, but also on the number of elements of the dispersed phase. A correlation for the collision probability between two bubbles is obtained, and this result was extended to the pair correlation function. For the case of systems with two characteristic sizes, a model was formulated for analyzing the interaction among bubbles of the two groups. The interaction of bubbles for one and two sized systems were related by a symmetry factor, which shows the dependence of the interaction among bubbles with the size distribution. By means of the automata simulation, the phenomena of bubble confinement and screening were characterized. It was found that the first phenomenon is stronger in systems with greater distance among bubbles, and that the second effect increases with void fraction and bubble number. (author)
Two-phase flow patterns and their relationship to two-phase heat transfer
International Nuclear Information System (INIS)
Hewitt, G.F.
1977-01-01
The objective of this lecture was to discuss the general nature of two phase flows, to define the various regimes of flow and to discuss the influence of these regimes on the heat transfer processes taking place. The methods of regime delineation are briefly described and regime descriptions introduced for both vertical and horizontal flows in tubes. ''Flow regime maps'' have been widely used as an aid to determination of the regime which occurs in a given situation. Some of the more widely used maps are described and the limitations of this approach discussed. There have been many attempts to obtain a better phenomenological description of two phase flow patterns. In this lecture, these attempts will be reviewed in the context of the bubble/plug, plug/churn and churn/annular flow transitions in vertical flow. The latter two transitions are related to the flooding/flow reversal phenomena. For horizontal flows, recent work on the onset of slugging will be reviewed. In flows with evaporation or condensation, the situation is influenced by departures from thermodynamic equilibrium and the types of departure observed are discuss briefly. Flow patterns and their relationships with heat transfer regimes are then reviewed for the case of condensation in horizontal tubes and evaporation in vertical tubes
Dynamic Modeling of Phase Crossings in Two-Phase Flow
DEFF Research Database (Denmark)
Madsen, Søren; Veje, Christian; Willatzen, Morten
2012-01-01
by a high resolution finite difference scheme due to Kurganov and Tadmore. The homogeneous formulation requires a set of thermodynamic relations to cover the entire range from liquid to gas state. This leads a number of numerical challenges since these relations introduce discontinuities in the derivative...... of the variables and are usually very slow to evaluate. To overcome these challenges, we use an interpolation scheme with local refinement. The simulations show that the method handles crossing of the saturation lines for both liquid to two-phase and two-phase to gas regions. Furthermore, a novel result obtained...
Two-phase flow induced parametric vibrations in structural systems
International Nuclear Information System (INIS)
Hara, Fumio
1980-01-01
This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)
Two phase cooling for superconducting magnets
International Nuclear Information System (INIS)
Eberhard, P.H.; Gibson, G.A.; Green, M.A.; Ross, R.R.; Smits, R.G.
1986-01-01
Comments on the use of two phase helium in a closed circuit tubular cooling system and some results obtained with the TPC superconducting magnet are given. Theoretical arguments and experimental evidence are given against a previously suggested method to determine helium two phase flow regimes. Two methods to reduce pressure in the magnet cooling tubes during quenches are discussed; 1) lowering the density of helium in the magnet cooling tubes and 2) proper location of pressure relief valves. Some techniques used to protect the refrigerator from too much cold return gas are also mentioned
Two phase cooling for superconducting magnets
International Nuclear Information System (INIS)
Eberhard, P.H.; Gibson, G.A.; Green, M.A.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Watt, R.D.
1986-01-01
Comments on the use of two phase helium in a closed circuit tubular cooling system and some results obtained with the TPC superconducting magnet are given. Theoretical arguments and experimental evidence are given against a previously suggested method to determine helium two phase flow regimes. Two methods to reduce pressure in the magnet cooling tubes during quenches are discussed; (1) lowering the density of helium in the magnet cooling tubes and (2) proper location of pressure relief valves. Some techniques used to protect the refrigerator from too much cold return gas are also mentioned. 10 refs., 1 fig., 5 tabs
Two phase transitions in Nuclear Physics
International Nuclear Information System (INIS)
Bes, D.R.
1985-01-01
The status of the art of the problem associated with two phase transitions in the nuclear matter, viz.: the disappearance of the nuclear superfluiditiy with the raising of the rotation velocity and the appearance of an octupolar deformation in the actinide zone, is presented. (L.C.) [pt
Mathematical modeling of disperse two-phase flows
Morel, Christophe
2015-01-01
This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, a...
Two-phase flow characteristics analysis code: MINCS
International Nuclear Information System (INIS)
Watanabe, Tadashi; Hirano, Masashi; Akimoto, Masayuki; Tanabe, Fumiya; Kohsaka, Atsuo.
1992-03-01
Two-phase flow characteristics analysis code: MINCS (Modularized and INtegrated Code System) has been developed to provide a computational tool for analyzing two-phase flow phenomena in one-dimensional ducts. In MINCS, nine types of two-phase flow models-from a basic two-fluid nonequilibrium (2V2T) model to a simple homogeneous equilibrium (1V1T) model-can be used under the same numerical solution method. The numerical technique is based on the implicit finite difference method to enhance the numerical stability. The code structure is highly modularized, so that new constitutive relations and correlations can be easily implemented into the code and hence evaluated. A flow pattern can be fixed regardless of flow conditions, and state equations or steam tables can be selected. It is, therefore, easy to calculate physical or numerical benchmark problems. (author)
Stratified steady and unsteady two-phase flows between two parallel plates
International Nuclear Information System (INIS)
Sim, Woo Gun
2006-01-01
To understand fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. Stratified steady and unsteady two-phase flows between two parallel plates have been studied to investigate the general characteristics of the flow related to flow-induced vibration. Based on the spectral collocation method, a numerical approach has been developed for the unsteady two-phase flow. The method is validated by comparing numerical result to analytical one given for a simple harmonic two-phase flow. The flow parameters for the steady two-phase flow, such as void fraction and two-phase frictional multiplier, are evaluated. The dynamic characteristics of the unsteady two-phase flow, including the void fraction effect on the complex unsteady pressure, are illustrated
Two-phase flow instrumentation and laser beams
International Nuclear Information System (INIS)
Delhaye, J.M.
1976-01-01
Some methods based on laser techniques in order to place emphasis on the relation between measured quantities and the primary variables entering the general equations of two-phase systems are reviewed and summarized. The case where the bubbles or droplets are so small that they act as individual scattering centers is excluded [fr
An introduction to two-phase flows
International Nuclear Information System (INIS)
Lemonnier, Herve
2006-01-01
This course aims at proposing the necessary background for a rational approach to two-phase flows which are notably present in numerous industrial devices and equipment designed to perform energy transfer or mass transfer. The first part proposes a phenomenological approach to main two-phase flow structures and presents their governing variables. The second part presents some proven measurement techniques. The third part focuses on modelling. It recalls the equation elaboration techniques which are based on basic principles of mechanics and thermodynamics and on the application of different averaging operators to these principles. Some useful models are then presented such as models of pressure loss in a duct. The last chapter addresses some fundamental elements of heat transfers in ebullition and condensation
Geometrical automata for two phase flow simulation
International Nuclear Information System (INIS)
Herrero, V.; Guido-Lavalle, G.; Clausse, A.
1996-01-01
An automaton is an entity defined by a mathematical state which changes following iterative rules representing the interaction with the neighborhood. A model of automata for two-phase flow simulation consisting in a field of disks which are allowed to change their radii and move in a plane is presented. The model is more general than the classical cellular automata in two respects: (1) the grid of cellular automata is dismissed in favor of a trajectory generator; and (2) the rules of interaction involve parameters intended to represent some of the most relevant variables governing the actual physical interactions between phases. Computational experiments show that the algorithm captures the essential physics underlying two-phase flow problems such as bubbly-slug pattern transition and void fraction development along tubes. A comparison with experimental data of void fraction profiles is presented, showing excellent agreement. (orig.)
Review of two-phase water hammer
International Nuclear Information System (INIS)
Beuthe, T.G.
1997-01-01
In a thermalhydraulic system like a nuclear power plant, where steam and water mix and are used to transport large amounts of energy, there is a potential to create two-phase water hammer. Large water hammer pressure transients are a threat to piping integrity and represent an important safety concern. Such events may cause unscheduled plant down time. The objective of this review is to provide a summary of the information on two-phase water hammer available in the open literature with particular emphasis on water hammer occurrences in nuclear power plants. Past reviews concentrated on studies concerned with preventing water hammer. The present review focuses on the fundamental experimental, analytical, and modelling studies. The papers discussed here were chosen from searches covering up to July 1993. (author)
Modelling aspects of two phase flow
International Nuclear Information System (INIS)
Mayinger, F.
1977-01-01
In two phase flow scaling is much more limited to very narrowly defined physical phenomena than in single phase fluids. For complex and combined phenomena it can be achieved not by using dimensionless numbers alone but in addition a detailed mathematical description of the physical problem - usually in the form of a computer program - must be available. An important role plays the scaling of the thermodynamic data of the modelling fluid. From a literature survey and from own scaling experiments the conclusion can be drawn that Freon is a quite suitable modelling fluid for scaling steam-water mixtures. However, whithout a theoretical description of the phenomena nondimensional numbers for scaling two phase flow must be handled very carefully. (orig.) [de
Pumped two-phase heat transfer loop
Edelstein, Fred
1988-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Study of nonequilibrium dispersed two phase flow
International Nuclear Information System (INIS)
Reyes, J.N. Jr.
1986-01-01
Understanding the behavior of liquid droplets in a superheated steam environment is essential to the accurate prediction of nuclear fuel rod surface temperatures during the blowdown and reflood phase of a loss-of-coolant-accident (LOCA). In response to this need, this treatise presents several original and significant contributions to the field of thermofluid physics. The research contained herein presents a statistical derivation of the two-phase mass, momentum, and energy-conservation equations using a droplet continuity equation analogous to that used in the Kinetic Theory of Gases. Unlike the Eulerian volume and time-averaged conservation equations generally used to describe dispersed two-phase flow behavior, this statistical averaging approach results in an additional mass momentum or energy term in each of the respective conservation equations. Further, this study demonstrates that current definitions of the volumetric vapor generation rate used in the mass conservation equation are inappropriate results under certain circumstances. The mass conservation equation derived herein is used to obtain a new definition for the volumetric vapor-generation rate. Last, a simple two phase phenomenological model, based on the statistically averaged conservation equations, is presented and solved analytically. It is shown that the actual quality and vapor temperature, under these circumstances, depend on a single dimensionless group
Modeling and numerical study of two phase flow
International Nuclear Information System (INIS)
Champmartin, A.
2011-01-01
This thesis describes the modelization and the simulation of two-phase systems composed of droplets moving in a gas. The two phases interact with each other and the type of model to consider directly depends on the type of simulations targeted. In the first part, the two phases are considered as fluid and are described using a mixture model with a drift relation (to be able to follow the relative velocity between the two phases and take into account two velocities), the two-phase flows are assumed at the equilibrium in temperature and pressure. This part of the manuscript consists of the derivation of the equations, writing a numerical scheme associated with this set of equations, a study of this scheme and simulations. A mathematical study of this model (hyperbolicity in a simplified framework, linear stability analysis of the system around a steady state) was conducted in a frame where the gas is assumed baro-tropic. The second part is devoted to the modelization of the effect of inelastic collisions on the particles when the time of the simulation is shorter and the droplets can no longer be seen as a fluid. We introduce a model of inelastic collisions for droplets in a spray, leading to a specific Boltzmann kernel. Then, we build caricatures of this kernel of BGK type, in which the behavior of the first moments of the solution of the Boltzmann equation (that is mass, momentum, directional temperatures, variance of the internal energy) are mimicked. The quality of these caricatures is tested numerically at the end. (author) [fr
Coupling two-phase fluid flow with two-phase darcy flow in anisotropic porous media
Chen, J.
2014-06-03
This paper reports a numerical study of coupling two-phase fluid flow in a free fluid region with two-phase Darcy flow in a homogeneous and anisotropic porous medium region. The model consists of coupled Cahn-Hilliard and Navier-Stokes equations in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition on the interface between the free flow and the porous media regions. Obtained results have shown the anisotropic properties effect on the velocity and pressure of the two-phase flow. 2014 Jie Chen et al.
Coupling Two-Phase Fluid Flow with Two-Phase Darcy Flow in Anisotropic Porous Media
Directory of Open Access Journals (Sweden)
Jie Chen
2014-06-01
Full Text Available This paper reports a numerical study of coupling two-phase fluid flow in a free fluid region with two-phase Darcy flow in a homogeneous and anisotropic porous medium region. The model consists of coupled Cahn-Hilliard and Navier-Stokes equations in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition on the interface between the free flow and the porous media regions. Obtained results have shown the anisotropic properties effect on the velocity and pressure of the two-phase flow.
Non-Darcy behavior of two-phase channel flow.
Xu, Xianmin; Wang, Xiaoping
2014-08-01
We study the macroscopic behavior of two-phase flow in porous media from a phase-field model. A dissipation law is first derived from the phase-field model by homogenization. For simple channel geometry in pore scale, the scaling relation of the averaged dissipation rate with the velocity of the two-phase flow can be explicitly obtained from the model which then gives the force-velocity relation. It is shown that, for the homogeneous channel surface, Dacry's law is still valid with a significantly modified permeability including the contribution from the contact line slip. For the chemically patterned surfaces, the dissipation rate has a non-Darcy linear scaling with the velocity, which is related to a depinning force for the patterned surface. Our result offers a theoretical understanding on the prior observation of non-Darcy behavior for the multiphase flow in either simulations or experiments.
Two-phase flow dynamics in ECC
International Nuclear Information System (INIS)
Albraaten, P.J.
1981-07-01
The present report summarizes the achievements within the project ''Two-phase Systems and ECC''. The results during 1978 - 1980 are accounted for in brief as they have been documented in earlier reports. The results during the first half of 1981 are accounted for in greater detail. They contain a new model for the Basset force and test runs with this model using the test code RISQUE. Furthermore, test runs have been performed with TRAC-PD2 MOD 1. This code was implemented on Edwards Pipe Blowdown experiment (a standard test case) and UC-Berkeley Reflooding experiment (a non-standard test case.) (Auth.)
Two phase cooling for superconducting magnets
International Nuclear Information System (INIS)
Eberhard, P.H.; Gibson, G.A.; Green, M.A.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Watt, R.D.
1985-08-01
A closed circuit tubular cooling system for superconducting magnets offers advantages of limiting boiloff and containing high pressures during quenches. Proper location of automatic valves to lower pressures and protect the refrigerator in the event of quenches is described. Theoretical arguments and exprimental evidence are given against a previously suggested method to determine He two phase flow regimes. If loss of flow occurs due to some types of refrigeration failure and transfer lines have enough heat leak to warm up, quenches are induced when the flow is restored. Examples are taken from experience with the TPC magnet
International Nuclear Information System (INIS)
Sullivan, J.P.; Houze, R.N.; Buenger, D.E.; Theofanous, T.G.
1981-01-01
Hot film Anemometry and Laser Doppler Velocimetry have been employed in this work to study the turbulence characteristics of Bubbly and Stratified two-phase flows, respectively. Extensive consistency checks were made to establish the reliability and hence the utility of these experimental techniques for the measurement of turbulence in two-phase flows. Buoyancy-driven turbulence in vertical bubbly flows has been identified experimentally and correlated in terms of a shear velocity superposition approach. This approach provides a criterion for the demarcation of the buoyancy-driven turbulence region from the wall shear-generated turbulence region. Our data confirm the roughly isotropic behavior expected for buoyancy-driven turbulence. Upgrading of our experimental system will permit investigations of the wall-shear dominated regime (i.e., isotropy, superposition approach, etc.). The stratified flow data demonstrate clearly that the maximum in the mean velocity profile does not coincide with the zero shear plane, indicating the existence of a negative eddy viscosity region. Previous studies do not take into account this difference and thus they yield incorrect friction factor data in addition to certain puzzling behavior in the upper wall region. The conditioned turbulence data in the wavy region indicate interesting trends and that an appropriate normalization of intensities must take into account the shear velocity at the interfacial (wavy) region
Computational methods for two-phase flow and particle transport
Lee, Wen Ho
2013-01-01
This book describes mathematical formulations and computational methods for solving two-phase flow problems with a computer code that calculates thermal hydraulic problems related to light water and fast breeder reactors. The physical model also handles the particle and gas flow problems that arise from coal gasification and fluidized beds. The second part of this book deals with the computational methods for particle transport.
Modeling of two-phase slug flow
International Nuclear Information System (INIS)
Fabre, J.; Line, A.
1992-01-01
When gas and liquid flow in a pipe, over a range of flow rates, a flow pattern results in which sequences of long bubbles, almost filling the pipe cross section, are successively followed by liquid slugs that may contain small bubbles. This flow pattern, usually called slug flow, is encountered in numerous practical situations, such as in the production of hydrocarbons in wells and their transportation in pipelines; the production of steam and water in geothermal power plants; the boiling and condensation in liquid-vapor systems of thermal power plants; emergency core cooling of nuclear reactors; heat and mass transfer between gas and liquid in chemical reactors. This paper provides a review of two phase slug flow modeling
Two-phase ozonation of chlorinated organics
International Nuclear Information System (INIS)
Bhattacharyya, D.; Freshour, A.; West, D.
1995-01-01
In the last few years the amount of research being conducted in the field of single-phase ozonation has grown extensively. However, traditional aqueous-phase ozonation systems are limited by a lack of selective oxidation potential, low ozone solubility in water, and slow intermediate decomposition rates. Furthermore, ozone may decompose before it can be utilized for pollutant destruction since ozone can be highly unstable in aqueous solutions. Naturally occurring compounds such as NaHCO 3 also affect ozone reactions by inhibiting the formation of OH-free radicals. To compensate for these factors, excess ozone is typically supplied to a reactor. Since ozone generation requires considerable electric power consumption (16 - 24 kWh/kg of O 3 ), attempts to enhance the ozone utilization rate and stability should lead to more efficient application of this process to hazardous waste treatment. To improve the process, ozonation may be more efficiently carried out in a two-phase system consisting of an inert solvent (saturated with O 3 ) contacted with an aqueous phase containing pollutants. The non-aqueous phase must meet the following criteria: (1) non-toxic, (2) very low vapor pressure, (3) high density (for ease of separation), (4) complete insolubility in water, (5) reusability, (6) selective pollutant extractability, (7) high oxidant solubility, and (8) extended O 3 stability. Previously published studies (1) have indicated that a number of fluorinated hydrocarbon compounds fit these criteria. For this project, FC40 (a product of 3M Co.) was chosen due to its low vapor pressure (3 mm Hg) and high specific gravity (1.9). The primary advantages of the FC40 solvent are that it is non-toxic, reusable, has an ozone solubility 10 times that of water, and that 85 % of the ozone remains in the solvent even after 2 hours. This novel two-phase process has been utilized to study the rapid destruction of organic chlorine compounds and organic mixtures
Two-phase flow models in unbounded two-phase critical flows
International Nuclear Information System (INIS)
Celata, G.P.; Cumo, M.; Farello, G.E.
1985-01-01
With reference to a Loss-of-Coolant Accident in Light Water Reactors, an analysis of the unbounded two-phase critical flow (i.e. the issuing two-phase jet) has been accomplished. Considering jets external shape, obtained by means of photographic pictures; pressure profiles inside the jet, obtained by means of a movable ''Pitot;'' and jet phases distribution information, obtained by means of X-rays pictures; a characterization of the flow pattern in the unbounded region of a two-phase critical flow is given. Jets X-ray pictures show the existence of a central high density ''core'' gradually evaporating all around, which gives place to a characteristic ''dartflow'' the length of which depends on stagnation thermodynamic conditions
Method and apparatus for monitoring two-phase flow. [PWR
Sheppard, J.D.; Tong, L.S.
1975-12-19
A method and apparatus for monitoring two-phase flow is provided that is particularly related to the monitoring of transient two-phase (liquid-vapor) flow rates such as may occur during a pressurized water reactor core blow-down. The present invention essentially comprises the use of flanged wire screens or similar devices, such as perforated plates, to produce certain desirable effects in the flow regime for monitoring purposes. One desirable effect is a measurable and reproducible pressure drop across the screen. The pressure drop can be characterized for various known flow rates and then used to monitor nonhomogeneous flow regimes. Another useful effect of the use of screens or plates in nonhomogeneous flow is that such apparatus tends to create a uniformly dispersed flow regime in the immediate downstream vicinity. This is a desirable effect because it usually increases the accuracy of flow rate measurements determined by conventional methods.
Study on flow instabilities in two-phase mixtures
International Nuclear Information System (INIS)
Ishii, M.
1976-03-01
Various mechanisms that can induce flow instabilities in two-phase flow systems are reviewed and their relative importance discussed. In view of their practical importance, the density-wave instabilities have been analyzed in detail based on the one-dimensional two-phase flow formulation. The dynamic response of the system to the inlet flow perturbations has been derived from the model; thus the characteristic equation that predicts the onset of instabilities has been obtained. The effects of various system parameters, such as the heat flux, subcooling, pressure, inlet velocity, inlet orificing, and exit orificing on the stability boundary have been analyzed. In addition to numerical solutions, some simple stability criteria under particular conditions have been obtained. Both results have been compared with various experimental data, and a satisfactory agreement has been demonstrated
Coupling two-phase fluid flow with two-phase darcy flow in anisotropic porous media
Chen, J.; Sun, S.; Chen, Z.
2014-01-01
in the free fluid region and the two-phase Darcy law in the anisotropic porous medium region. A Robin-Robin domain decomposition method is used for the coupled Navier-Stokes and Darcy system with the generalized Beavers-Joseph-Saffman condition
Two-phase flow in volatile oil reservoir using two-phase pseudo-pressure well test method
Energy Technology Data Exchange (ETDEWEB)
Sharifi, M.; Ahmadi, M. [Calgary Univ., AB (Canada)
2009-09-15
A study was conducted to better understand the behaviour of volatile oil reservoirs. Retrograde condensation occurs in gas-condensate reservoirs when the flowing bottomhole pressure (BHP) lowers below the dewpoint pressure, thus creating 4 regions in the reservoir with different liquid saturations. Similarly, when the BHP of volatile oil reservoirs falls below the bubblepoint pressure, two phases are created in the region around the wellbore, and a single phase (oil) appears in regions away from the well. In turn, higher gas saturation causes the oil relative permeability to decrease towards the near-wellbore region. Reservoir compositional simulations were used in this study to predict the fluid behaviour below the bubblepoint. The flowing bottomhole pressure was then exported to a well test package to diagnose the occurrence of different mobility regions. The study also investigated the use of a two-phase pseudo-pressure method on volatile and highly volatile oil reservoirs. It was concluded that this method can successfully predict the true permeability and mechanical skin. It can also distinguish between mechanical skin and condensate bank skin. As such, the two-phase pseudo-pressure method is particularly useful for developing after-drilling well treatment and enhanced oil recovery process designs. However, accurate relative permeability and PVT data must be available for reliable interpretation of the well test in volatile oil reservoirs. 18 refs., 3 tabs., 9 figs.
Two-phase flow measurement by pulsed neutron activation techniques
International Nuclear Information System (INIS)
Kehler, P.
1978-01-01
The Pulsed Neutron Activation (PNA) technique for measuring the mass flow velocity and the average density of two-phase mixtures is described. PNA equipment can be easily installed at different loops, and PNA techniques are non-intrusive and independent of flow regimes. These features of the PNA technique make it suitable for in-situ measurement of two-phase flows, and for calibration of more conventional two-phase flow measurement devices. Analytic relations governing the various PNA methods are derived. The equipment and procedures used in the first air-water flow measurement by PNA techniques are discussed, and recommendations are made for improvement of future tests. In the present test, the mass flow velocity was determined with an accuracy of 2 percent, and average densities were measured down to 0.08 g/cm 3 with an accuracy of 0.04 g/cm 3 . Both the accuracy of the mass flow velocity measurement and the lower limit of the density measurement are functions of the injected activity and of the total number of counts. By using a stronger neutron source and a larger number of detectors, the measurable density can be decreased by a factor of 12 to .007 g/cm 3 for 12.5 cm pipes, and to even lower ranges for larger pipes
Cold water injection into two-phase mixtures
International Nuclear Information System (INIS)
1989-07-01
This report presents the results of a review of the international literature regarding the dynamic loadings associated with the injection of cold water into two-phase mixtures. The review placed emphasis on waterhammer in nuclear power plants. Waterhammmer incidence data were reviewed for information related to thermalhydraulic conditions, underlying causes and consequential damage. Condensation induced waterhammer was found to be the most significant consequence of injecting cold water into a two-phase system. Several severe waterhammer incidents have been attributed to slug formation and steam bubble collapse under conditions of stratified steam and cold water flows. These phenomena are complex and not well understood. The current body of experimental and analytical knowledge is not large enough to establish maps of expected regimes of condensation induced waterhammer. The Electric Power Research Institute, in the United States, has undertaken a major research and development programme to develop the knowledge base for this area. The limited models and data currently available show that mechanical parameters are as important as thermodynamic conditions for the initiation of condensation induced waterhammer. Examples of bounds for avoiding two-phase waterhammer are given. These bounds are system specific and depend upon parameters such as pump capacity, pipe length and pipe orientation
Moerk, J. Steven (Inventor); Youngquist, Robert C. (Inventor); Werlink, Rudy J. (Inventor)
1999-01-01
A quality and/or flow meter employs a capacitance probe assembly for measuring the dielectric constant of flow stream, particularly a two-phase flow stream including liquid and gas components.ne dielectric constant of the flow stream varies depending upon the volume ratios of its liquid and gas components, and capacitance measurements can therefore be employed to calculate the quality of the flow, which is defined as the volume ratio of liquid in the flow to the total volume ratio of gas and liquid in the flow. By using two spaced capacitance sensors, and cross-correlating the time varying capacitance values of each, the velocity of the flow stream can also be determined. A microcontroller-based processing circuit is employed to measure the capacitance of the probe sensors.The circuit employs high speed timer and counter circuits to provide a high resolution measurement of the time interval required to charge each capacitor in the probe assembly. In this manner, a high resolution, noise resistant, digital representation of each of capacitance value is obtained without the need for a high resolution A/D converter, or a high frequency oscillator circuit. One embodiment of the probe assembly employs a capacitor with two ground plates which provide symmetry to insure that accurate measurements are made thereby.
Constitutive equations for two-phase flows
International Nuclear Information System (INIS)
Boure, J.A.
1974-12-01
The mathematical model of a system of fluids consists of several kinds of equations complemented by boundary and initial conditions. The first kind equations result from the application to the system, of the fundamental conservation laws (mass, momentum, energy). The second kind equations characterize the fluid itself, i.e. its intrinsic properties and in particular its mechanical and thermodynamical behavior. They are the mathematical model of the particular fluid under consideration, the laws they expressed are so called the constitutive equations of the fluid. In practice the constitutive equations cannot be fully stated without reference to the conservation laws. Two classes of model have been distinguished: mixture model and two-fluid models. In mixture models, the mixture is considered as a single fluid. Besides the usual friction factor and heat transfer correlations, a single constitutive law is necessary. In diffusion models, the mixture equation of state is replaced by the phasic equations of state and by three consitutive laws, for phase change mass transfer, drift velocity and thermal non-equilibrium respectively. In the two-fluid models, the two phases are considered separately; two phasic equations of state, two friction factor correlations, two heat transfer correlations and four constitutive laws are included [fr
Numerical calculation of two-phase flows
International Nuclear Information System (INIS)
Travis, J.R.; Harlow, F.H.; Amsden, A.A.
1975-06-01
The theoretical study of time-varying two-phase flow problems in several space dimensions introduces such a complicated set of coupled nonlinear partial differential equations that numerical solution procedures for high-speed computers are required in almost all but the simplest examples. Efficient attainment of realistic solutions for practical problems requires a finite- difference formulation that is simultaneously implicit in the treatment of mass convection, equations of state, and the momentum coupling between phases. Such a method is described, the equations on which it is based are discussed, and its properties are illustrated by means of examples. In particular, the capability for calculating physical instabilities and other time-varying dynamics, at the same time avoiding numerical instability is emphasized. The computer code is applicable to problems in reactor safety analysis, the dynamics of fluidized dust beds, raindrops or aerosol transport, and a variety of similar circumstances, including the effects of phase transitions and the release of latent heat or chemical energy. (U.S.)
Two-phase Heating in Flaring Loops
Zhu, Chunming; Qiu, Jiong; Longcope, Dana W.
2018-03-01
We analyze and model a C5.7 two-ribbon solar flare observed by the Solar Dynamics Observatory, Hinode, and GOES on 2011 December 26. The flare is made of many loops formed and heated successively over one and half hours, and their footpoints are brightened in the UV 1600 Å before enhanced soft X-ray and EUV missions are observed in flare loops. Assuming that anchored at each brightened UV pixel is a half flaring loop, we identify more than 6700 half flaring loops, and infer the heating rate of each loop from the UV light curve at the footpoint. In each half loop, the heating rate consists of two phases: intense impulsive heating followed by a low-rate heating that is persistent for more than 20 minutes. Using these heating rates, we simulate the evolution of their coronal temperatures and densities with the model of the “enthalpy-based thermal evolution of loops.” In the model, suppression of thermal conduction is also considered. This model successfully reproduces total soft X-ray and EUV light curves observed in 15 passbands by four instruments GOES, AIA, XRT, and EVE. In this flare, a total energy of 4.9 × 1030 erg is required to heat the corona, around 40% of this energy is in the slow-heating phase. About two-fifths of the total energy used to heat the corona is radiated by the coronal plasmas, and the other three fifth transported to the lower atmosphere by thermal conduction.
Ostwald ripening in two-phase mixtures
International Nuclear Information System (INIS)
Voorhees, P.W.
1982-01-01
Experimental measurements of the temperature of a rapidly solidified solid-liquid mixture have been made over a range of volume fractions solid 0.23 to 0.95. These experiments demonstrate the viability of measuring the change in interfacial curvature with time via precision thermometry. The experimental measurements also indicate that there is no radical change in interface morphology over a wide range of volume fractions solid. A solution to the multi-particle diffusion problem (MDP) has been constructed through the use of potential theory. The solution to the MDP was used to describe the diffusion field within a coarsening two-phase mixture consisting of dispersed spherical second-phase particles. Since this theory is based upon the MDP, interparticle diffusional interactions are specifically included in the treatment. As a result, the theory yields, for the first time, insights into the influence of the local distribution of curvature on a particle's coarsening rate. The effect of interparticle interactions on the collective behavior of an ensemble of coarsening particles was also investigated. It was found that any arbitrary distribution of particle radii will tend to a specific time independent distribution when the particle radii are scaled by the average particle radius. Furthermore, it was determined that with increasing volume fraction of coarsening phase, these time independent distributions become broader and more symmetric. It was also found that the ripening kinetics, as measured by the growth rate of the average particle size, increases by a factor of five upon increasing the volume fraction of coarsening phase from zero to 0.5
Characterization of horizontal air–water two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Kong, Ran; Kim, Seungjin, E-mail: skim@psu.edu
2017-02-15
Highlights: • A visualization study is performed to develop flow regime map in horizontal flow. • Database in horizontal bubbly flow is extended using a local conductivity probe. • Frictional pressure drop analysis is performed in horizontal bubbly flow. • Drift flux analysis is performed in horizontal bubbly flow. - Abstract: This paper presents experimental studies performed to characterize horizontal air–water two-phase flow in a round pipe with an inner diameter of 3.81 cm. A detailed flow visualization study is performed using a high-speed video camera in a wide range of two-phase flow conditions to verify previous flow regime maps. Two-phase flows are classified into bubbly, plug, slug, stratified, stratified-wavy, and annular flow regimes. While the transition boundaries identified in the present study compare well with the existing ones (Mandhane et al., 1974) in general, some discrepancies are observed for bubbly-to-plug/slug, and plug-to-slug transition boundaries. Based on the new transition boundaries, three additional test conditions are determined in horizontal bubbly flow to extend the database by Talley et al. (2015a). Various local two-phase flow parameters including void fraction, interfacial area concentration, bubble velocity, and bubble Sauter mean diameter are obtained. The effects of increasing gas flow rate on void fraction, bubble Sauter mean diameter, and bubble velocity are discussed. Bubbles begin to coalesce near the gas–liquid layer instead of in the highly packed region when gas flow rate increases. Using all the current experimental data, two-phase frictional pressure loss analysis is performed using the Lockhart–Martinelli method. It is found that the coefficient C = 24 yields the best agreement with the data with the minimum average difference. Moreover, drift flux analysis is performed to predict void-weighted area-averaged bubble velocity and area-averaged void fraction. Based on the current database, functional
Directory of Open Access Journals (Sweden)
Pusch G.
2006-11-01
Full Text Available A new 2-parameter desaturation function is introduced which offers a broader range of applicability to reservoir rock. Based on this function two-phase relative permeabilities are derived for oil phase and microemulsion flow. These functions are used to match a laboratory experiment by using surfactant flooding for a single surfactant system. Les auteurs présentent une nouvelle fonction de désaturation à deux paramètres qui offre une plus large gamme de possibilités d'application aux roches réservoir. On tire de cette fonction des perméabilités relatives biphasiques pour l'écoulement de la phase pétrole et d'une microémulsion. Ces fonctions sont utilisées pour reproduire une expérience de laboratoire avec injection de surfactant pour un seul système surfactant.
Parallel two-phase-flow-induced vibrations in fuel pin model
International Nuclear Information System (INIS)
Hara, Fumio; Yamashita, Tadashi
1978-01-01
This paper reports the experimental results of vibrations of a fuel pin model -herein meaning the essential form of a fuel pin from the standpoint of vibration- in a parallel air-and-water two-phase flow. The essential part of the experimental apparatus consisted of a flat elastic strip made of stainless steel, both ends of which were firmly supported in a circular channel conveying the two-phase fluid. Vibrational strain of the fuel pin model, pressure fluctuation of the two-phase flow and two-phase-flow void signals were measured. Statistical measures such as power spectral density, variance and correlation function were calculated. The authors obtained (1) the relation between variance of vibrational strain and two-phase-flow velocity, (2) the relation between variance of vibrational strain and two-phase-flow pressure fluctuation, (3) frequency characteristics of variance of vibrational strain against the dominant frequency of the two-phase-flow pressure fluctuation, and (4) frequency characteristics of variance of vibrational strain against the dominant frequency of two-phase-flow void signals. The authors conclude that there exist two kinds of excitation mechanisms in vibrations of a fuel pin model inserted in a parallel air-and-water two-phase flow; namely, (1) parametric excitation, which occurs when the fundamental natural frequency of the fuel pin model is related to the dominant travelling frequency of water slugs in the two-phase flow by the ratio 1/2, 1/1, 3/2 and so on; and (2) vibrational resonance, which occurs when the fundamental frequency coincides with the dominant frequency of the two-phase-flow pressure fluctuation. (auth.)
Vapor Compressor Driven Hybrid Two-Phase Loop, Phase I
National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will demonstrate a vapor compressor driven hybrid two-phase loop technology. The hybrid two-phase loop...
Virtual mass effects in two-phase flow. Topical report
International Nuclear Information System (INIS)
Cheng, L.Y.; Drew, D.A.; Lahey, R.T. Jr.
1978-03-01
The effect of virtual mass on phase separation during the acceleration of a two-phase mixture was studied. Virtual mass can be regarded as an induced inertia on the dispersed phase which is accelerating relative to the continuous phase, and it was found that the virtual mass acceleration is objective, implying an invariance with respect to reference frame. An objective form of the virtual acceleration was derived and required parameters were determined for limiting cases. Analyses determined that experiments on single bubble nozzle/diffuser flow cannot readily discriminate between various virtual mass acceleration models
Digital video image processing applications to two phase flow measurements
International Nuclear Information System (INIS)
Biscos, Y.; Bismes, F.; Hebrard, P.; Lavergne, G.
1987-01-01
Liquid spraying is common in various fields (combustion, cooling of hot surfaces, spray drying,...). For two phase flows modeling, it is necessary to test elementary laws (vaporizing drops, equation of motion of drops or bubbles, heat transfer..). For example, the knowledge of the laws related to the behavior of vaporizing liquid drop in a hot airstream and impinging drops on a hot surface is important for two phase flow modeling. In order to test these different laws in elementary cases, the authors developed different measurement techniques, associating video and microcomputers. The test section (built in perpex or glass) is illuminated with a thin sheet of light generated by a 15mW He-Ne laser and appropriate optical arrangement. Drops, bubbles or liquid film are observed at right angle by a video camera synchronised with a microcomputer either directly or with an optical device (lens, telescope, microscope) providing sufficient magnification. Digitizing the video picture in real time associated with an appropriate numerical treatment allows to obtain, in a non interfering way, a lot of informations relative to the pulverisation and the vaporization as function of space and time (drop size distribution; Sauter mean diameter as function of main flow parameters: air velocity, surface tension, temperature; isoconcentration curves, size evolution relative to vaporizing drops, film thickness evolution spreading on a hot surface...)
Two-phase flow boiling pressure drop in small channels
International Nuclear Information System (INIS)
Sardeshpande, Madhavi V.; Shastri, Parikshit; Ranade, Vivek V.
2016-01-01
Highlights: • Study of typical 19 mm steam generator tube has been undertaken in detail. • Study of two phase flow boiling pressure drop, flow instability and identification of flow regimes using pressure fluctuations is the main focus of present work. • Effect of heat and mass flux on pressure drop and void fraction was studied. • Flow regimes identified from pressure fluctuations data using FFT plots. • Homogeneous model predicted pressure drop well in agreement. - Abstract: Two-phase flow boiling in small channels finds a variety of applications in power and process industries. Heat transfer, boiling flow regimes, flow instabilities, pressure drop and dry out are some of the key issues related to two-phase flow boiling in channels. In this work, the focus is on pressure drop in two-phase flow boiling in tubes of 19 mm diameter. These tubes are typically used in steam generators. Relatively limited experimental database is available on 19 mm ID tube. Therefore, in the present work, the experimental set-up is designed for studying flow boiling in 19 mm ID tube in such a way that any of the different flow regimes occurring in a steam generator tube (from pre-heating of sub-cooled water to dry-out) can be investigated by varying inlet conditions. The reported results cover a reasonable range of heat and mass flux conditions such as 9–27 kW/m 2 and 2.9–5.9 kg/m 2 s respectively. In this paper, various existing correlations are assessed against experimental data for the pressure drop in a single, vertical channel during flow boiling of water at near-atmospheric pressure. A special feature of these experiments is that time-dependent pressures are measured at four locations along the channel. The steady-state pressure drop is estimated and the identification of boiling flow regimes is done with transient characteristics using time series analysis. Experimental data and corresponding results are compared with the reported correlations. The results will be
Measurement of Two-Phase Flow Characteristics Under Microgravity Conditions
Keshock, E. G.; Lin, C. S.; Edwards, L. G.; Knapp, J.; Harrison, M. E.; Xhang, X.
1999-01-01
This paper describes the technical approach and initial results of a test program for studying two-phase annular flow under the simulated microgravity conditions of KC-135 aircraft flights. A helical coil flow channel orientation was utilized in order to circumvent the restrictions normally associated with drop tower or aircraft flight tests with respect to two-phase flow, namely spatial restrictions preventing channel lengths of sufficient size to accurately measure pressure drops. Additionally, the helical coil geometry is of interest in itself, considering that operating in a microgravity environment vastly simplifies the two-phase flows occurring in coiled flow channels under 1-g conditions for virtually any orientation. Pressure drop measurements were made across four stainless steel coil test sections, having a range of inside tube diameters (0.95 to 1.9 cm), coil diameters (25 - 50 cm), and length-to-diameter ratios (380 - 720). High-speed video photographic flow observations were made in the transparent straight sections immediately preceding and following the coil test sections. A transparent coil of tygon tubing of 1.9 cm inside diameter was also used to obtain flow visualization information within the coil itself. Initial test data has been obtained from one set of KC-135 flight tests, along with benchmark ground tests. Preliminary results appear to indicate that accurate pressure drop data is obtainable using a helical coil geometry that may be related to straight channel flow behavior. Also, video photographic results appear to indicate that the observed slug-annular flow regime transitions agree quite reasonably with the Dukler microgravity map.
Reduced order modeling of flashing two-phase jets
Energy Technology Data Exchange (ETDEWEB)
Gurecky, William, E-mail: william.gurecky@utexas.edu; Schneider, Erich, E-mail: eschneider@mail.utexas.edu; Ballew, Davis, E-mail: davisballew@utexas.edu
2015-12-01
Highlights: • Accident simulation requires ability to quickly predict two-phase flashing jet's damage potential. • A reduced order modeling methodology informed by experimental or computational data is described. • Zone of influence volumes are calculated for jets of various upstream thermodynamic conditions. - Abstract: In the event of a Loss of Coolant Accident (LOCA) in a pressurized water reactor, the escaping coolant produces a highly energetic flashing jet with the potential to damage surrounding structures. In LOCA analysis, the goal is often to evaluate many break scenarios in a Monte Carlo style simulation to evaluate the resilience of a reactor design. Therefore, in order to quickly predict the damage potential of flashing jets, it is of interest to develop a reduced order model that relates the damage potential of a jet to the pressure and temperature upstream of the break and the distance from the break to a given object upon which the jet is impinging. This work presents framework for producing a Reduced Order Model (ROM) that may be informed by measured data, Computational Fluid Dynamics (CFD) simulations, or a combination of both. The model is constructed by performing regression analysis on the pressure field data, allowing the impingement pressure to be quickly reconstructed for any given upstream thermodynamic condition within the range of input data. The model is applicable to both free and fully impinging two-phase flashing jets.
Analytical study of solids-gas two phase flow
International Nuclear Information System (INIS)
Hosaka, Minoru
1977-01-01
Fundamental studies were made on the hydrodynamics of solids-gas two-phase suspension flow, in which very small solid particles are mixed in a gas flow to enhance the heat transfer characteristics of gas cooled high temperature reactors. Especially, the pressure drop due to friction and the density distribution of solid particles are theoretically analyzed. The friction pressure drop of two-phase flow was analyzed based on the analytical result of the single-phase friction pressure drop. The calculated values of solid/gas friction factor as a function of solid/gas mass loading are compared with experimental results. Comparisons are made for Various combinations of Reynolds number and particle size. As for the particle density distribution, some factors affecting the non-uniformity of distribution were considered. The minimum of energy dispersion was obtained with the variational principle. The suspension density of particles was obtained as a function of relative distance from wall and was compared with experimental results. It is concluded that the distribution is much affected by the particle size and that the smaller particles are apt to gather near the wall. (Aoki, K.)
CFD Simulations of Pb-Bi Two-Phase Flow
International Nuclear Information System (INIS)
Dostal, Vaclav; Zelezny, Vaclav; Zacha, Pavel
2008-01-01
In a Pb-Bi cooled direct contact steam generation fast reactor water is injected directly above the core, the produced steam is separated at the top and is send to the turbine. Neither the direct contact phenomenon nor the two-phase flow simulations in CFD have been thoroughly described yet. A first attempt in simulating such two-phase flow in 2D using the CFD code Fluent is presented in this paper. The volume of fluid explicit model was used. Other important simulation parameters were: pressure velocity relation PISO, discretization scheme body force weighted for pressure, second order upwind for momentum and CISCAM for void fraction. Boundary conditions were mass flow inlet (Pb-Bi 0 kg/s and steam 0.07 kg/s) and pressure outlet. The effect of mesh size (0.5 mm and 0.2 mm cells) was investigated as well as the effect of the turbulent model. It was found that using a fine mesh is very important in order to achieve larger bubbles and the turbulent model (k-ε realizable) is necessary to properly model the slug flow. The fine mesh and unsteady conditions resulted in computationally intense problem. This may pose difficulties in 3D simulations of the real experiments. (authors)
System identification on two-phase flow stability
International Nuclear Information System (INIS)
Wu Shaorong; Zhang Youjie; Wang Dazhong; Bo Jinghai; Wang Fei
1996-01-01
The theoretical principle, experimental method and results of interrelation analysis identification for the instability of two-phase flow are described. A completely new concept of test technology and method on two-phase flow stability was developed by using he theory of information science on system stability and system identification for two-phase flow stability in thermo-physics field. Application of this method would make it possible to identify instability boundary of two-phase flow under stable operation conditions of two-phase flow system. The experiment was carried out on the thermohydraulic test system HRTL-5. Using reverse repeated pseudo-random sequences of heating power as input signal sources and flow rate as response function in the test, the two-phase flow stability and stability margin of the natural circulation system are investigated. The effectiveness and feasibility of identifying two-phase flow stability by using this system identification method were experimentally demonstrated. Basic data required for mathematics modeling of two-phase flow and analysis of two-phase flow stability were obtained, which are useful for analyzing, monitoring of the system operation condition, and forecasting of two-phase flow stability in engineering system
Droplet Manipulations in Two Phase Flow Microfluidics
Pit, Arjen; Duits, Michael H.G.; Mugele, Friedrich Gunther
2015-01-01
Even though droplet microfluidics has been developed since the early 1980s, the number of applications that have resulted in commercial products is still relatively small. This is partly due to an ongoing maturation and integration of existing methods, but possibly also because of the emergence of
Experiments in polydisperse two-phase turbulent flows
International Nuclear Information System (INIS)
Bachalo, W.D.; Houser, M.J.
1985-01-01
Aspects of turbulent two-phase flow measurements obtained with a laser Doppler velocimeter that was modified to also obtain particle size were investigated. Simultaneous measurements of the particle size and velocity allowed the determination of the lag characteristics of particles over a range of sizes. Relatively large particles were found to respond well to the turbulent fluctuations in low speed flows. Measurements of sprays were obtained at various points throughout the spray plume. Velocity measurements for each drop size class were obtained and revealed the relative velocity relaxation with downstream distance. The evolution of the rms velocities for each size class was also examined. Difficulties associated with seeding polydispersions to obtain gas phase turbulence data were discussed. Several approaches for mitigating the errors due to seed particle concentration bias were reviewed
Forced two phase helium cooling of large superconducting magnets
International Nuclear Information System (INIS)
Green, M.A.; Burns, W.A.; Taylor, J.D.
1979-08-01
A major problem shared by all large superconducting magnets is the cryogenic cooling system. Most large magnets are cooled by some variation of the helium bath. Helium bath cooling becomes more and more troublesome as the size of the magnet grows and as geometric constraints come into play. An alternative approach to cooling large magnet systems is the forced flow, two phase helium system. The advantages of two phase cooling in many magnet systems are shown. The design of a two phase helium system, with its control dewar, is presented. The paper discusses pressure drop of a two phase system, stability of a two phase system and the method of cool down of a two phase system. The results of experimental measurements at LBL are discussed. Included are the results of cool down and operation of superconducting solenoids
Numerical method for two-phase flow discontinuity propagation calculation
International Nuclear Information System (INIS)
Toumi, I.; Raymond, P.
1989-01-01
In this paper, we present a class of numerical shock-capturing schemes for hyperbolic systems of conservation laws modelling two-phase flow. First, we solve the Riemann problem for a two-phase flow with unequal velocities. Then, we construct two approximate Riemann solvers: an one intermediate-state Riemann solver and a generalized Roe's approximate Riemann solver. We give some numerical results for one-dimensional shock-tube problems and for a standard two-phase flow heat addition problem involving two-phase flow instabilities
Summary on experimental methods for statistical transient analysis of two-phase gas-liquid flow
International Nuclear Information System (INIS)
Delhaye, J.M.; Jones, O.C. Jr.
1976-06-01
Much work has been done in the study of two-phase gas-liquid flows. Although it has been recognized superficially that such flows are not homogeneous in general, little attention has been paid to the inherent discreteness of the two-phase systems. Only relatively recently have fluctuating characteristics of two-phase flows been studied in detail. As a result, new experimental devices and techniques have been developed for use in measuring quantities previously ignored. This report reviews and summarizes most of these methods in an effort to emphasize the importance of the fluctuating nature of these flows and as a guide to further research in this field
Two-phase flow in beds of spherical particles
International Nuclear Information System (INIS)
Schulenberg, T.; Mueller, U.
1984-02-01
A refined model for two-phase flow in beds of uniform spherical particles is presented. It includes the influence of interfacial drag forces between liquid and gas, which are important in beds of coarse particles, and an incrase of porosity due to vapour channels or similiar irreversible bed disturbances, which occur in beds of fine particles. The model is based on the momentum equations for separated flow, which are closed with empirical relations for wall shear stress and interfacial drag. To improve this model it is applied to volumetrically heated beds on a adiabatic bottom, which are saturated and superimposed with a boiling liquid. In case of fine particles only an impermeable bottom is considered, whereas in case of coarse particles also beds on a permeable support are discussed. (orig.) [de
Dynamics Coefficient for Two-Phase Soil Model
Directory of Open Access Journals (Sweden)
Wrana Bogumił
2015-02-01
Full Text Available The paper investigates a description of energy dissipation within saturated soils-diffusion of pore-water. Soils are assumed to be two-phase poro-elastic materials, the grain skeleton of which exhibits no irreversible behavior or structural hysteretic damping. Description of motion and deformation of soil is introduced as a system of equations consisting of governing dynamic consolidation equations based on Biot theory. Selected constitutive and kinematic relations for small strains and rotation are used. This paper derives a closed form of analytical solution that characterizes the energy dissipation during steady-state vibrations of nearly and fully saturated poro-elastic columns. Moreover, the paper examines the influence of various physical factors on the fundamental period, maximum amplitude and the fraction of critical damping of the Biot column. Also the so-called dynamic coefficient which shows amplification or attenuation of dynamic response is considered.
Fluid-elastic force measurements acting on a tube bundle in two-phase cross flow
International Nuclear Information System (INIS)
Inada, Fumio; Kawamura, Koji; Yasuo, Akira
1996-01-01
Fluid-elastic force acting on a square tube bundle of P/D = 1.47 in air-water two-phase cross flow was measured to investigate the characteristics and to clarify whether the fluid elastic vibration characteristics could be expressed using two-phase mixture characteristics. Measured fluid elastic forces were separated into fluid-elastic force coefficients such as added mass, added stiffness, and added damping coefficient. The added damping coefficient was separated into a two-phase damping and a flow-dependent component as in previous research (Carlucci, 1981 and 1983; Pettigrew, 1994). These coefficients were nondimensionalized with two-phase mixture characteristics such as void fraction, mixture density and mixture velocity, which were obtained using the drift-flux model with consideration given to the model. The result was compared with the result obtained with the homogeneous model. It was found that fluid-elastic force coefficients could be expressed with two-phase flow mixture characteristics very well in the experimental result, and that better result can be derived using the slip model as compared to the homogeneous model. Added two-phase flow, which could be expressed as a function of void fraction, where two-phase damping was nondimensionalized with the relative velocity between the gas and liquid phases used as a reference velocity. Using these, the added stiffness coefficient and flow-dependent component of damping could be expressed very well as a function of nondimensional mixture velocity
Two-phase aqueous micellar systems: an alternative method for protein purification
Directory of Open Access Journals (Sweden)
Rangel-Yagui C. O.
2004-01-01
Full Text Available Two-phase aqueous micellar systems can be exploited in separation science for the extraction/purification of desired biomolecules. This article reviews recent experimental and theoretical work by Blankschtein and co-workers on the use of two-phase aqueous micellar systems for the separation of hydrophilic proteins. The experimental partitioning behavior of the enzyme glucose-6-phosphate dehydrogenase (G6PD in two-phase aqueous micellar systems is also reviewed and new results are presented. Specifically, we discuss very recent work on the purification of G6PD using: i a two-phase aqueous micellar system composed of the nonionic surfactant n-decyl tetra(ethylene oxide (C10E4, and (ii a two-phase aqueous mixed micellar system composed of C10E4 and the cationic surfactant decyltrimethylammonium bromide (C10TAB. Our results indicate that the two-phase aqueous mixed (C10E4/C10TAB micellar system can improve significantly the partitioning behavior of G6PD relative to that observed in the two-phase aqueous C10E4 micellar system.
Waves in separated two-phase flow
International Nuclear Information System (INIS)
Pols, R.M.
1998-06-01
across the wave front to the sides of the tube. In the modelling of the three-dimensional wave separate scales are defined relating to both the movement of liquid in axial direction and the movement of liquid in circumferential direction. On the basis of these scales the three-dimensional shallow water equations are simplified and are essentially decoupled in a first approximation. Providing the axial flow is simultaneously matched with an expression for the wave front the resulting system is shown to provide solutions for the bulk of the axial flow. The shape of the wave front is determined by the changes of the wave velocity across the wave front as a function of the liquid depth, similar to a shock wave moving in a tube. Results of the modelling are compared with experimental observations and discussed. In vertical annular flow the interfacial shear remains a significant feature acting to destabilise the interface which is characterised by finite amplitude disturbance waves. In this instance gravity acts perpendicular to the interface and it is the pressure of the gas flow which acts to restore those waves on the liquid film. An asymmetrical wave profile is sought by piecing together the solutions over the windward and leeward side of the wave. For periodic waves a matching solution is shown to be possible where the solutions for the windward and the leeward side of the wave are pieced together appropriately to ensure that mass and momentum are conserved. The model calculations of disturbance waves are compared with the observed behaviour of waves in vertical upward annular flow and in gas sheared falling films
Two-phase flow induced vibrations in CANDU steam generators
International Nuclear Information System (INIS)
Gidi, A.
2009-01-01
The U-Bend region of nuclear steam generators tube bundles have suffered from two-phase cross flow induced vibrations. Tubes in this region have experienced high amplitude vibrations leading to catastrophic failures. Turbulent buffeting and fluid-elastic instability has been identified as the main causes. Previous investigations have focused on flow regime and two-phase flow damping ratio. However, tube bundles in steam generators have vapour generated on the surface of the tubes, which might affect the flow regime, void fraction distribution, turbulent intensity levels and tube-flow interaction, all of which have the potential to change the tube vibration response. A cantilevered tube bundle made of electric cartridges heaters was built and tested in a Freon-11 flow loop at McMaster University. Tubes were arranged in a parallel triangular configuration. The bundle was exposed to two-phase cross flows consisting of different combinations of void from two sources, void generated upstream of the bundle and void generated at the surface of the tubes. Tube tip vibration response was measured optically and void fraction was measured by gamma densitometry technique. It was found that tube vibration amplitude in the transverse direction was reduced by a factor of eight for void fraction generated at the tube surfaces only, when compared to the upstream only void generation case. The main explanation for this effect is a reduction in the correlation length of the turbulent buffeting forcing function. Theoretical calculations of the tube vibration response due to turbulent buffeting under the same experimental conditions predicted a similar reduction in tube amplitude. The void fraction for the fluid-elastic instability threshold in the presence of tube bundle void fraction generation was higher than that for the upstream void fraction generation case. The first explanation of this difference is the level of turbulent buffeting forces the tube bundle was exposed to
Two-phase-flow cooling concept for fusion reactor blankets
International Nuclear Information System (INIS)
Bender, D.J.; Hoffman, M.A.
1977-01-01
The new two-phase heat transfer medium proposed is a mixture of potassium droplets and helium which permits blanket operation at hih temperature and low pressure, while maintaining acceptable pumping power requirements, coolant ducting size, and blanket structure fractions. A two-phase flow model is described. The helium pumping power and the primary heat transfer loop are discussed
Two-phase flow characterisation by nuclear magnetic resonance
International Nuclear Information System (INIS)
Leblond, J.; Javelot, S.; Lebrun, D.; Lebon, L.
1998-01-01
The results presented in this paper demonstrate the performance of the PFGSE-NMR to obtain a complete characterisation of two-phase flows. Different methods are proposed to characterise air-water flows in different regimes: stationary two-phase flows and flows in transient condition. Finally a modified PFGSE is proposed to analyse the turbulence of air-water bubbly flow. (author)
Unsteady State Two Phase Flow Pressure Drop Calculations
Ayatollahi, Shahaboddin
1992-01-01
A method is presented to calculate unsteady state two phase flow in a gas-liquid line based on a quasi-steady state approach. A computer program for numerical solution of this method was prepared. Results of calculations using the computer program are presented for several unsteady state two phase flow systems
A Complex Solar Coronal Jet with Two Phases
Energy Technology Data Exchange (ETDEWEB)
Chen, Jie; Su, Jiangtao; Deng, Yuanyong [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Priest, E. R., E-mail: chenjie@bao.ac.cn [Mathematical Institute, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom)
2017-05-01
Jets often occur repeatedly from almost the same location. In this paper, a complex solar jet was observed with two phases to the west of NOAA AR 11513 on 2012 July 2. If it had been observed at only moderate resolution, the two phases and their points of origin would have been regarded as identical. However, at high resolution we find that the two phases merge into one another and the accompanying footpoint brightenings occur at different locations. The phases originate from different magnetic patches rather than being one phase originating from the same patch. Photospheric line of sight (LOS) magnetograms show that the bases of the two phases lie in two different patches of magnetic flux that decrease in size during the occurrence of the two phases. Based on these observations, we suggest that the driving mechanism of the two successive phases is magnetic cancellation of two separate magnetic fragments with an opposite-polarity fragment between them.
Estimation of the sugar cane cultivated area from LANDSAT images using the two phase sampling method
Parada, N. D. J. (Principal Investigator); Cappelletti, C. A.; Mendonca, F. J.; Lee, D. C. L.; Shimabukuro, Y. E.
1982-01-01
A two phase sampling method and the optimal sampling segment dimensions for the estimation of sugar cane cultivated area were developed. This technique employs visual interpretations of LANDSAT images and panchromatic aerial photographs considered as the ground truth. The estimates, as a mean value of 100 simulated samples, represent 99.3% of the true value with a CV of approximately 1%; the relative efficiency of the two phase design was 157% when compared with a one phase aerial photographs sample.
Construction of the two-phase critical flow test facility
International Nuclear Information System (INIS)
Chung, C. H.; Chang, S. K.; Park, H. S.; Min, K. H.; Choi, N. H.; Kim, C. H.; Lee, S. H.; Kim, H. C.; Chang, M. H.
2002-03-01
The two-phase critical test loop facility has been constructed in the KAERI engineering laboratory for the simulation of small break loss of coolant accident entrained with non-condensible gas of SMART. The test facility can operate at 12 MPa of pressure and 0 to 60 C of sub-cooling with 0.5 kg/s of non- condensible gas injection into break flow, and simulate up to 20 mm of pipe break. Main components of the test facility were arranged such that the pressure vessel containing coolant, a test section simulating break and a suppression tank inter-connected with pipings were installed vertically. As quick opening valve opens, high pressure/temperature coolant flows through the test section forming critical two-phase flow into the suppression tank. The pressure vessel was connected to two high pressure N2 gas tanks through a control valve to control pressure in the pressure vessel. Another N2 gas tank was also connected to the test section for the non-condensible gas injection. The test facility operation was performed on computers supported with PLC systems installed in the control room, and test data such as temperature, break flow rate, pressure drop across test section, gas injection flow rate were all together gathered in the data acquisition system for further data analysis. This test facility was classified as a safety related high pressure gas facility in law. Thus the loop design documentation was reviewed, and inspected during construction of the test loop by the regulatory body. And the regulatory body issued permission for the operation of the test facility
Non-local two phase flow momentum transport in S BWR
International Nuclear Information System (INIS)
Espinosa P, G.; Salinas M, L.; Vazquez R, A.
2015-09-01
The non-local momentum transport equations derived in this work contain new terms related with non-local transport effects due to accumulation, convection, diffusion and transport properties for two-phase flow. For instance, they can be applied in the boundary between a two-phase flow and a solid phase, or in the boundary of the transition region of two-phase flows where the local volume averaging equations fail. The S BWR was considered to study the non-local effects on the two-phase flow thermal-hydraulic core performance in steady-state, and the results were compared with the classical local averaging volume conservation equations. (Author)
Non-local two phase flow momentum transport in S BWR
Energy Technology Data Exchange (ETDEWEB)
Espinosa P, G.; Salinas M, L.; Vazquez R, A., E-mail: gepe@xanum.uam.mx [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Area de Ingenieria en Recursos Energeticos, Apdo. Postal 55-535, 09340 Ciudad de Mexico (Mexico)
2015-09-15
The non-local momentum transport equations derived in this work contain new terms related with non-local transport effects due to accumulation, convection, diffusion and transport properties for two-phase flow. For instance, they can be applied in the boundary between a two-phase flow and a solid phase, or in the boundary of the transition region of two-phase flows where the local volume averaging equations fail. The S BWR was considered to study the non-local effects on the two-phase flow thermal-hydraulic core performance in steady-state, and the results were compared with the classical local averaging volume conservation equations. (Author)
Industrial aspects of gas-liquid two-phase flow
International Nuclear Information System (INIS)
Hewitt, G.F.
1977-01-01
The lecture begins by reviewing the various types of plant in which two phase flow occurs. Specifically, boiling plant, condensing plant and pipelines are reviewed, and the various two phase flow problems occurring in them are described. Of course, many other kinds of chemical engineering plant involve two phase flow, but are somewhat outside the scope of this lecture. This would include distillation columns, vapor-liquid separators, absorption towers etc. Other areas of industrial two phase flow which have been omitted for space reasons from this lecture are those concerned with gas/solids, liquid/solid and liquid/liquid flows. There then follows a description of some of the two phase flow processes which are relevant in industrial equipment and where special problems occur. The topics chosen are as follows: (1) pressure drop; (2) horizontal tubes - separation effects non-uniformites in heat transfer coefficient, effect of bends on dryout; (3) multicomponent mixtures - effects in pool boiling, mass transfer effects in condensation and Marangoni effects; (4) flow distribution - manifold problems in single phase flow, separation effects at a single T-junction in two phase flow and distribution in manifolds in two phase flow; (5) instability - oscillatory instability, special forms of instability in cryogenic systems; (6) nucleate boiling - effect of variability of surface, unresolved problems in forced convective nucleate boiling; and (7) shell side flows - flow patterns, cross flow boiling, condensation in cross flow
International Nuclear Information System (INIS)
Briola, Stefano; Di Marco, Paolo; Gabbrielli, Roberto
2017-01-01
A novel Combined Cooling, Heating and Power (CCHP) cycle, operating with two-phase devices for the compression and expansion processes and a single-component wet working fluid, is proposed. A detailed sensitivity analysis of the novel CCHP cycle has been investigated in order to evaluate, in terms of energy performance indicators, its potentiality to serve typical trigenerative tertiary and industrial end-users with different fixed operating temperatures. In general, the novel CCHP cycle is characterized by higher energy performance indicators than a separated energy production system. The comparison between the novel CCHP cycle and several commercialized CCHP systems has been performed in the case studies related to tertiary and industrial end-users. The novel CCHP cycle shows a trigenerative capability in wide ranges of the end-users demands without surplus or deficit of the electric or thermal powers. Furthermore, the maximum allowable capital cost of the whole novel CCHP plant (BEPCC), that will assure the profitability of the investment, is calculated in the tertiary and industrial end-users case studies. For the tertiary end-user, the capital costs of the commercialized CCHP are between the minimum and maximum BEPCC values. On the contrary, for the industrial end-user, they are lower than the minimum and maximum BEPCC values. - Highlights: • Novel CCHP cycle with two-phase expanders and compressors has been conceived. • Novel CCHP cycle has higher performances than a separated energy production system. • Novel CCHP cycle satisfies the user demands in wide ranges without surplus/deficit. • Tertiary user: novel CCHP cycle is competitive against marketed CCHP systems. • Industrial user: novel CCHP cycle is not competitive against marketed CCHP systems.
Research on one-dimensional two-phase flow
International Nuclear Information System (INIS)
Adachi, Hiromichi
1988-10-01
In Part I the fundamental form of the hydrodynamic basic equations for a one-dimensional two-phase flow (two-fluid model) is described. Discussions are concentrated on the treatment of phase change inertial force terms in the equations of motion and the author's equations of motion which have a remarkable uniqueness on the following three points. (1) To express force balance of unit mass two-phase fluid instead of that of unit volume two-phase fluid. (2) To pick up the unit existing mass and the unit flowing mass as the unit mass of two-phase fluid. (3) To apply the kinetic energy principle instead of the momentum low in the evaluation of steady inertial force term. In these three, the item (1) is for excluding a part of momentum change or kinetic energy change due to mass change of the examined part of fluid, which is independent of force. The item (2) is not to introduce a phenomenological physical model into the evaluation of phase change inertial force term. And the item (3) is for correctly applying the momentum law taking into account the difference of representative velocities between the main flow fluid (vapor phase or liquid phase) and the phase change part of fluid. In Part II, characteristics of various kinds of high speed two-phase flow are clarified theoretically by the basic equations derived. It is demonstrated that the steam-water two-phase critical flow with violent flashing and the airwater two-phase critical flow without phase change can be described with fundamentally the same basic equations. Furthermore, by comparing the experimental data from the two-phase critical discharge test and the theoretical prediction, the two-phase discharge coefficient, C D , for large sharp-edged orifice is determined as the value which is not affected by the experimental facility characteristics, etc. (author)
Two-phase flow heat transfer in nuclear reactor systems
International Nuclear Information System (INIS)
Koncar, Bostjan; Krepper, Eckhard; Bestion, Dominique; Song, Chul-Hwa; Hassan, Yassin A.
2013-01-01
Complete text of publication follows: Heat transfer and phase change phenomena in two-phase flows are often encountered in nuclear reactor systems and are therefore of paramount importance for their optimal design and safe operation.The complex phenomena observed especially during transient operation of nuclear reactor systems necessitate extensive theoretical and experimental investigations. This special issue brings seven research articles of high quality. Though small in number, they cover a wide range of topics, presenting high complexity and diversity of heat transfer phenomena in two-phase flow. In the last decades a vast amount of research has been devoted to theoretical work and computational simulations, yet the experimental work remains indispensable for understanding of two-phase flow phenomena and for model validation purposes. This is reflected also in this issue, where only one article is purely experimental, while three of them deal with theoretical modelling and the remaining three with numerical simulations. The experimental investigation of the critical heat flux (CHF) phenomena by means of photographic study is presented in the paper of J. Park et al. They have used a high-speed camera system to observe the transient boiling characteristics on a thin horizontal cylinder submerged in a pool of water or highly wetting liquid. Experiments show that the initial boiling process is strongly affected by the properties and wettability of the liquid. The authors have stressed the importance of the local scale observation leading to better understanding of the transient CHF phenomena. In the article of G. Espinosa-Paredes et al. a theoretical work concerning the derivation of transport equations for two-phase flow is presented. The author proposes a novel approach based on derivation of nonlocal volume averaged equations which contain new terms related to nonlocal transport effects. These non-local terms act as coupling elements between the phenomena
Regimes of Two-Phase Flow in Short Rectangular Channel
Chinnov, Evgeny A.; Guzanov, Vladimir V.; Cheverda, Vyacheslav; Markovich, Dmitry M.; Kabov, Oleg A.
2009-08-01
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.
What types of investors generate the two-phase phenomenon?
Ryu, Doojin
2013-12-01
We examine the two-phase phenomenon described by Plerou, Gopikrishnan, and Stanley (2003) [1] in the KOSPI 200 options market, one of the most liquid options markets in the world. By analysing a unique intraday dataset that contains information about investor type for each trade and quote, we find that the two-phase phenomenon is generated primarily by domestic individual investors, who are generally considered to be uninformed and noisy traders. In contrast, our empirical results indicate that trades by foreign institutions, who are generally considered informed and sophisticated investors, do not exhibit two-phase behaviour.
Two-phase-flow models and their limitations
International Nuclear Information System (INIS)
Ishii, M.; Kocamustafaogullari, G.
1982-01-01
An accurate prediction of transient two-phase flow is essential to safety analyses of nuclear reactors under accident conditions. The fluid flow and heat transfer encountered are often extremely complex due to the reactor geometry and occurrence of transient two-phase flow. Recently considerable progresses in understanding and predicting these phenomena have been made by a combination of rigorous model development, advanced computational techniques, and a number of small and large scale supporting experiments. In view of their essential importance, the foundation of various two-phase-flow models and their limitations are discussed in this paper
Thermo-Fluid Dynamics of Two-Phase Flow
Ishii, Mamrou
2011-01-01
"Thermo-fluid Dynamics of Two-Phase Flow, Second Edition" is focused on the fundamental physics of two-phase flow. The authors present the detailed theoretical foundation of multi-phase flow thermo-fluid dynamics as they apply to: Nuclear reactor transient and accident analysis; Energy systems; Power generation systems; Chemical reactors and process systems; Space propulsion; Transport processes. This edition features updates on two-phase flow formulation and constitutive equations and CFD simulation codes such as FLUENT and CFX, new coverage of the lift force model, which is of part
Enhanced mixing in two-phase Taylor-Couette flows
International Nuclear Information System (INIS)
Dherbecourt, Diane
2015-01-01
In the scope of the nuclear fuel reprocessing, Taylor-Couette flows between two concentric cylinders (the inner one in rotation and the outer one at rest) are used at laboratory scale to study the performances of new liquid/liquid extraction processes. Separation performances are strongly related to the mixing efficiency, the quantification of the latter is therefore of prime importance. A previous Ph.D. work has related the mixing properties to the hydrodynamics parameters in single-phase flow, using both experimental and numerical investigations. The Reynolds number, flow state and vortices height (axial wavelength) impacts were thus highlighted. This Ph.D. work extends the previous study to two-phase configurations. For experimental simplification, and to avoid droplets coalescence or breakage, spherical solid particles of PMMA from 800 μm to 1500 μm diameter are used to model rigid droplets. These beads are suspended in an aqueous solution of dimethyl sulfoxide (DMSO) and potassium Thiocyanate (KSCN). The experimental setup uses coupled Particle Image Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF) to access simultaneously the hydrodynamic and the mixing properties. Although the two phases are carefully chosen to match in density and refractive index, these precautions are not sufficient to ensure a good measurement quality, and a second PLIF channel is added to increase the precision of the mixing quantification. The classical PLIF channel monitors the evolution of Rhodamine WT concentration, while the additional PLIF channel is used to map a Fluorescein dye, which is homogeneously concentrated inside the gap. This way, a dynamic mask of the bead positions can be created and used to correct the Rhodamine WT raw images. Thanks to this experimental setup, a parametric study of the particles size and concentration is achieved. A double effect of the dispersed phase is evidenced. On one hand, the particles affect the flow hydrodynamic properties
Two phase flow problems in power station boilers
International Nuclear Information System (INIS)
Firman, E.C.
1974-01-01
The paper outlines some of the waterside thermal and hydrodynamic phenomena relating to design and operation of large boilers in central power stations. The associated programme of work is described with an outline of some results already obtained. By way of introduction, the principal features of conventional and nuclear drum boilers and once-through nuclear heat exchangers are described in so far as they pertain to this area of work. This is followed by discussion of the relevant physical phenomena and problems which arise. For example, the problem of steam entrainment from the drum into the tubes connecting it to the furnace wall tubes is related to its effects on circulation and possible mechanisms of tube failure. Other problems concern the transient associated with start-up or low load operation of plant. The requirement for improved mathematical representation of steady and dynamic performance is mentioned together with the corresponding need for data on heat transfer, pressure loss, hydrodynamic stability, consequences of deposits, etc. The paper concludes with reference to the work being carried out within the C.E.G.B. in relation to the above problems. The facilities employed and the specific studies being made on them are described: these range from field trials on operational boilers to small scale laboratory investigations of underlying two phase flow mechanisms and include high pressure water rigs and a freon rig for simulation studies
Transient two-phase performance of LOFT reactor coolant pumps
International Nuclear Information System (INIS)
Chen, T.H.; Modro, S.M.
1983-01-01
Performance characteristics of Loss-of-Fluid Test (LOFT) reactor coolant pumps under transient two-phase flow conditions were obtained based on the analysis of two large and small break loss-of-coolant experiments conducted at the LOFT facility. Emphasis is placed on the evaluation of the transient two-phase flow effects on the LOFT reactor coolant pump performance during the first quadrant operation. The measured pump characteristics are presented as functions of pump void fraction which was determined based on the measured density. The calculated pump characteristics such as pump head, torque (or hydraulic torque), and efficiency are also determined as functions of pump void fractions. The importance of accurate modeling of the reactor coolant pump performance under two-phase conditions is addressed. The analytical pump model, currently used in most reactor analysis codes to predict transient two-phase pump behavior, is assessed
Two-phase systems. Fundamentals and industrial applications
International Nuclear Information System (INIS)
Woillez, Jacques
2014-01-01
Two-phase flows are omnipresent in industrial processes in different sectors with the behaviour and control of non-mixing mixtures of gas and liquids, of several liquids, of solids and fluids which are present in the production of raw materials, in the environment, in energy production, in chemistry, in pharmaceutical or food industry. The author presents the fundamentals elements which are needed to perform hardware predictive calculations and to understand typical phenomena associated with these flows. The chapters address fluids mechanics (movement equations, Bernoulli equation, load losses, turbulence, heat exchange coefficients, thermodynamics, compressible flows), two-phase systems (characteristic values, modes of appearance of two-phase flows, conduct flows, suspension mechanics, mass transfers, similarity, numerical simulation), the applications (energy production, agitation and mixing, phase separation, sprays), and peculiar phenomena (Marangoni effect, the tea cup effect, entry jets, water hammer effect, sound speed, two-phase pumping, fluidization)
Visual Analysis of Inclusion Dynamics in Two-Phase Flow.
Karch, Grzegorz Karol; Beck, Fabian; Ertl, Moritz; Meister, Christian; Schulte, Kathrin; Weigand, Bernhard; Ertl, Thomas; Sadlo, Filip
2018-05-01
In single-phase flow visualization, research focuses on the analysis of vector field properties. In two-phase flow, in contrast, analysis of the phase components is typically of major interest. So far, visualization research of two-phase flow concentrated on proper interface reconstruction and the analysis thereof. In this paper, we present a novel visualization technique that enables the investigation of complex two-phase flow phenomena with respect to the physics of breakup and coalescence of inclusions. On the one hand, we adapt dimensionless quantities for a localized analysis of phase instability and breakup, and provide detailed inspection of breakup dynamics with emphasis on oscillation and its interplay with rotational motion. On the other hand, we present a parametric tightly linked space-time visualization approach for an effective interactive representation of the overall dynamics. We demonstrate the utility of our approach using several two-phase CFD datasets.
Metrology of two-phase flow: different methods
International Nuclear Information System (INIS)
Delhaye, J.M.; Galaup, J.P.; Reocreux, M.; Ricque, R.
Nine papers are presented concerning different methods of measuring two-phase flow. Some of the methods and equipment discussed include: radiation absorption, electromagnetic flowmeter, anemometry, resistance probes, phase indicating microthermocouples, optical probes, sampling methods, and pitot tubes
Qualitative behaviour of incompressible two-phase flows with phase ...
Indian Academy of Sciences (India)
Jan Prüss
2017-11-07
Nov 7, 2017 ... Qualitative behaviour of incompressible two-phase flows with phase ... Germany. 2Graduate School of Human and Environmental Studies, Kyoto University, ... Note that j is a dummy variable as it can be eliminated from the ...
International Nuclear Information System (INIS)
Boucker, M.; Laviaville, J.; Martin, A.; Bechaud, C.; Bestion, D.; Coste, P.
2004-01-01
The objective of this communication is to present some preliminary applications to pressurized thermal shock (PTS) investigations of the CFD (Computational Fluid Dynamics) two-phase flow solver of the new NEPTUNE thermal-hydraulics platform. In the framework of plant life extension, the Reactor Pressure Vessel (RPV) integrity is a major concern, and an important part of RPV integrity assessment is related to PTS analysis. In the case where the cold legs are partially filled with steam, it becomes a two-phase problem and new important effects occur, such as condensation due to the Emergency Core Cooling (ECC) injections of sub-cooled water. Thus, an advanced prediction of RPV thermal loading during these transients requires sophisticated two-phase, local scale, 3-dimensional codes. In that purpose, a program has been set up to extend the capabilities of the NEPTUNE two-phase CFD solver. A simple set of turbulence and condensation model for free surface steam-water flow has been tested in simulation of an ECC high pressure injection representing facility, using a full 3-dimensional mesh and the new NEPTUNE solver. Encouraging results have been obtained but it should be noticed that several sources of error can compensate for one another. Nevertheless, the computation presented here allows to be reasonable confident in the use of two-phase CFD in order to carry out refined analysis of two-phase PTS scenarios within the next years
Two-phase flow patterns in horizontal rectangular minichannel
Directory of Open Access Journals (Sweden)
Ron’shin Fedor
2016-01-01
Full Text Available The two-phase flow in a short horizontal channel of rectangular cross-section of 1 × 19 mm2 has been studied experimentally. Five conventional two-phase flow patterns have been detected (bubble, churn, stratified, annular and jet and transitions between them have been determined. It is shown that a change in the width of the horizontal channels has a substantial effect on the boundaries between the flow regimes.
Refrigeration. Two-Phase Flow. Flow Regimes and Pressure Drop
DEFF Research Database (Denmark)
Knudsen, Hans-Jørgen Høgaard
2002-01-01
The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature.......The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature....
Stochastic modelling of two-phase flows including phase change
International Nuclear Information System (INIS)
Hurisse, O.; Minier, J.P.
2011-01-01
Stochastic modelling has already been developed and applied for single-phase flows and incompressible two-phase flows. In this article, we propose an extension of this modelling approach to two-phase flows including phase change (e.g. for steam-water flows). Two aspects are emphasised: a stochastic model accounting for phase transition and a modelling constraint which arises from volume conservation. To illustrate the whole approach, some remarks are eventually proposed for two-fluid models. (authors)
Two-phase cooling fluids; Les fluides frigoporteurs diphasiques
Energy Technology Data Exchange (ETDEWEB)
Lallemand, A. [Institut National des Sciences Appliquees (INSA), 69 - Lyon (France)
1997-12-31
In the framework of the diminution of heat transfer fluid consumption, the concept of indirect refrigerating circuits, using cooling intermediate fluids, is reviewed and the fluids that are currently used in these systems are described. Two-phase cooling fluids advantages over single-phase fluids are presented with their thermophysical characteristics: solid fraction, two-phase mixture enthalpy, thermal and rheological properties, determination of heat and mass transfer characteristics, and cold storage through ice slurry
Review on two-phase flow instabilities in narrow spaces
International Nuclear Information System (INIS)
Tadrist, L.
2007-01-01
Instabilities in two-phase flow have been studied since the 1950s. These phenomena may appear in power generation and heat transfer systems where two-phase flow is involved. Because of thermal management in small size systems, micro-fluidics plays an important role. Typical processes must be considered when the channel hydraulic diameter becomes very small. In this paper, a brief review of two-phase flow instabilities encountered in channels having hydraulic diameters greater than 10 mm are presented. The main instability types are discussed according to the existing experimental results and models. The second part of the paper examines two-phase flow instabilities in narrow spaces. Pool and flow boiling cases are considered. Experiments as well as theoretical models existing in the literature are examined. It was found that several experimental works evidenced these instabilities meanwhile only limited theoretical developments exist in the literature. In the last part of the paper an interpretation of the two-phase flow instabilities linked to narrow spaces are presented. This approach is based on characteristic time scales of the two-phase flow and bubble growth in the capillaries
A turbulent two-phase flow model for nebula flows
International Nuclear Information System (INIS)
Champney, J.M.; Cuzzi, J.N.
1990-01-01
A new and very efficient turbulent two-phase flow numericaly model is described to analyze the environment of a protoplanetary nebula at a stage prior to the formation of planets. Focus is on settling processes of dust particles in flattened gaseous nebulae. The model employs a perturbation technique to improve the accuracy of the numerical simulations of such flows where small variations of physical quantities occur over large distance ranges. The particles are allowed to be diffused by gas turbulence in addition to settling under gravity. Their diffusion coefficients is related to the gas turbulent viscosity by the non-dimensional Schmidt number. The gas turbulent viscosity is determined by the means of the eddy viscosity hypothesis that assumes the Reynolds stress tensor proportional to the mean strain rate tensor. Zero- and two-equation turbulence models are employed. Modeling assumptions are detailed and discussed. The numerical model is shown to reproduce an existing analytical solution for the settling process of particles in an inviscid nebula. Results of nebula flows are presented taking into account turbulence effects of nebula flows. Diffusion processes are found to control the settling of particles. 24 refs
A two-phase model of aquifer heterogeneity
International Nuclear Information System (INIS)
Moltyaner, G.L.
1994-11-01
A two-phase model of a fluid-saturated geologic medium is developed with groundwater velocity (rather than the hydraulic conductivity) as the primary model parameter. The model describes the groundwater flow, contaminant transport processes, and geologic medium structure at the local-scale of a continuum representation and relates structure to processes quantitatively. In this model, the heterogeneity of a geologic medium is characterized either in terms of the spatial variability in the bulk (local-scale) fluid density and sediment density, or in terms of variability in the local-scale porosity and effective grain diameter. The local-scale continuity equations resulting from these properties are derived for both phases. The effective grain diameter is employed to quantify the geologic structure. Velocity is employed to quantify the transport process. Since structure controls process, a high correlation is observed between the effective grain diameter and velocity. The observed correlation leads to a new formulation of Darcy's law without invoking the concept of a fictitious (Darcy's) velocity. The local-scale groundwater flow equation is developed on the basis of the new formulation. (author). 16 refs., 4 figs
Acceleration of a two-phase flow by boiling, (3)
International Nuclear Information System (INIS)
Mori, Yasuo; Hijikata, Kunio; Iwata, Shoichiro
1976-01-01
Acceleration of two-component, two-phase flow has been studied, and a method using the volume expansion by boiling for accelerating fluid has been investigated. In this study, the phenomena of atomizing and boiling were separated, and the liquid with low boiling point was injected into water at lower than the saturation temperature, and was atomized. Then, this was mixed with high temperature liquid and was boiled. The uniform buffle flow was produced, and the phenomena were observed with a high speed camera. The process of acceleration and the acceleration performance were compared with the results of theoretical analysis described in the second report. The experiment was carried out with liquid R113, and at first, the mechanism of atomizing was studied. The atomizing was caused when the relative velocity between R113 and water was more than 4 m/s irrespective of water velocity. The distribution of the diameter of fine liquid drops was almost normal distribution. When the fine drops of R113 were mixed with the high temperature water, bubbles were produced, and the production rate showed definite dependence on the degree of overheating. The flow of bubbles was uniform. However, some of R113 did not become bubbles. The efficiency of acceleration was 1.0 which was independent of the degree of overheating. A further problem is to reduce the quantity of the liquid which does not boil. (Kato, T.)
International Nuclear Information System (INIS)
Burkholder, Michael B.; Litster, Shawn
2016-01-01
In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.
Energy Technology Data Exchange (ETDEWEB)
Burkholder, Michael B.; Litster, Shawn, E-mail: litster@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
2016-05-15
In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.
Contribution to the theory of the two phase blowdown phenomenon
International Nuclear Information System (INIS)
Hutcherson, M.N.
1975-12-01
In order to accurately model the two phase portion of a pressure vessel blowdown, it becomes necessary to understand the bubble growth mechanism within the vessel during the early period of the decompression, the two phase flow behavior within the vessel, and the applicability of the available two phase critical flow models to the blowdown transient. To aid in providing answers to such questions, a small scale, separate effects, isothermal blowdown experiment has been conducted in a small pressure vessel. The tests simulated a full open, double ended, guillotine break in a large diameter, short exhaust duct from the vessel. The vaporization process at the initiation of the decompression is apparently that of thermally dominated bubble growth originating from the surface cavities inside the system. Thermodynamic equilibrium of the remaining fluid within the vessel existed in the latter portion of the decompression. A nonuniform distribution of fluid quality within the vessel was also detected in this experiment. By comparison of the experimental results from this and other similar transient, two phase critical flow studies with steady state, small duct, two phase critical flow data, it is shown that transient, two phase critical flow in large ducts appears to be similar to steady state, two phase critical flow in small ducts. Analytical models have been developed to predict the blowdown characteristics of a system during subcooled decompression, the bubble growth regime of blowdown, and also in the nearly dispersed period of depressurization. This analysis indicates that the system pressure history early in the blowdown is dependent on the internal vessel surface area, the internal vessel volume, and also on the exhaust flow area from the system. This analysis also illustrates that the later period of decompression can be predicted based on thermodynamic equilibrium
Phase separation and pressure drop of two-phase flow in vertical manifolds
International Nuclear Information System (INIS)
Zetzmann, K.
1982-01-01
The splitting of a two-phase mass flow in a tube manifold results in a separation between liquid and gas phase. A study is presented of the phase distribution and the related two-phase pressure drop for vertical manifolds in the technically relevant geometry and flow parameter region of an air-water-flow. At the outlet changes in the gas/fluid-radio are observed which are proportional to this ratio at the inlet. The separation characteristic strongly depends on the massflow through the junction. Empirical equations are given to calculate the separation. Measuring the pressure drop at main- and secondary tube of the manifold the additional pressure drop can be obtained. If these results are related with the dynamic pressure at the inlet, two-phase resistance coefficients can be deduced, which may be tested by empirical relations. (orig.) [de
Fluid-elastic vibration in two-phase cross flow
International Nuclear Information System (INIS)
Sasakawa, T.; Serizawa, A.; Kawara, Z.
2003-01-01
The present work aims at clarifying the mechanisms of fluid elastic vibration of tube bundles in two-phase cross flow. The experiment is conducted using air-water two-phase flow under atmospheric pressure. The test section is a 1.03m long transparent acrylic square duct with 128 x 128 mm 2 cross section, which consists of 3 rod-rows with 5 rods in each row. The rods are 125mm long aluminum rods with 22 mm in diameter (p/D=1.45). The natural frequency of rod vibration is about 30Hz. The result indicated a diversion of observed trend in vibration behavior depending on two-phase flow patterns either bubbly flow or churn flow. Specifically, in churn flow, the fluid elastic vibration has been observed to occur when the frequency in void fraction fluctuation approached to the natural frequency of the rods, but this was not the case in fluid elastic vibration in bubbly flow. This fact suggests the existence of mechanisms closely coupled with two-phase flow structures depending on the flow patterns, that is, static two-phase character-controlled mechanism in bubbly flow and dynamic character- controlled in churn flow
Experimental investigation two phase flow in direct methanol fuel cells
International Nuclear Information System (INIS)
Mat, M. D.; Kaplan, Y.; Celik, S.; Oeztural, A.
2007-01-01
Direct methanol fuel cells (DMFC) have received many attentions specifically for portable electronic applications since it utilize methanol which is in liquid form in atmospheric condition and high energy density of the methanol. Thus it eliminates the storage problem of hydrogen. It also eliminates humidification requirement of polymeric membrane which is a problem in PEM fuel cells. Some electronic companies introduced DMFC prototypes for portable electronic applications. Presence of carbon dioxide gases due to electrochemical reactions in anode makes the problem a two phase problem. A two phase flow may occur at cathode specifically at high current densities due to the excess water. Presence of gas phase in anode region and liquid phase in cathode region prevents diffusion of fuel and oxygen to the reaction sites thus reduces the performance of the system. Uncontrolled pressure buildup in anode region increases methanol crossover through membrane and adversely effect the performance. Two phase flow in both anode and cathode region is very effective in the performance of DMYC system and a detailed understanding of two phase flow for high performance DMFC systems. Although there are many theoretical and experimental studies available on the DMFC systems in the literature, only few studies consider problem as a two-phase flow problem. In this study, an experimental set up is developed and species distributions on system are measured with a gas chromatograph. System performance characteristics (V-I curves) is measured depending on the process parameters (temperature, fuel ad oxidant flow rates, methanol concentration etc)
Interaction between local parameters of two-phase flow and random forces on a cylinder
International Nuclear Information System (INIS)
Sylviane Pascal-Ribot; Yves Blanchet; Franck Baj; Phillippe Piteau
2005-01-01
Full text of publication follows: In the frame of assessments of steam generator tube bundle vibrations, a study was conducted in order to investigate the effects of an air/water flow on turbulent buffeting forces induced on a cylinder. The main purpose is to relate the physical parameters characterizing an air/water two-phase crossflow with the structural loading of a fixed cylindrical tube. In this first approach, the experiments are carried out in a rectangular acrylic test section supplied with a vertical upward bubbly flow. This flow is transversally impeded by a fixed rigid 12,15 mm diameter cylinder. Different turbulence grids are used in order to modify two-phase characteristics such as bubble diameter, void fraction profile, fluctuation parameters. Preliminarily, a dimensional analysis of fluid-structure interaction under two-phase turbulent solicitations has enabled to identify a list of physically relevant variables which must be measured to evaluate the random forces. The meaning of these relevant parameters as well as the effect of flow patterns are discussed. Direct measurements of two-phase flow parameters are performed simultaneously with measurements of forces exerted on the cylinder. The main descriptive parameters of a two-phase flow are measured using a bi-optical probe, in particular void fraction profiles, interfacial velocities, bubble diameters, void fraction fluctuations. In the same time, the magnitude of random forces caused by two-phase flow is measured with a force transducer. A thorough analysis of the experimental data is then undertaken in order to correlate physical two-phase mechanisms with the random forces exerted on the cylinder. The hypotheses made while applying the dimensional analysis are verified and their pertinence is discussed. Finally, physical parameters involved in random buffeting forces applied on a transverse tube are proposed to scale the spectral magnitude of these forces and comparisons with other authors
Two-Phase Phenomena In Wet Flue Gas Desulfurization Process
International Nuclear Information System (INIS)
Minzer, U.; Moses, E.J.; Toren, M.; Blumenfeld, Y.
1998-01-01
In order to reduce sulfur oxides discharge, Israel Electric Corporation (IEC) is building a wet Flue Gas Desulfurization (FGD) facility at Rutenberg B power station. The primary objective of IEC is to minimize the occurrence of stack liquid discharge and avoid the discharge of large droplets, in order to prevent acid rain around the stack. Liquid discharge from the stack is the integrated outcome of two-phase processes, which are discussed in this work. In order to estimate droplets discharge the present investigation employs analytical models, empirical tests, and numerical calculations of two-phase phenomena. The two-phase phenomena are coupled and therefore cannot be investigated separately. The present work concerns the application of Computational Fluid Dynamic (CFD) as an engineering complementary tool in the IEC investigation
DISTRIBUTION OF TWO-PHASE FLOW IN A DISTRIBUTOR
Directory of Open Access Journals (Sweden)
AZRIDJAL AZIZ
2012-02-01
Full Text Available The flow configuration and distribution behavior of two-phase flow in a distributor made of acrylic resin have been investigated experimentally. In this study, air and water were used as two-phase flow working fluids. The distributor consists of one inlet and two outlets, which are set as upper and lower, respectively. The flow visualization at the distributor was made by using a high–speed camera. The flow rates of air and water flowing out from the upper and lower outlet branches were measured. Effects of inclination angle of the distributor were investigated. By changing the inclination angle from vertical to horizontal, uneven distributions were also observed. The distribution of two-phase flow through distributor tends even flow distribution on the vertical position and tends uneven distribution on inclined and horizontal positions. It is shown that even distribution could be achieved at high superficial velocities of both air and water.
Behavior of pumps conveying two-phase liquid flow
International Nuclear Information System (INIS)
Grison, Pierre; Lauro, J.-F.
1979-01-01
Determination of the two-phase flow (critical or otherwise) through a pump is an essential requirement for complete description of a loss of primary coolant accident in a PWR plant. Theoretical and experimental research at Electricite de France on this subject is described and problems associated with the introduction of a two-phase fluid (with mass transfer) are discussed, with an attempt to single out new phenomena involved and establish their effect on pump behavior. A complementary experimental investigation is described and the results of tests at pressures and temperatures up to 120 bars and 320 0 C respectively are compared with the theoretical model data [fr
Behavior of pumps conveying two-phase liquid flow
Energy Technology Data Exchange (ETDEWEB)
Grison, P; Lauro, J F [Electricite de France, 78 - Chatou. Direction des Etudes et Recherches
1979-01-01
Determination of the two-phase flow (critical or otherwise) through a pump is an essential requirement for complete description of a loss of primary coolant accident in a PWR plant. Theoretical and experimental research at Electricite de France on this subject is described and problems associated with the introduction of a two-phase fluid (with mass transfer) are discussed, with an attempt to single out new phenomena involved and establish their effect on pump behavior. A complementary experimental investigation is described and the results of tests at pressures and temperatures up to 120 bars and 320/sup 0/C respectively are compared with the theoretical model data.
Two-phase LMMHD mixer-development experiments
International Nuclear Information System (INIS)
Fabris, G.; Dunn, P.F.; Chow, J.C.F.
1978-01-01
The results of a series of experiments conducted to evaluate the fluid mechanical performance of various two-phase LMMHD mixer designs are presented. The results from both flow visualization studies of the local two-phase flows downstream from various mixer-element configurations and local measurements performed to characterize these flows are presented. A conceptual LMMHD mixer design is described that insures the generation of small bubbles, prevents the formation of gas slugs and separated regions, and favors the stabilization of a homogeneous foam flow
Shock wave of vapor-liquid two-phase flow
Institute of Scientific and Technical Information of China (English)
Liangju ZHAO; Fei WANG; Hong GAO; Jingwen TANG; Yuexiang YUAN
2008-01-01
The shock wave of vapor-liquid two-phase flow in a pressure-gain steam injector is studied by build-ing a mathematic model and making calculations. The results show that after the shock, the vapor is nearly com-pletely condensed. The upstream Mach number and the volume ratio of vapor have a great effect on the shock. The pressure and Mach number of two-phase shock con-form to the shock of ideal gas. The analysis of available energy shows that the shock is an irreversible process with entropy increase.
Two-phase flow model with nonequilibrium and critical flow
International Nuclear Information System (INIS)
Sureau, H.; Houdayer, G.
1976-01-01
The model proposed includes the three conservation equations (mass, momentum, energy) applied to the two phase flows and a fourth partial derivative equation which takes into account the nonequilibriums and describes the mass transfer process. With this model, the two phase critical flow tests performed on the Moby-Dick loop (CENG) with several geometries, are interpreted by a unique law. Extrapolations to industrial dimension problems show that geometry and size effects are different from those obtained with earlier models (Zaloudek, Moody, Fauske) [fr
A void fraction model for annular two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Tandon, T.N.; Gupta, C.P.; Varma, H.K.
1985-01-01
An analytical model has been developed for predicting void fraction in two-phase annular flow. In the analysis, the Lockhart-Martinelli method has been used to calculate two-phase frictional pressure drop and von Karman's universal velocity profile is used to represent the velocity distribution in the annular liquid film. Void fractions predicted by the proposed model are generally in good agreement with a available experimental data. This model appears to be as good as Smith's correlation and better than the Wallis and Zivi correlations for computing void fraction.
Mechanistic multidimensional analysis of horizontal two-phase flows
International Nuclear Information System (INIS)
Tselishcheva, Elena A.; Antal, Steven P.; Podowski, Michael Z.
2010-01-01
The purpose of this paper is to discuss the results of analysis of two-phase flow in horizontal tubes. Two flow situations have been considered: gas/liquid flow in a long straight pipe, and similar flow conditions in a pipe with 90 deg. elbow. The theoretical approach utilizes a multifield modeling concept. A complete three-dimensional two-phase flow model has been implemented in a state-of-the-art computational multiphase fluid dynamics (CMFD) computer code, NPHASE. The overall model has been tested parametrically. Also, the results of NPHASE simulations have been compared against experimental data for a pipe with 90 deg. elbow.
Energy Technology Data Exchange (ETDEWEB)
Sim, Woo Gun; Dagdan, Banzragch [Hannam Univ., Daejeon (Korea, Republic of)
2017-03-15
Two-phase cross flow exists in many shell-and-tube heat exchangers such as condensers, evaporators, and nuclear steam generators. The drag force acting on a tube bundle subjected to air/water flow is evaluated experimentally. The cylinders subjected to two-phase flow are arranged in a normal square array. The ratio of pitch to diameter is 1.35, and the diameter of the cylinder is 18 mm. The drag force along the flow direction on the tube bundles is measured to calculate the drag coefficient and the two-phase damping ratio. The two-phase damping ratios, given by the analytical model for a homogeneous two-phase flow, are compared with experimental results. The correlation factor between the frictional pressure drop and the hydraulic drag coefficient is determined from the experimental results. The factor is used to calculate the drag force analytically. It is found that with an increase in the mass flux, the drag force, and the drag coefficients are close to the results given by the homogeneous model. The result shows that the damping ratio can be calculated using the homogeneous model for bubbly flow of sufficiently large mass flux.
Numerical methods for two-phase flow with contact lines
Energy Technology Data Exchange (ETDEWEB)
Walker, Clauido
2012-07-01
This thesis focuses on numerical methods for two-phase flows, and especially flows with a moving contact line. Moving contact lines occur where the interface between two fluids is in contact with a solid wall. At the location where both fluids and the wall meet, the common continuum descriptions for fluids are not longer valid, since the dynamics around such a contact line are governed by interactions at the molecular level. Therefore the standard numerical continuum models have to be adjusted to handle moving contact lines. In the main part of the thesis a method to manipulate the position and the velocity of a contact line in a two-phase solver, is described. The Navier-Stokes equations are discretized using an explicit finite difference method on a staggered grid. The position of the interface is tracked with the level set method and the discontinuities at the interface are treated in a sharp manner with the ghost fluid method. The contact line is tracked explicitly and its dynamics can be described by an arbitrary function. The key part of the procedure is to enforce a coupling between the contact line and the Navier-Stokes equations as well as the level set method. Results for different contact line models are presented and it is demonstrated that they are in agreement with analytical solutions or results reported in the literature.The presented Navier-Stokes solver is applied as a part in a multiscale method to simulate capillary driven flows. A relation between the contact angle and the contact line velocity is computed by a phase field model resolving the micro scale dynamics in the region around the contact line. The relation of the microscale model is then used to prescribe the dynamics of the contact line in the macro scale solver. This approach allows to exploit the scale separation between the contact line dynamics and the bulk flow. Therefore coarser meshes can be applied for the macro scale flow solver compared to global phase field simulations
Experimental study on local resistance of two-phase flow through spacer grid with rod bundle
International Nuclear Information System (INIS)
Yan Chaoxing; Yan Changqi; Sun Licheng; Tian Qiwei
2015-01-01
The experimental study on local resistance of single-phase and two-phase flows through a spacer grid in a vertical channel with 3 × 3 rod bundle was carried out under the normal temperature and pressure. For the case of single-phase flow, the liquid Reynolds number covered the range of 290-18 007. For the case of two-phase flow, the ranges of gas and liquid superficial velocities were 0.013-3.763 m/s and 0.076-1.792 m/s, respectively. A correlation for predicting local resistance of single-phase flow was given based on experimental results. Eight classical two-phase viscosity formulae for homogeneous model were evaluated against the experimental data of two-phase flow. The results show that Dukler model predicts the experimental data well in the range of Re 1 < 9000 while McAdams correlation is the best one for Re 1 ≥ 9000. For all experimental data, Dukler model provides the best prediction with the mean relative error of 29.03%. A new correlation is fitted for the range of Re 1 < 9000 by considering mass quality, two- phase Reynolds number and liquid and gas densities, resulting in a good agreement with the experimental data. (authors)
Measurement of void fraction and bubble size distribution in two-phase flow system
International Nuclear Information System (INIS)
Huahun, G.
1987-01-01
The importance of study two phase flow parameter and microstructure has appeared increasingly, with the development of two-phase flow discipline. In the paper, the measurement methods of several important microstructure parameter in a two phase flow vertical channel have been studied. Using conductance probe the two phase flow pattern and the average void fraction have been measured previously by the authors. This paper concerns microstructure of the bubble size distribution and local void fraction. The authors studied the methods of measuring bubble velocity, size distribution and local void fraction using double conductance probes and a set of apparatus. Based on our experiments and Yoshihiro work, a formula of calculated local void fraction has been deduced by using the statistical characteristics of bubbles in two phase flow and the relation between calculated bubble size and voltage has been determined. Finally the authors checked by using photograph and fast valve, which is classical but reliable. The results are the same with what has been studied before
Application of two-phase flow for cooling of hybrid microchannel PV cells: A comparative study
International Nuclear Information System (INIS)
Valeh-e-Sheyda, Peyvand; Rahimi, Masoud; Karimi, Ebrahim; Asadi, Masomeh
2013-01-01
Highlights: ► Showing cooling potential of gas–liquid two-phase flow in microchannels for PV cell. ► Introducing the concept of using slug flow in microchannels for cooling of PV cells. ► In single-phase flow, increasing the liquid flow rate enhances the PV power. ► Showing that in two-phase flow the output power related the fluid flow regime. ► By coupling PV and microchannel an increase up to 38% in output power was observed. - Abstract: This paper reports the experimental data from performance of two-phase flows in a small hybrid microchannel solar cell. Using air and water as two-phase fluid, the experiments were conducted at indoor condition in an array of rectangular microchannels with a hydraulic diameter of 0.667 mm. The gas superficial velocity ranges were between 0 and 3.27 m s −1 while liquid flow rate was 0.04 m s −1 . The performance analysis of the PV cell at slug and transitional slug/annular flow regimes are the focus of this study. The influence of two-phase working fluid on PV cell cooling was compared with single-phase. In addition, the great potential of slug flow for heat removal enhancement in PV/T panel was investigated. The obtained data showed the proposed hybrid system could substantially increases the output power of PV solar cells
Numerical flow analyses of a two-phase hydraulic coupling
Energy Technology Data Exchange (ETDEWEB)
Hur, N.; Kwak, M.; Moshfeghi, M. [Sogang University, Seoul (Korea, Republic of); Chang, C.-S.; Kang, N.-W. [VS Engineering, Seoul (Korea, Republic of)
2017-05-15
We investigated flow characteristics in a hydraulic coupling at different charged water conditions and speed ratios. Hence, simulations were performed for three-dimensional two-phase flow by using the VOF method. The realizable k-ε turbulence model was adopted. To resolve the interaction of passing blades of the primary and secondary wheels, simulations were conducted in the unsteady framework using a sliding grid technique. The results show that the water-air distribution inside the wheel is strongly dependent upon both amount of charged water and speed ratio. Generally, air is accumulated in the center of the wheel, forming a toroidal shape wrapped by the circulating water. The results also show that at high speed ratios, the solid-body-like rotation causes dry areas on the periphery of the wheels and, hence, considerably decreases the circulating flow rate and the transmitted torque. Furthermore, the momentum transfer was investigated through the concept of a mass flux triangle based on the local velocity multiplied by the local mixture density instead of the velocity triangle commonly used in a single-phase turbomachine analysis. Also, the mass fluxes along the radius of the coupling in the partially charged and fully charged cases were found to be completely different. It is shown that the flow rate at the interfacial plane and also the transmitted torque are closely related and are strongly dependent upon both the amount of charged water and speed ratio. Finally, a conceptual categorization together with two comprehensive maps was provided for the torque transmission and also circulating flow rates. These two maps in turn exhibit valuable engineering information and can serve as bases for an optimal design of a hydraulic coupling.
Direct numerical simulation of reactor two-phase flows enabled by high-performance computing
Energy Technology Data Exchange (ETDEWEB)
Fang, Jun; Cambareri, Joseph J.; Brown, Cameron S.; Feng, Jinyong; Gouws, Andre; Li, Mengnan; Bolotnov, Igor A.
2018-04-01
Nuclear reactor two-phase flows remain a great engineering challenge, where the high-resolution two-phase flow database which can inform practical model development is still sparse due to the extreme reactor operation conditions and measurement difficulties. Owing to the rapid growth of computing power, the direct numerical simulation (DNS) is enjoying a renewed interest in investigating the related flow problems. A combination between DNS and an interface tracking method can provide a unique opportunity to study two-phase flows based on first principles calculations. More importantly, state-of-the-art high-performance computing (HPC) facilities are helping unlock this great potential. This paper reviews the recent research progress of two-phase flow DNS related to reactor applications. The progress in large-scale bubbly flow DNS has been focused not only on the sheer size of those simulations in terms of resolved Reynolds number, but also on the associated advanced modeling and analysis techniques. Specifically, the current areas of active research include modeling of sub-cooled boiling, bubble coalescence, as well as the advanced post-processing toolkit for bubbly flow simulations in reactor geometries. A novel bubble tracking method has been developed to track the evolution of bubbles in two-phase bubbly flow. Also, spectral analysis of DNS database in different geometries has been performed to investigate the modulation of the energy spectrum slope due to bubble-induced turbulence. In addition, the single-and two-phase analysis results are presented for turbulent flows within the pressurized water reactor (PWR) core geometries. The related simulations are possible to carry out only with the world leading HPC platforms. These simulations are allowing more complex turbulence model development and validation for use in 3D multiphase computational fluid dynamics (M-CFD) codes.
Microgravity two-phase flow and heat transfer
Gabriel, Kamiel S
2007-01-01
Advances in understanding the behaviour of multiphase thermal systems could lead to higher efficiency energy production systems, but such advances have been greatly hindered by the strong effect of gravitational acceleration on the flow. This book presents a coverage of various aspects of two-phase flow behaviour in the virtual absence of gravity.
Approximate characteristics for one-dimensional two-phase flows
International Nuclear Information System (INIS)
Sarayloo, A.; Peddleson, J.
1985-01-01
An approximate method for determining the characteristics associated with one-dimensional particulate two-phase flow models is presented. The method is based on iteration and is valid for small particulate volume fractions. The method is applied to several special cases involving incompressible particles suspended in a gas. The influences of certain changes in the physical model are investigated
TWO-PHASE EJECTOR of CARBON DIOXIDE HEAT PUMP CALCULUS
Directory of Open Access Journals (Sweden)
Sit B.M.
2010-12-01
Full Text Available It is presented the calculus of the two-phase ejector for carbon dioxide heat pump. The method of calculus is based on the method elaborated by S.M. Kandil, W.E. Lear, S.A. Sherif, and is modified taking into account entrainment ratio as the input for the calculus.
Stability of equilibria for a two-phase osmosis model
Lippoth, F.; Prokert, G.
2012-01-01
For a two-phase moving boundary problem modelling the motion of a semipermeable membrane by osmotic pressure and surface tension, we prove that the manifold of equilibria is locally exponentially attractive. Our method relies on maximal regularity results for parabolic systems with relaxation type
Numerical simulation of two phase flows in heat exchangers
International Nuclear Information System (INIS)
Grandotto Biettoli, M.
2006-04-01
The report presents globally the works done by the author in the thermohydraulic applied to nuclear reactors flows. It presents the studies done to the numerical simulation of the two phase flows in the steam generators and a finite element method to compute these flows. (author)
Determination of bubble parameters in two-phase flow
International Nuclear Information System (INIS)
Oliveira Lira, C.A.B. de.
1980-01-01
A development of a probe-detector system for measurement of bubble parameters like size, rise velocity and void fraction in two-phase flow is presented. The method uses an electro resistivity probe and a compact electronic circuit has been developed for obtain this purpose. (author)
Thermalhydraulic instability analysis of a two phase natural circulation loop
International Nuclear Information System (INIS)
Sesini, Paula Aida
1998-01-01
This work presents an analysis of a loop operating in natural circulation regime. Experiments were done in a rectangular closed circuit in one and two-phase flows. Numerical analysis were performed initially with the CIRNAT code and afterwards with RELAP5/MOD2. The limitations of CIRNAT were studied and new developments for this code are proposed. (author)
Controlling two-phase flow in microfluidic systems using electrowetting
Gu, H.
2011-01-01
Electrowetting (EW)-based digital microfluidic systems (DMF) and droplet-based two-phase flow microfluidic systems (TPF) with closed channels are the most widely used microfluidic platforms. In general, these two approaches have been considered independently. However, integrating the two
One-dimensional two-phase thermal hydraulics (ENSTA course)
International Nuclear Information System (INIS)
Olive, J.
1995-11-01
This course is part of the ENSTA 3rd year thermal hydraulics program (nuclear power option). Its purpose is to provide the theoretical basis and main physical notions pertaining to two-phase flow, mainly focussed on water-steam flows. The introduction describes the physical specificities of these flows, emphasizing their complexity. The mathematical bases are then presented (partial derivative equations), leading to a one-dimensional type, simplified description. Balances drawn up for a pipe length volume are used to introduce the mass conservation. motion and energy equations for each phase. Various postulates used to simplify two-phase models are presented, culminating in homogeneous model definitions and equations, several common examples of which are given. The model is then applied to the calculation of pressure drops in two-phase flows. This involves presenting the models most frequently used to represent pressure drops by friction or due to pipe irregularities, without giving details (numerical values of parameters). This chapter terminates with a brief description of static and dynamic instabilities in two-phase flows. Finally, heat transfer conditions frequently encountered in liquid-steam flows are described, still in the context of a 1D model. This chapter notably includes reference to under-saturated boiling conditions and the various forms of DNB. The empirical heat transfer laws are not discussed in detail. Additional material is appended, some of which is in the form of corrected exercises. (author). 6 appends
Two-phase flow instrumentation research at RPI
International Nuclear Information System (INIS)
Lahey, R.T. Jr.; Krycuk, G.
1979-01-01
Novel instrumentation for the measurement of void fraction and phase velocity was developed. An optical digital interferometer and a dual beam x-ray equipment were designed for detection of voids. Pitot tube measurements were made to understand two-phase flow phenomena in liquid phase velocity
Two Phase Flow Split Model for Parallel Channels | Iloeje | Nigerian ...
African Journals Online (AJOL)
The model and code are capable of handling single and two phase flows, steady states and transients, up to ten parallel flow paths, simple and complicated geometries, including the boilers of fossil steam generators and nuclear power plants. A test calculation has been made with a simplified three-channel system ...
A semi-empirical two phase model for rocks
International Nuclear Information System (INIS)
Fogel, M.B.
1993-01-01
This article presents data from an experiment simulating a spherically symmetric tamped nuclear explosion. A semi-empirical two-phase model of the measured response in tuff is presented. A comparison is made of the computed peak stress and velocity versus scaled range and that measured on several recent tuff events
Two-phase alkali-metal experiments in reduced gravity
International Nuclear Information System (INIS)
Antoniak, Z.I.
1986-06-01
Future space missions envision the use of large nuclear reactors utilizing either a single or a two-phase alkali-metal working fluid. The design and analysis of such reactors require state-of-the-art computer codes that can properly treat alkali-metal flow and heat transfer in a reduced-gravity environment. A literature search of relevant experiments in reduced gravity is reported on here, and reveals a paucity of data for such correlations. The few ongoing experiments in reduced gravity are noted. General plans are put forth for the reduced-gravity experiments which will have to be performed, at NASA facilities, with benign fluids. A similar situation exists regarding two-phase alkali-metal flow and heat transfer, even in normal gravity. Existing data are conflicting and indequate for the task of modeling a space reactor using a two-phase alkali-metal coolant. The major features of past experiments are described here. Data from the reduced-gravity experiments with innocuous fluids are to be combined with normal gravity data from the two-phase alkali-metal experiments. Analyses undertaken here give every expectation that the correlations developed from this data base will provide a valid representation of alkali-metal heat transfer and pressure drop in reduced gravity
Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces
International Nuclear Information System (INIS)
Brauner, N.; Rovinsky, J.; Maron, D.M.
1995-01-01
The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the 'flow monograms' describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the 'interface monograms', whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system 'operational monogram'. The 'operational monogram' enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop
Magnitude and sign correlations in conductance fluctuations of horizontal oil water two-phase flow
International Nuclear Information System (INIS)
Zhu, L; Jin, N D; Gao, Z K; Zong, Y B; Zhai, L S; Wang, Z Y
2012-01-01
In experiment we firstly define five typical horizontal oil-water flow patterns. Then we introduce an approach for analyzing signals by decomposing the original signals increment into magnitude and sign series and exploring their scaling properties. We characterize the nonlinear and linear properties of horizontal oil-water two-phase flow, which relate to magnitude and sign series respectively. We find that the joint distribution of different scaling exponents can effectively identify flow patterns, and the detrended fluctuation analysis (DFA) on magnitude and sign series can represent typical horizontal oil-water two-phase flow dynamics characteristics. The results indicate that the magnitude and sign decomposition method can be a helpful tool for characterizing complex dynamics of horizontal oil-water two-phase flow.
Visualization of two-phase flow in metallic pipes using neutron radiographic technique
International Nuclear Information System (INIS)
Luiz, L.C.; Crispim, V.R.
2007-01-01
The study of two-phase flow is a matter of great interest both for the engineering and oil industries. The production of oil and natural gas involves the transportation of fluids in their liquid and gaseous states, respectively, to the processing plant for refinement. The forecasting of two-phase flow in oil pipes is of the utmost important yet an extremely difficult task. With the development of the electronic imaging system, installed in J-9 irradiation channel of the IEN/CNEN Argonauta Reactor, it is possible to visualize the different types of two phase air-water flows in small-diameter metallic pipes. After developing the captured image the liquid-gas drift flux correlation as well as the void fraction in relation to the injected air outflow for a fixed water outflow can be obtained. (author)
Analysis of phase dynamics in two-phase flow using latticegas automata
International Nuclear Information System (INIS)
Ohashi, H.; Hashimoto, Y.; Tsumaya, A.; Chen, Y.; Akiyama, M.
1998-01-01
In this paper, we describe lattice gas automaton models appropriate for two-phase flow simulation and their applications to study various phase dynamics of two-fluid mixtures. Several algorithms are added to the original immiscible Lattice Gas model to adjust surface tension and to introduce density difference between two fluids. Surface tension is controlled by the collision rules an difference in density is due to nonlocal forces between automaton particles. We simulate the relative motion of the dispersed phase in another continuous fluid. Deformation and disintegration of rising drops are reproduced. The interaction between multiple drops is also observed in calculations. Furutre, we obtain the transition of the two-phase flow pattern from bubbly, slug to annular flow. Density difference of two phase is one of the key ingredients to generate the annular flow pattern
Magnetic liquid metal two-phase flow research. Phase 1. Final report
International Nuclear Information System (INIS)
Graves, R.D.
1983-04-01
The Phase I research demonstrates the feasibility of the magnetic liquid metal (MLM) two-phase flow concept. A dispersion analysis is presented based on a complete set of two-phase-flow equations augmented to include stresses due to magnetic polarization of the fluid. The analysis shows that the stability of the MLM two-phase flow is determined by the magnetic Mach number, the slip ratio, geometry of the flow relative to the applied magnetic field, and by the voidage dependence of the interfacial forces. Results of a set of experiments concerned with magnetic effects on the dynamics of single bubble motion in an aqueous-based, viscous, conducting magnetic fluid are presented. Predictions in the theoretical literature are qualitatively verified using a bench-top experimental apparatus. In particular, applied magnetic fields are seen to lead to reduced bubble size at fixed generating orifice pressure
Analysis of forced convective transient boiling by homogeneous model of two-phase flow
International Nuclear Information System (INIS)
Kataoka, Isao
1985-01-01
Transient forced convective boiling is of practical importance in relation to the accident analysis of nuclear reactor etc. For large length-to-diameter ratio, the transient boiling characteristics are predicted by transient two-phase flow calculations. Based on homogeneous model of two-phase flow, the transient forced convective boiling for power and flow transients are analysed. Analytical expressions of various parameters of transient two-phase flow have been obtained for several simple cases of power and flow transients. Based on these results, heat flux, velocity and time at transient CHF condition are predicted analytically for step and exponential power increases, and step, exponential and linear velocity decreases. The effects of various parameters on heat flux, velocity and time at transient CHF condition have been clarified. Numerical approach combined with analytical method is proposed for more complicated cases. Solution method for pressure transient are also described. (author)
Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces
Energy Technology Data Exchange (ETDEWEB)
Brauner, N.; Rovinsky, J.; Maron, D.M. [Tel-Aviv Univ. (Israel)
1995-09-01
The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the `flow monograms` describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the `interface monograms`, whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system `operational monogram`. The `operational monogram` enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop.
Two-phase flow stability structure in a natural circulation system
Energy Technology Data Exchange (ETDEWEB)
Zhou, Zhiwei [Nuclear Engineering Laboratory Zurich (Switzerland)
1995-09-01
The present study reports a numerical analysis of two-phase flow stability structures in a natural circulation system with two parallel, heated channels. The numerical model is derived, based on the Galerkin moving nodal method. This analysis is related to some design options applicable to integral heating reactors with a slightly-boiling operation mode, and is also of general interest to similar facilities. The options include: (1) Symmetric heating and throttling; (2) Asymmetric heating and symmetric throttling; (3) Asymmetric heating and throttling. The oscillation modes for these variants are discussed. Comparisons with the data from the INET two-phase flow stability experiment have qualitatively validated the present analysis.
Investigation of the propagation characteristics in turbulent dispersed two-phase flow
International Nuclear Information System (INIS)
Sami, S.M.
1980-01-01
The propagation characteristics of turbulent dispersed two-phase flows have been studied experimentally using the Pitot tube associated with a conical hot-film anemometer. It is found that the mixture velocity increases with decreasing volumetric mixing ratio of the air and water. The void fraction distribution shows homogeneity across the test section in the special case of fully developed boundary layer two-phase flow. An expression is obtained which relates the local mixture velocity to the local void fraction, gas and liquid densities, and volumetric gas-liquid ratio
Two-phase cross-flow-induced forces acting on a circular cylinder
International Nuclear Information System (INIS)
Hara, F.
1982-01-01
This paper clarifies the characteristics of unsteady flow-induced lift and drag forces acting on a circular cylinder immersed perpendicular to a two-phase bubbly air-water flow, in conjunction with Karman vortex shedding and pressure fluctuations. Experimental results presented show that Karman vortex shedding disappears over a certain value of air concentration in the two-phase flow. Related to this disappearance, flow-induced forces are rather small and periodical in low air concentration but become very large and random in higher air concentration. 7 refs
High speed motion neutron radiography of two-phase flow
International Nuclear Information System (INIS)
Robinson, A.H.; Wang, S.L.
1983-01-01
Current research in the area of two-phase flow utilizes a wide variety of sensing devices, but some limitations exist on the information which can be obtained. Neutron radiography is a feasible alternative to ''see'' the two-phase flow. A system to perform neutron radiographic analysis of dynamic events which occur on the order of several milliseconds has been developed at Oregon State University. Two different methods have been used to radiograph the simulated two-phase flow. These are pulsed, or ''flash'' radiography, and high speed movie neutron radiography. The pulsed method serves as a ''snap-shot'' with an exposure time ranging from 10 to 20 milliseconds. In high speed movie radiography, a scintillator is used to convert neutrons into light which is enhanced by an optical intensifier and then photographed by a high speed camera. Both types of radiography utilize the pulsing capability of the OSU TRIGA reactor. The principle difficulty with this type of neutron radiography is the fogging of the image due to the large amount of scattering in the water. This difficulty can be overcome by using thin regions for the two-phase flow or using heavy water instead of light water. The results obtained in this paper demonstrate the feasibility of using neutron radiography to obtain data in two-phase flow situations. Both movies and flash radiographs have been obtained of air bubbles in water and boiling from a heater element. The neutron radiographs of the boiling element show both nucleate boiling and film boiling. (Auth.)
A double parameters measurement of steam-water two-phase flow with single orifice
International Nuclear Information System (INIS)
Zhong Shuoping; Tong Yunxian; Yu Meiying
1992-08-01
A double parameters measurement of steam-water two-phase flow with single orifice is described. An on-line measurement device based on micro-computer has been developed. The measured r.m.s error of steam quality is less than 6.5% and the measured relative r.m.s. error of mass flow rate is less than 9%
A Dual-Stage Two-Phase Model of Selective Attention
Hubner, Ronald; Steinhauser, Marco; Lehle, Carola
2010-01-01
The dual-stage two-phase (DSTP) model is introduced as a formal and general model of selective attention that includes both an early and a late stage of stimulus selection. Whereas at the early stage information is selected by perceptual filters whose selectivity is relatively limited, at the late stage stimuli are selected more efficiently on a…
Evaluation of Low-Cost Topologies for Two-Phase Induction Motor Drives, in Industrial Applications
DEFF Research Database (Denmark)
Blaabjerg, Frede; Lungeanu, Florin; Skaug, Kenneth
2002-01-01
on the other side. Another contradiction comes from the benefits as well as from the drawbacks related with the ac running capacitor. It is concluded that the two-phase induction motor drives are more depending on the load characteristic than the three-phase motor drives, while the best topology...
Conceptual plan: Two-Phase Flow Laboratory Program for the Waste Isolation Pilot Plant
International Nuclear Information System (INIS)
Howarth, S.M.
1993-07-01
The Salado Two-Phase Flow Laboratory Program was established to address concerns regarding two-phase flow properties and to provide WIPP-specific, geologically consistent experimental data to develop more appropriate correlations for Salado rock to replace those currently used in Performance Assessment models. Researchers in Sandia's Fluid Flow and Transport Department originally identified and emphasized the need for laboratory measurements of Salado threshold pressure and relative permeability. The program expanded to include the measurement of capillary pressure, rock compressibility, porosity, and intrinsic permeability and the assessment of core damage. Sensitivity analyses identified the anhydrite interbed layers as the most likely path for the dissipation of waste-generated gas from waste-storage rooms because of their relatively high permeability. Due to this the program will initially focus on the anhydrite interbed material. The program may expand to include similar rock and flow measurements on other WIPP materials including impure halite, pure halite, and backfill and seal materials. This conceptual plan presents the scope, objectives, and historical documentation of the development of the Salado Two-Phase Flow Program through January 1993. Potential laboratory techniques for assessing core damage and measuring porosity, rock compressibility, capillary and threshold pressure, permeability as a function of stress, and relative permeability are discussed. Details of actual test designs, test procedures, and data analysis are not included in this report, but will be included in the Salado Two-Phase Flow Laboratory Program Test Plan pending the results of experimental and other scoping activities in FY93
Multiparticle imaging velocimetry measurements in two-phase flow
International Nuclear Information System (INIS)
Hassan, Y.A.
1998-01-01
The experimental flow visualization tool, Particle Image Velocimetry (PIV), is being extended to determine the velocity fields in two and three-dimensional, two-phase fluid flows. In the past few years, the technique has attracted quite a lot of interest. PIV enables fluid velocities across a region of a flow to be measured at a single instant in time in global domain. This instantaneous velocity profile of a given flow field is determined by digitally recording particle (microspheres or bubbles) images within the flow over multiple successive video frames and then conducting flow pattern identification and analysis of the data. This paper presents instantaneous velocity measurements in various two and three- dimensional, two-phase flow situations. (author)
Study of two-phase underexpanded jets by gas jet
International Nuclear Information System (INIS)
Uchida, Mitsunori; Someya, Satoshi; Okamoto, Koji
2008-01-01
When a heat exchange in a Fast Breeder Reactor cracks, a sodium-water reaction occurs. When a tube cracks, highly pressurized water or steam escapes into the surrounding liquid sodium and a sodium-water reaction occurs forming the disodium oxide. The disodium oxide caught in the steam jet strikes other tubes in the reactor. The struck disodium oxide can then cause these tubes to crack. The release of steam into the liquid sodium media is a two-phase flow involving underexpansion. In this paper qualitative measurement of the underexpanded gas jet which injected into water was carried our for the purpose of analyzing the behavior of the two-phase flow. (author)
Reactor vessel and core two-phase flow ultrasonic densitometer
International Nuclear Information System (INIS)
Arave, A.E.
1979-01-01
A local ultrasonic density (LUD) detector has been developed by EG and G Idaho, Inc., at the Idaho National Engineering Laboratory (INEL) for the Loss-of-Fluid Test (LOFT) reactor vessel and core two-phase flow density measurements. The principle of operating the sensor is the change in propagation time of a torsional ultrasonic wave in a metal transmission line as a function of the density of the surrounding media. A theoretical physics model is presented which represents the total propagation time as a function of the sensor modulus of elasticity and polar moment of inertia. Separate effects tests and two-phase flow tests have been conducted to characterize the detector. Tests show the detector can perform in a 343 0 C pressurized water reactor environment and measure the average density of the media surrounding the sensor
Stability of interfacial waves in two-phase flows
Energy Technology Data Exchange (ETDEWEB)
Liu, W S [Ontario Hydro, Toronto, ON (Canada)
1996-12-31
The influence of the interfacial pressure and the flow distribution in the one-dimensional two-fluid model on the stability problems of interfacial waves is discussed. With a proper formulation of the interfacial pressure, the following two-phase phenomena can be predicted from the stability and stationary criteria of the interfacial waves: onset of slug flow, stationary hydraulic jump in a stratified flow, flooding in a vertical pipe, and the critical void fraction of a bubbly flow. It can be concluded that the interfacial pressure plays an important role in the interfacial wave propagation of the two-fluid model. The flow distribution parameter may enhance the flow stability range, but only plays a minor role in the two-phase characteristics. (author). 20 refs., 3 tabs., 4 figs.
Macroscopic balance equations for two-phase flow models
International Nuclear Information System (INIS)
Hughes, E.D.
1979-01-01
The macroscopic, or overall, balance equations of mass, momentum, and energy are derived for a two-fluid model of two-phase flows in complex geometries. These equations provide a base for investigating methods of incorporating improved analysis methods into computer programs, such as RETRAN, which are used for transient and steady-state thermal-hydraulic analyses of nuclear steam supply systems. The equations are derived in a very general manner so that three-dimensional, compressible flows can be analysed. The equations obtained supplement the various partial differential equation two-fluid models of two-phase flow which have recently appeared in the literature. The primary objective of the investigation is the macroscopic balance equations. (Auth.)
Numerical simulation for two-phase jet problem
International Nuclear Information System (INIS)
Lee, W.H.; Shah, V.L.
1981-01-01
A computer program TWOP was developed for obtaining the numerical solutions of three-dimensional, transient, two-phase flow system with nonequilibrium and nonhomogeneous conditions. TWOP employs two-fluid model and a set of the conservation equations formulated by Harlow and Amsden along with their Implicit Multi-Field (IMF) numerical technique that allows all degrees of couplings between the two fields. We have further extended the procedure of Harlow and Amsden by incorporating the implicit couplings of phase transition and interfacial heat transfer terms in the energy equations. Numerical results of two tested problems are presented to demonstrate the capabilities of the TWOP code. The first problem is the separation of vapor and liquid, showing that the code can handle the computational difficulties such as liquid packing and sharp interface phenomena. The second problem is the high pressure two-phase jet impinged on vertical plate, demonstrating the important role of the interfacial mass and momentum exchange
Mathematical modeling and the two-phase constitutive equations
International Nuclear Information System (INIS)
Boure, J.A.
1975-01-01
The problems raised by the mathematical modeling of two-phase flows are summarized. The models include several kinds of equations, which cannot be discussed independently, such as the balance equations and the constitutive equations. A review of the various two-phase one-dimensional models proposed to date, and of the constitutive equations they imply, is made. These models are either mixture models or two-fluid models. Due to their potentialities, the two-fluid models are discussed in more detail. To avoid contradictions, the form of the constitutive equations involved in two-fluid models must be sufficiently general. A special form of the two-fluid models, which has particular advantages, is proposed. It involves three mixture balance equations, three balance equations for slip and thermal non-equilibriums, and the necessary constitutive equations [fr
Turbine flow meter response in two-phase flows
International Nuclear Information System (INIS)
Shim, W.J.; Dougherty, T.J.; Cheh, H.Y.
1996-01-01
The purpose of this paper is to suggest a simple method of calibrating turbine flow meters to measure the flow rates of each phase in a two-phase flow. The response of two 50.8 mm (2 inch) turbine flow meters to air-water, two-phase mixtures flowing vertically in a 57 mm I.D. (2.25 inch) polycarbonate tube has been investigated for both upflow and downflow. The flow meters were connected in series with an intervening valve to provide an adjustable pressure difference between them. Void fractions were measured by two gamma densitometers, one upstream of the flow meters and the other downstream. The output signal of the turbine flow meters was found to depend only on the actual volumetric flow rate of the gas, F G , and liquid, F L , at the location of the flow meter
Visualization in cryogenic environment: Application to two-phase studies
Rousset, Bernard; Chatain, Denis; Puech, Laurent; Thibault, Pierre; Viargues, François; Wolf, Pierre-Etienne
2009-10-01
This paper reviews recent technical developments devoted to the study of cryogenic two-phase fluids. These techniques span from simple flow visualization to quantitative measurements of light scattering. It is shown that simple flow pattern configurations are obtained using classical optical tools (CCD cameras, endoscopes), even in most severe environments (high vacuum, high magnetic field). Quantitative measurements include laser velocimetry, particle sizing, and light scattering analysis. In the case of magnetically compensated gravity boiling oxygen, optical access is used to control the poistioning of a bubble subject to buoyancy forces in an experimental cell. Flow visualization on a two-phase superfluid helium pipe-flow, performed as a support of LHC cooldown studies, leads to flow pattern characterization. Visualization includes stratified and atomized flows. Thanks to the low refractive index contrast between the liquid and its vapor, quantitative results on droplet densities can be obtained even in a multiple scattering regime.
Transition from boiling to two-phase forced convection
International Nuclear Information System (INIS)
Maroti, L.
1985-01-01
The paper presents a method for the prediction of the boundary points of the transition region between fully developed boiling and two-phase forced convection. It is shown that the concept for the determination of the onset of fully developed boiling can also be applied for the calculation of the point where the heat transfer is effected again by the forced convection. Similarly, the criterion for the onset of nucleate boiling can be used for the definition of the point where boiling is completely suppressed and pure two-phase forced convection starts. To calculate the heat transfer coefficient for the transition region, an equation is proposed that applies the boundary points and a relaxation function ensuring the smooth transition of the heat transfer coefficient at the boundaries
A new correlation for two-phase critical discharge coefficient
International Nuclear Information System (INIS)
Park, Jong Woon; Chun, Moon Hyun
1989-01-01
A new simple correlation for subcooled and two-phase critical flow discharge coefficient has been developed by stepwise regression technique. The new discharge coefficient has three independent variables and they are length to hydraulic diameter ratio, degree of subcooling, and stagnation temperature. The new discharge coefficient is applied as a multiplier to homogeneous equilibrium model and Abauf's single phase critical mass flux calculation equation. This method has been tested for its accuracy by comparing with experimental data. Results of the comparison show that the agreement between the predictions with new correlation and the experimental data is good for pipes and nozzles with vertical upward flow for subcooled upstream condition and nozzles with horizontal configuration for two-phase upstream condition
Peptide-tagged proteins in aqueous two-phase systems
Nilsson, Anna
2002-01-01
This thesis deals with proteins containing peptide tags for improved partitioning in aqueous two-phase systems. Qualitatively the peptide-tagged protein partitioning could be predicted from peptide data, i.e. partitioning trends found for peptides were also found for the peptide-tagged proteins. However, full effect of the tag as expected from peptide partitioning was not found in the tagged protein. When alkyl-ethylene oxide surfactant was included in a two-polymer system, almost full effect...
Recent advances in two-phase flow numerics
International Nuclear Information System (INIS)
Mahaffy, J.H.; Macian, R.
1997-01-01
The authors review three topics in the broad field of numerical methods that may be of interest to individuals modeling two-phase flow in nuclear power plants. The first topic is iterative solution of linear equations created during the solution of finite volume equations. The second is numerical tracking of macroscopic liquid interfaces. The final area surveyed is the use of higher spatial difference techniques
Recent advances in two-phase flow numerics
Energy Technology Data Exchange (ETDEWEB)
Mahaffy, J.H.; Macian, R. [Pennsylvania State Univ., University Park, PA (United States)
1997-07-01
The authors review three topics in the broad field of numerical methods that may be of interest to individuals modeling two-phase flow in nuclear power plants. The first topic is iterative solution of linear equations created during the solution of finite volume equations. The second is numerical tracking of macroscopic liquid interfaces. The final area surveyed is the use of higher spatial difference techniques.
Two-phase titration of cerium(3) by permanganate
International Nuclear Information System (INIS)
Lazarev, A.I.; Lazareva, V.I.; Gerko, V.V.
1986-01-01
Reaction of cerium (3) and permanganate was investigated at a room temperature depending on PH, concentrations of pyrophosphate, cerium (3), tetraphenylphosphonium and foreign compounds. Selective method of two-phase titration determination of cerium (3) by permanganate without using silver compounds, preliminary separation of chlorides, nitrates, was developed. The method was tested using alloys based on iron, nickel, REE, copper, cobalt (S r ≤0.008). Correctness is proved with method of standard additives
Laser Doppler measurements in two-phase flows
International Nuclear Information System (INIS)
Durst, F.; Zare, M.
1976-01-01
Basic theory for laser-Doppler velocity measurements of large reflecting or refracting surfaces is provided. It is shown that the Doppler-signals contain information of the velocity and size of the large bodies, and relationships for transforming velocity and radius of curvature of moving spheres are presented. Preliminary experiments verified the analytical findings and demonstrated the applicability of the method to some two-phase flows
Two-phase flow instability and propagation of disturbances
International Nuclear Information System (INIS)
Yadigaroglu, G.
1984-01-01
Various mechanisms of static and dynamic macroinstabilities, appearing in two-phase flows, have been considered. Types of instabilities, conditioned by the form of hydraulic characteristics of the channel and density waves are analyzed in detail. Problems of instabilities in nuclear reactor circuits, in particular problems of instabilities, conditioned by water and steam mixing and vapour condensation, and problems of steam generator operation instability are discussed
Interfacial structures in downward two-phase bubbly flow
International Nuclear Information System (INIS)
Paranjape, S.S.; Kim, S.; Ishii, M.; Kelly, J.
2003-01-01
Downward two-phase flow was studied considering its significance in view of Light Water Reactor Accidents (LWR) such as Loss of Heat Sink (LOHS) by feed water loss or secondary pipe break. The flow studied, was an adiabatic, air-water, co-current, vertically downward two-phase flow. The experimental test sections had internal hydraulic diameters of 25.4 mm and 50.8 mm. Flow regime map was obtained using the characteristic signals obtained from an impedance void meter, employing neural network based identification methodology to minimize the subjective judgment in determining the flow regimes. A four sensor conductivity probe was used to measure the local two phase flow parameters, which characterize the interfacial structures. The local time averaged two-phase flow parameters measured were: void fraction (α), interfacial area concentration (a i ), bubble velocity (v g ), and Sauter mean diameter (D Sm ). The flow conditions were from the bubbly flow regime. The local profiles of these parameters as well as their axial development revealed the nature of the interfacial structures and the bubble interaction mechanisms occurring in the flow. Furthermore, this study provided a good database for the development of the interfacial area transport equation, which dynamically models the changes in the interfacial area along the flow field. An interfacial area transport equation was developed for downward flow based on that developed for the upward flow, with certain modifications in the bubble interaction terms. The area averaged values of the interfacial area concentration were compared with those predicted by the interfacial area transport model. (author)
Remediation in clay using two-phase vacuum extraction
International Nuclear Information System (INIS)
Lindhult, E.C.; Tarsavage, J.M.; Foukaris, K.A.
1995-01-01
Soil and groundwater contamination in a tight clay usually requires costly and/or time consuming remediation, due to the inherently low hydraulic conductivity of the soil. However, Dames and Moore is successfully using an innovative, cost-effective two-phase vacuum extraction (VE) technology at a former gasoline service station. Dramatic decreases in BTEX concentrations in onsite and downgradient monitoring wells are apparent
Phase separation and shape deformation of two-phase membranes
International Nuclear Information System (INIS)
Jiang, Y.; Lookman, T.; Saxena, A.
2000-01-01
Within a coupled-field Ginzburg-Landau model we study analytically phase separation and accompanying shape deformation on a two-phase elastic membrane in simple geometries such as cylinders, spheres, and tori. Using an exact periodic domain wall solution we solve for the shape and phase separating field, and estimate the degree of deformation of the membrane. The results are pertinent to preferential phase separation in regions of differing curvature on a variety of vesicles. (c) 2000 The American Physical Society
Two-phase computer codes for zero-gravity applications
International Nuclear Information System (INIS)
Krotiuk, W.J.
1986-10-01
This paper discusses the problems existing in the development of computer codes which can analyze the thermal-hydraulic behavior of two-phase fluids especially in low gravity nuclear reactors. The important phenomenon affecting fluid flow and heat transfer in reduced gravity is discussed. The applicability of using existing computer codes for space applications is assessed. Recommendations regarding the use of existing earth based fluid flow and heat transfer correlations are made and deficiencies in these correlations are identified
Fluid dynamics of cryogenic two-phase flows
International Nuclear Information System (INIS)
Verfondern, K.; Jahn, W.
2004-01-01
The objective of this study was to examine the flow behavior of a methane hydrate/methane-liquid hydrogen dispersed two-phase fluid through a given design of a moderator chamber for the ESS target system. The calculations under simplified conditions, e.g., taking no account of heat input from outside, have shown that the computer code used, CFX, was able to simulate the behavior of the two-phase flow through the moderator chamber, producing reasonable results up to a certain level of the solid phase fraction, that allowed a continuous flow process through the chamber. Inlet flows with larger solid phase fractions than 40 vol% were found to be a ''problem'' for the computer code. From the computer runs based on fractions between 20 and 40 vol%, it was observed that with increasing solid phase fraction at the inlet, the resulting flow pattern revealed a strong tendency for blockage within the chamber, supported by the ''heavy weight'' of the pellets compared to the carrying liquid. Locations which are prone to the development of such uneven flow behavior are the areas around the turning points in the semispheres and near the exit of the moderator. The considered moderator chamber with horizontal inlet and outlet flow for a solid-liquid two-phase fluid does not seem to be an appropriate design. (orig.)
Instrumentation for localized measurements in two-phase flow conditions
International Nuclear Information System (INIS)
Neff, G.G.; Averill, R.H.; Shurts, S.W.
1979-01-01
Three types of instrumentation that have been developed by EG and G Idaho, Inc., and its predecessor, Aerojet Nuclear company, at the Idaho National Engineering Laboratory to investigate two-phase flow phenomenon in a nuclear reactor at the Loss-of-Fluid Test (LOFT) facility are discussed: (a) a combination drag disc-turbine transducer (DTT), (b) a multibeam nuclear hardened gamma densitometer system, and (c) a conductivity sensitive liquid level transducer (LLT). The DTT obtains data on the complex problem of two-phase flow conditions in the LOFT primary coolant system during a loss-os-coolant experiment (LOCE). The discussion of the DTT describes how a turbine, measuring coolant velocity, and a drag disc, measuring coolant momentum flux, can provide valuable mass flow data. The nuclear hardened gamma densitometer is used to obtain density and flow regime information for two-phase flow in the LOFT primary coolant system during a LOCE. The LLT is used to measure water and steam conditions within the LOFT reactor core during a LOCE. The LLT design and the type of data obtained are described
An objective indicator for two-phase flow pattern transition
International Nuclear Information System (INIS)
Hervieua, E.; Seleghim, P. Jr.
1998-01-01
This work concerns the development of a methodology the objective of which is to characterize and diagnose two-phase flow regime transitions. The approach is based on the fundamental assumption that a transition flow is less stationary than a flow with an established regime. During the first time, the efforts focused on: (1) the design and construction of an experimental loop, allowing to reproduce the main horizontal two-phase flow patterns, in a stable and controlled way; (2) the design and construction of an electrical impedance probe, providing an imaged information of the spatial phase distribution in the pipe; and (3) the systematic study of the joint time-frequency and time-scale analysis methods, which permitted to define an adequate parameter quantifying the unstationarity degree. During the second time, in order to verify the fundamental assumption, a series of experiments were conducted, the objective of which was to demonstrate the correlation between unstationarity and regime transition. The unstationarity degree was quantified by calculating the Gabor's transform time-frequency covariance of the impedance probe signals. Furthermore, the phenomenology of each transition was characterized by the joint moments and entropy. The results clearly show that the regime transitions are correlated with local time-frequency covariance peaks, which demonstrates that these regime transitions are characterized by a loss of stationarity. Consequently, the time-frequency covariance constitutes an objective two-phase flow regime transition indicator. (orig.)
An objective indicator for two-phase flow pattern transition
International Nuclear Information System (INIS)
Hervieu, E.; Seleghim, P. Jr.
1998-01-01
This work concerns the development of a methodology which objective is to characterize and diagnose two-phase flow regime transitions. The approach is based on the fundamental assumption that a transition flow is less stationary than a flow with an established regime. In a first time, the efforts focused on: the design and construction of an experimental loop, allowing to reproduce the main horizontal two-phase flow patterns, in a stable and controlled way; the design and construction of an electrical impedance probe, providing an imaged information of the spatial phase distribution in the pipe; the systematic study of the joint time-frequency and time-scale analysis methods, which permitted to define an adequate parameter quantifying the unstationarity degree. In a second time, in order to verify the fundamental assumption, a series of experiments were conducted, which objective was to demonstrate the correlation between unstationarity and regime transition. The unstationarity degree was quantified by calculating the Gabor's transform time-frequency covariance of the impedance probe signals. Furthermore, the phenomenology of each transition was characterized by the joint moments and entropy. The results clearly show that the regime transitions are correlated with local time-frequency covariance peaks, which demonstrates that these regime transitions are characterized by a loss of stationarity. Consequently, the time-frequency covariance constitutes an objective two-phase flow regime transition indicator. (author)
Random signal tomographical analysis of two-phase flow
International Nuclear Information System (INIS)
Han, P.; Wesser, U.
1990-01-01
This paper reports on radiation tomography which is a useful tool for studying the internal structures of two-phase flow. However, general tomography analysis gives only time-averaged results, hence much information is lost. As a result, it is sometimes difficult to identify the flow regime; for example, the time-averaged picture does not significantly change as an annual flow develops from a slug flow. A two-phase flow diagnostic technique based on random signal tomographical analysis is developed. It extracts more information by studying the statistical variation of the measured signal with time. Local statistical parameters, including mean value, variance, skewness and flatness etc., are reconstructed from the information obtained by a general tomography technique. More important information are provided by the results. Not only the void fraction can be easily calculated, but also the flow pattern can be identified more objectively and more accurately. The experimental setup is introduced. It consisted of a two-phase flow loop, an X-ray system, a fan-like five-beam detector system and a signal acquisition and processing system. In the experiment, for both horizontal and vertical test sections (aluminum and steel tube with Di/Do = 40/45 mm), different flow situations are realized by independently adjusting air and water mass flow. Through a glass tube connected with the test section, some typical flow patterns are visualized and used for comparing with the reconstruction results
The Condensation effect on the two-phase flow stability
International Nuclear Information System (INIS)
Abdou Mohamed, Hesham Nagah
2005-01-01
A one-dimensional analytical model has been developed to be used for the linear analysis of density-wave oscillations in a parallel heated channel and a natural circulation loop.The heater and the riser sections are divided into a single-phase and a two-phase region.The two-phase region is represented by the drift-flux model. The model accounts for aphasic slip and subcooled boiling.The localized friction at the heater and the riser exit is treated considering the two-phase mixture.Also the effects of the condensation in the riser and the change in the system pressure have been studied.The exact equation for the heated channel and the total loop pressure drop is perturbed around the steady state.he stability characteristics of the heated channel and the loop are investigated using the Root finding method criterion.The results are summarized on instability maps in the plane of subcooled boiling number vs. phase change number (i.e., inlet subcooling vs. heater heat flux).The predictions of the model are compared with experimental results published in open literature. The results show that, the treatment effect of localized friction in two-phase mixtures stabilizes the system and improves the agreement of the calculations with the experimental results.For a parallel heated channel, the results indicate a more stable system with high inlet restriction, low outlet restriction, and high inlet velocity. And for a natural circulation loop, an increase in the inlet restriction broadened the range of the continuous circulation mode and stabilized the system, a decrease in the exit restriction or the liquid charging level shifted to the right the range of the continuous circulation mode and stabilized the system and an increase in the riser condensation shifted to the right the range of the continuous circulation mode and stabilized the system.The results show that the model agrees well with the available experimental data. In particular, the results show the significance of
International Nuclear Information System (INIS)
Yonomoto, Taisuke; Tasaka, Kanji
1988-01-01
A theoretical and experimental study was conducted to understand two-phase flow discharged from a stratified two-phase region through a small break. This problem is important for an analysis of a small break loss-of-coolant accident (LOCA) in a light water reactor (LWR). The present theoretical results show that a break quality is a function of h/h b , where h is the elevation difference between a bulk water level in the upstream region and break and b the suffix for entrainment initiation. This result is consistent with existing eperimental results in literature. An air-water experiment was also conducted changing a break orientation as an experimental parameter to develop and assess the model. Comparisons between the model and the experimental results show that the present model can satisfactorily predict the flow rate and the quality at the break without using any adjusting constant when liquid entrainment occurs in a stratified two-phase region. When gas entrainment occurs, the experimental data are correlated well by using a single empirical constant. (author)
Long-wave equivalent viscoelastic solids for porous rocks saturated by two-phase fluids
Santos, J. E.; Savioli, G. B.
2018-04-01
Seismic waves traveling across fluid-saturated poroelastic materials with mesoscopic-scale heterogeneities induce fluid flow and Biot's slow waves generating energy loss and velocity dispersion. Using Biot's equations of motion to model these type of heterogeneities would require extremely fine meshes. We propose a numerical upscaling procedure to determine the complex and frequency dependent P-wave and shear moduli of an effective viscoelastic medium long-wave equivalent to a poroelastic solid saturated by a two-phase fluid. The two-phase fluid is defined in terms of capillary pressure and relative permeability flow functions. The P-wave and shear effective moduli are determined using harmonic compressibility and shear experiments applied on representative samples of the bulk material. Each experiment is associated with a boundary value problem that is solved using the finite element method. Since a poroelastic solid saturated by a two-phase fluid supports the existence of two slow waves, this upscaling procedure allows to analyze their effect on the mesoscopic-loss mechanism in hydrocarbon reservoir formations. Numerical results show that a two-phase Biot medium model predicts higher attenuation than classic Biot models.
Results of two-phase natural circulation in hot-leg U-bend simulation experiments
International Nuclear Information System (INIS)
Ishii, M.; Lee, S.Y.; Abou El-Seoud, S.
1987-01-01
In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed using two different thermal-hydraulic loops. The main focus of the experiment was the two-phase flow behavior in the hot-leg U-bend typical of BandW LWR systems. The first group of experiments was carried out in the nitrogen gas-water adiabatic simulation loop and the second in the Freon 113 boiling and condensation loop. Both of the loops have been designed as a flow visualization facility and built according to the two-phase flow scaling criteria developed under this program. The nitrogen gas-water system has been used to isolate key hydrodynamic phenomena such as the phase distribution, relative velocity between phases, two-phase flow regimes and flow termination mechanisms, whereas the Freon loop has been used to study the effect of fluid properties, phase changes and coupling between hydrodynamic and heat transfer phenomena. Significantly different behaviors have been observed due to the non-equilibrium phase change phenomena such as the flashing and condensation in the Freon loop. The phenomena created much more unstable hydrodynamic conditions which lead to cyclic or oscillatory flow behaviors
International Nuclear Information System (INIS)
Mesquita, R.N. de; Masotti, P.H.F.; Penha, R.M.L.; Andrade, D.A.; Sabundjian, G.; Torres, W.M.
2012-01-01
Highlights: ► A fuzzy classification system for two-phase flow instability patterns is developed. ► Flow patterns are classified based on images of natural circulation experiments. ► Fuzzy inference is optimized to use single grayscale profiles as input. - Abstract: Two-phase flow on natural circulation phenomenon has been an important theme on recent studies related to nuclear reactor designs. The accuracy of heat transfer estimation has been improved with new models that require precise prediction of pattern transitions of flow. In this work, visualization of natural circulation cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. A Fuzzy Flow-type Classification System (FFCS) was developed to classify these patterns based only on image extracted features. Image acquisition and temperature measurements were simultaneously done. Experiments in natural circulation facility were adjusted to generate a series of characteristic two-phase flow instability periodic cycles. The facility is composed of a loop of glass tubes, a heat source using electrical heaters, a cold source using a helicoidal heat exchanger, a visualization section and thermocouples positioned over different loop sections. The instability cyclic period is estimated based on temperature measurements associated with the detection of a flow transition image pattern. FFCS shows good results provided that adequate image acquisition parameters and pre-processing adjustments are used.
Void fraction prediction in two-phase flows independent of the liquid phase density changes
International Nuclear Information System (INIS)
Nazemi, E.; Feghhi, S.A.H.; Roshani, G.H.
2014-01-01
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. - Highlights: • Void fraction was predicted independent of density changes. • Recorded counts of detectors/void fraction were used as inputs/output of ANN. • ANN eliminated necessity of recalibration in changeable density of two-phase flows
International Nuclear Information System (INIS)
Goto, Shoji; Ishizaki, Yasuo; Ohashi, Hirotada; Akiyama, Mamoru
1995-01-01
Simulation of transient two-phase flow has been performed by solving transient hydrodynamic equations. However, constitution relations used in this simulation are primarily based on steady-state experimental results. Thus it is important to understand the transient behavior of bubbles and slugs, in particular, transient behavior of the void fraction, the interfacial area and the flow pattern, to confirm the applicability of the present simulation method and to advance two-phase flow simulation further. The present study deals with measurement of transient two-phase flow. We have measured local and instantaneous void fractions using imaging techniques, and compared the experimental data with simulation results. (author)
Energy Technology Data Exchange (ETDEWEB)
Delhaye, J M; Jones, Jr, O C
1976-06-01
Much work has been done in the study of two-phase gas-liquid flows. Although it has been recognized superficially that such flows are not homogeneous in general, little attention has been paid to the inherent discreteness of the two-phase systems. Only relatively recently have fluctuating characteristics of two-phase flows been studied in detail. As a result, new experimental devices and techniques have been developed for use in measuring quantities previously ignored. This report reviews and summarizes most of these methods in an effort to emphasize the importance of the fluctuating nature of these flows and as a guide to further research in this field.
Developing two-phase flow modelling concepts for rock fractures
Energy Technology Data Exchange (ETDEWEB)
Keto, V. (Fortum Nuclear Services Oy, Espoo (Finland))
2010-01-15
The Finnish nuclear waste disposal company, Posiva Oy, is planning an underground repository for spent nuclear fuel to be constructed on the island of Olkiluoto on the south-west coast of Finland. One element of the site investigations conducted at Olkiluoto is the excavation of the underground rock characterisation facility (ONKALO) that will be extended to the final disposal depth (approximately -400 m). The bedrock around the excavated tunnel volume is fully saturated with groundwater, which water commonly contains a mixture of dissolved gases. These gases remain dissolved due to the high hydrostatic pressure. During tunnel excavation work the natural hydrostatic pressure field is disturbed and the water pressure will decrease close to the atmospheric pressure in the immediate vicinity of the tunnel. During this pressure drop two-phase flow conditions (combined flow of both water and gas) may develop in the vicinity of the underground opening, as the dissolved gas is exsoluted under the low pressure (the term exsolution refers here to release of the dissolved gas molecules from the water phase into a separate gas phase). This report steers towards concept development for numerical two-phase flow modeling for fractured rock. The focus is on the description of gas phase formation process under disturbed hydraulic conditions by exsolution of dissolved gases from groundwater, and on understanding the effects of a possibly formed gas phase on groundwater flow conditions in rock fractures. A mathematical model of three mutually coupled nonlinear partial differential equations for two-phase flow is presented and corresponding constitutional relationships are introduced and discussed. Illustrative numerical simulations are performed in a simplified setting using COMSOL Multiphysics 3.5a - software package. Shortcomings and conceptual problems are discussed. (orig.)
Developing two-phase flow modelling concepts for rock fractures
International Nuclear Information System (INIS)
Keto, V.
2010-01-01
The Finnish nuclear waste disposal company, Posiva Oy, is planning an underground repository for spent nuclear fuel to be constructed on the island of Olkiluoto on the south-west coast of Finland. One element of the site investigations conducted at Olkiluoto is the excavation of the underground rock characterisation facility (ONKALO) that will be extended to the final disposal depth (approximately -400 m). The bedrock around the excavated tunnel volume is fully saturated with groundwater, which water commonly contains a mixture of dissolved gases. These gases remain dissolved due to the high hydrostatic pressure. During tunnel excavation work the natural hydrostatic pressure field is disturbed and the water pressure will decrease close to the atmospheric pressure in the immediate vicinity of the tunnel. During this pressure drop two-phase flow conditions (combined flow of both water and gas) may develop in the vicinity of the underground opening, as the dissolved gas is exsoluted under the low pressure (the term exsolution refers here to release of the dissolved gas molecules from the water phase into a separate gas phase). This report steers towards concept development for numerical two-phase flow modeling for fractured rock. The focus is on the description of gas phase formation process under disturbed hydraulic conditions by exsolution of dissolved gases from groundwater, and on understanding the effects of a possibly formed gas phase on groundwater flow conditions in rock fractures. A mathematical model of three mutually coupled nonlinear partial differential equations for two-phase flow is presented and corresponding constitutional relationships are introduced and discussed. Illustrative numerical simulations are performed in a simplified setting using COMSOL Multiphysics 3.5a - software package. Shortcomings and conceptual problems are discussed. (orig.)
Two-phase exchangers with small temperature differences
International Nuclear Information System (INIS)
Moracchioli, R.; Marie, G.; Lallee, J. de.
1976-01-01
The possibility in using heat available at low temperature level is shown (industrial wastes, solar energy, geothermal energy, heat power from seas). Special emphasis is put on the importance of heat exchangers that commonly should be evaporators and condensors working with small temperature differences (20 to 100 deg C). The expansion of the so-called ''new'' energies or recovery processes will depend on the physical performance of exchangers (Rankine two-phase cycles) and cost of the elementary exchange interfaces and assembling technics [fr
Flow patterns in vertical two-phase flow
International Nuclear Information System (INIS)
McQuillan, K.W.; Whalley, P.B.
1985-01-01
This paper is concerned with the flow patterns which occur in upwards gas-liquid two-phase flow in vertical tubes. The basic flow patterns are described and the use of flow patter maps is discussed. The transition between plug flow and churn flow is modelled under the assumption that flooding of the falling liquid film limits the stability of plug flow. The resulting equation is combined with other flow pattern transition equations to produce theoretical flow pattern maps, which are then tested against experimental flow pattern data. Encouraging agreement is obtained
Two-phase flow measurement based on oblique laser scattering
Vendruscolo, Tiago P.; Fischer, Robert; Martelli, Cícero; Rodrigues, Rômulo L. P.; Morales, Rigoberto E. M.; da Silva, Marco J.
2015-07-01
Multiphase flow measurements play a crucial role in monitoring productions processes in many industries. To guarantee the safety of processes involving multiphase flows, it is important to detect changes in the flow conditions before they can cause damage, often in fractions of seconds. Here we demonstrate how the scattering pattern of a laser beam passing a two-phase flow under an oblique angle to the flow direction can be used to detect derivations from the desired flow conditions in microseconds. Applying machine-learning techniques to signals obtained from three photo-detectors we achieve a compact, versatile, low-cost sensor design for safety applications.
Flooding and flow reversal of two-phase annular flow
International Nuclear Information System (INIS)
Asahi, Y.
1978-01-01
The flooding and flow reversal conditions of two-phase annular flow are mathematically defined in terms of a characteristic function representing a force balance. Sufficiently below the flooding point in counter-current flow, the interface is smooth and the characteristic equation reduces to the Nusselt relationship. Just below flooding point and above the flow reversal point in cocurrent flow, the interface is 'wavy', so that the interfacial shear effect plays an important role. The theoretical analysis is compared with experimental results by others. It is suggested that the various length effects which have been experimentally observed may be accounted for by the spatial variation of the droplet entrainment. (Auth.)
A study of critical two-phase flow models
International Nuclear Information System (INIS)
Siikonen, T.
1982-01-01
The existing computer codes use different boundary conditions in the calculation of critical two-phase flow. In the present study these boundary conditions are compared. It is shown that the boundary condition should be determined from the hydraulic model used in the computer code. The use of a correlation, which is not based on the hydraulic model used, leads often to bad results. Usually a good agreement with data is obtained in the calculation as far as the critical mass flux is concerned, but the agreement is not so good in the pressure profiles. The reason is suggested to be mainly in inadequate modeling of non-equilibrium effects. (orig.)
Design and construction of two phases flow meter
International Nuclear Information System (INIS)
Nor Paiza Mohamad Hasan
2002-01-01
This paper deals with design of the gamma ray correlometer and flow loop system for measuring the velocity between two parallel cross-sections of a pipeline. In the laboratory, the radioisotope source and detector were collimated by brass with small beam slit respectively. The flow loop system consists of transparent pipeline, adjustable frequency pump and water container. As a result, when the construction of the flow loop and correlometer is completed, the velocity of two phases flow can be measured by the cross-correlation techniques. (Author)
Experimental and numerical investigation on two-phase flow instabilities
Energy Technology Data Exchange (ETDEWEB)
Ruspini, Leonardo Carlos
2013-03-01
Two-phase flow instabilities are experimentally and numerically studied within this thesis. In particular, the phenomena called Ledinegg instability, density wave oscillations and pressure drop oscillations are investigated. The most important investigations regarding the occurrence of two-phase flow instabilities are reviewed. An extensive description of the main contributions in the experimental and analytical research is presented. In addition, a critical discussion and recommendations for future investigations are presented. A numerical framework using a hp-adaptive method is developed in order to solve the conservation equations modelling general thermo-hydraulic systems. A natural convection problem is analysed numerically in order to test the numerical solver. Moreover, the description of an adaptive strategy to solve thermo-hydraulic problems is presented. In the second part of this dissertation, a homogeneous model is used to study Ledinegg, density wave and pressure drop oscillations phenomena numerically. The dynamic characteristics of the Ledinegg (flow excursion) phenomenon are analysed through the simulation of several transient examples. In addition, density wave instabilities in boiling and condensing systems are investigated. The effects of several parameters, such as the fluid inertia and compressibility volumes, on the stability limits of Ledinegg and density wave instabilities are studied, showing a strong influence of these parameters. Moreover, the phenomenon called pressure drop oscillations is numerically investigated. A discussion of the physical representation of several models is presented with reference to the obtained numerical results. Finally, the influence of different parameters on these phenomena is analysed. In the last part, an experimental investigation of these phenomena is presented. The designing methodology used for the construction of the experimental facility is described. Several simulations and a non
Laser doppler anemometry in single- and two-phase flows
International Nuclear Information System (INIS)
Durst, F.
1976-01-01
The present report gives an introduction into laser-Doppler anemometry and tries to explain the basic physical principles of this measuring technique. Moire fringe patterns are used in order to visually model LDA-signals and to explain the basic difference in optical systems. It is pointed out that LDA measurements in highly turbulent flows and in two-phase flows should be attempted with direction sensitive instruments only. Some of the optical systems developed by the author and his collaborators are introduced and their functioning in measurements is demonstrated. These measurements embrace investigations in a number of single-phase flows including flames. (orig.) [de
Current capabilities of transient two-phase flow instruments
International Nuclear Information System (INIS)
Solbrig, C.W.; Kondic, N.N.
1979-01-01
The measurement of two phase flow phenomena in transient conditions representative of a Loss-of-Coolant Accident requires the use of sophisticated instruments and the further development of other instruments. Measurements made in large size pipes are often flow regime dependent. The flow regimes encountered depend upon the system geometry, transient effects, heat transfer, etc. The geometries in which these measurements must be made, the instruments which are currently used, new instruments being developed, the facilities used to calibrate these instruments, and the improvements which must be made to measurement capabilities are described
Modulating patterns of two-phase flow with electric fields.
Liu, Dingsheng; Hakimi, Bejan; Volny, Michael; Rolfs, Joelle; Anand, Robbyn K; Turecek, Frantisek; Chiu, Daniel T
2014-07-01
This paper describes the use of electro-hydrodynamic actuation to control the transition between three major flow patterns of an aqueous-oil Newtonian flow in a microchannel: droplets, beads-on-a-string (BOAS), and multi-stream laminar flow. We observed interesting transitional flow patterns between droplets and BOAS as the electric field was modulated. The ability to control flow patterns of a two-phase fluid in a microchannel adds to the microfluidic tool box and improves our understanding of this interesting fluid behavior.
Dynamic modelling for two-phase flow systems
International Nuclear Information System (INIS)
Guerra, M.A.
1991-06-01
Several models for two-phase flow have been studied, developing a thermal-hydraulic analysis code with one of these models. The program calculates, for one-dimensional cases with variable flow area, the transient behaviour of system process variables, when the boundary conditions (heat flux, flow rate, enthalpy and pressure) are functions of time. The modular structure of the code, eases the program growth. In fact, the present work is the basis for a general purpose accident and transient analysis code in nuclear reactors. Code verification has been made against RETRAN-02 results. Satisfactory results have been achieved with the present version of the code. (Author) [es
Research on boiling and two-phase flow
International Nuclear Information System (INIS)
Marinsek, Z.; Gaspersic, B.; Pavselj, D.; Tomsic, M.
1977-01-01
Report consists of three contributions. Experimental apparatus with pressure chamber (up to 25 bar and 250 deg C) was constructed including optical bubble detection device, and test measurements of mutual influence of boiling bubbles from two adjacent nucleation sites were performed; for analyses, a computer programme package for coincidence analyses of events was made, including data acquisition hardware. Two-phase pressure drop in subcooled Vertical annular water flow was measured, for pressures up to 10 bar, mass velocity 500 to 760 kg/m 2 s and vapour quality 0 to .01. Results agree fairly well with Martinelli-Nelson model
A real two-phase submarine debris flow and tsunami
International Nuclear Information System (INIS)
Pudasaini, Shiva P.; Miller, Stephen A.
2012-01-01
The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include a dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the
Interfacial area measurements in two-phase flow
International Nuclear Information System (INIS)
Veteau, J.-M.
1979-08-01
A thorough understanding of two-phase flow requires the accurate measurement of the time-averaged interfacial area per unit volume (also called the time-averaged integral specific area). The so-called 'specific area' can be estimated by several techniques described in the literature. These different methods are reviewed and the flow conditions which lead to a rigourous determination of the time-averaged integral specific area are clearly established. The probe technique, involving local measurements seems very attractive because of its large range of application [fr
A real two-phase submarine debris flow and tsunami
Energy Technology Data Exchange (ETDEWEB)
Pudasaini, Shiva P.; Miller, Stephen A. [Department of Geodynamics and Geophysics, Steinmann Institute, University of Bonn Nussallee 8, D-53115, Bonn (Germany)
2012-09-26
The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include a dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the
Heat transfer in two-phase flow of helium
International Nuclear Information System (INIS)
Subbotin, V.I.; Deev, V.I.; Solodovnikov, V.V.; Arkhipov, V.V.
1986-01-01
The results of experimental study of heat transfer in two-phase helium flow are presented. The effect of operating parameters (pressure, mass velocity, heat flux and quality) on boiling heat transfer intensity was investigated. A significant influence of boiling process prehistory on heat transfer coefficients was demonstrated. On the basis of experimental data obtained three typical regimes of flow boiling heat transfer were found. Analogy of heat transfer in flow boiling and pool boiling of helium and noncryogenic liquids was established. Correlations were developed which are in close agreement with available heat transfer data
Numerical simulation of two phase flows in heat exchangers
International Nuclear Information System (INIS)
Grandotto Biettoli, M.
2006-04-01
The author gives an overview of his research activity since 1981. He first gives a detailed presentation of properties and equations of two-phase flows in heat exchangers, and of their mathematical and numerical investigation: semi-local equations (mass conservation, momentum conservation and energy conservation), homogenized conservation equations (mass, momentum and enthalpy conservation, boundary conditions), equation closures, discretization, resolution algorithm, computational aspects and applications. Then, he reports the works performed in the field of turbulent flows, hyperbolic methods, low Mach methods, the Neptune project, and parallel computing
Numerical simulation of two-phase flow with front-capturing
International Nuclear Information System (INIS)
Tzanos, C.P.; Weber, D.P.
2000-01-01
Because of the complexity of two-phase flow phenomena, two-phase flow codes rely heavily on empirical correlations. This approach has a number of serious shortcomings. Advances in parallel computing and continuing improvements in computer speed and memory have stimulated the development of numerical simulation tools that rely less on empirical correlations and more on fundamental physics. The objective of this work is to take advantage of developments in massively parallel computing, single-phase computational fluid dynamics of complex systems, and numerical methods for front capturing in two-phase flows to develop a computer code for direct numerical simulation of two-phase flow. This includes bubble/droplet transport, interface deformation and topology change, bubble-droplet interactions, interface mass, momentum, and energy transfer. In this work, the Navier-Stokes and energy equations are solved by treating both phases as a single fluid with interfaces between the two phases, and a discontinuity in material properties across the moving interfaces. The evolution of the interfaces is simulated by using the front capturing technique of the level-set methods. In these methods, the boundary of a two-fluid interface is modeled as the zero level set of a smooth function φ. The level-set function φ is defined as the signed distance from the interface (φ is negative inside a droplet/bubble and positive outside). Compared to other front-capturing or front-tracking methods, the level-set approach is relatively easy to implement even in three-dimensional flows, and it has been shown to simulate well the coalescence and breakup of droplets/bubbles
Dynamic Modeling Strategy for Flow Regime Transition in Gas-Liquid Two-Phase Flows
Directory of Open Access Journals (Sweden)
Xia Wang
2012-12-01
Full Text Available In modeling gas-liquid two-phase flows, the concept of flow regimes has been widely used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are flow regime dependent. Current nuclear reactor safety analysis codes, such as RELAP5, classify flow regimes using flow regime maps or transition criteria that were developed for steady-state, fully-developed flows. As two-phase flows are dynamic in nature, it is important to model the flow regime transitions dynamically to more accurately predict the two-phase flows. The present work aims to develop a dynamic modeling strategy to determine flow regimes in gas-liquid two-phase flows through introduction of interfacial area transport equations (IATEs within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation of the interfacial area, fluid particle (bubble or liquid droplet disintegration, boiling and evaporation, and the destruction of the interfacial area, fluid particle coalescence and condensation. For flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shapes, namely group-1 and group-2 bubbles. A preliminary approach to dynamically identify the flow regimes is discussed, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration. The flow regime predicted with this method shows good agreement with the experimental observations.
Two-group interfacial area concentration correlations of two-phase flows in large diameter pipes
International Nuclear Information System (INIS)
Shen, Xiuzhong; Hibiki, Takashi
2015-01-01
The reliable empirical correlations and models are one of the important ways to predict the interfacial area concentration (IAC) in two-phase flows. However, up to now, no correlation or model is available for the prediction of the IAC in the two-phase flows in large diameter pipes. This study collected an IAC experimental database of two-phase flows taken under various flow conditions in large diameter pipes and presented a systematic way to predict the IAC for two-phase flows from bubbly, cap-bubbly to churn flow in large diameter pipes by categorizing bubbles into two groups (group-1: spherical and distorted bubble, group-2: cap bubble). Correlations were developed to predict the group-1 void fraction from the void fraction of all bubble. The IAC contribution from group-1 bubbles was modeled by using the dominant parameters of group-1 bubble void fraction and Reynolds number based on the parameter-dependent analysis of Hibiki and Ishii (2001, 2002) using one-dimensional bubble number density and interfacial area transport equations. A new drift velocity correlation for two-phase flow with large cap bubbles in large diameter pipes was derived in this study. By comparing the newly-derived drift velocity correlation with the existing drift velocity correlation of Kataoka and Ishii (1987) for large diameter pipes and using the characteristics of the representative bubbles among the group 2 bubbles, we developed the model of IAC and bubble size for group 2 cap bubbles. The developed models for estimating the IAC are compared with the entire collected database. A reasonable agreement was obtained with average relative errors of ±28.1%, ±54.4% and ±29.6% for group 1, group 2 and all bubbles respectively. (author)
Two-phase flow instabilities in a silicon microchannels heat sink
International Nuclear Information System (INIS)
Bogojevic, D.; Sefiane, K.; Walton, A.J.; Lin, H.; Cummins, G.
2009-01-01
Two-phase flow instabilities are highly undesirable in microchannels-based heat sinks as they can lead to temperature oscillations with high amplitudes, premature critical heat flux and mechanical vibrations. This work is an experimental study of boiling instabilities in a microchannel silicon heat sink with 40 parallel rectangular microchannels, having a length of 15 mm and a hydraulic diameter of 194 μm. A series of experiments have been carried out to investigate pressure and temperature oscillations during the flow boiling instabilities under uniform heating, using water as a cooling liquid. Thin nickel film thermometers, integrated on the back side of a heat sink with microchannels, were used in order to obtain a better insight related to temperature fluctuations caused by two-phase flow instabilities. Flow regime maps are presented for two inlet water temperatures, showing stable and unstable flow regimes. It was observed that boiling leads to asymmetrical flow distribution within microchannels that result in high temperature non-uniformity and the simultaneously existence of different flow regimes along the transverse direction. Two types of two-phase flow instabilities with appreciable pressure and temperature fluctuations were observed, that depended on the heat to mass flux ratio and inlet water temperature. These were high amplitude/low frequency and low amplitude/high frequency instabilities. High speed camera imaging, performed simultaneously with pressure and temperature measurements, showed that inlet/outlet pressure and the temperature fluctuations existed due to alternation between liquid/two-phase/vapour flows. It was also determined that the inlet water subcooling condition affects the magnitudes of the temperature oscillations in two-phase flow instabilities and flow distribution within the microchannels.
Lattice Boltzmann model for simulating immiscible two-phase flows
International Nuclear Information System (INIS)
Reis, T; Phillips, T N
2007-01-01
The lattice Boltzmann equation is often promoted as a numerical simulation tool that is particularly suitable for predicting the flow of complex fluids. This paper develops a two-dimensional 9-velocity (D2Q9) lattice Boltzmann model for immiscible binary fluids with variable viscosities and density ratio using a single relaxation time for each fluid. In the macroscopic limit, this model is shown to recover the Navier-Stokes equations for two-phase flows. This is achieved by constructing a two-phase component of the collision operator that induces the appropriate surface tension term in the macroscopic equations. A theoretical expression for surface tension is determined. The validity of this analysis is confirmed by comparing numerical and theoretical predictions of surface tension as a function of density. The model is also shown to predict Laplace's law for surface tension and Poiseuille flow of layered immiscible binary fluids. The spinodal decomposition of two fluids of equal density but different viscosity is then studied. At equilibrium, the system comprises one large low viscosity bubble enclosed by the more viscous fluid in agreement with theoretical arguments of Renardy and Joseph (1993 Fundamentals of Two-Fluid Dynamics (New York: Springer)). Two other simulations, namely the non-equilibrium rod rest and the coalescence of two bubbles, are performed to show that this model can be used to simulate two fluids with a large density ratio
Experimental study of two-phase natural circulation circuit
Energy Technology Data Exchange (ETDEWEB)
Lemos, Wanderley Freitas; Su, Jian, E-mail: wlemos@lasme.coppe.ufrj.br, E-mail: sujian@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Faccini, Jose Luiz Horacio, E-mail: faccini@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), RIo de Janeiro, RJ (Brazil). Lab. de Termo-Hidraulica Experimental
2012-07-01
This paper reports an experimental study on the behavior of fluid flow in natural circulation under single-and two-phase flow conditions. The natural circulation circuit was designed based on concepts of similarity and scale in proportion to the actual operating conditions of a nuclear reactor. This test equipment has similar performance to the passive system for removal of residual heat presents in Advanced Pressurized Water Reactors (A PWR). The experiment was carried out by supplying water to primary and secondary circuits, as well as electrical power resistors installed inside the heater. Power controller has available to adjust the values for supply of electrical power resistors, in order to simulate conditions of decay of power from the nuclear reactor in steady state. Data acquisition system allows the measurement and control of the temperature at different points by means of thermocouples installed at several points along the circuit. The behavior of the phenomenon of natural circulation was monitored by a software with graphical interface, showing the evolution of temperature measurement points and the results stored in digital format spreadsheets. Besides, the natural circulation flow rate was measured by a flowmeter installed on the hot leg. A flow visualization technique was used the for identifying vertical flow regimes of two-phase natural circulation. Finally, the Reynolds Number was calculated for the establishment of a friction factor correlation dependent on the scale geometrical length, height and diameter of the pipe. (author)
Droplets formation and merging in two-phase flow microfluidics.
Gu, Hao; Duits, Michel H G; Mugele, Frieder
2011-01-01
Two-phase flow microfluidics is emerging as a popular technology for a wide range of applications involving high throughput such as encapsulation, chemical synthesis and biochemical assays. Within this platform, the formation and merging of droplets inside an immiscible carrier fluid are two key procedures: (i) the emulsification step should lead to a very well controlled drop size (distribution); and (ii) the use of droplet as micro-reactors requires a reliable merging. A novel trend within this field is the use of additional active means of control besides the commonly used hydrodynamic manipulation. Electric fields are especially suitable for this, due to quantitative control over the amplitude and time dependence of the signals, and the flexibility in designing micro-electrode geometries. With this, the formation and merging of droplets can be achieved on-demand and with high precision. In this review on two-phase flow microfluidics, particular emphasis is given on these aspects. Also recent innovations in microfabrication technologies used for this purpose will be discussed.
Numerical calculation of two-phase turbulent jets
Energy Technology Data Exchange (ETDEWEB)
Saif, A.A.
1995-05-01
Two-phase turbulent round jets were numerically simulated using a multidimensional two-phase CFD code based on the two-fluid model. The turbulence phenomena were treated with the standard k-{epsilon} model. It was modified to take into account the additional dissipation of turbulent kinetic energy by the dispersed phase. Within the context of the two-fluid model it is more appropriate and physically justified to treat the diffusion by an interfacial force in the momentum equation. In this work, the diffusion force and the additional dissipation effect by the dispersed phase were modeled starting from the classical turbulent energy spectrum analysis. A cut-off frequency was proposed to decrease the dissipation effect by the dispersed phase when large size particles are introduced in the flow. The cut-off frequency combined with the bubble-induced turbulence effect allows for an increase in turbulence for large particles. Additional care was taken in choosing the right kind of experimental data from the literature so that a good separate effect test was possible for their models. The models predicted the experimental data very closely and they were general enough to predict extreme limit cases: water-bubble and air-droplet jets.
Computer simulation of two-phase flow in nuclear reactors
International Nuclear Information System (INIS)
Wulff, W.
1993-01-01
Two-phase flow models dominate the requirements of economic resources for the development and use of computer codes which serve to analyze thermohydraulic transients in nuclear power plants. An attempt is made to reduce the effort of analyzing reactor transients by combining purpose-oriented modelling with advanced computing techniques. Six principles are presented on mathematical modeling and the selection of numerical methods, along with suggestions on programming and machine selection, all aimed at reducing the cost of analysis. Computer simulation is contrasted with traditional computer calculation. The advantages of run-time interactive access operation in a simulation environment are demonstrated. It is explained that the drift-flux model is better suited than the two-fluid model for the analysis of two-phase flow in nuclear reactors, because of the latter's closure problems. The advantage of analytical over numerical integration is demonstrated. Modeling and programming techniques are presented which minimize the number of needed arithmetical and logical operations and thereby increase the simulation speed, while decreasing the cost. (orig.)
Experimental study of two-phase natural circulation circuit
International Nuclear Information System (INIS)
Lemos, Wanderley Freitas; Su, Jian; Faccini, Jose Luiz Horacio
2012-01-01
This paper reports an experimental study on the behavior of fluid flow in natural circulation under single-and two-phase flow conditions. The natural circulation circuit was designed based on concepts of similarity and scale in proportion to the actual operating conditions of a nuclear reactor. This test equipment has similar performance to the passive system for removal of residual heat presents in Advanced Pressurized Water Reactors (A PWR). The experiment was carried out by supplying water to primary and secondary circuits, as well as electrical power resistors installed inside the heater. Power controller has available to adjust the values for supply of electrical power resistors, in order to simulate conditions of decay of power from the nuclear reactor in steady state. Data acquisition system allows the measurement and control of the temperature at different points by means of thermocouples installed at several points along the circuit. The behavior of the phenomenon of natural circulation was monitored by a software with graphical interface, showing the evolution of temperature measurement points and the results stored in digital format spreadsheets. Besides, the natural circulation flow rate was measured by a flowmeter installed on the hot leg. A flow visualization technique was used the for identifying vertical flow regimes of two-phase natural circulation. Finally, the Reynolds Number was calculated for the establishment of a friction factor correlation dependent on the scale geometrical length, height and diameter of the pipe. (author)
Two-phase flow in a diverging nozzle
International Nuclear Information System (INIS)
Wadle, M.
1986-05-01
Stationary two-phase flow experiments were performed with steam-water and air-water mixtures in a well-instrumented horizontal diverging nozzle. The test section consisted of a constant diameter tube, the friction-section, followed by an expansion, the diffusor, which has a tanh-contour and finally another constant diameter tube. The diameter ratio sigma=D1/D2 is 16/80. For the steam-water experiments the flow parameters were: 0 2 and for air-water mixtures (0 2 ). The initial conditions were varied to achieve subcritical and critical mass flow rates. A new model for the pressure recovery in an abrupt expansion is presented. It is based on the superficial velocity concept and agrees well with the steam-water and the water-air experimental data as well as with the experiments of other authors. The experiments were also calculated with the two-phase code DUESE. The Drift-Flux models in this code as well as the constitutive correlations and their empirical constants could be tested. It is shown, that a 1D Drift-Flux code can handle the highly transient flow in the diffusor if the proper drift model is used. In a 1D simulation it is only necessary that the computational flow area is expanded to its full width within an axial length which is equivalent to the real contour. (orig./GL) [de
Droplets Formation and Merging in Two-Phase Flow Microfluidics
Directory of Open Access Journals (Sweden)
Hao Gu
2011-04-01
Full Text Available Two-phase flow microfluidics is emerging as a popular technology for a wide range of applications involving high throughput such as encapsulation, chemical synthesis and biochemical assays. Within this platform, the formation and merging of droplets inside an immiscible carrier fluid are two key procedures: (i the emulsification step should lead to a very well controlled drop size (distribution; and (ii the use of droplet as micro-reactors requires a reliable merging. A novel trend within this field is the use of additional active means of control besides the commonly used hydrodynamic manipulation. Electric fields are especially suitable for this, due to quantitative control over the amplitude and time dependence of the signals, and the flexibility in designing micro-electrode geometries. With this, the formation and merging of droplets can be achieved on-demand and with high precision. In this review on two-phase flow microfluidics, particular emphasis is given on these aspects. Also recent innovations in microfabrication technologies used for this purpose will be discussed.
The PDF method for Lagrangian two-phase flow simulations
International Nuclear Information System (INIS)
Minier, J.P.; Pozorski, J.
1996-04-01
A recent turbulence model put forward by Pope (1991) in the context of PDF modelling has been used. In this approach, the one-point joint velocity-dissipation pdf equation is solved by simulating the instantaneous behaviour of a large number of Lagrangian fluid particles. Closure of the evolution equations of these Lagrangian particles is based on stochastic models and more specifically on diffusion processes. Such models are of direct use for two-phase flow modelling where the so-called fluid seen by discrete inclusions has to be modelled. Full Lagrangian simulations have been performed for shear-flows. It is emphasized that this approach gives far more information than traditional turbulence closures (such as the K-ε model) and therefore can be very useful for situations involving complex physics. It is also believed that the present model represents the first step towards a complete Lagrangian-Lagrangian model for dispersed two-phase flow problems. (authors). 21 refs., 6 figs
Studying Suspended Sediment Mechanism with Two-Phase PIV
Matinpour, H.; Atkinson, J. F.; Bennett, S. J.; Guala, M.
2017-12-01
Suspended sediment transport affects soil erosion, agriculture and water resources quality. Turbulent diffusion is the most primary force to maintain sediments in suspension. Although extensive previous literature have been studying the interactions between turbulent motion and suspended sediment, mechanism of sediments in suspension is still poorly understood. In this study, we investigate suspension of sediments as two distinct phases: one phase of sediments and another phase of fluid with turbulent motions. We designed and deployed a state-of-the-art two-phase PIV measurement technique to discriminate these two phases and acquire velocities of each phase separately and simultaneously. The technique that we have developed is employing a computer-vision based method, which enables us to discriminate sediment particles from fluid tracer particles based on two thresholds, dissimilar particle sizes and different particle intensities. Results indicate that fluid turbulence decreases in the presence of suspended sediments. Obtaining only sediment phase consecutive images enable us to compute fluctuation sediment concentration. This result enlightens understanding of complex interaction between the fluctuation velocities and the fluctuation of associated mass and compares turbulent viscosity with turbulent eddy diffusivity experimentally.
Ferrofluid-in-oil two-phase flow patterns in a flow-focusing microchannel
Sheu, T. S.; Chen, Y. T.; Lih, F. L.; Miao, J. M.
This study investigates the two-phase flow formation process of water-based Fe3O4 ferrofluid (dispersed phase) in a silicon oil (continuous phase) flow in the microfluidic flow-focusing microchannel under various operational conditions. With transparent PDMS chip and optical microscope, four main two-phase flow patterns as droplet flow, slug flow, ring flow and churn flow are observed. The droplet shape, size, and formation mechanism were also investigated under different Ca numbers and intended to find out the empirical relations. The paper marks an original flow pattern map of the ferrofluid-in-oil flows in the microfluidic flow-focusing microchannels. The flow pattern transiting from droplet flow to slug flow appears for an operational conditions of QR < 1 and Lf / W < 1. The power law index that related Lf / W to QR was 0.36 in present device.
Investigation of Power Losses of Two-Stage Two-Phase Converter with Two-Phase Motor
Directory of Open Access Journals (Sweden)
Michal Prazenica
2011-01-01
Full Text Available The paper deals with determination of losses of two-stage power electronic system with two-phase variable orthogonal output. The simulation is focused on the investigation of losses in the converter during one period in steady-state operation. Modeling and simulation of two matrix converters with R-L load is shown in the paper. The simulation results confirm a very good time-waveform of the phase current and the system seems to be suitable for low-cost application in automotive/aerospace industries and in application with high frequency voltage sources.
Mixed convection in a two-phase flow cooling loop
International Nuclear Information System (INIS)
Janssens-Maenhout, G.; Daubner, M.; Knebel, J.U.
2002-03-01
This report summarizes the numerical simulations using the CFD code CFX4.1 which has additional models for subcooled flow boiling phenomena and the interfacial forces. The improved CFX4.1 code can be applied to the design of boiling induced mixed convection cooling loops in a defined parameter range. The experimental part describes the geysering experiments and the instability effects on the two-phase natural circulation flow. An experimentally validated flow pattern map in the Phase Change Number - Subcooling Number (N PCh - N Sub ) diagram defines the operational range in which flow instabilities such as geysering can be expected. One important perspective of this combined experimental/numerical work, which is in the field of two-phase flow, is its application to the development of accelerator driven systems (ADS). The main objective on an ADS is its potential to transmute minor actinides and long-lived fission products, thus participating in closing the fuel cycle. The development of an ADS is an important issue within the Euratom Fifth FP on Partitioning and Transmutation. One concept of an ADS, which is investigated in more detail within the ''preliminary design study of an experimental ADS'' Project (PDS-XADS) of the Euratom Fifth FP, is the XADS lead-bismuth cooled Experimental ADS of ANSALDO. An essential feature of this concept is the natural circulation of the primary coolant within the reactor pool. The natural circulation, which is driven by the density differences between the blanket and the heat exchanger, is enhanced by the injection of the nitrogen cover gas through spargers located in a riser part just above the blanket. This so-called gas-lift pump system has not been investigated in more detail nor has this gas-lift pump system been numerically/experimentally confirmed. The knowledge gained within the SUCO Programe, i.e. the modelling of the interfacial forces, the experimental work on flow instabilities and the modelling of the interfacial area
Mixed convection in a two-phase flow cooling loop
Energy Technology Data Exchange (ETDEWEB)
Janssens-Maenhout, G.; Daubner, M.; Knebel, J.U.
2002-03-01
This report summarizes the numerical simulations using the CFD code CFX4.1 which has additional models for subcooled flow boiling phenomena and the interfacial forces. The improved CFX4.1 code can be applied to the design of boiling induced mixed convection cooling loops in a defined parameter range. The experimental part describes the geysering experiments and the instability effects on the two-phase natural circulation flow. An experimentally validated flow pattern map in the Phase Change Number - Subcooling Number (N{sub PCh} - N{sub Sub}) diagram defines the operational range in which flow instabilities such as geysering can be expected. One important perspective of this combined experimental/numerical work, which is in the field of two-phase flow, is its application to the development of accelerator driven systems (ADS). The main objective on an ADS is its potential to transmute minor actinides and long-lived fission products, thus participating in closing the fuel cycle. The development of an ADS is an important issue within the Euratom Fifth FP on Partitioning and Transmutation. One concept of an ADS, which is investigated in more detail within the ''preliminary design study of an experimental ADS'' Project (PDS-XADS) of the Euratom Fifth FP, is the XADS lead-bismuth cooled Experimental ADS of ANSALDO. An essential feature of this concept is the natural circulation of the primary coolant within the reactor pool. The natural circulation, which is driven by the density differences between the blanket and the heat exchanger, is enhanced by the injection of the nitrogen cover gas through spargers located in a riser part just above the blanket. This so-called gas-lift pump system has not been investigated in more detail nor has this gas-lift pump system been numerically/experimentally confirmed. The knowledge gained within the SUCO Programe, i.e. the modelling of the interfacial forces, the experimental work on flow instabilities and the
Frictional pressure drop of gas liquid two-phase flow in pipes
International Nuclear Information System (INIS)
Shannak, Benbella A.
2008-01-01
Experiments of air water two-phase flow frictional pressure drop of vertical and horizontal smooth and relatively rough pipes were conducted, respectively. The result demonstrated that the frictional pressure drop increases with increasing relative roughness of the pipe. However, the influence of the relative roughness becomes more evident at higher vapour quality and higher mass flux. A new prediction model for frictional pressure drop of two-phase flow in pipes is proposed. The model includes a new definition of the Reynolds number and the friction factor of two-phase flow. The proposed model fits the presented experimental data very well, for vertical, horizontal, smooth and rough pipes. Therefore, the reproductive accuracy of the model is tested on the experimental data existing in the open literature and compared with the most common models. The statistical comparison, based on the Friedel's Data-Bank containing of about 16,000 measured data, demonstrated that the proposed model is the best overall agreement with the data. The model was tested for a wide range of flow types, fluid systems, physical properties and geometrical parameters, typically encountered in industrial piping systems. Hence, calculating based on the new approach is sufficiently accurate for engineering purposes
ESR imaging investigations of two-phase systems.
Herrmann, Werner; Stösser, Reinhard; Borchert, Hans-Hubert
2007-06-01
The possibilities of electron spin resonance (ESR) and electron spin resonance imaging (ESRI) for investigating the properties of the spin probes TEMPO and TEMPOL in two-phase systems have been examined in the systems water/n-octanol, Miglyol/Miglyol, and Precirol/Miglyol. Phases and regions of the phase boundary could be mapped successfully by means of the isotropic hyperfine coupling constants, and, moreover, the quantification of rotational and lateral diffusion of the spin probes was possible. For the quantitative treatment of the micropolarity, a simplified empirical model was established on the basis of the Nernst distribution and the experimentally determined isotropic hyperfine coupling constants. The model does not only describe the summarized micropolarities of coexisting phases, but also the region of the phase boundary, where solvent molecules of different polarities and tendencies to form hydrogen bonds compete to interact with the NO group of the spin probe. Copyright 2007 John Wiley & Sons, Ltd.
Characterization of the two-phase Taylor Couette flow
International Nuclear Information System (INIS)
Mehel A; Gabillet B; Djeridi H
2005-01-01
The focus of the present study concerns the effects of a dispersed phase on the structure of a quasi periodic Couette Taylor flow. The two phase flow patterns are investigated experimentally for the Taylor number Ta=780. Small bubbles (0.035 times as small as the gap) are generated by agitation of the upper free surface. Larger bubbles (0.15 times as small as the gap) are produced by injection at the bottom of the apparatus associated with a pressure drop. Void fraction, bubble size and velocity are measured, as well as the azimuthal and axial velocity components of the liquid. A premature transition to turbulence is pointed out and discussed according to the bubble size and their localization in the gap. (authors)
Response of two-phase droplets to intense electromagnetic radiation
Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.
1993-01-01
The response of two-phase droplets to intense radiant heating is studied to determine the incident power that is required for causing explosive boiling in the liquid phase. The droplets studied consist of strongly absorbing coal particles dispersed in a weakly absorbing water medium. Experiments are performed by confining droplets (radii of 37, 55, and 80 microns) electrodynamically and irradiating them from two sides with pulsed laser beams. Emphasis is placed on the transition region from accelerated droplet vaporization to droplet superheating and explosive boiling. The time scale observed for explosive boiling is more than 2 orders of magnitude longer than published values for pure liquids. The delayed response is the result of energy transfer limitations between the absorbing solid phase and the surrounding liquid.
Particle clustering within a two-phase turbulent pipe jet
Lau, Timothy; Nathan, Graham
2016-11-01
A comprehensive study of the influence of Stokes number on the instantaneous distributions of particles within a well-characterised, two-phase, turbulent pipe jet in a weak co-flow was performed. The experiments utilised particles with a narrow size distribution, resulting in a truly mono-disperse particle-laden jet. The jet Reynolds number, based on the pipe diameter, was in the range 10000 developed technique. The results show that particle clustering is significantly influenced by the exit Stokes number. Particle clustering was found to be significant for 0 . 3 financial contributions by the Australian Research Council (Grant No. DP120102961) and the Australian Renewable Energy Agency (Grant No. USO034).
Unsteady interfacial coupling of two-phase flow models
International Nuclear Information System (INIS)
Hurisse, O.
2006-01-01
The primary coolant circuit in a nuclear power plant contains several distinct components (vessel, core, pipes,...). For all components, specific codes based on the discretization of partial differential equations have already been developed. In order to obtain simulations for the whole circuit, the interfacial coupling of these codes is required. The approach examined within this work consists in coupling codes by providing unsteady information through the coupling interface. The numerical technique relies on the use of an interface model, which is combined with the basic strategy that was introduced by Greenberg and Leroux in order to compute approximations of steady solutions of non-homogeneous hyperbolic systems. Three different coupling cases have been examined: (i) the coupling of a one-dimensional Euler system with a two-dimensional Euler system; (ii) the coupling of two distinct homogeneous two-phase flow models; (iii) the coupling of a four-equation homogeneous model with the standard two-fluid model. (author)
Mathematical model of two-phase flow in accelerator channel
Directory of Open Access Journals (Sweden)
О.Ф. Нікулін
2010-01-01
Full Text Available The problem of two-phase flow composed of energy-carrier phase (Newtonian liquid and solid fine-dispersed phase (particles in counter jet mill accelerator channel is considered. The mathematical model bases goes on the supposition that the phases interact with each other like independent substances by means of aerodynamics’ forces in conditions of adiabatic flow. The mathematical model in the form of system of differential equations of order 11 is represented. Derivations of equations by base physical principles for cross-section-averaged quantity are produced. The mathematical model can be used for estimation of any kinematic and thermodynamic flow characteristics for purposely parameters optimization problem solving and transfer functions determination, that take place in counter jet mill accelerator channel design.
Two-phase titration of cerium(III) by permanganate
International Nuclear Information System (INIS)
Lazarev, A.I.; Lazareva, V.I.; Gerko, V.V.
1987-01-01
This paper presents a method for the two-phase titrimetric determination of cerium(III) with permanganate which does not require an expenditure of sugar and preliminary removal of chlorides and nitrates. The interaction of cerium(III) with permanganate at room temperature was studied as a function of the pH, the concentration of pyrophosphate, tetraphenylphosphonium (TPP), permanganate, and extraneous compounds, the rate of titration, and the time of stay of the solution in air before titration. The investigations were conducted according to the following methodology: water, solution of cerium(III) pyrophosphate, and TPP were introduced into an Erlenmeyer flask with a side branch near the bottom for clearer observation of the color of the chloroform phase. The authors established the given pH value, poured the water into a volume of 50 ml, and added chloroform. The result was titrated with permanganate solutions of various concentrations until a violet color appeared in the chloroform phase
Interfacial shear modeling in two-phase annular flow
International Nuclear Information System (INIS)
Kumar, R.; Edwards, D.P.
1996-11-01
A new interfacial shear stress model called the law of the interface model, based on the law of the wall approach in turbulent flows, has been developed and locally applied in a fully developed, adiabatic, two-phase annular flow in a duct. Numerical results have been obtained using this model in conjunction with other models available in the literature that are required for the closure of the continuity and momentum equations. These results have been compared with droplet velocity data (using laser Doppler velocimetry and hot film anemometry), void fraction data (using gamma densitometry) and pressure drop data obtained in a R-134A refrigerant test facility. Droplet velocity results match the experimental data well, however, the prediction of the void fraction is less accurate. The poor prediction of void fraction, especially for the low void fraction cases, appears to be due to the lack of a good mechanistic model for entrainment
Interfacial shear modeling in two-phase annular flow
International Nuclear Information System (INIS)
Kumar, R.; Edwards, D.P.
1996-07-01
A new interfacial shear stress model called the law of the interface model, based on the law of the wall approach in turbulent flows, has been developed and locally applied in a fully developed, adiabatic, two-phase annular flow in a duct. Numerical results have been obtained using this model in conjunction with other models available in the literature that are required for the closure of the continuity and momentum equations. These results have been compared with droplet velocity data (using laser Doppler velocimetry and hot film anemometry), void fraction data (using gamma densitometry) and pressure drop data obtained in a R-134A refrigerant test facility. Droplet velocity results match the experimental data well, however, the prediction of the void fraction is less accurate. The poor prediction of void fraction, especially for the low void fraction cases, appears to be due to the lack of a good mechanistic model for entrainment
Numerical modeling of two-phase transonic flow
Czech Academy of Sciences Publication Activity Database
Halama, Jan; Benkhaldoun, F.; Fořt, Jaroslav
2010-01-01
Roč. 80, č. 88 (2010), s. 1624-1635 ISSN 0378-4754 Grant - others:GA ČR(CZ) GA201/08/0012 Program:GA Institutional research plan: CEZ:AV0Z20760514 Keywords : two - phase flow * condensation * fractional step method Subject RIV: BK - Fluid Dynamics Impact factor: 0.812, year: 2010 http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V0T-4VNK68X-2-R&_cdi=5655&_user=640952&_pii=S0378475409000421&_origin=search&_coverDate=04%2F30%2F2010&_sk=999199991&view=c&wchp=dGLzVlb-zSkWb&md5=5ba607428fac339a3e5f67035d3996d0&ie=/sdarticle.pdf
Two-phase flow instabilities in a vertical annular channel
Energy Technology Data Exchange (ETDEWEB)
Babelli, I.; Nair, S.; Ishii, M. [Purdue Univ., West Lafayette, IN (United States)
1995-09-01
An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.
Two-phase flow experiments through intergranular stress corrosion cracks
International Nuclear Information System (INIS)
Collier, R.P.; Norris, D.M.
1984-01-01
Experimental studies of critical two-phase water flow, through simulated and actual intergranular stress corrosion cracks, were performed to obtain data to evaluate a leak flow rate model and investigate acoustic transducer effectiveness in detecting and sizing leaks. The experimental program included a parametric study of the effects of crack geometry, fluid stagnation pressure and temperature, and crack surface roughness on leak flow rate. In addition, leak detection, location, and leak size estimation capabilities of several different acoustic transducers were evaluated as functions of leak rate and transducer position. This paper presents flow rate data for several different cracks and fluid conditions. It also presents the minimum flows rate detected with the acoustic sensors and a relationship between acoustic signal strength and leak flow rate
Two-Phase Algorithm for Optimal Camera Placement
Directory of Open Access Journals (Sweden)
Jun-Woo Ahn
2016-01-01
Full Text Available As markers for visual sensor networks have become larger, interest in the optimal camera placement problem has continued to increase. The most featured solution for the optimal camera placement problem is based on binary integer programming (BIP. Due to the NP-hard characteristic of the optimal camera placement problem, however, it is difficult to find a solution for a complex, real-world problem using BIP. Many approximation algorithms have been developed to solve this problem. In this paper, a two-phase algorithm is proposed as an approximation algorithm based on BIP that can solve the optimal camera placement problem for a placement space larger than in current studies. This study solves the problem in three-dimensional space for a real-world structure.
Study on hydrodynamic crisis of two-phase flow
International Nuclear Information System (INIS)
Nigmatulin, B.I.; Ivandaev, A.I.
1977-01-01
The phenomenon of hydrodynamic crisis (locking) of a two-phase flow is investigated. A model of a disperseannular flow with an effective monodisperse nucleus is used for describing the motion of a mixture under near-critical conditions. Main differential equations of a flow in a channel are given; in particular, the differential laws of variation of the effective diameters of drops in the nucleus as a result of mass exchange between the mixture components are singled out. Questions of concretization of the model are discussed. The conditions for the attainment of the maximum rate of flow of the gas through the channel are studied, as well as the effect of the flow prehistory on the formation of critical conditions in the outlet cross-section
Study on hydrodynamic crisis of two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Nigmatulin, B I; Ivandaev, A I [Moskovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Mekhaniki
1977-01-01
The phenomenon of hydrodynamic crisis (locking) of a two-phase flow is investigated. A model of a disperse annular flow with an effective monodisperse nucleus is used for describing the motion of a mixture under near-critical conditions. Main differential equations of a flow in a channel are given; in particular, the differential laws of variation of the effective diameters of drops in the nucleus as a result of mass exchange between the mixture components are singled out. Questions of concretization of the model are discussed. The conditions for the attainment of the maximum rate of flow of the gas through the channel are studied, as well as the effect of the flow prehistory on the formation of critical conditions in the outlet cross-section.
Gulping phenomena in transient countercurrent two-phase flow
International Nuclear Information System (INIS)
Tehrani, Ali A.K.
2001-04-01
Apart from previous work on countercurrent gas-liquid flow, transient tank drainage through horizontal off-take pipes is described, including experimental procedure, flow pattern on observations and countercurrent flow limitation results. A separate chapter is devoted to countercurrent two-phase flow in a pressurised water reactor hot-leg scaled model. Results concerning low head flooding, high head and loss of bowl flooding, transient draining of the steam generator and pressure variation and bubble detachment are presented. The following subjects are covered as well: draining of sealed tanks of vertical pipes, unsteady draining of closed vessel via vertical tube, unsteady filling of a closed vessel via vertical tube from a constant head reservoir. Practical significance of the results obtained is discussed
Sputtering of two-phase AgxCuγ alloys
International Nuclear Information System (INIS)
Bibic, N.; Milosavljevic, M.; Perusko, D.; Wilson, I.H.
1992-01-01
Elemental sputtering yields from two phase AgCu alloys were measured for 20, 40 and 50 at % Ag. Argon ion bombardment energies were in the range 35-55 keV and the ion dose was 1 x 10 19 ions cm -2 . The sputtering yield for silver was found to be considerably below what was expected by simple selective sputtering of a two component alloy. Analysis by electron probe X-ray microanalysis and scanning electron microscopy of the eroded surface indicated that surface diffusion of copper from copper rich grains and geometrical constraints in the dense cone forest on Cu/Ag eutectic regions combine to reduce the sputtering yield for silver. (author)
Measurement of two-phase flow momentum with force transducers
International Nuclear Information System (INIS)
Hardy, J.E.; Smith, J.E.
1990-01-01
Two strain-gage-based drag transducers were developed to measure two-phase flow in simulated pressurized water reactor (PWR) test facilities. One transducer, a drag body (DB), was designed to measure the bidirectional average momentum flux passing through an end box. The second drag sensor, a break through detector (BTD), was designed to sense liquid downflow from the upper plenum to the core region. After prototype sensors passed numerous acceptance tests, transducers were fabricated and installed in two experimental test facilities, one in Japan and one in West Germany. High-quality data were extracted from both the DBs and BTDs for a variety of loss-of-coolant accident (LOCA) scenarios. The information collected from these sensors has added to the understanding of the thermohydraulic phenomena that occur during the refill/reflood stage of a LOCA in a PWR. 9 refs., 15 figs
Flooding in counter-current two-phase flow
International Nuclear Information System (INIS)
Ragland, W.A.; Ganic, E.N.
1982-01-01
Flooding is a phenomenon which is best described as the transition from counter-current to co-current flow. Early notice was taken of this phenomenon in the chemical engineering industry. Flooding also plays an important role in the field of two-phase heat transfer since it is a limit for many systems involving counter-current flow. Practical applications of flooding limited processes include wickless thermosyphons and the emergency core cooling system (ECCS) of pressurized water nuclear reactors. The phenomenon of flooding also is involved in the behavior of nuclear reactor core materials during severe accident conditions where flooding is one of the mechanisms governing the motion of the molten fuel pin cladding
Modeling two-phase ferroelectric composites by sequential laminates
International Nuclear Information System (INIS)
Idiart, Martín I
2014-01-01
Theoretical estimates are given for the overall dissipative response of two-phase ferroelectric composites with complex particulate microstructures under arbitrary loading histories. The ferroelectric behavior of the constituent phases is described via a stored energy density and a dissipation potential in accordance with the theory of generalized standard materials. An implicit time-discretization scheme is used to generate a variational representation of the overall response in terms of a single incremental potential. Estimates are then generated by constructing sequentially laminated microgeometries of particulate type whose overall incremental potential can be computed exactly. Because they are realizable, by construction, these estimates are guaranteed to conform with any material constraints, to satisfy all pertinent bounds and to exhibit the required convexity properties with no duality gap. Predictions for representative composite and porous systems are reported and discussed in the light of existing experimental data. (paper)
Two-phase flow and heat transfer under low gravity
Frost, W.
1981-01-01
Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.
Characteristics of two-phase flows in large diameter channels
Energy Technology Data Exchange (ETDEWEB)
Schlegel, J.P., E-mail: schlegelj@mst.edu [Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, 301 W 14th St., Rolla, MO 65401 (United States); Hibiki, T.; Ishii, M. [School of Nuclear Engineering, Purdue University, 400 Central Dr., West Lafayette, IN 47907 (United States)
2016-12-15
Two-phase flows in large diameter channels have a great deal of importance in a wide variety of industrial applications. Nuclear systems, petroleum refineries, and chemical processes make extensive use of larger systems. Flows in such channels have very different properties from flows in smaller channels which are typically used in experimental research. In this paper, the various differences between flows in large and small channels are highlighted using the results of previous experimental and analytical research. This review is followed by a review of recent experiments in and model development for flows in large diameter channels performed by the authors. The topics of these research efforts range from void fraction and interfacial area concentration measurement to flow regime identification and modeling, drift-flux modeling for high void fraction conditions, and evaluation of interfacial area transport models for large diameter channels.
Flooding in counter-current two-phase flow
Energy Technology Data Exchange (ETDEWEB)
Ragland, W.A.; Ganic, E.N.
1982-01-01
Flooding is a phenomenon which is best described as the transition from counter-current to co-current flow. Early notice was taken of this phenomenon in the chemical engineering industry. Flooding also plays an important role in the field of two-phase heat transfer since it is a limit for many systems involving counter-current flow. Practical applications of flooding limited processes include wickless thermosyphons and the emergency core cooling system (ECCS) of pressurized water nuclear reactors. The phenomenon of flooding also is involved in the behavior of nuclear reactor core materials during severe accident conditions where flooding is one of the mechanisms governing the motion of the molten fuel pin cladding.
The pdf approach to turbulent polydispersed two-phase flows
Minier, Jean-Pierre; Peirano, Eric
2001-10-01
The purpose of this paper is to develop a probabilistic approach to turbulent polydispersed two-phase flows. The two-phase flows considered are composed of a continuous phase, which is a turbulent fluid, and a dispersed phase, which represents an ensemble of discrete particles (solid particles, droplets or bubbles). Gathering the difficulties of turbulent flows and of particle motion, the challenge is to work out a general modelling approach that meets three requirements: to treat accurately the physically relevant phenomena, to provide enough information to address issues of complex physics (combustion, polydispersed particle flows, …) and to remain tractable for general non-homogeneous flows. The present probabilistic approach models the statistical dynamics of the system and consists in simulating the joint probability density function (pdf) of a number of fluid and discrete particle properties. A new point is that both the fluid and the particles are included in the pdf description. The derivation of the joint pdf model for the fluid and for the discrete particles is worked out in several steps. The mathematical properties of stochastic processes are first recalled. The various hierarchies of pdf descriptions are detailed and the physical principles that are used in the construction of the models are explained. The Lagrangian one-particle probabilistic description is developed first for the fluid alone, then for the discrete particles and finally for the joint fluid and particle turbulent systems. In the case of the probabilistic description for the fluid alone or for the discrete particles alone, numerical computations are presented and discussed to illustrate how the method works in practice and the kind of information that can be extracted from it. Comments on the current modelling state and propositions for future investigations which try to link the present work with other ideas in physics are made at the end of the paper.
Ductile fracture of two-phase welds under 77K
International Nuclear Information System (INIS)
Yushchenko, K.A.; Voronin, S.A.; Pustovit, A.I.; Shavel', A.V.
1984-01-01
The effect of the type of welding and fillers on crack resistance of welded joints high-strength steel EhP810 and its various compounds with steels EhP666, 08Kh18N10T has been studied. For the welding of steel EhP810 with steels EhP810, EhP666, 08Kh18N10T electron-beam, automatic, argon tungsten arc with non-consumable electrode with various fillers, as well as argon metal-arc welding with consumable electrode, were used. It is shown, that for a joint, made by electron-beam welding, parameters σsub(u), Ksub(IcJ), KCV are higher than for a joint of a similar phase structure made using filler wire EhP659-VI. It is explained by the fact, that during electron-beam welding joint metal refining takes place, which removes gases. In welded joints of chP810 steel, having joints with austenitic structure, characteristic of crack resistance Ssub(c) increases by more than 0.2 mm in contrast to two-phase joints, which conventional yield strength at 77 K exceeds 1000 MPa. It is worth mentioning, that for other classes of steels formation of two-phase structure of joint increases welded joint resistance to brittle fracture. It is possible to obtain the required structure of joint with assigned level of resistance to brittle fracture by means of the use of different fillers, optimum and welding procedure, regulaing the part of the basic metal in joint content
Flashing liquid jets and two-phase droplet dispersion
International Nuclear Information System (INIS)
Cleary, Vincent; Bowen, Phil; Witlox, Henk
2007-01-01
The large-scale release of a liquid contained at upstream conditions above its local atmospheric boiling point is a scenario often given consideration in process industry risk analysis. Current-hazard quantification software often employs simplistic equilibrium two-phase approaches. Scaled water experiments have been carried out measuring droplet velocity and droplet size distributions for a range of exit orifice aspect ratios (L/d) and conditions representing low to high superheat. 2D Phase-Doppler Anemometry has been utilised to characterise droplet kinematics and spray quality. Droplet size correlations have been developed for non-flashing, the transition between non-flashing and flashing, and fully flashing jets. Using high-speed shadowography, transition between regimes is defined in terms of criteria identified in the external flow structure. An overview companion paper provides a wider overview of the problem and reports implementation of these correlations into consequence models and subsequent validation. The fluid utilised throughout is water, hence droplet correlations are developed in non-dimensional form to allow extrapolation to other fluids through similarity scaling, although verification of model performance for other fluids is required in future studies. Data is reduced via non-dimensionalisation in terms of the Weber number and Jakob number, essentially representing the fluid mechanics and thermodynamics of the system, respectively. A droplet-size distribution correlation has also been developed, conveniently presented as a volume undersize distribution based on the Rosin-Rammler distribution. Separate correlations are provided for sub-cooled mechanical break-up and fully flashing jets. This form of correlation facilitates rapid estimates of likely mass rainout quantities, as well as full distribution information for more rigorous two-phase thermodynamic modelling in the future
Psychological distress through immigration: the two-phase temporal pattern?
Ritsner, M; Ponizovsky, A
1999-01-01
A large community sample, cross-sectional and in part longitudinal design, and comparison groups was used to determine the timing of psychological distress among immigrants. A total of 2,378 adult immigrants from the former Soviet Union to Israel completed the self-administered questionnaire Talbieh Brief Distress Inventory. The aggregate levels of distress and six psychological symptoms--obsessiveness, hostility, interpersonal sensitivity, depression, anxiety, and paranoid ideation--were compared at 20 intervals covering 1 to 60 months after resettlement. The level of psychological distress was significantly higher in the immigrants than that of Israeli natives but not in the potential immigrant controls. A two-phase temporal pattern of development of psychological distress was revealed consisting of escalation and reduction phases. The escalation phase was characterized by an increase in distress levels until the 27th month after arrival (a peak) and the reduction phase led to a decline returning to normal levels. The 1-month prevalence rate was 15.6% for the total sample, and for highly distressed subjects it reached 24% at the 27th month after arrival, and it declined to 4% at the 44th month. The time pattern of distress shared males and females, married and divorced/widowed (but not singles), as well as subjects of all age groups (except for immigrants in their forties). The two-phase pattern of distress obtained according to cross-sectional data was indirectly confirmed through a longitudinal way. Claims of early euphoric or distress-free period followed by mental health crisis frequently referred to in the literature on migration was not supported by this study.
Damping and fluidelastic instability in two-phase cross-flow heat exchanger tube arrays
Moran, Joaquin E.
flux, and its dependency is a function of void fraction. A dimensional analysis was carried out to investigate the relationship between damping and two-phase flow related parameters. As a result, the inclusion of surface tension in the form of the Capillary number appears to be useful when combined with the two-phase component of the damping ratio (interfacial damping). A strong dependence of damping on flow regime was observed when plotting the interfacial damping versus the void fraction, introducing an improvement over the previous result obtained by normalizing the two-phase damping, which does not exhibit this behaviour. The interfacial velocity model was selected to represent the fluidelastic data in two-phase experiments, due to the inclusion of the tube array geometry and density ratio effects, which does not exist for the pitch velocity approach. An essential component in reliably establishing the velocity threshold for fluidelastic instability, is a measure of the energy dissipation available in the system to balance the energy input from the flow. The present analysis argues that the damping in-flow is not an appropriate measure and demonstrates that the use of quiescent fluid damping provides a better measure of the energy dissipation, which produces a much more logical trend in the stability behaviour. This value of damping, combined with the RAD density and the interfacial velocity, collapses the available data well and provides the expected trend of two-phase flow stability data over the void fraction range from liquid to gas flows. The resulting stability maps represent a significant improvement over existing maps for predicting fluidelastic instability of tube bundles in two-phase flows. This result also tends to confirm the hypothesis that the basic mechanism of fluidelastic instability is the same for single and two-phase flows.
First-order system least squares and the energetic variational approach for two-phase flow
Adler, J. H.; Brannick, J.; Liu, C.; Manteuffel, T.; Zikatanov, L.
2011-07-01
This paper develops a first-order system least-squares (FOSLS) formulation for equations of two-phase flow. The main goal is to show that this discretization, along with numerical techniques such as nested iteration, algebraic multigrid, and adaptive local refinement, can be used to solve these types of complex fluid flow problems. In addition, from an energetic variational approach, it can be shown that an important quantity to preserve in a given simulation is the energy law. We discuss the energy law and inherent structure for two-phase flow using the Allen-Cahn interface model and indicate how it is related to other complex fluid models, such as magnetohydrodynamics. Finally, we show that, using the FOSLS framework, one can still satisfy the appropriate energy law globally while using well-known numerical techniques.
Two-Phase Immiscible Flows in Porous Media: The Mesocopic Maxwell–Stefan Approach
DEFF Research Database (Denmark)
Shapiro, Alexander
2015-01-01
We develop an approach to coupling between viscous flows of the two phases in porous media, based on the Maxwell–Stefan formalism. Two versions of the formalism are presented: the general form, and the form based on the interaction of the flowing phases with the interface between them. The last...... of mixing” between the flowing phases. Comparison to the available experimental data on the steady-state two-phase relative permeabilities is presented....... approach is supported by the description of the flow on the mesoscopic level, as coupled boundary problems for the Brinkmann or Stokes equations. It becomes possible, in some simplifying geometric assumptions, to derive exact expressions for the phenomenological coefficients in the Maxwell–Stefan transport...
Influence and applicability of wire-mesh sensor to acquire two phase flow dynamics
International Nuclear Information System (INIS)
Kanai, Taizo; Furuya, Masahiro; Arai, Takahiro; Shirakawa, Kenetsu
2011-01-01
Wire-mesh sensors (WMS) are able to measure void distributions and velocity profile at high speed. Immersing the wire-mesh affects the structure of two-phase flow. Experiments were performed for single rising air bubble in a vertical pipe of i.d. 50 mm and 224 mm at water velocities ranging from 0.05 to 0.52 m/s and 0.42 to 0.83 m/s. Distortion of a relatively large bubble with the wire-mesh was small in the water velocity over 0.25 m/s and confirmed by cross-correlation analysis as well. Bubble rising velocity acquired by WMS is in good agreement with that estimated high-speed camera in the experimental range. WMS has applicability to acquire two phase flow dynamics in the water velocity over 0.25 m/s. (author)
Workshop on Two-Phase Fluid Behavior in a Space Environment
Swanson, Theodore D. (Editor); Juhasz, AL (Editor); Long, W. Russ (Editor); Ottenstein, Laura (Editor)
1989-01-01
The Workshop was successful in achieving its main objective of identifying a large number of technical issues relating to the design of two-phase systems for space applications. The principal concern expressed was the need for verified analytical tools that will allow an engineer to confidently design a system to a known degree of accuracy. New and improved materials, for such applications as thermal storage and as heat transfer fluids, were also identified as major needs. In addition to these research efforts, a number of specific hardware needs were identified which will require development. These include heat pumps, low weight radiators, advanced heat pipes, stability enhancement devices, high heat flux evaporators, and liquid/vapor separators. Also identified was the need for a centralized source of reliable, up-to-date information on two-phase flow in a space environment.
Generalized network modeling of capillary-dominated two-phase flow.
Raeini, Ali Q; Bijeljic, Branko; Blunt, Martin J
2018-02-01
We present a generalized network model for simulating capillary-dominated two-phase flow through porous media at the pore scale. Three-dimensional images of the pore space are discretized using a generalized network-described in a companion paper [A. Q. Raeini, B. Bijeljic, and M. J. Blunt, Phys. Rev. E 96, 013312 (2017)2470-004510.1103/PhysRevE.96.013312]-which comprises pores that are divided into smaller elements called half-throats and subsequently into corners. Half-throats define the connectivity of the network at the coarsest level, connecting each pore to half-throats of its neighboring pores from their narrower ends, while corners define the connectivity of pore crevices. The corners are discretized at different levels for accurate calculation of entry pressures, fluid volumes, and flow conductivities that are obtained using direct simulation of flow on the underlying image. This paper discusses the two-phase flow model that is used to compute the averaged flow properties of the generalized network, including relative permeability and capillary pressure. We validate the model using direct finite-volume two-phase flow simulations on synthetic geometries, and then present a comparison of the model predictions with a conventional pore-network model and experimental measurements of relative permeability in the literature.
Generalized network modeling of capillary-dominated two-phase flow
Raeini, Ali Q.; Bijeljic, Branko; Blunt, Martin J.
2018-02-01
We present a generalized network model for simulating capillary-dominated two-phase flow through porous media at the pore scale. Three-dimensional images of the pore space are discretized using a generalized network—described in a companion paper [A. Q. Raeini, B. Bijeljic, and M. J. Blunt, Phys. Rev. E 96, 013312 (2017), 10.1103/PhysRevE.96.013312]—which comprises pores that are divided into smaller elements called half-throats and subsequently into corners. Half-throats define the connectivity of the network at the coarsest level, connecting each pore to half-throats of its neighboring pores from their narrower ends, while corners define the connectivity of pore crevices. The corners are discretized at different levels for accurate calculation of entry pressures, fluid volumes, and flow conductivities that are obtained using direct simulation of flow on the underlying image. This paper discusses the two-phase flow model that is used to compute the averaged flow properties of the generalized network, including relative permeability and capillary pressure. We validate the model using direct finite-volume two-phase flow simulations on synthetic geometries, and then present a comparison of the model predictions with a conventional pore-network model and experimental measurements of relative permeability in the literature.
Possible effects of two-phase flow pattern on the mechanical behavior of mudstones
Goto, H.; Tokunaga, T.; Aichi, M.
2016-12-01
To investigate the influence of two-phase flow pattern on the mechanical behavior of mudstones, laboratory experiments were conducted. In the experiment, air was injected from the bottom of the water-saturated Quaternary Umegase mudstone sample under hydrostatic external stress condition. Both axial and circumferential strains at half the height of the sample and volumetric discharge of water at the outlet were monitored during the experiment. Numerical simulation of the experiment was tried by using a simulator which can solve coupled two-phase flow and poroelastic deformation assuming the extended-Darcian flow with relative permeability and capillary pressure as functions of the wetting-phase fluid saturation. In the numerical simulation, the volumetric discharge of water was reproduced well while both strains were not. Three dimensionless numbers, i.e., the viscosity ratio, the Capillary number, and the Bond number, which characterize the two-phase flow pattern (Lenormand et al., 1988; Ewing and Berkowitz, 1998) were calculated to be 2×10-2, 2×10-11, and 7×10-11, respectively, in the experiment. Because the Bond number was quite small, it was possible to apply Lenormand et al. (1988)'s diagram to evaluate the flow regime, and the flow regime was considered to be capillary fingering. While, in the numerical simulation, air moved uniformly upward with quite low non-wetting phase saturation conditions because the fluid flow obeyed the two-phase Darcy's law. These different displacement patterns developed in the experiment and assumed in the numerical simulation were considered to be the reason why the deformation behavior observed in the experiment could not be reproduced by numerical simulation, suggesting that the two-phase flow pattern could affect the changes of internal fluid pressure patterns during displacement processes. For further studies, quantitative analysis of the experimental results by using a numerical simulator which can solve the coupled
Extension of CFD Codes Application to Two-Phase Flow Safety Problems - Phase 3
International Nuclear Information System (INIS)
Bestion, D.; Anglart, H.; Mahaffy, J.; Lucas, D.; Song, C.H.; Scheuerer, M.; Zigh, G.; Andreani, M.; Kasahara, F.; Heitsch, M.; Komen, E.; Moretti, F.; Morii, T.; Muehlbauer, P.; Smith, B.L.; Watanabe, T.
2014-11-01
. Identification of needs for additional experimental validation; - identification of a matrix of numerical benchmarks of special interest for the selected NRS problems; - establish the foundation of Best Practice Guidelines for two-phase CFD application to the selected NRS problems. This document is an extension of the first report produced by the Writing Group 3. A few NRS problems where two-phase CFD may bring real benefit are first selected to be further analysed in more detail according to some criteria. They must be high priority issues from the point of view of nuclear safety with some investigations going on and CFD investigations must have a reasonable chance to be successful in a reasonable period of time. They must address both the present generation of PWR and BWR and the Generation 3 water reactors and should possibly address all flow regimes so that they may, to some extent, envelop many other issues. A general multi-step methodology for application of two-phase CFD to nuclear safety issues is proposed. Many options are possible when using two phase CFD, for the basic model (one-fluid, two-fluid, multi-field,...), for the averaging or filtering of turbulent and two-phase scales (using RANS, LES,...), for the treatment of the interface either by an Interface Tracking Method or statistically by a volume fraction, an interfacial area equation,... The choices have to be justified after an in-depth analysis of the issue and an identification of all basic flow processes. Then closure relations have to be selected or developed for interfacial transfers, turbulent transfers and wall transfers, and a test matrix has to be established to validate all the models in a separate effect way. The method has been applied to the selected issues resulting in an updated state of the art and gaps were identified in the modelling. Available data for validation were reviewed and needs of additional data were identified. Verification tests were also identified. A few benchmarks are proposed
International Nuclear Information System (INIS)
Choi, Chi Woong; Yu, Dong In; Kim, Moo Hwan
2010-01-01
There are two kinds of models in two-phase pressured drop; homogeneous flow model and separated flow model. Many previous researchers have developed correlations for two-phase pressure drop in a microchannel. Most correlations were modified Lockhart and Martinelli's correlation, which was based on the separated flow model. In this study, experiments for adiabatic liquid water and nitrogen gas flow in rectangular microchannels were conducted to investigate two-phase pressure drop in the rectangular microchannels. Two-phase frictional pressure drop in the rectangular microchannels is highly related with flow regime. Homogeneous model with six two-phase viscosity models: Owen(21)'s, MacAdams(22)'s, Cicchitti et al.(23)'s, Dukler et al.(24)'s, Beattie and Whalley(25)'s, Lin et al.(26)'s models and six separated flow models: Lockhart and Martinelli(27)'s, Chisholm(31)'s, Zhang et al.(15)'s, Lee and Lee(5)'s, Moriyama and Inue(4)'s, Qu and Mudawar(8)'s models were assessed with our experimental data. The best two-phase viscosity model is Beattie and Whalley's model. The best separated flow model is Qu and Mudawar's correlation. Flow regime dependency in both homogeneous and separated flow models was observed. Therefore, new flow pattern based correlations for both homogeneous and separated flow models were individually proposed
Creep of Two-Phase Microstructures for Microelectronic Applications
Energy Technology Data Exchange (ETDEWEB)
Reynolds, Heidi Linch [Univ. of California, Berkeley, CA (United States)
1998-12-01
The mechanical properties of low-melting temperature alloys are highly influenced by their creep behavior. This study investigates the dominant mechanisms that control creep behavior of two-phase, low-melting temperature alloys as a function of microstructure. The alloy systems selected for study were In-Ag and Sn-Bi because their eutectic compositions represent distinctly different microstructure.” The In-Ag eutectic contains a discontinuous phase while the Sn-Bi eutectic consists of two continuous phases. In addition, this work generates useful engineering data on Pb-free alloys with a joint specimen geometry that simulates microstructure found in microelectronic applications. The use of joint test specimens allows for observations regarding the practical attainability of superplastic microstructure in real solder joints by varying the cooling rate. Steady-state creep properties of In-Ag eutectic, Sn-Bi eutectic, Sn-xBi solid-solution and pure Bi joints have been measured using constant load tests at temperatures ranging from O°C to 90°C. Constitutive equations are derived to describe the steady-state creep behavior for In-Ageutectic solder joints and Sn-xBi solid-solution joints. The data are well represented by an equation of the form proposed by Dom: a power-law equation applies to each independent creep mechanism. Rate-controlling creep mechanisms, as a function of applied shear stress, test temperature, and joint microstructure, are discussed. Literature data on the steady-state creep properties of Sn-Bi eutectic are reviewed and compared with the Sn-xBi solid-solution and pure Bi joint data measured in the current study. The role of constituent phases in controlling eutectic creep behavior is discussed for both alloy systems. In general, for continuous, two-phase microstructure, where each phase exhibits significantly different creep behavior, the harder or more creep resistant phase will dominate the creep behavior in a lamellar microstructure. If a
The pressure effects on two-phase anaerobic digestion
International Nuclear Information System (INIS)
Chen, Yuling; Rößler, Benjamin; Zielonka, Simon; Lemmer, Andreas; Wonneberger, Anna-Maria; Jungbluth, Thomas
2014-01-01
Highlights: • The pressure effect on anaerobic digestion up to 9 bar was examined. • Increasing pressure decreased pH value in the anaerobic filter. • Increasing pressure increased methane content. • Increasing pressure decreased specific methane yield slightly. • The pressurized methane reactor was very stable and performed well. - Abstract: Two-phase pressurized anaerobic digestion is a novel process aimed at facilitating injection of the produced biogas into the natural gas grid by integrating the fermentative biogas production and upgrading it to substitute natural gas. In order to understand the mechanisms, knowledge of pressure effects on anaerobic digestion is required. To examine the effects of pressure on the anaerobic digestion process, a two-phase anaerobic digestion system was built up in laboratory scale, including three acidogenesis-leach-bed-reactors and one pressure-resistant anaerobic filter. Four different pressure levels (the absolute pressure of 1 bar, 3 bar, 6 bar and 9 bar) were applied to the methane reactor in sequence, with the organic loading rate maintained at approximately 5.1 kgCOD m −3 d −1 . Gas production, gas quality, pH value, volatile fatty acids, alcohol, ammonium-nitrogen, chemical oxygen demand (COD) and alkaline buffer capacity were analyzed. No additional caustic chemicals were added for pH adjustment throughout the experiment. With the pressure increasing from 1.07 bar to 8.91 bar, the pH value decreased from 7.2 to 6.5, the methane content increased from 66% to 75%, and the specific methane yield was slightly reduced from 0.33 l N g −1 COD to 0.31 l N g −1 COD. There was almost no acid-accumulation during the entire experiment. The average COD-degradation grade was always more than 93%, and the average alkaline buffering capacity (VFA/TIC ratio) did not exceed 0.2 at any pressure level. The anaerobic filter showed a very stable performance, regardless of the pressure variation
Statistical descriptions of polydisperse turbulent two-phase flows
Energy Technology Data Exchange (ETDEWEB)
Minier, Jean-Pierre, E-mail: jean-pierre.minier@edf.fr
2016-12-15
Disperse two-phase flows are flows containing two non-miscible phases where one phase is present as a set of discrete elements dispersed in the second one. These discrete elements, or ‘particles’, can be droplets, bubbles or solid particles having different sizes. This situation encompasses a wide range of phenomena, from nano-particles and colloids sensitive to the molecular fluctuations of the carrier fluid to inertia particles transported by the large-scale motions of turbulent flows and, depending on the phenomenon studied, a broad spectrum of approaches have been developed. The aim of the present article is to analyze statistical models of particles in turbulent flows by addressing this issue as the extension of the classical formulations operating at a molecular or meso-molecular level of description. It has a three-fold purpose: (1) to bring out the thread of continuity between models for discrete particles in turbulent flows (above the hydrodynamical level of description) and classical mesoscopic formulations of statistical physics (below the hydrodynamical level); (2) to reveal the specific challenges met by statistical models in turbulence; (3) to establish a methodology for modeling particle dynamics in random media with non-zero space and time correlations. The presentation is therefore centered on organizing the different approaches, establishing links and clarifying physical foundations. The analysis of disperse two-phase flow models is developed by discussing: first, approaches of classical statistical physics; then, by considering models for single-phase turbulent flows; and, finally, by addressing current formulations for discrete particles in turbulent flows. This brings out that particle-based models do not cease to exist above the hydrodynamical level and offer great interest when combined with proper stochastic formulations to account for the lack of equilibrium distributions and scale separation. In the course of this study, general
Directory of Open Access Journals (Sweden)
Mahood Hameed B.
2016-01-01
Full Text Available An analytical model for the convective heat transfer coefficient and the two-phase bubble size of a three-phase direct contact heat exchanger was developed. Until the present, there has only been a theoretical model available that deals with a single two-phase bubble and a bubble train condensation in an immiscible liquid. However, to understand the actual heat transfer process within the three-phase direct contact condenser, characteristic models are required. A quasi - steady energy equation in a spherical coordinate system with a potential flow assumption and a cell model configuration has been simplified and solved analytically. The convective heat transfer in terms of Nu number has been derived, and it was found to be a function to Pe number and a system void fraction. In addition, the two-phase bubble size relates to the system void fraction and has been developed by solving a simple energy balance equation and using the derived convective heat transfer coefficient expression. Furthermore, the model correlates well with previous experimental data and theoretical results.
Mathematical well-posedness of a two-fluid equations for bubbly two-phase flows
International Nuclear Information System (INIS)
Okawa, Tomio; Kataoka, Isao
2000-01-01
It is widely known that two-fluid equations used in most engineering applications do not satisfy the necessary condition for being mathematical well-posed as initial-value problems. In the case of stratified two-phase flows, several researchers have revealed that differential models satisfying the necessary condition are to be derived if the pressure difference between the phases is related to the spatial gradient of the void fraction through the effects of gravity or surface tension. While, in the case of dispersed two-phase flows, no physically reasonable method to derive mathematically well-posed two-fluid model has been proposed. In the present study, particularly focusing on the effect of interfacial pressure terms, we derived the mathematically closed form of the volume-averaged two-fluid model for bubbly two-phase flows. As a result of characteristic analyses, it was shown that the proposed two-fluid equations satisfy the necessary condition of mathematical well-posedness if the void fraction is sufficiently small. (author)
The three-dimensional transient two-phase flow computer programme BACCHUS-3D/TP
International Nuclear Information System (INIS)
Bottoni, M.; Dorr, B.; Homann, C.
1992-04-01
The three-dimensional single-phase flow version of the BACCHUS code, which describes the thermal behaviour of a coolant in hexagonal bundle geometry, developed earlier, provided the basis for the development of the two-phase flow version documented in this report. A detailed description is given of the two-phase Slip Model (SM), and of the Homogeneous Equilibrium Model (HEM) as a subcase, which presents several improvements from both viewpoints of physical modelling and numerical treatment, with respect to usual models found in the literature. The most advanced Separated Phases Model (SPM) is then described in all analytical details necessary to fully understand its implementation in the code. Poblems related to the link between the two above models into an integrated code version are then discussed. The code provides an additional option for modelling of active or passive, permeable or impermeable blockages. This option is documented separately. New numerical methods for solving the algebraic systems of equations derived from the linearization of the fundamental equations have completely superseded previous ones and are explained in detail. Eventually a section is dedicated to an overview of the code verification, made over several years, which goes from steady state single-phase unheated bundle experiments up to fast transient two-phase flow experiments in electrically heated 37-pin bundles. (orig.) [de
Two-phase flow degradation on Fukushima-Daiichi Unit 2 RCIC turbine performance
International Nuclear Information System (INIS)
Lopez, Hector; Erkan, Nejdet; Okamoto, Koji
2016-01-01
After the Fukushima accident, several investigation reports, including experiments and simulations have been done for each of the affected units to completely understand the accident progression and use their results to improve the knowledge of severe accident management and the severe codes performance. In Unit 2, the major uncertainties are related with the reactor core isolation cooling (RCIC) system performance during the accident progression especially focused in the RCIC turbine, which is assumed to work in two-phase flow. The main objective of this study is to analyze the RCIC turbine performance under two-phase flow scenarios under the assumption that the power produced by the turbine is lower than expected due to the liquid phase in the flow. A degradation coefficient quantifying the turbine power reduction is developed as a function of the flow quality by using the sonic speed reduction at critical flow conditions principle obtained by applying the non-homogeneous equilibrium model (NHEM). The degradation coefficient was applied to RELAP/ScdapSIM severe accident code showing a drastic reduction of the turbine-generated power during two-phase flow and obtaining a RCIC system behavior closer to the Tokyo electric power company (TEPCO) investigation report conclusions. (author)
Experimental study on liquid velocity in upward and downward two-phase flows
International Nuclear Information System (INIS)
Sun, X.; Paranjape, S.; Kim, S.; Ozar, B.; Ishii, M.
2003-01-01
Local characteristics of the liquid phase in upward and downward air-water two-phase flows were experimentally investigated in a 50.8-mm inner-diameter round pipe. An integral Laser Doppler Anemometry (LDA) system was used to measure the axial liquid velocity and its fluctuations. No effect of the flow direction on the liquid velocity radial profile was observed in single-phase liquid benchmark experiments. Local multi-sensor conductivity probes were used to measure the radial profiles of the bubble velocity and the void fraction. The measurement results in the upward and downward two-phase flows are compared and discussed. The results in the downward flow demonstrated that the presence of the bubbles tended to flatten the liquid velocity radial profile, and the maximum liquid velocity could occur off the pipe centerline, in particular at relatively low flow rates. However, the maximum liquid velocity always occurred at the pipe center in the upward flow. Also, noticeable turbulence enhancement due to the bubbles in the two-phase flows was observed in the current experimental flow conditions. Furthermore, the distribution parameter and the void weighted area-averaged drift velocity were obtained based on the definitions
Self-organizing maps applied to two-phase flow on natural circulation loop study
International Nuclear Information System (INIS)
Castro, Leonardo Ferreira
2016-01-01
Two-phase flow of liquid and gas is found in many closed circuits using natural circulation for cooling purposes. Natural circulation phenomenon is important on recent nuclear power plant projects for decay heat removal. The Natural Circulation Facility (Circuito de Circulacao Natural CCN) installed at Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN, is an experimental circuit designed to provide thermal hydraulic data related to single and two-phase flow under natural circulation conditions. This periodic flow oscillation behavior can be observed thoroughly in this facility due its glass-made tubes transparency. The heat transfer estimation has been improved based on models that require precise prediction of pattern transitions of flow. This work presents experiments realized at CCN to visualize natural circulation cycles in order to classify two-phase flow patterns associated with phase transients and static instabilities of flow. Images are compared and clustered using Kohonen Self-organizing Maps (SOM's) applied on different digital image features. The Full Frame Discret Cosine Transform (FFDCT) coefficients were used as input for the classification task, enabling good results. FFDCT prototypes obtained can be associated to each flow pattern, enabling a better comprehension of each observed instability. A systematic test methodology was used to verify classifier robustness.
Study of single- and two-phase fluid transfer between subchannels at Kumamoto University
International Nuclear Information System (INIS)
Sadatomi, Michio
2004-01-01
Firstly, the definitions of turbulent mixing, void drift and diversion cross-flow, which are three components of fluid transfer between subchannels, are given together with the relations of each component with equilibrium or non-equilibrium two-phase subchannel flows. Secondly, measuring techniques of the three components are briefly presented in turn together with typical measurement results. In turbulent mixing measurement, a tracer injection method has been adopted at Kumamoto University, while an isokinetic discharge method for both void drift an diversion cross-flow measurements. In the experiment of hydraulically non-equilibrium flow with both void drift and/or diversion cross-flow, experimental data on flow redistribution process have been obtained. The data include the axial variations of gas and liquid flow rates and void fraction in each subchannel and pressure difference between the subchannels. After analyzing these variations, some correlations on the void drift and the diversion cross-flow are obtained. Finally, a subchannel analysis code used at Kumamoto University is presented together with the results of its validation test against the experimental data on flow redistribution process mentioned above. The code is based on a two-phase two-fluid model, and is applicable to adiabatic two-phase flows under steady state condition. Basic equations in the code are the conservation equations of mass, axial momentum and lateral momentum, while the constitutive equations include the correlations of void diffusion coefficient, both interfacial and wall friction coefficients for the cross-flow, etc. (author)
Simulation experiments for hot-leg U-bend two-phase flow phenomena
International Nuclear Information System (INIS)
Ishii, M.; Hsu, J.T.; Tucholke, D.; Lambert, G.; Kataoka, I.
1986-01-01
In order to study the two-phase natural circulation and flow termination during a small break loss of coolant accident in LWR, simulation experiments have been performed. Based on the two-phase flow scaling criteria developed under this program, an adiabatic hot leg U-bend simulation loop using nitrogen gas and water and a Freon 113 boiling and condensation loop were built. The nitrogen-water system has been used to isolate key hydrodynamic phenomena from heat transfer problems, whereas the Freon loop has been used to study the effect of phase changes and fluid properties. Various tests were carried out to establish the basic mechanism of the flow termination and reestablishment as well as to obtain essential information on scale effects of parameters such as the loop frictional resistance, thermal center, U-bend curvature and inlet geometry. In addition to the above experimental study, a preliminary modeling study has been carried out for two-phase flow in a large vertical pipe at relatively low gas fluxes typical of natural circulation conditions
Multiphysics modeling of two-phase film boiling within porous corrosion deposits
Energy Technology Data Exchange (ETDEWEB)
Jin, Miaomiao, E-mail: mmjin@mit.edu; Short, Michael, E-mail: hereiam@mit.edu
2016-07-01
Porous corrosion deposits on nuclear fuel cladding, known as CRUD, can cause multiple operational problems in light water reactors (LWRs). CRUD can cause accelerated corrosion of the fuel cladding, increase radiation fields and hence greater exposure risk to plant workers once activated, and induce a downward axial power shift causing an imbalance in core power distribution. In order to facilitate a better understanding of CRUD's effects, such as localized high cladding surface temperatures related to accelerated corrosion rates, we describe an improved, fully-coupled, multiphysics model to simulate heat transfer, chemical reactions and transport, and two-phase fluid flow within these deposits. Our new model features a reformed assumption of 2D, two-phase film boiling within the CRUD, correcting earlier models' assumptions of single-phase coolant flow with wick boiling under high heat fluxes. This model helps to better explain observed experimental values of the effective CRUD thermal conductivity. Finally, we propose a more complete set of boiling regimes, or a more detailed mechanism, to explain recent CRUD deposition experiments by suggesting the new concept of double dryout specifically in thick porous media with boiling chimneys. - Highlights: • A two-phase model of CRUD's effects on fuel cladding is developed and improved. • This model eliminates the formerly erroneous assumption of wick boiling. • Higher fuel cladding temperatures are predicted when accounting for two-phase flow. • Double-peaks in thermal conductivity vs. heat flux in experiments are explained. • A “double dryout” mechanism in CRUD is proposed based on the model and experiments.
Experimental validation of a numerical model of two-phase displacement in porous medium
International Nuclear Information System (INIS)
Genty, A.
1996-01-01
Burial in geological layers appears to be an interesting solution to dispose of radioactive wastes. This thesis analyzes and simulates the behaviour of gas produced by waste barrels corrosion. The released contaminated gas drains the water initially present in the host rock and yields a water-gas two phase flow. A literature survey of two phase flow shows that fluid interfaces may display instabilities for definite flow characteristics. When the displacement is stable a smooth interface proceeds through the porous medium. When the interface shows fingering, the displacement is said to be 'viscous-unstable', and when the front is jagged the displacement is called 'capillary' displacement. A dimensional analysis of classical equations governing two phase flow in porous media is combined with a classification of dominant forces to define an original map of flow regimes that includes gravitational forces. The map is based on three dimensionless numbers and predicts a priori the flow type. For typical data describing a radioactive waste repository a 'viscous-unstable' displacement is predicted by the map. We simulate water-gas displacement with a numerical model previously developed; this code, based on the Muskat model, uses the mixed-hybrid finite elements technique and is therefore well adapted for tracking moving interfaces. Fluxes are well conserved, however instabilities cannot be simulated. We assume that there is always a scale to be found where instabilities can be averaged and we try to validate the model with experimental two phase flows. We performed laboratory water-gas flow experiments for a variety of flow conditions. The observed displacement types are consistent with the map of flow regimes. Good agreement with numerical simulations is obtained when precise parameters of the displacements are available, in particular relative permeability curves. We conclude that our model allows a first approach of migration of gas near a radioactive waste repository
Biogasification of solid wastes by two-phase anaerobic fermentation
International Nuclear Information System (INIS)
Ghosh, S.; Vieitez, E.R.; Liu, T.; Kato, Y.
1997-01-01
Municipal, industrial and agricultural solid wastes, and biomass deposits, cause large-scale pollution of land and water. Gaseous products of waste decomposition pollute the air and contribute to global warming. This paper describes the development of a two-phase fermentation system that alleviates methanogenic inhibition encountered with high-solids feed, accelerates methane fermentation of the solid bed, and captures methane (renewable energy) for captive use to reduce global warming. The innovative system consisted of a solid bed reactor packed with simulated solid waste at a density of 160 kg/m 3 and operated with recirculation of the percolated culture (bioleachate) through the bed. A rapid onset of solids hydrolysis, acidification, denitrification and hydrogen gas formation was observed under these operating conditions. However, these fermentative reactions stopped at a total fatty acids concentration of 13,000 mg/l (as acetic) at pH 5, with a reactor head-gas composition of 75 percent carbon dioxide, 20 percent nitrogen, 2 percent hydrogen and 3 percent methane. Fermentation inhibition was alleviated by moving the bioleachate to a separate methane-phase fermenter, and recycling methanogenic effluents at pH 7 to the solid bed. Coupled operation of the two reactors promoted methanogenic conversion of the high-solids feed. (author)
Two phases of the anyon gas and broken T symmetry
International Nuclear Information System (INIS)
Canright, G.S.; Rojo, A.G.
1991-01-01
This paper reports the first exact finite-temperature study of anyons. The authors' method is an extension to finite T of earlier numerical work with small numbers of anyons on a lattice. We study the spontaneous magnetization M 0 (T), since the signature has been identified as a key signature of broken T symmetry for anyon models. Our results confirm the two-phase picture suggested by earlier work: The authors find a low-temperature regime where M 0 is very small or zero, and a high-temperature regime where M 0 is of O(0.1 μ B ) per particle. In the high-temperature regime the authors can obtain an excellent estimate of M 0 (T) in the thermodynamic limit (which we call M 0 ∞ ). since our finite-size results extrapolate smoothly with little scatter. The authors' values for M 0 ∞ can then be compared with the results of μSR experiments on high-temperature superconductors, which set an upper experimental bound on the internal fields from such moments. The authors find that M 0 ∞ in a bulk material of many planes will almost certainly give a signal well above this threshold if (and only if) the planes are ordered ferromagnetically. In the antiferromagnetic case (which is strongly favored energetically) the signal from M 0 ∞ is probably undetectable. Finally, we estimate the transition temperature T c from our finite-size studies, obtaining a value on the order of a few hundred Kelvins
System for recording and displaying two-phase flow topographies
International Nuclear Information System (INIS)
Cary, C.N.; Block, J.A.
1979-01-01
A system of hardware and software has been developed and used to record and display in various forms details of the countercurrent flow topographies occurring in a scaled Pressurized Water Reactor downcomer annulus. An array of 288 conductivity sensors was mounted in a 1/15 scale PWR annulus. At each moment in time, the state of each probe indicates the presence or absence of water in this immediate vicinity. An electronic data acquisition system records the states of all probes 108 times per second on magnetic tape; software routines retrieve the data and reconstruct visual analogs of the flow topographies. The instantaneous two-phase state of the annulus at each instant can be displayed on a hard copy plotter or on a CRT screen. By synchronizing a camera drive with the CRT display, 16mm films have been made recreating the flow process at full speed and at various slow motion rates. All data obtained are stored in computer files in numerical form and can be subjected to various types of quantitative analysis to assist in advanced code development and verification
Passive Two-Phase Cooling of Automotive Power Electronics: Preprint
Energy Technology Data Exchange (ETDEWEB)
Moreno, G.; Jeffers, J. R.; Narumanchi, S.; Bennion, K.
2014-08-01
Experiments were conducted to evaluate the use of a passive two-phase cooling strategy as a means of cooling automotive power electronics. The proposed cooling approach utilizes an indirect cooling configuration to alleviate some reliability concerns and to allow the use of conventional power modules. An inverter-scale proof-of-concept cooling system was fabricated, and tests were conducted using the refrigerants hydrofluoroolefin HFO-1234yf and hydrofluorocarbon HFC-245fa. Results demonstrated that the system can dissipate at least 3.5 kW of heat with 250 cm3 of HFC-245fa. An advanced evaporator design that incorporates features to improve performance and reduce size was conceived. Simulation results indicate its thermal resistance can be 37% to 48% lower than automotive dual side cooled power modules. Tests were also conducted to measure the thermal performance of two air-cooled condensers--plain and rifled finned tube designs. The results combined with some analysis were then used to estimate the required condenser size per operating conditions and maximum allowable system (i.e., vapor and liquid) temperatures.
Transient boiling in two-phase helium natural circulation loops
Furci, H.; Baudouy, B.; Four, A.; Meuris, C.
2014-01-01
Two-phase helium natural circulation loops are used for cooling large superconducting magnets, as CMS for LHC. During normal operation or in the case of incidents, transients are exerted on the cooling system. Here a cooling system of this type is studied experimentally. Sudden power changes are operated on a vertical-heated-section natural convection loop, simulating a fast increase of heat deposition on magnet cooling pipes. Mass flow rate, heated section wall temperature and pressure drop variations are measured as a function of time, to assess the time behavior concerning the boiling regime according to the values of power injected on the heated section. The boiling curves and critical heat flux (CHF) values have been obtained in steady state. Temperature evolution has been observed in order to explore the operating ranges where heat transfer is deteriorated. Premature film boiling has been observed during transients on the heated section in some power ranges, even at appreciably lower values than the CHF. A way of attenuating these undesired temperature excursions has been identified through the application of high enough initial heating power.
Two-phase flow characteristics of HFC and HCFC fluid
International Nuclear Information System (INIS)
Ueno, T.; Matsuda, K.; Kusakabe, T.
1998-01-01
Some two-phase flow characteristics of HFC and HCFC fluid have been investigated experimentally. Fluids used in this experiment are HCFC22 (hereinafter called 'R22'), HCFC123 (hereinafter called 'R123') and Mixture of HFC fluid (hereinafter called 'R407C'). The fluid R407C are mixture of HFC32, HFC134a and HFC125, and their concentrations are 23wt%, 52wt% and 25wt%, respectively. This paper presents main flow parameters such as void fraction, interfacial velocities, bubble diameter distribution and pressure drop multiplier, which can characterize flow behavior. The void fractions and interfacial velocities were measured at some local positions in the single pipe using the bi-optical probe(hereinafter called 'BOP'). The procedure to calculate the void fraction from the void signals obtained by BOP were adopted the so-called slice method. The effects of slice levels on the void fraction were discussed taking into account bubble diameter. The new correlation of slice level as the function of void fraction has been proposed. The area-averaged void fractions obtained from BOP's void signals using new correlation were compared with void fractions obtained from pressure drops. The area-averaged interfacial velocities were also compared with the superficial gas velocities. It was concluded that the accuracy of BOP measurements are 5% for void fraction and less than 8.5% for interfacial velocity
Two-phase flow field simulation of horizontal steam generators
Energy Technology Data Exchange (ETDEWEB)
Rabiee, Ataollah; Kamalinia, Amir Hossein; Hadad, Kamal [School of Mechanical Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)
2017-02-15
The analysis of steam generators as an interface between primary and secondary circuits in light water nuclear power plants is crucial in terms of safety and design issues. VVER-1000 nuclear power plants use horizontal steam generators which demand a detailed thermal hydraulics investigation in order to predict their behavior during normal and transient operational conditions. Two phase flow field simulation on adjacent tube bundles is important in obtaining logical numerical results. However, the complexity of the tube bundles, due to geometry and arrangement, makes it complicated. Employment of porous media is suggested to simplify numerical modeling. This study presents the use of porous media to simulate the tube bundles within a general-purpose computational fluid dynamics code. Solved governing equations are generalized phase continuity, momentum, and energy equations. Boundary conditions, as one of the main challenges in this numerical analysis, are optimized. The model has been verified and tuned by simple two-dimensional geometry. It is shown that the obtained vapor volume fraction near the cold and hot collectors predict the experimental results more accurately than in previous studies.
Entrainment in vertical annular two-phase flow
International Nuclear Information System (INIS)
Sawant, Pravin; Ishii, Mamoru; Mori, Michitsugu
2009-01-01
Prediction of amount of entrained droplets or entrainment fraction in annular two-phase flow is essential for the estimation of dryout condition and analysis of post dryout heat transfer in light water nuclear reactors and steam boilers. In this study, air-water and organic fluid (Freon-113) annular flow entrainment experiments have been carried out in 9.4 and 10.2 mm diameter test sections, respectively. Both the experiments covered three distinct pressure conditions and wide range of liquid and gas flow conditions. The organic fluid experiments simulated high pressure steam-water annular flow conditions. In each of the experiments, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using a liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant et al. (2008a) for the prediction of entrainment fraction is further improved in this study in order to account for the existence of critical gas and liquid flow rates below which no entrainment is possible. Additionally, a new correlation is proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction condition. The improved correlation successfully predicted the newly collected air-water and Freon-113 entrainment fraction data. Furthermore, the correlations satisfactorily compared with the air-water, helium-water and air-genklene experimental data measured by Willetts (1987). (author)
Experimental investigation of a two-phase nozzle flow
International Nuclear Information System (INIS)
Kedziur, F.; John, H.; Loeffel, R.; Reimann, J.
1980-07-01
Stationary two-phase flow experiments with a convergent nozzle are performed. The experimental results are appropriate to validate advanced computer codes, which are applied to the blowdown-phase of a loss-of-coolant accident (LOCA). The steam-water experiments present a broad variety of initial conditions: the pressure varies between 2 and 13 MPa, the void fraction between 0 (subcooled) and about 80%, a great number of critical as well as subcritical experiments with different flow pattern is investigated. Additional air-water experiments serve for the separation of phase transition effects. The transient acceleration of the fluid in the LOCA-case is simulated by a local acceleration in the experiment. The layout of the nozzle and the applied measurement technique allow for a separate testing of blowdown-relevant, physical models and the determination of empirical model parameters, respectively. The measured quantities are essentially the mass flow rate, quality, axial pressure and temperature profiles as well as axial and radial density/void profiles obtained by a γ-ray absorption device. Moreover, impedance probes and a pitot probe are used. Observed phenomena like a flow contraction, radial pressure and void profiles as well as the appearance of two chocking locations are described, because their examination is rather instructive about the refinement of a program. The experimental facilities as well as the data of 36 characteristic experiments are documented. (orig.) [de
Dielectric barrier discharge in a two-phase mixture
Energy Technology Data Exchange (ETDEWEB)
Ye Qizheng; Zhang Ting; Lu Fei; Li Jin; He Zhenghao; Lin Fuchang [College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)
2008-01-21
This paper reports the experimental investigation of the dielectric barrier discharge in which the gap area is filled with a two-phase mixture (TPM), air and solid particles. We found that there are two kinds of discharges in the TPM. One is the surface discharge generated on the surface of the solid particles and the other is the filament discharge generated in the air void. For the case of low volume fraction of solid particles, the surface discharge starts to occur when the applied voltage is higher than the onset voltage. At a further voltage increase, the filament discharge takes place at the same time. For the case of high volume fraction, such as the packed-bed reactor, only the surface discharge exists. Under the condition of the same volume fraction, the larger the diameter of the solid particles, the lower the surface discharge onset voltage. As a conclusion, we think that the plasma reactor using the form of low volume fraction of solid particles may be a better choice for waste-gas treatment enhanced by catalysts.
Abnormal breakdown characteristic in a two-phase mixture
International Nuclear Information System (INIS)
Ye Qizheng; Li Jin; Lu Fei
2006-01-01
A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, U TPM , increases gradually with an increase in the macroparticle number density (m). The voltage U TPM is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage U TPM increases gradually at low m values and decreases gradually at high m values. The voltage U TPM at pd 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field
A two-phase full-wave superconducting rectifier
International Nuclear Information System (INIS)
Ariga, T.; Ishiyama, A.
1989-01-01
A two-phase full-wave superconducting rectifier has been developed as a small cryogenic power supply of superconducting magnets for magnetically levitation trains. Those magnets are operated in the persistent current mode. However, small ohmic loss caused at resistive joints and ac loss induced by the vibration of the train cannot be avoided. Therefore, the low-power cryogenic power supply is required to compensate for the reduction in magnet current. The presented superconducting rectifier consists of two identical full-wave rectifiers connected in series. Main components of each rectifier are a troidal shape superconducting set-up transformer and two thermally controlled switches. The test results using a 47.5 mH load magnet at 0.2 Hz and 0.5 Hz operations are described. To estimate the characteristics of the superconducting rectifier, the authors have developed a simulation code. From the experiments and the simulations, the transfer efficiency is examined. Furthermore, the optimal design of thermally controlled switches based on the finite element analysis is also discussed
Two-phase flow modeling in the rod bundle subchannel analysis
International Nuclear Information System (INIS)
Hisashi, Ninokata
2006-01-01
the NASCA code capabilities for BT is described. There a combination of experimental and computational fluid dynamics approaches is undertaken to construct a two-phase fluid dynamics database. The experimental approach consists of 1) high-resolution air-water tests performed under the room-temperature and atmospheric pressure conditions for the inter-subchannel exchanges, three-dimensional behaviors of liquid films, and spacer effects; and 2) integral steam-water tests performed at high-temperature and at higher pressure. In the integral tests, state-of the- arts of multi-phase flow measurement technologies are applied in order to obtain local and instantaneous data that reveal underlying detailed physical processes including high resolution void distributions inside a 4 x 4 bundle, liquid film thickness and two-phase flow regime. The analytical approach consists of computational multi-phase fluid dynamics (CMFD) applicable to two-phase flows. A physical interpretation of the equilibrium two-phase flow redistribution inside a rod bundle is discussed that is considered to closely be related to the void drift phenomena. Identification of interactions among dominant factors is a main objective of the integral test and acquired data will be utilized in verifying the improved subchannel code. Construction of a complete set of two-phase fluid dynamics database will be made by supplementing missing data regions with the aid of numerical analyses. Dependency on important state variables is extracted from the database and prototype constitutive equations are going to be proposed in the final stage of the project. (author)
Two-phase flow modeling in the rod bundle subchannel analysis
International Nuclear Information System (INIS)
Hisashi, Ninokata
2004-01-01
methodology adopted to improve the NASCA code capabilities for BT is described. There a combination of experimental and computational fluid dynamics approaches is undertaken to construct a two-phase fluid dynamics database. The experimental approach consists of 1) high-resolution air-water tests performed under the room-temperature and atmospheric pressure conditions for the inter-subchannel exchanges, three-dimensional behaviors of liquid films, and spacer effects; and 2) integral steam-water tests performed at high-temperature and at higher pressure. In the integral tests, state-of-the- arts of multi-phase flow measurement technologies are applied in order to obtain local and instantaneous data that reveal underlying detailed physical processes including high resolution void distributions inside a 4 x 4 bundle, liquid film thickness and two-phase flow regime. The analytical approach consists of computational multi-phase fluid dynamics (CMFD) applicable to two-phase flows. A physical interpretation of the equilibrium two-phase flow redistribution inside a rod bundle is discussed that is considered to closely be related to the void drift phenomena. Identification of interactions among dominant factors is a main objective of the integral test and acquired data will be utilized in verifying the improved subchannel code. Construction of a complete set of two-phase fluid dynamics database will be made by supplementing missing data regions with the aid of numerical analyses. Dependency on important state variables is extracted from the database and prototype constitutive equations are going to be proposed in the final stage of the project. (author)
Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis
International Nuclear Information System (INIS)
Brokate, M.; Botkin, N.D.; Pykhteev, O.A.
2012-01-01
The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcy's law. The hysteretic relation between the capillary pressures and the saturations is described by a play-type hysteresis operator. We propose a numerical algorithm for treating the arising system of equations, discuss finite element schemes and present simulation results for the case of two phases.
Numerical simulation for a two-phase porous medium flow problem with rate independent hysteresis
Brokate, M.
2012-05-01
The paper is devoted to the numerical simulation of a multiphase flow in porous medium with a hysteretic relation between the capillary pressures and the saturations of the phases. The flow model we use is based on Darcys law. The hysteretic relation between the capillary pressures and the saturations is described by a play-type hysteresis operator. We propose a numerical algorithm for treating the arising system of equations, discuss finite element schemes and present simulation results for the case of two phases. © 2011 Elsevier B.V. All rights reserved.
Design and construction of an experiment for two-phase flow in fractured porous media
Energy Technology Data Exchange (ETDEWEB)
Ayala, R.E.G.; Aziz, K.
1993-08-01
In numerical reservoir simulation naturally fractured reservoirs are commonly divided into matrix and fracture systems. The high permeability fractures are usually entirely responsible for flow between blocks and flow to the wells. The flow in these fractures is modeled using Darcy`s law and its extension to multiphase flow by means of relative permeabilities. The influence and measurement of fracture relative permeability for two-phase flow in fractured porous media have not been studied extensively, and the few works presented in the literature are contradictory. Experimental and numerical work on two-phase flow in fractured porous media has been initiated. An apparatus for monitoring this type of flow was designed and constructed. It consists of an artificially fractured core inside an epoxy core holder, detailed pressure and effluent monitoring, saturation measurements by means of a CT-scanner and a computerized data acquisition system. The complete apparatus was assembled and tested at conditions similar to the conditions expected for the two-phase flow experiments. Fine grid simulations of the experimental setup-were performed in order to establish experimental conditions and to study the effects of several key variables. These variables include fracture relative permeability and fracture capillary pressure. The numerical computations show that the flow is dominated by capillary imbibition, and that fracture relative permeabilities have only a minor influence. High oil recoveries without water production are achieved due to effective water imbibition from the fracture to the matrix. When imbibition is absent, fracture relative permeabilities affect the flow behavior at early production times.
Simulation of two-phase flows by domain decomposition
International Nuclear Information System (INIS)
Dao, T.H.
2013-01-01
This thesis deals with numerical simulations of compressible fluid flows by implicit finite volume methods. Firstly, we studied and implemented an implicit version of the Roe scheme for compressible single-phase and two-phase flows. Thanks to Newton method for solving nonlinear systems, our schemes are conservative. Unfortunately, the resolution of nonlinear systems is very expensive. It is therefore essential to use an efficient algorithm to solve these systems. For large size matrices, we often use iterative methods whose convergence depends on the spectrum. We have studied the spectrum of the linear system and proposed a strategy, called Scaling, to improve the condition number of the matrix. Combined with the classical ILU pre-conditioner, our strategy has reduced significantly the GMRES iterations for local systems and the computation time. We also show some satisfactory results for low Mach-number flows using the implicit centered scheme. We then studied and implemented a domain decomposition method for compressible fluid flows. We have proposed a new interface variable which makes the Schur complement method easy to build and allows us to treat diffusion terms. Using GMRES iterative solver rather than Richardson for the interface system also provides a better performance compared to other methods. We can also decompose the computational domain into any number of sub-domains. Moreover, the Scaling strategy for the interface system has improved the condition number of the matrix and reduced the number of GMRES iterations. In comparison with the classical distributed computing, we have shown that our method is more robust and efficient. (author) [fr
Abnormal breakdown characteristic in a two-phase mixture
Energy Technology Data Exchange (ETDEWEB)
Ye Qizheng; Li Jin; Lu Fei [College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan, 430074 (China)
2006-05-21
A two-phase mixture (TPM) is a mixture of gas and macroparticles of high concentration. Based on Townsend's theory, a new cell-iterative model in analytical form for the breakdown mechanism in TPM is presented. Compared with the original cell-iterative model in our previous paper, the obstructive factor of the macroparticles that influences the electron avalanche propagation is considered, except for the macroparticles distorting the electrical field and capture of the electrons. The cell attractive parameter k is presented according to the classical continuum theory for field charging. The modified Paschen law for a TPM is presented to calculate the breakdown voltage. The breakdown voltage of the TPM, U{sub TPM}, increases gradually with an increase in the macroparticle number density (m). The voltage U{sub TPM} is lower than that of the pure gas at low m values and larger at high m values. With a decrease of the macroparticle volume fraction and the dielectric mismatch, the voltage U{sub TPM} increases gradually at low m values and decreases gradually at high m values. The voltage U{sub TPM} at pd 200 cm Torr is lower than that at pd = 760 cm Torr for low m values and larger for high m values. This kind of abnormal breakdown characteristic in the TPM occurs in the case of high macroparticle volume fraction. On the other hand, the minimum of the TPM's Paschen curve increases with increase in m. It provides the possibility and the conditions of greatly increasing the breakdown voltage in a nearly uniform field.
Development of two-phase Flow Model, 'SOBOIL', for Sodium
International Nuclear Information System (INIS)
Hahn, Do Hee; Chang, Won Pyo; Kim, In Chul; Kwon, Young Min; Lee, Yong Bum
2000-03-01
The objective of this research is to develop a sodium two-phase flow analysis model, 'SOBOIL', for the assessment of the initial stage of the KALIMER HCDA (Hypotherical Core Disruptive Accident). The 'SOBOIL' is basically similar to the multi-bubble slug ejection model used in SAS2A[1]. When a bubble is formed within the liquid slug, the bubble fills the whole cross section of the coolant channel except for a film left on the cladding or on the structure. Up to nine bubbles, separated by the liquid slugs, are allowed in the channel at any time. Each liquid slug flow rate in the model is performed in 2 steps. In the first step, the preliminary flow rate in the liquid slug is calculated neglecting the effect of changes in the vapor bubble pressures over the time step. The temperature and pressure distributions, and interface velocity at the interface between the liquid slug and vapor bubble are also calculated during this process. The new vapor temperature and pressure are then determined from the balance between the net energy transferred into the vapor and the change of the vapor energy. The liquid flow is finally calculated considering the change of the vapor pressure over a time step and the calculation is repeated until specified elapsed time is met. Continuous effort, therefore, must be made on the examination and improvement for the model to become reliable. To this end, much interest must be concentrated in the relevant international collaborations for access to a reference model or test data for the verification
Two-phase transformation of lepidocrocite to maghemite
Dekkers, M. J.; Gapeev, A. K.; Gendler, T. S.; Gribov, S. K.; Shcherbakov, V. P.
2003-04-01
A detailed investigation of CRM acquired at different stages of the transformation lepidocrocite -> maghemite -> hematite is carried out. Apparently, at least two-stage lepidocrocite maghemite transformation was revealed from: a) the two-peak Ms(T) curve; b) the observation of constricted hysteresis loops appearing after annealing fresh lepidocrocite samples at elevated temperatures; c) continuous monitoring (for 500 hrs) of CRM acquisition at elevated temperatures. For the latter two sets of CRM acquisition experiments at 12 temperatures from 175C to 550C in the presence of 0.1 mT magnetic field were performed: 1) with fine dispersed natural lepidocrocite grains in a kaolin matrix (about 1 volume % of lepidocrocite), 2) for lepidocrocite peaces 3x3x3 mm in size. In both cases the CRM was detected already at 175C after 1 day of annealing. Note that this temperature is lower than the temperature of the TGA peak of the lepidocrocite -> maghemite transformation. Mossbauer spectra obtained from the peaces after annealing at 225C during 6 and 14 hours, respectively, revealed significantly different patterns. Unexpectadly, fine dispersed maghemite grains formed due the lepidocrocite dehydration in the first peace (6 hrs of annealing) occurred to be more ordered than those of from the second peace. The samples are subjected to the X-ray analysis in an attempt to clarify the observed difference. The observed phenomena can be explained by the two-phase conception of the transformation lepidocrocite -> maghemite. First the precipitation of small superparamagnetic particles of maghemite takes place growing with time. Second, these grains coalesce with each other resulting in appearance of the antiphase boundaries decreasing the susceptibility, slowing down the process of CRM acquisition and generating the constricted hysteresis loops. The work is supported by INTAS 99-1273.
International Nuclear Information System (INIS)
Lahey, Richard T.; Drew, Donald A.
2001-01-01
This paper reviews the state-of-the-art in the prediction of multidimensional multiphase flow and heat transfer phenomena using a four field, two-fluid model. It is shown that accurate mechanistic computational fluid dynamic (CFD) predictions are possible for a wide variety of adiabatic and diabatic flows using this computational model. In particular, the model is able to predict the bubbly air/water upflow data of Serizawa (Serizawa, A., 1974. Fluid dynamic characteristics of two-phase flow. Ph.D. thesis, (Nuclear Engineering), Kyoto University, Japan), the downflow data of Wang et al. (Wang, S.K., Lee, S.J., Lahey Jr., R.T., Jones, O.C., 1987. 3-D turbulence structure and phase distribution measurements in bubbly two-phase flows. Int. J. Multiphase Flow 13 (3), 327-343), the isosceles triangle upflow data of Lopez de Bertodano et al. (Lopez de Bertodano, M., Lahey Jr., R.T., Jones, O.C., 1994b. Phase distribution in bubbly two-phase flow in vertical ducts. Int. J. Multiphase Flow 20 (5), 805-818), the heated annular R-113 subcooled boiling data of Velidandala, et al. (Velidandla, V., Pulta, S., Roy, P., Kaira, S.P., 1995. Velocity field in turbulent subcooled boiling flow. ASME Preprint HTD-314, 107-123) and the R-113 CHF data of Hino and Ueda (Hino, R., Ueda, T., 1985. Studies on heat transfer and flow characteristics in subcooled boiling-part 2, flow characteristics. Int. J. Multiphase Flow 11, 283-297). It can also predict external two-phase flows, such as those for spreading two-phase jets (Bonetto, F., Lahey Jr., R.T., 1993. An experimental study on air carryunder due to a plunging liquid jet. Int. J. Multiphase Flow 19 (2), 281-294) and multiphase flows around the hull of naval surface ships (Carrica, P.M., Bonetto, F., Drew, D.A., Lahey, R.T., 1999. A polydispersed model for bubbly two-phase flow around a surface ship. Int. J. Multiphase Flow 25 (2), 257-305)
Interfacial Instability in Two-Phase Flow: Manipulating Coalescence and Condensation
National Aeronautics and Space Administration — Two-phase flow under microgravity conditions presents a number of technical challenges ( and ). Life support and habitation depend on systems that use two-phase flow...
Two-phase flow structure in large diameter pipes
International Nuclear Information System (INIS)
Smith, T.R.; Schlegel, J.P.; Hibiki, T.; Ishii, M.
2012-01-01
Highlights: ► Local profiles of various quantities measured in large diameter pipe. ► Database for interfacial area in large pipes extended to churn-turbulent flow. ► Flow regime map confirms previous models for flow regime transitions. ► Data will be useful in developing interfacial area transport models for large pipes. - Abstract: Flow in large pipes is important in a wide variety of applications. In the nuclear industry in particular, understanding of flow in large diameter pipes is essential in predicting the behavior of reactor systems. This is especially true of natural circulation Boiling Water Reactor (BWR) designs, where a large-diameter chimney above the core provides the gravity head to drive circulation of the coolant through the reactor. The behavior of such reactors during transients and during normal operation will be predicted using advanced thermal–hydraulics analysis codes utilizing the two-fluid model. Essential to accurate two-fluid model calculations is reliable and accurate computation of the interfacial transfer terms. These interfacial transfer terms can be expressed as the product of one term describing the potential driving the transfer and a second term describing the available surface area for transfer, or interfacial area concentration. Currently, the interfacial area is predicted using flow regime dependent empirical correlations; however the interfacial area concentration is best computed through the use of the one-dimensional interfacial area transport equation (IATE). To facilitate the development of IATE source and sink term models in large-diameter pipes a fundamental understanding of the structure of the two-phase flow is essential. This understanding is improved through measurement of the local void fraction, interfacial area concentration and gas velocity profiles in pipes with diameters of 0.102 m and 0.152 m under a wide variety of flow conditions. Additionally, flow regime identification has been performed to
Experimental CFD grade data for stratified two-phase flows
Energy Technology Data Exchange (ETDEWEB)
Vallee, Christophe, E-mail: c.vallee@fzd.d [Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, D-01314 Dresden (Germany); Lucas, Dirk; Beyer, Matthias; Pietruske, Heiko; Schuetz, Peter; Carl, Helmar [Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, D-01314 Dresden (Germany)
2010-09-15
Stratified two-phase flows were investigated at two test facilities with horizontal test-sections. For both, rectangular channel cross-sections were chosen to provide optimal observation possibilities for the application of optical measurement techniques. In order to show the local flow structure, high-speed video observation was applied, which delivers the high-resolution in space and time needed for CFD code validation. The first investigations were performed in the Horizontal Air/Water Channel (HAWAC), which is made of acrylic glass and allows the investigation of air/water co-current flows at atmospheric pressure and room temperature. At the channel inlet, a special device was designed for well-defined and adjustable inlet boundary conditions. For the quantitative analysis of the optical measurements performed at the HAWAC, an algorithm was developed to recognise the stratified interface in the camera frames. This allows to make statistical treatments for comparison with CFD calculation results. As an example, the unstable wave growth leading to slug flow is shown from the test-section inlet. Moreover, the hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was investigated in this closed channel. The structure of the hydraulic jump over time is revealed by the calculation of the probability density of the water level. A series of experiments show that the hydraulic jump profile and its position from the inlet vary substantially with the inlet boundary conditions due to the momentum exchange between the phases. The second channel is built in the pressure chamber of the TOPFLOW test facility, which is used to perform air/water and steam/water experiments at pressures of up to 5.0 MPa and temperatures of up to 264 {sup o}C, but under pressure equilibrium with the vessel inside. In the present experiment, the test-section represents a flat model of the hot leg of the German Konvoi pressurised water reactor scaled at
Experimental CFD grade data for stratified two-phase flows
International Nuclear Information System (INIS)
Vallee, Christophe; Lucas, Dirk; Beyer, Matthias; Pietruske, Heiko; Schuetz, Peter; Carl, Helmar
2010-01-01
Stratified two-phase flows were investigated at two test facilities with horizontal test-sections. For both, rectangular channel cross-sections were chosen to provide optimal observation possibilities for the application of optical measurement techniques. In order to show the local flow structure, high-speed video observation was applied, which delivers the high-resolution in space and time needed for CFD code validation. The first investigations were performed in the Horizontal Air/Water Channel (HAWAC), which is made of acrylic glass and allows the investigation of air/water co-current flows at atmospheric pressure and room temperature. At the channel inlet, a special device was designed for well-defined and adjustable inlet boundary conditions. For the quantitative analysis of the optical measurements performed at the HAWAC, an algorithm was developed to recognise the stratified interface in the camera frames. This allows to make statistical treatments for comparison with CFD calculation results. As an example, the unstable wave growth leading to slug flow is shown from the test-section inlet. Moreover, the hydraulic jump as the quasi-stationary discontinuous transition between super- and subcritical flow was investigated in this closed channel. The structure of the hydraulic jump over time is revealed by the calculation of the probability density of the water level. A series of experiments show that the hydraulic jump profile and its position from the inlet vary substantially with the inlet boundary conditions due to the momentum exchange between the phases. The second channel is built in the pressure chamber of the TOPFLOW test facility, which is used to perform air/water and steam/water experiments at pressures of up to 5.0 MPa and temperatures of up to 264 o C, but under pressure equilibrium with the vessel inside. In the present experiment, the test-section represents a flat model of the hot leg of the German Konvoi pressurised water reactor scaled at 1
Statistics of light deflection in a random two-phase medium
International Nuclear Information System (INIS)
Sviridov, A P
2007-01-01
The statistics of the angles of light deflection during its propagation in a random two-phase medium with randomly oriented phase interfaces is considered within the framework of geometrical optics. The probabilities of finding a randomly walking photon in different phases of the inhomogeneous medium are calculated. Analytic expressions are obtained for the scattering phase function and the scattering phase matrix which relates the Stokes vector of the incident light beam with the Stokes vectors of deflected beams. (special issue devoted to multiple radiation scattering in random media)
Prediction of pressure drop and CCFL breakdown in countercurrent two-phase flow
International Nuclear Information System (INIS)
Ostrogorsky, A.G.; Gay, R.R.; Lahey, R.T. Jr.
1983-01-01
A steady-state analytical has been developed to predict channel pressure drop as a function of inlet vapor flow rate and applied heat flux during conditions of countercurrent two-phase flow. The interfacial constitutive relations utilized are flow surface dependent and allow for the existence of either smooth or way liquid films. A computer code was developed to solve the analytical model. Predictions of Δp versus vapor flow rate were found to agree favorably with experimental data from adiabatic, air/water systems. In addition, the model was used to predict countercurrent flow conditions in heated channels characteristic of a BWR/4 nuclear reactor fuel assembly
Cosolutes effects on aqueous two-phase systems equilibrium formation studied by physical approaches.
Bertoluzzo, M Guadalupe; Rigatuso, Rubén; Farruggia, Beatriz; Nerli, Bibiana; Picó, Guillermo
2007-10-01
The effect of urea and sodium salts of monovalent halides on the aqueous polyethyleneglycol solution and binodal diagrams of polyethyleneglycol-potassium phosphate (polyethyleneglycol of molecular mass 1500, 4000, 6000 and 8000) were studied using different physical approaches. The effect of these solutes on the binodal diagram for polyethyleneglycol-potassium phosphate was also investigated. The cosolutes affected in a significant manner the water structured around the ethylene chain of polyethyleneglycol inducing a lost of this. The equilibrium curves for the aqueous two-phase systems were fitting very well by a sigmoidal function with two parameters, which are closely related with the cosolute structure making or breaking capacity on the water ordered.
Review of mathematical and physical basis of two-phase flow modelling
International Nuclear Information System (INIS)
Bottoni, M.; Sengpiel, W.
1992-08-01
Starting from a continuum-mechanical approach, this report gives a detailed overview of the deduction of conservation equations for the analytical description of two-phase flows by means of an adequate averaging process resulting in a two-fluid model and a homogeneous mixture model. The mathematical process of averaging leads to macroscopic formulations of stress terms and interfacial interaction terms. These terms depend on microscopic variables and thus give some helpful insight into the physical processes which have to be described by constitutive relations. (orig.) [de
Features of two-phase flow in a microchannel of 0.05×20 mm
Ronshin, Fedor
2017-10-01
We have studied the two-phase flow in a microchannel with cross-section of 0.05×20 mm2. The following two-phase flow regimes have been registered: jet, bubble, stratified, annular, and churn ones. The main features of flow regimes in this channel such as formation of liquid droplets in all two-phase flows have been distinguished.
Rolling effects on two-phase flow pattern and void fraction
International Nuclear Information System (INIS)
Yan Changqi; Yu Kaiqiu; Luan Feng; Cao Xiaxin
2008-01-01
The experimental and theoretical study was carried out for the upward gas-liquid two-phase explained reasonably through the analysis of slip ratio of two-phase flow and theoretical analysis using momentum equation of two-phase flow separating model. (authors)
Measurement of two phase flow properties using the nuclear reactor instruments
International Nuclear Information System (INIS)
Albrecht, R.W.; Washington Univ., Seattle; Crowe, R.D.; Dailey, D.J.; Kosaly, G.; Damborg, M.J.
1982-01-01
A procedure is introduced for characterizing one dimensional, two phase flow in terms of three properties; propagation, structure, and dynamics. It is shown that all of these properties can be measured by analyzing the response of the reactor neutron field to a two phase flow perturbation. Therefore, a nuclear reactor can be regarded as a two phase flow instrument. (author)
One-dimensional transient unequal velocity two-phase flow by the method of characteristics
International Nuclear Information System (INIS)
Rasouli, F.
1981-01-01
An understanding of two-phase flow is important when one is analyzing the accidental loss of coolant or when analyzing industrial processes. If a pipe in the steam generator of a nuclear reactor breaks, the flow will remain critical (or choked) for almost the entire blowdown. For this reason the knowledge of the two-phase maximum (critical) flow rate is important. A six-equation model--consisting of two continuity equations, two energy equations, a mixture momentum equation, and a constitutive relative velocity equation--is solved numerically by the method of characteristics for one-dimensional, transient, two-phase flow systems. The analysis is also extended to the special case of transient critical flow. The six-equation model is used to study the flow of a nonequilibrium sodium-argon system in a horizontal tube in which the nonequilibrium sodium-argon system in a horizontal tube in which the critical flow condition is at the entrance. A four-equation model is used to study the pressure-pulse propagation rate in an isothermal air-water system, and the results that are found are compared with the experimental data. Proper initial and boundary conditions are obtained for the blowdown problem. The energy and mass exchange relations are evaluated by comparing the model predictions with results of void-fraction and heat-transfer experiments. A simplified two-equation model is obtained for the special case of two incompressible phases. This model is used in the preliminary analysis of batch sedimentation. It is also used to predict the shock formation in the gas-solid fluidized bed
Hydrodynamics of single- and two-phase flow in inclined rod arrays
International Nuclear Information System (INIS)
Todreas, N.E.
1984-01-01
Required inputs for thermal-hydraulic codes are constitutive relations for fluid-solid flow resistance, in single-phase flow, and interfacial momentum exchange (relative phase motion), in two-phase flow. An inclined rod array air-water experiment was constructed to study the hydrodynamics of multidimensional porous medium flow in rod arrays. Velocities, pressures, bubble distributions, and void fractions were measured in inline and rotational square rod arrays of P/d = 1.5, at 0, 30, 45, and 90 degree inclinations to the vertical flow direction. Constitutive models for single-phase flow resistance are reviewed, new comprehensive models developed, and an assessment with previously published and new data made. The principle of superimposing one-dimensional correlations proves successful for turbulent single-phase inclined flow. For bubbly two-phase yawed flow through incline rod arrays a new flow separation phenomena was observed and modeled. Bubbles of diameters significantly smaller than the rod diameter travel along the rod axis, while larger diameter bubbles move through the rod array gaps. The outcome is a flow separation not predictable with current interfacial momentum exchange models. This phenomenon was not observed in rotated square rod arrays. Current interfacial momentum exchange models were confirmed for this rod arrangement. Models for the two phase flow resistance multiplier for cross flow were reviewed and compared with data from cross and yawed flow rod arrays. Both drag and lift components of the multiplier were well predicted by the homogenous model. Other models reviewed overpredicted the data by a factor of two
International Nuclear Information System (INIS)
Huang, Dong; Gao, Puzhen; Chen, Chong; Lan, Shu
2013-01-01
Highlights: • Most of the slip ratio models and the Lockhart–Martinelli parameter based models give similar results. • The drift flux void fraction models give relatively small values. • The effect of void fraction correlations on two-phase friction pressure drop is inconspicuous. • The effect of void fraction correlations on two-phase acceleration pressure drop is significant. - Abstract: The void fraction of water during flow boiling in vertical narrow rectangular channel is experimentally investigated. The void fraction is indirectly determined using the present experimental data with various void fraction correlations or models published in the open literature. The effects of mass flux, mass quality, system pressure and inlet subcooling on the void fraction and pressure drop are discussed in detail. In addition, comparison and discussion among the numerous void fraction correlations are carried out. The effect of void fraction correlations on two-phase pressure drop is presented as well. The results reveal that most of the slip ratio correlations and the Lockhart–Martinelli parameter based void fraction correlations have results close to each other at mass quality higher than 0.2. The drift flux void fraction correlations give small values which are incompatible with other models making it inapplicable for narrow rectangular channel. The alteration of void fraction correlations has an inconspicuous effect on two-phase frictional pressure drop, while an obvious effect on two-phase accelerational pressure drop during flow boiling in narrow rectangular channel
Inverse modeling for the determination of hydrogeological parameters of a two-phase system
International Nuclear Information System (INIS)
Finsterle, S.
1993-02-01
Investigations related to the disposal of radioactive wastes in Switzerland consider formations containing natural gas as potential rocks for a repository. Moreover, gas generation in the repository itself may lead to an unsaturated zone of significant extent and impact on the system's performance. The site characterization procedure requires the estimation of hydraulic properties being used as input parameters for a two-phase two-component numerical simulator. In this study, estimates of gas-related formation parameters are obtained by inverse modeling. Based on discrete observations of the system's state, model parameters can be estimated within the framework of a given conceptual model by means of optimization techniques. This study presents the theoretical background that related field data to the model parameters. A parameter estimation procedure is proposed and implemented in a computer code for automatic model calibration. This tool allows identification of key parameters affecting flow of water and gas in porous media. The inverse modeling approach is verified using data from a synthetic laboratory experiment. In addition, the Gas test performed at the Grimsel Test Site is analyzed in order to demonstrate the applicability of the proposed procedure when used with data from a real geologic environment. Estimation of hydrogeologic parameters by automatic model calibration improves the understanding of the two-phase flow processes and therefore increases the reliability of the subsequent simulation runs. (author) figs., tabs., refs
Inverse modeling for the determination of hydrogeological parameters of a two-phase system
International Nuclear Information System (INIS)
Finsterle, S.
1993-01-01
Investigations related to the disposal of radioactive wastes in Switzerland are dealing with formations containing natural gas as potential host rock for a repository. Moreover, gas generation in the repository itself may lead to an unsaturated zone of significant extent and impact on the system's performance. The site characterization procedure requires the estimation of hydraulic properties being used as input parameters for a two-phase two-component numerical simulator. In this study, estimates of gas related formation parameters are obtained by inverse modeling. Based on discrete observations of the system's state, model parameters can be estimated within the framework of a given conceptual model by means of optimization techniques. This study presents the theoretical background that relates field data to the model parameters. A parameter estimation procedure is proposed and implemented in a computer code for automatic model calibration. This tool allows to identify key parameters affecting flow of water and gas in porous media. The inverse modeling approach is verified using data from a synthetic laboratory experiment. In addition, the Gastest performed at the Grimsel Test Site is analyzed in order to demonstrate the applicability of the proposed procedure when used with data from a real geologic environment. Estimation of hydrogeologic parameters by automatic model calibration improves the understanding of the two-phase flow processes and therefore increases the reliability of the subsequent simulation runs. (author) figs., tabs., 100 refs
A study of Two-Phase Flow Regime Maps in Vertical and Horizontal Pipes
International Nuclear Information System (INIS)
Kim, Kyung Doo; Kang, Doo Hyuk
2007-10-01
A safety analysis code to design a pressurized water reactor and to obtain the licences including entire proprietary rights is under development in domestic research and development project. The purpose and scope of this report is to develop the flow regimes related models for inter-phase friction, wall frictions, wall heat transfer, and inter-phase heat and mass transfer in two-phase three-field equations. In order to choose choose the flow regime criteria, we have investigated various exiting best-estimate T/H codes in this chapter 2. They are the RELAP5-3D, TRAC-M, CATHARE, MARS codes. Around 500 references used in these codes have been collected and reviewed. Also we have investigated eleven papers in detail. In chapter 3, based on the selected flow regimes, the flow regime maps for a gas-liquid flow in horizontal and vertical tubes have decided including the mechanisms of flow regime transition regions. Conclusively, the process will be presented for choosing the best flow regime maps which occur in gas-liquid two-phase flow in horizontal and vertical pipes. We will look forward to decide the constitutive relations based upon the flow regime maps that are determined in this works. The constitutive relations will be used for the code under development
Energy Technology Data Exchange (ETDEWEB)
Mesquita, R.N.; Libardi, R.M.P.; Masotti, P.H.F.; Sabundjian, G.; Andrade, D.A.; Umbehaun, P.E.; Torres, W.M.; Conti, T.N.; Macedo, L.A. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Nuclear Engineering Center], e-mail: rnavarro@ipen.br
2009-07-01
Visualization of natural circulation test loop cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. Experimental studies on natural circulation flow were originally related to accidents and transient simulations relative to nuclear reactor systems with light water refrigeration. In this regime, fluid circulation is mainly caused by a driving force ('thermal head') which arises from density differences due to temperature gradient. Natural circulation phenomenon has been important to provide residual heat removal in cases of 'loss of pump power' or plant shutdown in nuclear power plant accidents. The new generation of compact nuclear reactors includes natural circulation of their refrigerant fluid as a security mechanism in their projects. Two-phase flow patterns have been studied for many decades, and the related instabilities have been object of special attention recently. Experimental facility is an all glass-made cylindrical tubes loop which contains about twelve demineralized water liters, a heat source by an electrical resistor immersion heater controlled by a Variac, and a helicoidal heat exchanger working as cold source. Data is obtained through thermo-pairs distributed over the loop and CCD cameras. Artificial intelligence based algorithms are used to improve (bubble) border detection and patterns recognition, in order to estimate and characterize, phase transitions patterns and correlate them with the periodic static instability (chugging) cycle observed in this circuit. Most of initial results show good agreement with previous numerical studies in this same facility. (author)
International Nuclear Information System (INIS)
Mesquita, R.N.; Libardi, R.M.P.; Masotti, P.H.F.; Sabundjian, G.; Andrade, D.A.; Umbehaun, P.E.; Torres, W.M.; Conti, T.N.; Macedo, L.A.
2009-01-01
Visualization of natural circulation test loop cycles is used to study two-phase flow patterns associated with phase transients and static instabilities of flow. Experimental studies on natural circulation flow were originally related to accidents and transient simulations relative to nuclear reactor systems with light water refrigeration. In this regime, fluid circulation is mainly caused by a driving force ('thermal head') which arises from density differences due to temperature gradient. Natural circulation phenomenon has been important to provide residual heat removal in cases of 'loss of pump power' or plant shutdown in nuclear power plant accidents. The new generation of compact nuclear reactors includes natural circulation of their refrigerant fluid as a security mechanism in their projects. Two-phase flow patterns have been studied for many decades, and the related instabilities have been object of special attention recently. Experimental facility is an all glass-made cylindrical tubes loop which contains about twelve demineralized water liters, a heat source by an electrical resistor immersion heater controlled by a Variac, and a helicoidal heat exchanger working as cold source. Data is obtained through thermo-pairs distributed over the loop and CCD cameras. Artificial intelligence based algorithms are used to improve (bubble) border detection and patterns recognition, in order to estimate and characterize, phase transitions patterns and correlate them with the periodic static instability (chugging) cycle observed in this circuit. Most of initial results show good agreement with previous numerical studies in this same facility. (author)
International Nuclear Information System (INIS)
Lim, I. C.; Seo, C. G.; Jeong, J. H.; Lee, B. H.; Choi, Y. S.
2001-01-01
For the application of dynamic neutron radiography to the two-phase flow research using HANARO, several experimental items to which the radiography technique is beneficial were identified through the review of the outputs from the related researches and the discussions with experts. Also, the investigation of the equipments including the beam port, camera and converter was made and a hardware and a software for image processing were equipped. It was confirmed that the calibration curve for the attenuation of neutron beam in fluid which is required for the two-phase flow experiment could be obtained by the computer code calculation. Based on the investigation results on the equipment and the results from the measurement of BNCT beam characteristics, a high speed camera and an image intensifier will be purchased. Then, the high speed dynamic neutron radiography facility for two-phase flow experiments will be fully equipped
Energy Technology Data Exchange (ETDEWEB)
Lim, I. C.; Seo, C. G.; Jeong, J. H.; Lee, B. H.; Choi, Y. S
2001-01-01
For the application of dynamic neutron radiography to the two-phase flow research using HANARO, several experimental items to which the radiography technique is beneficial were identified through the review of the outputs from the related researches and the discussions with experts. Also, the investigation of the equipments including the beam port, camera and converter was made and a hardware and a software for image processing were equipped. It was confirmed that the calibration curve for the attenuation of neutron beam in fluid which is required for the two-phase flow experiment could be obtained by the computer code calculation. Based on the investigation results on the equipment and the results from the measurement of BNCT beam characteristics, a high speed camera and an image intensifier will be purchased. Then, the high speed dynamic neutron radiography facility for two-phase flow experiments will be fully equipped.
Design of a Subscale Propellant Slag Evaluation Motor Using Two-Phase Fluid Dynamic Analysis
Whitesides, R. Harold; Dill, Richard A.; Purinton, David C.; Sambamurthi, Jay K.
1996-01-01
Small pressure perturbations in the Space Shuttle Reusable Solid Rocket Motor (RSRM) are caused by the periodic expulsion of molten aluminum oxide slag from a pool that collects in the aft end of the motor around the submerged nozzle nose during the last half of motor operation. It is suspected that some motors produce more slag than others due to differences in aluminum oxide agglomerate particle sizes that may relate to subtle differences in propellant ingredient characteristics such as particle size distributions or processing variations. A subscale motor experiment was designed to determine the effect of propellant ingredient characteristics on the propensity for slag production. An existing 5 inch ballistic test motor was selected as the basic test vehicle. The standard converging/diverging nozzle was replaced with a submerged nose nozzle design to provide a positive trap for the slag that would increase the measured slag weights. Two-phase fluid dynamic analyses were performed to develop a nozzle nose design that maintained similitude in major flow field features with the full scale RSRM. The 5 inch motor was spun about its longitudinal axis to further enhance slag collection and retention. Two-phase flow analysis was used to select an appropriate spin rate along with other considerations, such as avoiding bum rate increases due to radial acceleration effects. Aluminum oxide particle distributions used in the flow analyses were measured in a quench bomb for RSRM type propellants with minor variations in ingredient characteristics. Detailed predictions for slag accumulation weights during motor bum compared favorably with slag weight data taken from defined zones in the subscale motor and nozzle. The use of two-phase flow analysis proved successful in gauging the viability of the experimental program during the planning phase and in guiding the design of the critical submerged nose nozzle.
International Nuclear Information System (INIS)
Ruspini, L.C.
2012-01-01
Highlights: ► The stability influence of piping fluid inertia on two-phase instabilities is studied. ► Inlet inertia stabilizes the system while outlet inertia destabilizes it. ► High-order modes oscillations are found and analyzed. ► The effect of compressible volumes in the system is studied. ► Inlet compressibility destabilizes the system while outlet comp. stabilizes it. - Abstract: The most common kind of static and dynamic two-phase flow instabilities namely Ledinegg and density wave oscillations are studied. A new model to study two-phase flow instabilities taking into account general parameters from real systems is proposed. The stability influence of external parameters such as the fluid inertia and the presence of compressible gases in the system is analyzed. High-order oscillation modes are found to be related with the fluid inertia of external piping. The occurrence of high-order modes in experimental works is analyzed with focus on the results presented in this work. Moreover, both inertia and compressibility are proven to have a high impact on the stability limits of the systems. The performed study is done by modeling the boiling channel using a one dimensional equilibrium model. An incompressible transient model describes the evolution of the flow and pressure in the non-heated regions and an ideal gas model is used to simulate the compressible volumes in the system. The use of wavelet decomposition analysis is proven to be an efficient tool in stability analysis of several frequencies oscillations.
Validation of model predictions of pore-scale fluid distributions during two-phase flow
Bultreys, Tom; Lin, Qingyang; Gao, Ying; Raeini, Ali Q.; AlRatrout, Ahmed; Bijeljic, Branko; Blunt, Martin J.
2018-05-01
Pore-scale two-phase flow modeling is an important technology to study a rock's relative permeability behavior. To investigate if these models are predictive, the calculated pore-scale fluid distributions which determine the relative permeability need to be validated. In this work, we introduce a methodology to quantitatively compare models to experimental fluid distributions in flow experiments visualized with microcomputed tomography. First, we analyzed five repeated drainage-imbibition experiments on a single sample. In these experiments, the exact fluid distributions were not fully repeatable on a pore-by-pore basis, while the global properties of the fluid distribution were. Then two fractional flow experiments were used to validate a quasistatic pore network model. The model correctly predicted the fluid present in more than 75% of pores and throats in drainage and imbibition. To quantify what this means for the relevant global properties of the fluid distribution, we compare the main flow paths and the connectivity across the different pore sizes in the modeled and experimental fluid distributions. These essential topology characteristics matched well for drainage simulations, but not for imbibition. This suggests that the pore-filling rules in the network model we used need to be improved to make reliable predictions of imbibition. The presented analysis illustrates the potential of our methodology to systematically and robustly test two-phase flow models to aid in model development and calibration.
Purification of plant plasma membranes by two-phase partitioning and measurement of H+ pumping.
Lund, Anette; Fuglsang, Anja Thoe
2012-01-01
Purification of plasma membranes by two-phase partitioning is based on the separation of microsomal membranes, dependent on their surface hydrophobicity. Here we explain the purification of plasma membranes from a relatively small amount of material (7-30 g). The fluorescent probe ACMA (9-amino-6-chloro-2-metoxyacridine) accumulates inside the vesicles upon protonation. Quenching of ACMA in the solution corresponds to the H(+) transport across the plasma membrane. Before running the assay, the plasma membranes are incubated with the detergent Brij-58 in order to create inside-out vesicles.Purification of plasma membranes by two-phase partitioning is based on the separation of microsomal membranes, dependent on their surface hydrophobicity. Here we explain the purification of plasma membranes from a relatively small amount of material (7-30 g). The fluorescent probe ACMA (9-amino-6-chloro-2-metoxyacridine) accumulates inside the vesicles upon protonation. Quenching of ACMA in the solution corresponds to the H(+) transport across the plasma membrane. Before running the assay, the plasma membranes are incubated with the detergent Brij-58 in order to create inside-out vesicles.
Hydrodynamics of single- and two-phase flow in inclined rod arrays
International Nuclear Information System (INIS)
Ebeling-Koning, D.B.; Todreas, N.E.
1983-09-01
Required inputs for thermal-hydraulic codes are constitutive relations for fluid-solid flow resistance, in single-phase flow, and interfacial momentum exchange (relative phase motion), in two-phase flow. An inclined rod array air-water experiment was constructed to study the hydrodynamics of multidimensional porous medium flow in rod arrays. Velocities, pressures, and bubble distributions were measured in square rod arrays of P/d = 1.5, at 0, 30, 45, and 90 degree inclinations to the vertical flow direction. Constitutive models for single-phase flow resistance are reviewed, new comprehensive models developed, and an assessment with previously published and new data made. The principle of superimposing one-dimensional correlations proves successful for turbulent single-phase inclined flow. For bubbly two-phase incline flow a new flow separation phenomena was observed and modeled. A two-region liquid velocity model is developed to explain the experimentally observed phenomena. Fundamental data for bubbles rising in rod arrays were also taken
A Two-Phase Solid/Fluid Model for Dense Granular Flows Including Dilatancy Effects
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Narbona-Reina, Gladys
2015-04-01
We propose a thin layer depth-averaged two-phase model to describe solid-fluid mixtures such as debris flows. It describes the velocity of the two phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure, that itself modifies the friction within the granular phase (Iverson et al., 2010). The model is derived from a 3D two-phase model proposed by Jackson (2000) based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work (Bouchut et al., 2014). In particular, Pitman and Le replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's equations. We close the mixture equations by a weak compressibility relation involving a critical density, or equivalently a critical pressure. Moreover, we relax one boundary condition, making it possible for the fluid to escape the granular media when compression of the granular mass occurs. Furthermore, we introduce second order terms in the equations making it possible to describe the evolution of the pore fluid pressure in response to the compression/dilatation of the granular mass without prescribing an extra ad-hoc equation for the pore pressure. We prove that the energy balance associated with this Jackson closure is dissipative, as well as its thin layer associated model. We present several numerical tests for the 1D case that are compared to the
Two-phase pressure drop and heat transfer of sodium at forced convection
International Nuclear Information System (INIS)
Grieb, G.
1989-04-01
Experiments with sodium for the two-phase pressure drop in vertical tubes with upward flow (internal diameters 6 and 9 mm) performed at the Joint Research Centre (JRC) of the European Communities in Ispra, Italy, and at the Nuclear Research Centre in Karlsruhe (KfK) were evaluated and analysed. Furthermore, experiments for the single-phase and two-phase heat transfer in the grid spaced twelve-rod bundle (p d /d =1.3, rod diameter 8 mm) with flow in axial direction performed at the JRC were evaluated and analysed. The pressure drop measurements were carried out at moderate to high mass flow rates (30 to 4500 kg/(m 2 s)) and at moderate pressures (50 to 300 kPa, density ratio ρ f /ρ g = 950 to 5400). The measurements for the single-phase heat transfer at high heat fluxes (0.16 to 1.6 MW/m 2 ) were carried out in the Reynolds number region (3100 2 s)) and at high heat fluxes (0.46 to 1.6 MW/m 2 ) within the temperature range from 870 to 970 0 C. For the subsequent calculation of the experiments relating to the two-phase pressure drop a computer program was developed, which is based on the so-called slip model. It requires a friction pressure loss correlation and a slip correlation. The tested correlations were not suitable for describing the experimental measurements. Accordingly, simplified equations of momentum were used to develop a new slip correlation for the case of annular flow together with the annular-mist flow, the most important two-phase flow regimes for sodium in the measurement range. After the inception of the entrainment - transition from the annular flow to the annular-mist flow - an even larger fraction of liquid enters the vapour core in the form of droplets, as the vapour quality increases. An equation was formulated for the slip in this region and adapted to the experiments via coefficients. (orig./GL) [de
International Nuclear Information System (INIS)
Saito, Y.; Hibiki, T.; Mishima, K.; Nishihara, H.; Yamamoto, A.; Kanda, K.; Tobita, Y.; Konishi, K.; Matsubayashi, M.
1998-01-01
In a core melt accident of a fast breeder reactor there is a possibility of boiling of fuel-steel mixture in the containment pool. In relation to safety evaluation on severe accident, it is indispensable to evaluate the recriticality of melted core. Gas-liquid two-phase flow with a large density difference is formed due to the boiling of fuel-steel mixture. Although the large density difference may affect the basic characteristics of two-phase flow, little work has been performed so far on two-phase flow with large density difference has not been performed well. In this study, visualization and void fraction measurement of gas-liquid metal two-phase flow were performed by using neutron radiography. The effect of the large density difference between gas and liquid phases on the basic flow characteristics of two-phase flow was clarified. (author)
Self-organizing maps applied to two-phase flow on natural circulation loop studies
Energy Technology Data Exchange (ETDEWEB)
Castro, Leonardo F.; Cunha, Kelly de P.; Andrade, Delvonei A.; Sabundjian, Gaiane; Torres, Walmir M.; Macedo, Luiz A.; Rocha, Marcelo da S.; Masotti, Paulo H.F.; Mesquita, Roberto N. de, E-mail: rnavarro@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
2015-07-01
Two-phase flow of liquid and gas is found in many closed circuits using natural circulation for cooling purposes. Natural circulation phenomenon is important on recent nuclear power plant projects for heat removal on 'loss of pump power' or 'plant shutdown' accidents. The accuracy of heat transfer estimation has been improved based on models that require precise prediction of pattern transitions of flow. Self-Organizing Maps are trained to digital images acquired on natural circulation flow instabilities. This technique will allow the selection of the more important characteristics associated with each flow pattern, enabling a better comprehension of each observed instability. This periodic flow oscillation behavior can be observed thoroughly in this facility due its glass-made tubes transparency. The Natural Circulation Facility (Circuito de Circulacao Natural - CCN) installed at Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN, is an experimental circuit designed to provide thermal hydraulic data related to one and two phase flow under natural circulation conditions. (author)
Second-law analysis of a two-phase self-pumping solar water heater
International Nuclear Information System (INIS)
Walker, H.A.; Davidson, J.H.
1992-01-01
In this paper entropy generated by operation of a two-phase self-pumping solar water heater under Solar Rating and Certification Corporation rating conditions is computed numerically in a methodology based on an exergy cascade. An order of magnitude analysis shows that entropy generation is dominated by heat transfer across temperature differences. Conversion of radiant solar energy incident on the collector to thermal energy within the collector accounts for 87.1 percent of total entropy generation. Thermal losses are responsible for 9.9 percent of total entropy generation, and heat transfer across the condenser accounts for 2.4 percent of the total entropy generation. Mixing in the tempering valve is responsible for 0.7 percent of the total entropy generation. Approximately one half of the entropy generated by thermal losses is attributable to the self-pumping process. The procedure to determine total entropy generation can be used in a parametric study to evaluate the performance of two-phase hot water heating systems relative to other solar water heating options
Two-phase modeling of DDT: Structure of the velocity-relaxation zone
International Nuclear Information System (INIS)
Kapila, A.K.; Son, S.F.; Bdzil, J.B.; Menikoff, R.; Stewart, D.S.
1997-01-01
The structure of the velocity relaxation zone in a hyperbolic, nonconservative, two-phase model is examined in the limit of large drag, and in the context of the problem of deflagration-to-detonation transition in a granular explosive. The primary motivation for the study is the desire to relate the end states across the relaxation zone, which can then be treated as a discontinuity in a reduced, equivelocity model, that is computationally more efficient than its parent. In contrast to a conservative system, where end states across thin zones of rapid variation are determined principally by algebraic statements of conservation, the nonconservative character of the present system requires an explicit consideration of the structure. Starting with the minimum admissible wave speed, the structure is mapped out as the wave speed increases. Several critical wave speeds corresponding to changes in the structure are identified. The archetypal structure is partly dispersed, monotonic, and involves conventional hydrodynamic shocks in one or both phases. The picture is reminiscent of, but more complex than, what is observed in such (simpler) two-phase media as a dusty gas. copyright 1997 American Institute of Physics
A multi-scale network method for two-phase flow in porous media
Energy Technology Data Exchange (ETDEWEB)
Khayrat, Karim, E-mail: khayratk@ifd.mavt.ethz.ch; Jenny, Patrick
2017-08-01
Pore-network models of porous media are useful in the study of pore-scale flow in porous media. In order to extract macroscopic properties from flow simulations in pore-networks, it is crucial the networks are large enough to be considered representative elementary volumes. However, existing two-phase network flow solvers are limited to relatively small domains. For this purpose, a multi-scale pore-network (MSPN) method, which takes into account flow-rate effects and can simulate larger domains compared to existing methods, was developed. In our solution algorithm, a large pore network is partitioned into several smaller sub-networks. The algorithm to advance the fluid interfaces within each subnetwork consists of three steps. First, a global pressure problem on the network is solved approximately using the multiscale finite volume (MSFV) method. Next, the fluxes across the subnetworks are computed. Lastly, using fluxes as boundary conditions, a dynamic two-phase flow solver is used to advance the solution in time. Simulation results of drainage scenarios at different capillary numbers and unfavourable viscosity ratios are presented and used to validate the MSPN method against solutions obtained by an existing dynamic network flow solver.
A multi-scale network method for two-phase flow in porous media
International Nuclear Information System (INIS)
Khayrat, Karim; Jenny, Patrick
2017-01-01
Pore-network models of porous media are useful in the study of pore-scale flow in porous media. In order to extract macroscopic properties from flow simulations in pore-networks, it is crucial the networks are large enough to be considered representative elementary volumes. However, existing two-phase network flow solvers are limited to relatively small domains. For this purpose, a multi-scale pore-network (MSPN) method, which takes into account flow-rate effects and can simulate larger domains compared to existing methods, was developed. In our solution algorithm, a large pore network is partitioned into several smaller sub-networks. The algorithm to advance the fluid interfaces within each subnetwork consists of three steps. First, a global pressure problem on the network is solved approximately using the multiscale finite volume (MSFV) method. Next, the fluxes across the subnetworks are computed. Lastly, using fluxes as boundary conditions, a dynamic two-phase flow solver is used to advance the solution in time. Simulation results of drainage scenarios at different capillary numbers and unfavourable viscosity ratios are presented and used to validate the MSPN method against solutions obtained by an existing dynamic network flow solver.
Single- and two-phase flow characterization using optical fiber bragg gratings.
Baroncini, Virgínia H V; Martelli, Cicero; da Silva, Marco José; Morales, Rigoberto E M
2015-03-17
Single- and two-phase flow characterization using optical fiber Bragg gratings (FBGs) is presented. The sensor unit consists of the optical fiber Bragg grating positioned transversely to the flow and fixed in the pipe walls. The hydrodynamic pressure applied by the liquid or air/liquid flow to the optical fiber induces deformation that can be detected by the FBG. Given that the applied pressure is directly related to the mass flow, it is possible to establish a relationship using the grating resonance wavelength shift to determine the mass flow when the flow velocity is well known. For two phase flows of air and liquid, there is a significant change in the force applied to the fiber that accounts for the very distinct densities of these substances. As a consequence, the optical fiber deformation and the correspondent grating wavelength shift as a function of the flow will be very different for an air bubble or a liquid slug, allowing their detection as they flow through the pipe. A quasi-distributed sensing tool with 18 sensors evenly spread along the pipe is developed and characterized, making possible the characterization of the flow, as well as the tracking of the bubbles over a large section of the test bed. Results show good agreement with standard measurement methods and open up plenty of opportunities to both laboratory measurement tools and field applications.
Phase-field-based lattice Boltzmann modeling of large-density-ratio two-phase flows
Liang, Hong; Xu, Jiangrong; Chen, Jiangxing; Wang, Huili; Chai, Zhenhua; Shi, Baochang
2018-03-01
In this paper, we present a simple and accurate lattice Boltzmann (LB) model for immiscible two-phase flows, which is able to deal with large density contrasts. This model utilizes two LB equations, one of which is used to solve the conservative Allen-Cahn equation, and the other is adopted to solve the incompressible Navier-Stokes equations. A forcing distribution function is elaborately designed in the LB equation for the Navier-Stokes equations, which make it much simpler than the existing LB models. In addition, the proposed model can achieve superior numerical accuracy compared with previous Allen-Cahn type of LB models. Several benchmark two-phase problems, including static droplet, layered Poiseuille flow, and spinodal decomposition are simulated to validate the present LB model. It is found that the present model can achieve relatively small spurious velocity in the LB community, and the obtained numerical results also show good agreement with the analytical solutions or some available results. Lastly, we use the present model to investigate the droplet impact on a thin liquid film with a large density ratio of 1000 and the Reynolds number ranging from 20 to 500. The fascinating phenomena of droplet splashing is successfully reproduced by the present model and the numerically predicted spreading radius exhibits to obey the power law reported in the literature.
Regularized lattice Boltzmann model for immiscible two-phase flows with power-law rheology
Ba, Yan; Wang, Ningning; Liu, Haihu; Li, Qiang; He, Guoqiang
2018-03-01
In this work, a regularized lattice Boltzmann color-gradient model is developed for the simulation of immiscible two-phase flows with power-law rheology. This model is as simple as the Bhatnagar-Gross-Krook (BGK) color-gradient model except that an additional regularization step is introduced prior to the collision step. In the regularization step, the pseudo-inverse method is adopted as an alternative solution for the nonequilibrium part of the total distribution function, and it can be easily extended to other discrete velocity models no matter whether a forcing term is considered or not. The obtained expressions for the nonequilibrium part are merely related to macroscopic variables and velocity gradients that can be evaluated locally. Several numerical examples, including the single-phase and two-phase layered power-law fluid flows between two parallel plates, and the droplet deformation and breakup in a simple shear flow, are conducted to test the capability and accuracy of the proposed color-gradient model. Results show that the present model is more stable and accurate than the BGK color-gradient model for power-law fluids with a wide range of power-law indices. Compared to its multiple-relaxation-time counterpart, the present model can increase the computing efficiency by around 15%, while keeping the same accuracy and stability. Also, the present model is found to be capable of reasonably predicting the critical capillary number of droplet breakup.
OCV Hysteresis in Li-Ion Batteries including Two-Phase Transition Materials
Directory of Open Access Journals (Sweden)
Michael A. Roscher
2011-01-01
Full Text Available The relation between batteries' state of charge (SOC and open-circuit voltage (OCV is a specific feature of electrochemical energy storage devices. Especially NiMH batteries are well known to exhibit OCV hysteresis, and also several kinds of lithium-ion batteries show OCV hysteresis, which can be critical for reliable state estimation issues. Electrode potential hysteresis is known to result from thermodynamical entropic effects, mechanical stress, and microscopic distortions within the active electrode materials which perform a two-phase transition during lithium insertion/extraction. Hence, some Li-ion cells including two-phase transition active materials show pronounced hysteresis referring to their open-circuit voltage. This work points out how macroscopic effects, that is, diffusion limitations, superimpose the latte- mentioned microscopic mechanisms and lead to a shrinkage of OCV hysteresis, if cells are loaded with high current rates. To validate the mentioned interaction, Li-ion cells' state of charge is adjusted to 50% with various current rates, beginning from the fully charged and the discharged state, respectively. As a pronounced difference remains between the OCV after charge and discharge adjustment, obviously the hysteresis vanishes as the target SOC is adjusted with very high current rate.
Two-phase flow simulation of scour around a cylindrical pile
Nagel, T.; Chauchat, J.; Bonamy, C.; Liu, X.; Cheng, Z.; Hsu, T. J.
2017-12-01
Scour around structures is a major engineering issue that requires a detailed description of the flow field but also a consistent description of sediment transport processes that could not only be related to bed shear stress, like Shields parameter based sediment transport formula. In order to address this issue we used a multi-dimensional two-phase flow solver, sedFoam-2.0 (Chauchat et al., GMD 2017) implemented under the open-source CFD toolbox OpenFoam. Three-dimensional simulations have been performed on Roulund et al. (JFM 2005) configurations for clear-water and live bed cases. The k-omega model from Wilcox (AIAA Journal 2006) is used for the turbulent stress and the granular rheology μ(I) is used for the granular stress in the live bed case. The hydrodynamic is validated on the clear water case and the numerical results obtained for the live bed case provide a proof of concept that two-phase flow model is applicable to such problem with quantitative results for the prediction of scour depth upstream and downstream the cylinder at short timescales, up to 300s. Analyzing the simulation results in term of classical dimensionless sediment transport flux versus Shields parameter allows to get more insight into the fine scale sediment transport mechanisms involved in the scour process.
Pressure Drop Correlations of Single-Phase and Two-Phase Flow in Rolling Tubes
International Nuclear Information System (INIS)
Xia-xin Cao; Chang-qi Yan; Pu-zhen Gao; Zhong-ning Sun
2006-01-01
A series of experimental studies of frictional pressure drop for single phase and two-phase bubble flow in smooth rolling tubes were carried out. The tube inside diameters were 15 mm, 25 mm and 34.5 mm respectively, the rolling angles of tubes could be set as 10 deg. and 20 deg., and the rolling periods could be set as 5 s, 10 s and 15 s. Combining with the analysis of single-phase water motion, it was found that the traditional correlations for calculating single-phase frictional coefficient were not suitable for the rolling condition. Based on the experimental data, a new correlation for calculating single-phase frictional coefficient under rolling condition was presented, and the calculations not only agreed well with the experimental data, but also could display the periodically dynamic characteristics of frictional coefficients. Applying the new correlation to homogeneous flow model, two-phase frictional pressure drop of bubble flow in rolling tubes could be calculated, the results showed that the relative error between calculation and experimental data was less than ± 25%. (authors)
Two-Phase Flow in Pipes: Numerical Improvements and Qualitative Analysis for a Refining Process
Directory of Open Access Journals (Sweden)
Teixeira R.G.D.
2015-03-01
Full Text Available Two-phase flow in pipes occurs frequently in refineries, oil and gas production facilities and petrochemical units. The accurate design of such processing plants requires that numerical algorithms be combined with suitable models for predicting expected pressure drops. In performing such calculations, pressure gradients may be obtained from empirical correlations such as Beggs and Brill, and they must be integrated over the total length of the pipe segment, simultaneously with the enthalpy-gradient equation when the temperature profile is unknown. This paper proposes that the set of differential and algebraic equations involved should be solved as a Differential Algebraic Equations (DAE System, which poses a more CPU-efficient alternative to the “marching algorithm” employed by most related work. Demonstrating the use of specific regularization functions in preventing convergence failure in calculations due to discontinuities inherent to such empirical correlations is also a key feature of this study. The developed numerical techniques are then employed to examine the sensitivity to heat-transfer parameters of the results obtained for a typical refinery two-phase flow design problem.
Quasistatic analysis on configuration of two-phase flow in Y-shaped tubes
Zhong, Hua
2014-12-01
We investigate the two-phase flow in a horizontally placed Y-shaped tube with different Young\\'s angle and width in each branch. By using a quasistatic approach, we can determine the specific contact position and the equilibrium contact angle of fluid in each branch based on the minimization problem of the free energy of the system. The wettability condition and the width of the two branches play important roles in the distribution of fluid in each branch. We also consider the effect of gravity. Some fluid in the upper branch will be pulled down due to the competition of the surface energy and the gravitational energy. The result provides some insights on the theory of two-phase flow in porous media. In particular, it highlights that the inhomogeneous wettability distribution affects the direction of the fluid penetrating a given porous medium domain. It also sheds light on the current debate whether relative permeability may be considered as a full tensor rather than a scalar.
Rosa, P A J; Azevedo, A M; Sommerfeld, S; Bäcker, W; Aires-Barros, M R
2011-01-01
The biotech industry is, nowadays, facing unparalleled challenges due to the enhanced demand for biotechnology-based human therapeutic products, such as monoclonal antibodies (mAbs). This has led companies to improve substantially their upstream processes, with the yield of monoclonals increasing to titers never seen before. The downstream processes have, however, been overlooked, leading to a production bottleneck. Although chromatography remains the workhorse of most purification processes, several limitations, such as low capacity, scale-related packing problems, low chemical and proteolytic stability and resins' high cost, have arisen. Aqueous two-phase extraction (ATPE) has been successfully revisited as a valuable alternative for the capture of antibodies. One of the important remaining questions for this technology to be adopted by the biotech industries is, now, how it compares to the currently established platforms in terms of costs and environmental impact. In this report, the economical and environmental sustainability of the aqueous two-phase extraction process is evaluated and compared to the currently established protein A affinity chromatography. Accordingly, the ATPE process was shown to be considerably advantageous in terms of process economics, especially when processing high titer cell culture supernatants. This alternative process is able to purify continuously the same amount of mAbs reducing the annual operating costs from 14.4 to 8.5 million (US$/kg) when cell culture supernatants with mAb titers higher than 2.5 g/L are processed. Copyright © 2011 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Marcel, C P [Instituto Balseiro, Universidad Nacional de Cuyo, Centro Atomico Bariloche (Argentina)
2002-07-01
The classical mathematical treatment of two-phase flows is based on the average of the conservation equations for each phase.In this work, a complementary approach to the modeling of these systems based on statistical population balances of aut omata sets is presented.Automata are entities defined by mathematical states that change following iterative rules representing interactions with the neighborhood.A model of automata for two-phase flow simulation is presented.This model consists of fie lds of virtual spheres that change their volumes and move around a certain environment.The model is more general than the classical cellular automata in two respects: the grid of cellular automata is dismissed in favor of a trajectory generator, and the rules of interaction involve parameters representing the actual physical interactions between phases.Automata simulation was used to study unsolved two-phase flow problems involving high heat flux rates. One system described in this work consists of a vertical channel with saturated water at normal pressure heated from the lower surface.The heater causes water to boil and starts the bubble production.We used cellular automata to describe two-phase flows and the interaction with the heater.General rule s for such cellular automata representing bubbles moving in stagnant liquid were used, with special attention to correct modeling of different mechanisms of heat transfer.The results of the model were compared to previous experiments and correlations finding good agreement.One of the most important findings is the confirmation of Kutateladze's idea about a close relation between the start of critical heat flux and a change in the flow's topology.This was analyzed using a control volume located in the upper surface of the heater.A strong decrease in the interfacial surface just before the CHF start was encountered.The automata describe quite well some characteristic parameters such as the shape of the local void fraction in the
77 FR 27144 - Airworthiness Directives; Agusta S.p.A. Helicopters
2012-05-09
... Agusta, S.p.A., Via Giovanni Agusta 520, 21017 Cascina Costa di Samarate (VA), Italy, ATTN: Giovanni... written comments, data, or views. We also invite comments relating to the economic, environmental, energy.... Discussion The European Aviation Safety Agency (EASA), which is the Technical Agent for Italy, a Member State...
Generic two-phase coexistence in the quadratic contact process
Energy Technology Data Exchange (ETDEWEB)
Guo, Xiaofang [Iowa State Univ., Ames, IA (United States)
2009-01-01
This thesis focuses on the demonstration of the existence of and analysis of phenomena related to the discontinuous non-equilibrium phase transition between an active (or reactive) state and a poisoned (or extinguished) state occurring in a stochastic lattice-gas realization of Schloegl’s second model for autocatalysis.
International Nuclear Information System (INIS)
Kalteh, Mohammad; Abbassi, Abbas; Saffar-Avval, Majid; Harting, Jens
2011-01-01
In this paper, laminar forced convection heat transfer of a copper-water nanofluid inside an isothermally heated microchannel is studied numerically. An Eulerian two-fluid model is considered to simulate the nanofluid flow inside the microchannel and the governing mass, momentum and energy equations for both phases are solved using the finite volume method. For the first time, the detailed study of the relative velocity and temperature of the phases are presented and it has been observed that the relative velocity and temperature between the phases is very small and negligible and the nanoparticle concentration distribution is uniform. However, the two-phase modeling results show higher heat transfer enhancement in comparison to the homogeneous single-phase model. Also, the heat transfer enhancement increases with increase in Reynolds number and nanoparticle volume concentration as well as with decrease in the nanoparticle diameter, while the pressure drop increases only slightly.
Physical, experimental and numerical study of fundamental mechanisms involved in two-phase flows
International Nuclear Information System (INIS)
Mathieu, Benoit
2003-01-01
In this work, small-scale phenomena in two-phase flows with phase change are studied. First, some fundamental phenomena related to the heat and mass transfer at small scale are recalled. A physical model is then built in order to describe moving contact lines with phase change. In the second part, a numerical simulation method is built, that is able to describe the growth of a single bubble on a heated wall. Compared to existing methods, major improvements are obtained with respect to the conservation of the mass, the spurious currents related to interfacial forces and the physical description of the contact lines. Finally, an experimental investigation of the singular heat and mass transfer at the contact line is carried out. Preliminary results obtained on a simplified configuration are presented. (author) [fr
Development of a EIT Measurement System for Image Reconstruction of Two-Phase Flow
International Nuclear Information System (INIS)
Hyun, Jong Kwan
2000-02-01
In the thermal-hydraulic system of a nuclear power plant as well as in many engineering areas, it is common to encounter the two-phase flow phenomenon. It is essential to understand the mechanism of the two-phase flow for the analysis and design of the relevant systems. To obtain the detail information on air bubbles moving in the two-phase flow many various experiments have been attempted. One of them is the EIT (Electrical Impedance Tomography) method, which is getting popular in recent days. The EIT is less expensive than other methods because the system is relatively simple and easy to construct compared to other methods. Nowadays it becomes one of the reliable and efficient methods for estimating the inner structure of the given object and has a wide spectrum of applications in various fields. Especially, even though the spatial resolution of EIT is inferior to those of X-ray and MRI, its temporal resolution is excellent. And its small size and easiness to operate provides itself with the portability. For these reasons, the EIT is properly used in the medical field as an complementary equipment and its use will be expanded in the future. The EIT technology in the area of nuclear energy is suitable for studying the two-phase flow which is necessary for designing the thermal hydraulic system because it can reduce the uncertainty of information. The EIT is also so fast to get the result data during the experiment that it is possible to apply it to the thermal hydraulic system in which the physical process is usually fast. Although the EIT is apply to the complicated structure of rod bundle, its basic principles are the same as of the simple geometrical structure. The adaptation of EIT to the two-phase flow of complicated geometrical structure gives the superior results to those of other methods and it is possible to use it in the reactor thermal hydraulic system as a monitoring equipment. However, even the application fields of the EIT are very wide and its
Joekar-Niasar, Vahid; Hassanizadeh, S. Majid
2012-01-01
The capillary pressure-saturation (P c-S w) relationship is one of the central constitutive relationships used in two-phase flow simulations. There are two major concerns regarding this relation. These concerns are partially studied in a
International Nuclear Information System (INIS)
Nakamura, Hideo
1996-05-01
The slug flow transitions and related phenomena for horizontal two-phase flows were studied for a better prediction of two-phase flows that typically appear during the reactor loss-of-coolant accidents (LOCAs). For better representation of the flow conditions experimentally, two large-scaled facility: TPTF for high-pressure steam/water two-phase flows and large duct test facility for air/water two-phase flows, were used. The visual observation of the flow using a video-probe was performed in the TPTF experiments for good understanding of the phenomena. The currently-used models and correlations based mostly on the small-scale low-pressure experiments were reviewed and improved based on these experimental results. The modified Taitel-Dukler model for prediction of transition into slug flow from wavy flow and the modified Steen-Wallis correlation for prediction of onset of liquid entrainment from the interfacial waves were obtained. An empirical correlation for the gas-liquid interfacial friction factor was obtained further for prediction of liquid levels at wavy flow. The region of slug flow regime that is generally under influences of the channel height and system pressure was predicted well when these models and correlations were applied together. (author). 90 refs
Immiscible two-phase fluid flows in deformable porous media
Lo, Wei-Cheng; Sposito, Garrison; Majer, Ernest
Macroscopic differential equations of mass and momentum balance for two immiscible fluids in a deformable porous medium are derived in an Eulerian framework using the continuum theory of mixtures. After inclusion of constitutive relationships, the resulting momentum balance equations feature terms characterizing the coupling among the fluid phases and the solid matrix caused by their relative accelerations. These terms, which imply a number of interesting phenomena, do not appear in current hydrologic models of subsurface multiphase flow. Our equations of momentum balance are shown to reduce to the Berryman-Thigpen-Chen model of bulk elastic wave propagation through unsaturated porous media after simplification (e.g., isothermal conditions, neglect of gravity, etc.) and under the assumption of constant volume fractions and material densities. When specialized to the case of a porous medium containing a single fluid and an elastic solid, our momentum balance equations reduce to the well-known Biot model of poroelasticity. We also show that mass balance alone is sufficient to derive the Biot model stress-strain relations, provided that a closure condition for porosity change suggested by de la Cruz and Spanos is invoked. Finally, a relation between elastic parameters and inertial coupling coefficients is derived that permits the partial differential equations of the Biot model to be decoupled into a telegraph equation and a wave equation whose respective dependent variables are two different linear combinations of the dilatations of the solid and the fluid.
Features of two-phase flow in a microchannel of 0.05×20 mm
Directory of Open Access Journals (Sweden)
Ronshin Fedor
2017-01-01
Full Text Available We have studied the two-phase flow in a microchannel with cross-section of 0.05×20 mm2. The following two-phase flow regimes have been registered: jet, bubble, stratified, annular, and churn ones. The main features of flow regimes in this channel such as formation of liquid droplets in all two-phase flows have been distinguished.
Two-Phase Annular Flow in Helical Coil Flow Channels in a Reduced Gravity Environment
Keshock, Edward G.; Lin, Chin S.
1996-01-01
A brief review of both single- and two-phase flow studies in curved and coiled flow geometries is first presented. Some of the complexities of two-phase liquid-vapor flow in curved and coiled geometries are discussed, and serve as an introduction to the advantages of observing such flows under a low-gravity environment. The studies proposed -- annular two-phase air-water flow in helical coil flow channels are described. Objectives of the studies are summarized.
Characteristics of low-mass-velocity vertical gas-liquid two-phase flow
International Nuclear Information System (INIS)
Adachi, Hiromichi; Abe, Yutaka; Kimura, Ko-ji
1995-01-01
In the present paper, characteristics of low mass velocity two-phase flow was analyzed based on a concept that pressure energy of two-phase flow is converted into acceleration work, gravitational work and frictional work, and the pressure energy consumption rate should be minimum at the stable two-phase flow condition. Experimental data for vertical upward air-water two-phase flow at atmospheric pressure was used to verify this concept and the turbulent model used in this method is optimized with the data. (author)
International Nuclear Information System (INIS)
Ahmad, M.
2007-09-01
Maldistribution of liquid-vapour two phase flows causes a significant decrease of the thermal and hydraulic performance of evaporators in thermodynamic vapour compression cycles. A first experimental installation was used to visualize the two phase flow evolution between the expansion valve and the evaporator inlet. A second experimental set-up simulating a compact heat exchanger has been designed to identify the functional and geometrical parameters creating the best distribution of the two phases in the different channels. An analysis and a comprehension of the relation between the geometrical and functional parameters with the flow pattern inside the header and the two phase distribution, has been established. A numerical simulations of a stratified flow and a stratified jet flow have been carried out using two CFD codes: FLUENT and NEPTUNE. In the case of a fragmented jet configuration, a global definition of the interfacial area concentration for a separated phases and dispersed phases flow has been established and a model calculating the fragmented mass fraction has been developed. (author)
Hendricks, R. C.; Braun, M. J.; Mullen, R. L.
1986-01-01
In systems where the design inlet and outlet pressure P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.
Cihan, Abdullah; Birkholzer, Jens; Trevisan, Luca; Gonzalez-Nicolas, Ana; Illangasekare, Tissa
2017-01-01
Incorporating hysteresis into models is important to accurately capture the two phase flow behavior when porous media systems undergo cycles of drainage and imbibition such as in the cases of injection and post-injection redistribution of CO2 during geological CO2 storage (GCS). In the traditional model of two-phase flow, existing constitutive models that parameterize the hysteresis associated with these processes are generally based on the empirical relationships. This manuscript presents development and testing of mathematical hysteretic capillary pressure—saturation—relative permeability models with the objective of more accurately representing the redistribution of the fluids after injection. The constitutive models are developed by relating macroscopic variables to basic physics of two-phase capillary displacements at pore-scale and void space distribution properties. The modeling approach with the developed constitutive models with and without hysteresis as input is tested against some intermediate-scale flow cell experiments to test the ability of the models to represent movement and capillary trapping of immiscible fluids under macroscopically homogeneous and heterogeneous conditions. The hysteretic two-phase flow model predicted the overall plume migration and distribution during and post injection reasonably well and represented the postinjection behavior of the plume more accurately than the nonhysteretic models. Based on the results in this study, neglecting hysteresis in the constitutive models of the traditional two-phase flow theory can seriously overpredict or underpredict the injected fluid distribution during post-injection under both homogeneous and heterogeneous conditions, depending on the selected value of the residual saturation in the nonhysteretic models.
Mathematical models for two-phase stratified pipe flow
Energy Technology Data Exchange (ETDEWEB)
Biberg, Dag
2005-06-01
The simultaneous transport of oil, gas and water in a single multiphase flow pipe line has for economical and practical reasons become common practice in the gas and oil fields operated by the oil industry. The optimal design and safe operation of these pipe lines require reliable estimates of liquid inventory, pressure drop and flow regime. Computer simulations of multiphase pipe flow have thus become an important design tool for field developments. Computer simulations yielding on-line monitoring and look ahead predictions are invaluable in day-to-day field management. Inaccurate predictions may have large consequences. The accuracy and reliability of multiphase pipe flow models are thus important issues. Simulating events in large pipelines or pipeline systems is relatively computer intensive. Pipe-lines carrying e.g. gas and liquefied gas (condensate) may cover distances of several hundred km in which transient phenomena may go on for months. The evaluation times associated with contemporary 3-D CFD models are thus not compatible with field applications. Multiphase flow lines are therefore normally simulated using specially dedicated 1-D models. The closure relations of multiphase pipe flow models are mainly based on lab data. The maximum pipe inner diameter, pressure and temperature in a multiphase pipe flow lab is limited to approximately 0.3 m, 90 bar and 60{sup o}C respectively. The corresponding field values are, however, much higher i.e.: 1 m, 1000 bar and 200{sup o}C respectively. Lab data does thus not cover the actual field conditions. Field predictions are consequently frequently based on model extrapolation. Applying field data or establishing more advanced labs will not solve this problem. It is in fact not practically possible to acquire sufficient data to cover all aspects of multiphase pipe flow. The parameter range involved is simply too large. Liquid levels and pressure drop in three-phase flow are e.g. determined by 13 dimensionless parameters
Radiogauging to investigate two phase flow. Graduation report
International Nuclear Information System (INIS)
Corten, G.P.
1992-01-01
New measuring methods are developed and are tested with the small reactor simulator MIDAS (Mini Dodewaard ASsembly). The purpose of this work is to be able to measure accurately as many different properties of the flow as possible in the coming bigger simulator SIDAS (Simulated Dodewaard ASsembly). In SIDAS the flow around a fuel assembly of the Dutch Dodewaard reactor will be simulated. An extensive evaluation of the gamma detection system showed that the detection system could be simplified strongly. The simplified system is used to measure the radial and axial distribution of the void fraction in the core of MIDAS for three different operating conditions. Two new measuring methods have been developed and tested. A method to estimate the probability density of the void fraction in time. Due to the nonlinear relation between transmission and void fraction the determined average value of the void fraction in general will contain a systematic error. In this investigation it is shown that this error can be maximally 7.5% in MIDAS and maximally 25% in SIDAS. Therefore a new measuring method has been developed in which the true probability density of the void fraction in time is approximated by two different values of the void fraction, each with a certain probability. With this new method firstly the average void fraction can be determined much more precisely and secondly it often can be used to determine the flow pattern. (orig./WL)
Horizontal two phase flow pattern identification by neural networks
International Nuclear Information System (INIS)
Crivelaro, Kelen Cristina Oliveira; Seleghim Junior, Paulo; Hervieu, Eric
1999-01-01
A multiphase fluid can flow according to several flow regimes. The problem associated with multiphase systems are basically related to the behavior of macroscopic parameters, such as pressure drop, thermal exchanges and so on, and their strong correlation to the flow regime. From the industrial applications point of view, the safety and longevity of equipment and systems can only be assured when they work according to the flow regimes for which they were designed to. This implies in the need to diagnose flow regimes in real time. The automatic diagnosis of flow regimes represents an objective of extreme importance, mainly for applications on nuclear and petrochemical industries. In this work, a neural network is used in association to a probe of direct visualization for the identification of a gas-liquid flow horizontal regimes, developed in an experimental circuit. More specifically, the signals produced by the probe are used to compose a qualitative image of the flow, which is promptly sent to the network for the recognition of the regimes. Results are presented for different transitions among the flow regimes, which demonstrate the extremely satisfactory performance of the diagnosis system. (author)
Radiogauging to investigate two phase flow. Graduation report
Energy Technology Data Exchange (ETDEWEB)
Corten, G P
1992-11-12
New measuring methods are developed and are tested with the small reactor simulator MIDAS (Mini Dodewaard ASsembly). The purpose of this work is to be able to measure accurately as many different properties of the flow as possible in the coming bigger simulator SIDAS (Simulated Dodewaard ASsembly). In SIDAS the flow around a fuel assembly of the Dutch Dodewaard reactor will be simulated. An extensive evaluation of the gamma detection system showed that the detection system could be simplified strongly. The simplified system is used to measure the radial and axial distribution of the void fraction in the core of MIDAS for three different operating conditions. Two new measuring methods have been developed and tested. A method to estimate the probability density of the void fraction in time. Due to the nonlinear relation between transmission and void fraction the determined average value of the void fraction in general will contain a systematic error. In this investigation it is shown that this error can be maximally 7.5% in MIDAS and maximally 25% in SIDAS. Therefore a new measuring method has been developed in which the true probability density of the void fraction in time is approximated by two different values of the void fraction, each with a certain probability. With this new method firstly the average void fraction can be determined much more precisely and secondly it often can be used to determine the flow pattern. (orig./WL).
Deformation of two-phase aggregates using standard numerical methods
Duretz, Thibault; Yamato, Philippe; Schmalholz, Stefan M.
2013-04-01
Geodynamic problems often involve the large deformation of material encompassing material boundaries. In geophysical fluids, such boundaries often coincide with a discontinuity in the viscosity (or effective viscosity) field and subsequently in the pressure field. Here, we employ popular implementations of the finite difference and finite element methods for solving viscous flow problems. On one hand, we implemented finite difference method coupled with a Lagrangian marker-in-cell technique to represent the deforming fluid. Thanks to it Eulerian nature, this method has a limited geometric flexibility but is characterized by a light and stable discretization. On the other hand, we employ the Lagrangian finite element method which offers full geometric flexibility at the cost of relatively heavier discretization. In order to test the accuracy of the finite difference scheme, we ran large strain simple shear deformation of aggregates containing either weak of strong circular inclusion (1e6 viscosity ratio). The results, obtained for different grid resolutions, are compared to Lagrangian finite element results which are considered as reference solution. The comparison is then used to establish up to which strain can finite difference simulations be run given the nature of the inclusions (dimensions, viscosity) and the resolution of the Eulerian mesh.
Acceleration of two-phase flow by boiling, 1
International Nuclear Information System (INIS)
Hara, Toshitsugu; Uchida, Motokazu; Mitani, Akio; Mori, Yasuo; Hijikata, Kunio.
1975-01-01
This paper reports on the experimental results concerning the acceleration mechanism of the liquid used for liquid metal magnetohydrodynamic power generation. The experiment simulated two-component flow by injecting low boiling point liquid (R113) which is not soluble in main high temperature flow (hot water). From the boiling of this two component flow, the relations among the acceleration performance of the liquid, the number and frequency of bubbles generated from liquid drops, and the growth velocity of the bubbles have been investigated. All the injected liquid drops did not necessarily boil even if they were heated above the saturation temperature. The probability of boiling of the liquid drops becomes larger as the temperature difference between two liquids becomes larger. The bubble generation frequency distributed around the mean elapsed time of the liquid drops. The larger temperature difference between two liquids presents sharper distribution. The radius of bubbles increased proportionally to the two-thirds power of the elapsed time and also to two-thirds power of the temperature difference. The liquid acceleration performance by bubbles increased as the bubble generation frequency distribution becomes sharpe. (Tai, I.)
Design aspects of gamma densitometers for void fraction measurements in small scale two-phase flows
International Nuclear Information System (INIS)
Chan, A.M.C.; Banerjee, S.
1981-01-01
Design procedure for a single-beam gamma densitometer operated in the count mode is described. The design is simple, compact and is particularly suited for small scale two-phase flow experiments with thin-metal walled or non-metallic test sections. The choice of gamma sources, scintillators and signal processing systems is discussed. The procedure has been applied by the authors in the design of densitometers for two transient experiments: refilling and rewetting experiments and flow boiling experiments. Good average void measurements were obtained for relatively fast transients. It has also been shown that some useful flow parameters other than void fractions can be obtained if two or more densitometers are used, eg, the average rewetting and entrained liquid velocities in the refilling and rewetting experiments, and the average void velocity in the flow boiling experiments. (orig.)
Condensation shocks in high momentum two-phase flows in condensing injectors
International Nuclear Information System (INIS)
Anand, G.; Christensen, R.N.
1993-01-01
This study presents a phenomenological and mathematical model of condensation shocks in high momentum two-phase flows in condensing injectors. The characteristics of the shock were related to the mode of vapor bubble collapse. Using cavitation terminology, the bubble collapse can be classified as inertially controlled or thermally controlled. Inertial bubble collapse occurs rapidly whereas, a thermally controlled collapse results in a significantly longer collapse time. The interdependence between the bubble collapse mode and the momentum and pressure of the flow, was analyzed in this study. For low-temperature-high-velocity flows a steep pressure rise with complete condensation was obtained. For a high-temperature-low velocity flow with noncondensables, low pressure recovery with incomplete condensation was observed. These trends are in agreement with previous experimental observations
Transient behavior of natural circulation for boiling two-phase flow, 2
International Nuclear Information System (INIS)
Aritomi, Masanori; Chiang, Jing-Hsien; Mori, Michitugu.
1991-01-01
In this set of experiments, natural circulation in boiling two-phase flow has been investigated for power transients, simulating the start-up process in a natural circulation BWR. This was done in order to understand the underlying mechanism of thermo-hydraulic instability which may appear during a start-up. In this paper, geysering is dealt with especially and the driving mechanism is clarified by investigating the stability related to effects of inlet velocity, subcooling, temperature in an outlet plenum and non-heated length between heated section and the outlet plenum. Furthermore, by considering these results and the operational experience in the Dodewaard reactor, recommendations on how the thermo-hydraulic instabilities can be prevented from occurring are proposed concerning a reactor configuration and start-up procedure for natural circulation BWRs. (author)
Heat transfer characteristics of the two-phase closed thermosyphon (wickless heat pipe)
International Nuclear Information System (INIS)
Andros, F.E.; Florschuetz, L.W.
1982-01-01
Steady-state heat transfer characteristics and heat transfer limits (dry-out) for a vertical stainless steel tubular two-phase closed thermosyphon with Freon-113 working fluid are reported as a function of certain geometric parameters and liquid fill quantity. Condenser section heat transfer characteristics agreed reasonably well with existing laminar film condensation correlations and were found to be independent of the evaporator section, except for larger liquid fills. Evaporator characteristics were quite complex and appeared, under some conditions, to be coupled to condenser characteristics through effects of system pressure and/or surface wave as present on the descending condensate film. A laminar thin film evaporation model was found to give reasonable agreement with local evaporator temperature measurements in those regions of the evaporator where a continuous film apparently persisted. The measured heat transfer characteristics are interpreted relative to an earlier investigation by the authors in which flow characteristics in a similar device were visually and photographically observed. 10 references
Local two-phase modeling of the water-steam flows occurring in steam generators
International Nuclear Information System (INIS)
Denefle, Romain
2013-01-01
The present study is related to the need of modeling the two-phase flows occurring in a steam generator (liquid at inlet and vapour at outlet). The choice is made to investigate a hybrid modeling of the flow, considering the gas phase as two separated fields, each one being modeled with different closure laws. In so doing, the small and spherical bubbles are modeled through a dispersed approach within the two-fluid model, and the distorted bubbles are simulated with an interface locating method. The main outcome is about the implementation, the verification and the validation of the model dedicated to the large and distorted bubbles, as well as the coupling of the two approaches for the gas, allowing the presentation of demonstration calculations using the so-called hybrid approach. (author)
Contribution to the dynamical study of gas-liquid two-phase flows
International Nuclear Information System (INIS)
Lewi, Joseph.
1975-01-01
A single system of equations valid for two-phase flows at any time and anywhere was searched for. The mathematical theory of distributions was used. The results obtained was applied to the turbulent flow of an emulsion in a canal of constant section. It is shown that the use of distribution conservation equations makes it possible to determine the shapes of the mean velocity profiles, to obtain a relation between the friction coefficient and a Reynolds number introduced in a logical way, and to express the total pressure drop in the canal. Three experiments were carried out to compare the performance of various optical methods used for displaying bubble liquid-gas flows, and, within the limits of these methods, to study the interaction between the bubbles and the sensible end of variable impedance probe, and the granulometry of the emulsion in the vicinity of the probe [fr
Nonlinear Analysis of Two-phase Circumferential Motion in the Ablation Circumstance
Xiao-liang, Xu; Hai-ming, Huang; Zi-mao, Zhang
2010-05-01
In aerospace craft reentry and solid rocket propellant nozzle, thermal chemistry ablation is a complex process coupling with convection, heat transfer, mass transfer and chemical reaction. Based on discrete vortex method (DVM), thermal chemical ablation model and particle kinetic model, a computational module dealing with the two-phase circumferential motion in ablation circumstance is designed, the ablation velocity and circumferential field can be thus calculated. The calculated nonlinear time series are analyzed in chaotic identification method: relative chaotic characters such as correlation dimension and the maximum Lyapunov exponent are calculated, fractal dimension of vortex bulbs and particles distributions are also obtained, thus the nonlinear ablation process can be judged as a spatiotemporal chaotic process.
Numerical Predictions of Bubbly Two-Phase Flows with OpenFOAM
Directory of Open Access Journals (Sweden)
Edouard Michta
2012-12-01
Full Text Available A new model for simulation of bubbly two-phase flows has been developed and implemented into an open-source Computational Fluid Dynamics (CFD code OpenFOAM. The model employs the two-fluid framework with closure relationships for the interfacial momentum transfer. The bubble size is calculated based on the solution of the transport equation of the interfacial area concentration. The predictions are validated against selected data obtained in the DEDALE experiment and containing the measured void fraction, the phasic velocities and the interfacial area concentration. In general, good agreement between calculated and measured data is demonstrated; however, the relative phasic velocity is systematically over-predicted. The levels of void fraction and the observed wall void peaking are well captured in the calculations.
Sensitivity studies on the multi-sensor conductivity probe measurement technique for two-phase flows
Energy Technology Data Exchange (ETDEWEB)
Worosz, Ted [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 230 Reber Building, University Park, PA 16802 (United States); Bernard, Matt [The United States Nuclear Regulatory Commission, 11545 Rockville Pike, Rockville, MD 20852 (United States); Kong, Ran; Toptan, Aysenur [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 230 Reber Building, University Park, PA 16802 (United States); Kim, Seungjin, E-mail: skim@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, 230 Reber Building, University Park, PA 16802 (United States); Hoxie, Chris [The United States Nuclear Regulatory Commission, 11545 Rockville Pike, Rockville, MD 20852 (United States)
2016-12-15
Highlights: • Revised conductivity probe circuit to eliminate signal “ghosting” among sensors. • Higher sampling frequencies suggested for bubble number frequency and a{sub i} measurements. • Two-phase parameter sensitivity to measurement duration and bubble number investigated. • Sensors parallel to pipe wall recommended for symmetric bubble velocity measurements. • Sensor separation distance ratio (s/d) greater than four minimizes bubble velocity error. - Abstract: The objective of this study is to advance the local multi-sensor conductivity probe measurement technique through systematic investigation into several practical aspects of a conductivity probe measurement system. Firstly, signal “ghosting” among probe sensors is found to cause artificially high bubble velocity measurements and low interfacial area concentration (a{sub i}) measurements that depend on sampling frequency and sensor impedance. A revised electrical circuit is suggested to eliminate this artificial variability. Secondly, the sensitivity of the probe measurements to sampling frequency is investigated in 13 two-phase flow conditions with superficial liquid and gas velocities ranging from 1.00–5.00 m/s and 0.17–2.0 m/s, respectively. With increasing gas flow rate, higher sampling frequencies, greater than 100 kHz in some cases, are required to adequately capture the bubble number frequency and a{sub i} measurements. This trend is due to the increase in gas velocity and the transition to the slug flow regime. Thirdly, the sensitivity of the probe measurements to the measurement duration as well as the sample number is investigated for the same flow conditions. Measurements of both group-I (spherical/distorted) and group-II (cap/slug/churn-turbulent) bubbles are found to be relatively insensitive to both the measurement duration and the number of bubbles, as long as the measurements are made for a duration long enough to capture a collection of samples characteristic to a
A two-phase sampling design for increasing detections of rare species in occupancy surveys
Pacifici, Krishna; Dorazio, Robert M.; Dorazio, Michael J.
2012-01-01
1. Occupancy estimation is a commonly used tool in ecological studies owing to the ease at which data can be collected and the large spatial extent that can be covered. One major obstacle to using an occupancy-based approach is the complications associated with designing and implementing an efficient survey. These logistical challenges become magnified when working with rare species when effort can be wasted in areas with none or very few individuals. 2. Here, we develop a two-phase sampling approach that mitigates these problems by using a design that places more effort in areas with higher predicted probability of occurrence. We compare our new sampling design to traditional single-season occupancy estimation under a range of conditions and population characteristics. We develop an intuitive measure of predictive error to compare the two approaches and use simulations to assess the relative accuracy of each approach. 3. Our two-phase approach exhibited lower predictive error rates compared to the traditional single-season approach in highly spatially correlated environments. The difference was greatest when detection probability was high (0·75) regardless of the habitat or sample size. When the true occupancy rate was below 0·4 (0·05-0·4), we found that allocating 25% of the sample to the first phase resulted in the lowest error rates. 4. In the majority of scenarios, the two-phase approach showed lower error rates compared to the traditional single-season approach suggesting our new approach is fairly robust to a broad range of conditions and design factors and merits use under a wide variety of settings. 5. Synthesis and applications. Conservation and management of rare species are a challenging task facing natural resource managers. It is critical for studies involving rare species to efficiently allocate effort and resources as they are usually of a finite nature. We believe our approach provides a framework for optimal allocation of effort while
The difficult challenge of a two-phase CFD modelling for all flow regimes
International Nuclear Information System (INIS)
Bestion, D.
2014-01-01
Highlights: • The theoretical difficulties for modelling all flow regimes at CFD scale are identified. • The choice of the number of fields and of the time and space averaging or filtering are discussed and clarified. • Closure issues related to an all flow regime CFD model are listed and the main difficulties are identified. - Abstract: System thermalhydraulic codes model all two-phase flow regimes but they are limited to a macroscopic description. Two-phase CFD tools predict two-phase flow with a much finer space resolution but the current modelling capabilities are limited to dispersed bubbly or droplet flow and separate-phase flow. Much less experience exists on more complex flow regimes which combine the existence of dispersed fields with the presence of large interfaces such as a free surface or a film surface. A list of possible reactor issues which might benefit from an “all flow regime CFD model” is given. The first difficulty is to identify the various types of local flow configuration. It is shown that a 4-field model has much better capabilities than a two-fluid approach to identify most complex regimes. Then the choice between time averaging, space averaging, or even ensemble averaging is discussed. It is shown that only the RANS-2-fluid and a space-filtered 4-field model may be reasonably envisaged. The latter has the capabilities to identify all types of interfaces and should be privileged if a good accuracy is expected or if time fluctuations in intermittent flow have to be predicted while the former may be used when a high accuracy is not necessary and if time fluctuations in intermittent flow are not of interest. Finally the closure issue is presented including wall transfers, interfacial transfers, mass transfers between dispersed and continuous fields, and turbulent transfers. An important effort is required to model all interactions between sub-filter phenomena and the transfers from the sub-filter domain to the simulated domain. The
Syntrophic acetate oxidation in two-phase (acid-methane) anaerobic digesters.
Shimada, T; Morgenroth, E; Tandukar, M; Pavlostathis, S G; Smith, A; Raskin, L; Kilian, R E
2011-01-01
The microbial processes involved in two-phase anaerobic digestion were investigated by operating a laboratory-scale acid-phase (AP) reactor and analyzing two full-scale, two-phase anaerobic digesters operated under mesophilic (35 °C) conditions. The digesters received a blend of primary sludge and waste activated sludge (WAS). Methane levels of 20% in the laboratory-scale reactor indicated the presence of methanogenic activity in the AP. A phylogenetic analysis of an archaeal 16S rRNA gene clone library of one of the full-scale AP digesters showed that 82% and 5% of the clones were affiliated with the orders Methanobacteriales and Methanosarcinales, respectively. These results indicate that substantial levels of aceticlastic methanogens (order Methanosarcinales) were not maintained at the low solids retention times and acidic conditions (pH 5.2-5.5) of the AP, and that methanogenesis was carried out by hydrogen-utilizing methanogens of the order Methanobacteriales. Approximately 43, 31, and 9% of the archaeal clones from the methanogenic phase (MP) digester were affiliated with the orders Methanosarcinales, Methanomicrobiales, and Methanobacteriales, respectively. A phylogenetic analysis of a bacterial 16S rRNA gene clone library suggested the presence of acetate-oxidizing bacteria (close relatives of Thermacetogenium phaeum, 'Syntrophaceticus schinkii,' and Clostridium ultunense). The high abundance of hydrogen consuming methanogens and the presence of known acetate-oxidizing bacteria suggest that acetate utilization by acetate oxidizing bacteria in syntrophic interaction with hydrogen-utilizing methanogens was an important pathway in the second-stage of the two-phase digestion, which was operated at high ammonium-N concentrations (1.0 and 1.4 g/L). A modified version of the IWA Anaerobic Digestion Model No. 1 (ADM1) with extensions for syntrophic acetate oxidation and weak-acid inhibition adequately described the dynamic profiles of volatile acid production
2018-01-01
Set IV is a new addition to the previous Sets I, II and III. It contains 23 invited chapters from international specialists on the topics of numerical modeling of pulsating heat pipes and of slug flows with evaporation; lattice Boltzmann modeling of pool boiling; fundamentals of boiling in microchannels and microfin tubes, CO2 and nanofluids; testing and modeling of micro-two-phase cooling systems for electronics; and various special topics (flow separation in microfluidics, two-phase sensors, wetting of anisotropic surfaces, ultra-compact heat exchangers, etc.). The invited authors are leading university researchers and well-known engineers from leading corporate research laboratories (ABB, IBM, Nokia Bell Labs). Numerous "must read" chapters are also included here for the two-phase community. Set IV constitutes a "must have" engineering and research reference together with previous Sets I, II and III for thermal engineering researchers and practitioners.
Validation of Friction Models in MARS-MultiD Module with Two-Phase Cross Flow Experiment
International Nuclear Information System (INIS)
Choi, Chi-Jin; Yang, Jin-Hwa; Cho, Hyoung-Kyu; Park, Goon-Cher; Euh, Dong-Jin
2015-01-01
In the downcomer of Advanced Power Reactor 1400 (APR1400) which has direct vessel injection (DVI) lines as an emergency core cooling system, multidimensional two-phase flow may occur due to the Loss-of-Coolant-Accident (LOCA). The accurate prediction about that is high relevance to evaluation of the integrity of the reactor core. For this reason, Yang performed an experiment that was to investigate the two-dimensional film flow which simulated the two-phase cross flow in the upper downcomer, and obtained the local liquid film velocity and thickness data. From these data, it could be possible to validate the multidimensional modules of system analysis codes. In this study, MARS-MultiD was used to simulate the Yang's experiment, and obtained the local variables. Then, the friction models used in MARS-MultiD were validated by comparing the two-phase flow experimental results with the calculated local variables. In this study, the two-phase cross flow experiment was modeled by the MARS-MultiD. Compared with the experimental results, the calculated results by the code properly presented mass conservation which could be known from the relation between the liquid film velocity and thickness at the same flow rate. The magnitude and direction of the liquid film, however, did not follow well with experimental results. According to the results of Case-2, wall friction should be increased, and interfacial friction should be decreased in MARS-MultiD. These results show that it is needed to modify the friction models in the MARS-MultiD to simulate the two-phase cross flow
International Nuclear Information System (INIS)
Huang, Si; Su, Xianghui; Guo, Jing; Yue, Le
2014-01-01
Highlights: • The transient gas–liquid two-phase flow fields in the self-priming centrifugal pump are simulated. • The self-priming time and performance are estimated. • The air void fraction and two phase distribution are obtained.· The hole on the volute plays a significant role for gas exhausting. • The frequency of the impulsive pressure basically conforms to that of the air exhausted out of the pump. - Abstract: Self-priming pumps start up without pre-irrigation, and then work as common pumps when air in the pump is exhausted. The transient gas–liquid flow at the start-up stage inside a self-priming pump is an interesting process which greatly influences performance of the pump. In this paper, a conventional vertical self-priming centrifugal pump was selected as the object. Using unsteady numerical simulation, the authors investigated the transient gas–liquid two-phase flow in the self-priming centrifugal pump during the self-priming process. The main innovation in the simulation was that a section of the suction pipe filled with air was set as the initial condition, which conformed to the actual self-priming conditions. The gas–liquid two-phase distribution, the pressure and velocity in relation to time were computed and analyzed. Flow rates of both phases with time at the pump inlet and outlet were obtained based on the simulation, which could be used to estimate the self-priming time and other performance parameters. Finally, the numerical method and results for gas–liquid two-phase flow in the self-priming pump was partly validated by the pump performance test
International Nuclear Information System (INIS)
Zhou, Xinquan; Doup, Benjamin; Sun, Xiaodong
2013-01-01
Liquid-phase turbulence measurements were performed in an air–water two-phase flow loop with a circular test section of 50 mm inner diameter using a particle image velocimetry (PIV) system. An optical phase separation method-–planar laser-induced fluorescence (PLIF) technique—which uses fluorescent particles and an optical filtration technique, was employed to separate the signals of the fluorescent seeding particles from those due to bubbles and other noises. An image pre-processing scheme was applied to the raw PIV images to remove the noise residuals that are not removed by the PLIF technique. In addition, four-sensor conductivity probes were adopted to measure the radial distribution of the void fraction. Two benchmark tests were performed: the first was a comparison of the PIV measurement results with those of similar flow conditions using thermal anemometry from previous studies; the second quantitatively compared the superficial liquid velocities calculated from the local liquid velocity and void fraction measurements with the global liquid flow rate measurements. The differences of the superficial liquid velocity obtained from the two measurements were bounded within ±7% for single-phase flows and two-phase bubbly flows with the area-average void fraction up to 18%. Furthermore, a preliminary uncertainty analysis was conducted to investigate the accuracy of the two-phase PIV measurements. The systematic uncertainties due to the circular pipe curvature effects, bubble surface reflection effects and other potential uncertainty sources of the PIV measurements were discussed. The purpose of this work is to facilitate the development of a measurement technique (PIV-PLIF) combined with image pre-processing for the liquid-phase turbulence in gas–liquid two-phase flows of relatively high void fractions. The high-resolution data set can be used to more thoroughly understand two-phase flow behavior, develop liquid-phase turbulence models, and assess high
Chiaramonte, Francis; Motil, Brian; McQuillen, John
2014-01-01
The Two-phase Heat Transfer International Topical Team consists of researchers and members from various space agencies including ESA, JAXA, CSA, and RSA. This presentation included descriptions various fluid experiments either being conducted by or planned by NASA for the International Space Station in the areas of two-phase flow, flow boiling, capillary flow, and crygenic fluid storage.
Analytic approximations for the elastic moduli of two-phase materials
DEFF Research Database (Denmark)
Zhang, Z. J.; Zhu, Y. K.; Zhang, P.
2017-01-01
Based on the models of series and parallel connections of the two phases in a composite, analytic approximations are derived for the elastic constants (Young's modulus, shear modulus, and Poisson's ratio) of elastically isotropic two-phase composites containing second phases of various volume...
Strong enhancement of streaming current power by application of two phase flow
Xie, Yanbo; Sherwood, John D.; Shui, Lingling; van den Berg, Albert; Eijkel, Jan C.T.
2011-01-01
We show that the performance of a streaming-potential based microfluidic energy conversion system can be strongly en-hanced by the use of two phase flow. In single-phase systems, the internal conduction current induced by the streaming poten-tial limits the output power, while in a two-phase system
Numerical simulation for gas-liquid two-phase flow in pipe networks
International Nuclear Information System (INIS)
Li Xiaoyan; Kuang Bo; Zhou Guoliang; Xu Jijun
1998-01-01
The complex pipe network characters can not directly presented in single phase flow, gas-liquid two phase flow pressure drop and void rate change model. Apply fluid network theory and computer numerical simulation technology to phase flow pipe networks carried out simulate and compute. Simulate result shows that flow resistance distribution is non-linear in two phase pipe network
Mass flow rate measurements in two-phase mixtrues with stagnation probes
International Nuclear Information System (INIS)
Fincke, J.R.; Deason, V.A.
1979-01-01
Applications of stagnation probes to the measurement of mass flow rate in two-phase flows are discussed. Descriptions of several stagnation devices, which have been evaluated at the Idaho National Engineering Laboratory, are presented along with modeling techniques and two-phase flow data
Effects of Particles Collision on Separating Gas–Particle Two-Phase Turbulent Flows
Sihao, L. V.; Yang, Weihua; Li, Xiangli; Li, Guohui
2013-01-01
A second-order moment two-phase turbulence model incorporating a particle temperature model based on the kinetic theory of granular flow is applied to investigate the effects of particles collision on separating gas–particle two-phase turbulent
Symmetrical components and power analysis for a two-phase microgrid system
DEFF Research Database (Denmark)
Alibeik, M.; Santos Jr., E. C. dos; Blaabjerg, Frede
2014-01-01
This paper presents a mathematical model for the symmetrical components and power analysis of a new microgrid system consisting of three wires and two voltages in quadrature, which is designated as a two-phase microgrid. The two-phase microgrid presents the following advantages: 1) constant power...
Modeling and Performance of a Self-Excited Two-Phase Reluctance ...
African Journals Online (AJOL)
A self-excited two-phase reluctance generator (SETPRG) with balanced stator winding is presented. A unique balanced two-phase stator winding was designed with emphasis on obtaining a stator MMF waveform with minimum space harmonics. Then a mathematical model by which the dynamic behavior of the generator ...
Design and development of drag-disc flowmeter for measurement of transient two-phase flow
International Nuclear Information System (INIS)
Sreenivas Rao, G.; Kukreja, V.; Dolas, P.K.; Venkat Raj, V.
1990-01-01
Experiments have been carried out to test the suitability of drag-disc flowmeter for measuring two-phase flow. Calibration tests carried out under single-phase and two-phase flow conditions have confirmed the suitability of the drag-disc flowmeter. The experimental work and the results obtained are presented and discussed in the paper. (author). 3 refs., 6 figs
Numerical simulation and experimental verification of a flat two-phase thermosyphon
International Nuclear Information System (INIS)
Zhang Ming; Liu Zhongliang; Ma Guoyuan; Cheng Shuiyuan
2009-01-01
The flat two-phase thermosyphon is placed between the heat source and the heat sink, which can achieve the uniform heat flux distribution and improve the performance of heat sink. In this paper, a two-dimensional heat and mass transfer model for a disk-shaped flat two-phase thermosyphon is developed. By solving the equations of continuity, momentum and energy numerically, the vapor velocity and temperature distributions of the flat two-phase thermosyphon are obtained. An analysis is also carried out on the ability of flat two-phase thermosyphon to spread heat and remove hot spots. In order to observe boiling and condensation phenomena, a transparent flat two-phase thermosyphon is manufactured and studied experimentally. The experimental results are compared with numerical results, which verify the physical and mathematical model of the flat two-phase thermosyphon. In order to study the main factors affecting the axial thermal resistance of two-phase thermosyphon, the temperatures inside the flat two-phase thermosyphon are measured and analyzed
The potential of cloud point system as a novel two-phase partitioning system for biotransformation.
Wang, Zhilong
2007-05-01
Although the extractive biotransformation in two-phase partitioning systems have been studied extensively, such as the water-organic solvent two-phase system, the aqueous two-phase system, the reverse micelle system, and the room temperature ionic liquid, etc., this has not yet resulted in a widespread industrial application. Based on the discussion of the main obstacles, an exploitation of a cloud point system, which has already been applied in a separation field known as a cloud point extraction, as a novel two-phase partitioning system for biotransformation, is reviewed by analysis of some topical examples. At the end of the review, the process control and downstream processing in the application of the novel two-phase partitioning system for biotransformation are also briefly discussed.
Operation of a forced two phase cooling system on a large superconducting magnet
International Nuclear Information System (INIS)
Green, M.A.; Burns, W.A.; Eberhard, P.H.; Gibson, G.H.; Pripstein, M.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Van Slyke, H.
1980-05-01
This paper describes the operation of a forced two phase cooling system on a two meter diameter superconducting solenoid. The magnet is a thin high current density superconducting solenoid which is cooled by forced two phase helium in tubes around the coil. The magnet, which is 2.18 meters in diameter and 3.4 meters long, has a cold mass of 1700 kg. The two phase cooling system contains less than 300 liters of liquid helium, most of which is contained in a control dewar. This paper describes the operating characteristics of the LBL two phase forced cooling system during cooldown and warm up. The paper presents experimental data on operations of the magnet using either a helium pump or the refrigerator compressor to circulate two phase helium through the superconducting coil cooling tubes
Two phase flow measurement and visualization using Wire Mesh Sensors (WMS)
International Nuclear Information System (INIS)
Rajalakshmi, R.; Robin, Roshini; Rama Rao, A.
2016-01-01
Two phase flow behavior studies have gained importance in nuclear power plants to enhance fuel performance and safety. In this paper, taking into consideration low cost, high space-time resolution and instantaneous mapping, electrical sensors such as wire mesh sensors (WMS) is proposed for measurement of void distribution and its visualization. The sensor works on the conductivity principle and by measuring the variations in conductivity values of the two phases, the flow distributions can be identified. This paper describes the conceptual design of the WMS for two phase void measurements, Mathematical modeling of the sensor for data evaluation, modeling of the sensor geometry and FEM simulation studies for optimizing sensor geometry and excitation parameters, CFD two phase flows simulations, development of suitable algorithm and programming for two phase visualization and void distribution studies, prototype sensor fabrication and testing
Phenomenological studies of two-phase flow processes for nuclear waste isolation
International Nuclear Information System (INIS)
Pruess, K.; Finsterle, S.; Persoff, P.; Oldenburg, C.
1994-01-01
The US civilian radioactive waste management program is unique in its focus on a site in the unsaturated zone, at Yucca Mountain, Nevada. Two-phase flow phenomena can also play an important role in repositories beneath the water table where gas is generated by corrosion, hydrolysis, and biological degradation of the waste packages. An integrated program has been initiated to enhance our understanding of two-phase flow behavior in fractured rock masses. The studies include two-phase (gas-liquid) flow experiments in laboratory specimens of natural rock fractures, analysis and modeling of heterogeneity and instability effects in two-phase flow, and design and interpretation of field experiments by means of numerical simulation. We present results that identify important aspects of two-phase flow behavior on different space and time scales which are relevant to nuclear waste disposal in both unsaturated and saturated formations
International Nuclear Information System (INIS)
Xing, Dianchuan; Yan, Changqi; Sun, Licheng; Jin, Guangyuan; Tan, Sichao
2013-01-01
Highlights: ► Two-phase flow frictional resistance in narrow duct in rolling is studied. ► Frictional resistance behaviors in rolling are divided into three regions. ► Transient frictional pressure drop fluctuates synchronously with rolling motion. ► Conventional correlations are evaluated against experimental data in rolling motion. ► New correlation for transient frictional resistance in rolling motion is developed. - Abstract: Frictional resistance of air-water two-phase flow in a narrow rectangular duct subjected to rolling motion was investigated experimentally. Time-averaged and transient frictional pressure drop under rolling condition were compared with conventional correlation in laminar flow region (Re l l ⩽ 1400) and turbulent flow region (Re l > 1400) respectively. The result shows that, despite no influence on time-averaged frictional resistance, rolling motion does induce periodical fluctuation of the pressure drop in laminar and transition flow regions. Transient frictional pressure drop fluctuates synchronously with the rolling motion both in laminar and in transition flow region, while it is nearly invariable in turbulent flow region. The fluctuation amplitude of the Relative frictional pressure gradient decreases with the increasing of the superficial velocities. Lee and Lee (2002) correlation and Chisholm (1967) correlation could satisfactorily predict time-averaged frictional pressure drop under rolling conditions, whereas poorly predict the transient frictional pressure drop when it fluctuates periodically. A new correlation with better accuracy for predicting the transient frictional pressure drop in rolling motion is achieved by modifying the Chisholm (1967) correlation on the basis of analyzing the present experimental results with a great number of data points
A green deep eutectic solvent-based aqueous two-phase system for protein extracting
International Nuclear Information System (INIS)
Xu, Kaijia; Wang, Yuzhi; Huang, Yanhua; Li, Na; Wen, Qian
2015-01-01
Highlights: • A strategy for the protein purification with a deep eutectic solvent(DES)-based aqueous two-phase system. • Choline chloride-glycerin DES was selected as the extraction solvent. • Bovine serum albumin and trypsin were used as the analytes. • Aggregation phenomenon was detected in the mechanism research. - Abstract: As a new type of green solvent, deep eutectic solvent (DES) has been applied for the extraction of proteins with an aqueous two-phase system (ATPS) in this work. Four kinds of choline chloride (ChCl)-based DESs were synthesized to extract bovine serum albumin (BSA), and ChCl-glycerol was selected as the suitable extraction solvent. Single factor experiments have been done to investigate the effects of the extraction process, including the amount of DES, the concentration of salt, the mass of protein, the shaking time, the temperature and PH value. Experimental results show 98.16% of the BSA could be extracted into the DES-rich phase in a single-step extraction under the optimized conditions. A high extraction efficiency of 94.36% was achieved, while the conditions were applied to the extraction of trypsin (Try). Precision, repeatability and stability experiments were studied and the relative standard deviations (RSD) of the extraction efficiency were 0.4246% (n = 3), 1.6057% (n = 3) and 1.6132% (n = 3), respectively. Conformation of BSA was not changed during the extraction process according to the investigation of UV–vis spectra, FT-IR spectra and CD spectra of BSA. The conductivity, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to explore the mechanism of the extraction. It turned out that the formation of DES–protein aggregates play a significant role in the separation process. All the results suggest that ChCl-based DES-ATPS are supposed to have the potential to provide new possibilities in the separation of proteins
A numerical study of steady-state two-phase flow in porous media
Energy Technology Data Exchange (ETDEWEB)
Knudsen, Henning Arendt
2002-07-01
Two-phase flow in porous media means the simultaneous flow of two phases, say two liquids, e.g., oil and water. This flow is restrained to be within a porous medium. For example sandstone and limestone are typical porous stones that can contain oil and gas in nature. In the extraction of oil from reservoirs, oil is usually displaced by water. So on a large scale we can consider it to be a displacement process. However, on pore scale the ''mix'' and flow processes are complicated. Idealistically, one might consider the search for truth a sufficient motivation for work in this field. Nevertheless, from an economic and technological point of view, enhanced oil recovery is the main motivation for the study of two-phase flow in porous media. Luckily, there are additional systems in real world that falls into this category. One such system is the flow of water and pollutants in aquifers. General knowledge in the field might be beneficial for preserving ground water reserves in the future. In the laboratory one often encounters artificially made porous media. For example glass beads between two glass plates. Therein, one of the phases flowing may be a mixture of glycerol and water. The other phase can be air which then is the non-wetting phase; air does not wet glass. It can also be silicone oil, and in that case the water/glycerol is normally the nonwetting phase. There are other possibilities. In general, laboratory studies are performed on systems on pore scale. The flow properties on the various length scales found in flow systems in nature depend on these properties on pore scale. The so-called upscaling problem concerns how to relate pore scale properties with properties on larger scales. The scope of this thesis is the study of properties on pore scale. The upscaling problem, which is a large research field in itself, is thus outside the scope of this thesis. The results of Paper 3 is an exception since they may infer also to larger scales than
A preliminary stability analysis of MYRRHA Primary Heat Exchanger two-phase tube bundle
Energy Technology Data Exchange (ETDEWEB)
Castelliti, Diego [Studiecentrum voor kernenergie – Centre d’étude de l’énergie nucléaire (SCK-CEN), Boeretang 200, Mol (Belgium); GeNERG – DIME/TEC, University of Genova, Via all’Opera Pia 15/a, 16145 Genova (Italy); Lomonaco, Guglielmo, E-mail: guglielmo.lomonaco@unige.it [GeNERG – DIME/TEC, University of Genova, Via all’Opera Pia 15/a, 16145 Genova (Italy); INFN, Via Dodecaneso 33, 16146 Genova (Italy)
2016-08-15
Highlights: • MYRRHA is a pool-type LBE-cooled ADS, operable also as a critical reactor. • MYRRHA is a high priority infrastructure for nuclear research in Europe. • PHX (primary side: LBE, secondary side: two-phase water), is a MYRRHA key component. • The original MYRRHA PHX design does not offer a fully satisfying response to DWO. • The adoption of an orifice allows extending considerably the stability of MYRRHA PHX. - Abstract: The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project, started at SCK·CEN since 1999, aims at the construction of a pool-type sub-critical Accelerator-Driven System (ADS) which could also operate as a critical reactor. The primary system, enclosed in the primary vessel, is filled with Lead Bismuth Eutectic (LBE) which acts as primary coolant. The power is then delivered through four heat exchangers to four secondary loops. The secondary cooling fluid is two-phase water operating at relatively low pressure (16 bar). Four aero-condensers act as heat sinks, since MYRRHA design does not foresee any electricity generation. The MYRRHA Primary Heat eXchangers (PHXs) cover a role of fundamental importance in normal operation and accidental conditions, being part of the primary and secondary cooling system and of the Decay Heat Removal (DHR) system. It is thus highly relevant to understand the PHXs behavior under all the potential working conditions. In particular, the stability of the PHXs must be guaranteed under all operating conditions. System code models play an important role in understanding and predicting the behavior of the reactor in all conditions, from steady state to operational and accidental transients, and simulating all the postulated scenarios. A solid PHX design requires a complete assessment of two-phase flow instabilities in the secondary system water tube bundle and the potential implementation of a suitable stabilizing device (orifice) to reduce the impact of the perturbations along
Pressure distribution over tube surfaces of tube bundle subjected to two phase cross flow
International Nuclear Information System (INIS)
Sim, Woo Gun
2013-01-01
Two phase vapor liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two phase flow, it is essential to obtain detailed information about the characteristics of a two phase flow. The characteristics of a two phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid dynamic force acting on the cylinder owing to the pressure distribution. A two phase flow was pre mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two phase cross flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results
Two-phase flow and cross-mixing measurements in a rod bundle
International Nuclear Information System (INIS)
Yloenen, A.; Prasser, H.-M.
2011-01-01
The wire-mesh sensor technique has been used for the first time to study two-phase flow and liquid mixing in a rod bundle. A dedicated test facility (SUBFLOW) was constructed at Paul Scherrer Institut (PSI) in a co-operation with the Swiss Federal Institute of Technology (ETH Zurich). Simultaneous injection of salt water as tracer and air bubbles can be used to quantify the enhancement of liquid mixing in two-phase flow when the results are compared with the single-phase mixing experiment with the same test parameters. The second aspect in the current experiments is the two-phase flow in bundle geometry. (author)
A study of water hammer phenomena in a one-component two-phase bubbly flow
International Nuclear Information System (INIS)
Fujii, Terushige; Akagawa, Koji
2000-01-01
Water hammer phenomena caused by a rapid valve closure, that is, shock phenomena in two-phase flows, are an important problem for the safety assessment of a hypothetical LOCA. This paper presents the results of experimental and analytical studies of the water hammer phenomena in a one-component tow-phase bubbly flow. In order to clarify the characteristics of water hammer phenomena, experiments for a one-component two-phase flow of Freon R-113 were conducted and a numerical simulation of pressure transients was developed. An overall picture of the water hammer phenomena in a one-component two-phase flow is presented an discussed. (author)
Two-phase flow measurements with advanced instrumented spool pieces and local conductivity probes
International Nuclear Information System (INIS)
Turnage, K.G.; Davis, C.E.
1979-01-01
A series of two-phase, air-water and steam-water tests performed with instrumented spool pieces and with conductivity probes obtained from Atomic Energy of Canada, Ltd. is described. The behavior of the three-beam densitometer, turbine meter, and drag flowmeter is discussed in terms of two-phase models. Application of some two-phase mass flow models to the recorded spool piece data is made and preliminary results are shown. Velocity and void fraction information derived from the conductivity probes is presented and compared to velocities and void fractions obtained using the spool piece instrumentation
Validation of two-phase flow code THYC on VATICAN experiment
International Nuclear Information System (INIS)
Maurel, F.; Portesse, A.; Rimbert, P.; Thomas, B.
1997-01-01
As part of a comprehensive program for THYC validation (THYC is a 3-dimensional two-phase flow computer code for PWR core configuration), an experimental project > has been initiated by the Direction des Etudes et Recherches of Electricite de France. Two mock-ups tested in Refrigerant-114, VATICAN-1 (with simple space grids) and VATICAN-2 (with mixing grids) were set up to investigate void fraction distributions using a single beam gamma densitometer. First, experiments were conducted with the VATICAN-1 mock-up. A set of constitutive laws to be used in rod bundles was determined but some doubts still remain for friction losses closure laws for oblique flow over tubes. From VATICAN-2 tests, calculations were performed using the standard set of correlations. Comparison with the experimental data shows an underprediction of void fraction by THYC in disturbed regions. Analyses highlight the poor treatment of axial relative velocity in these regions. A fitting of the radial and axial relative velocity values in the disturbed region improves the prediction of void fraction by the code but without any physical explanation. More analytical experiments should be carried out to validate friction losses closure laws for oblique flows and relative velocity downstream of a mixing grid. (author)
Validation of two-phase flow code THYC on VATICAN experiment
Energy Technology Data Exchange (ETDEWEB)
Maurel, F.; Portesse, A.; Rimbert, P.; Thomas, B. [EDF/DER, Dept. TTA, 78 - Chatou (France)
1997-12-31
As part of a comprehensive program for THYC validation (THYC is a 3-dimensional two-phase flow computer code for PWR core configuration), an experimental project <
Soares, Ruben R G; Azevedo, Ana M; Van Alstine, James M; Aires-Barros, M Raquel
2015-08-01
For half a century aqueous two-phase systems (ATPSs) have been applied for the extraction and purification of biomolecules. In spite of their simplicity, selectivity, and relatively low cost they have not been significantly employed for industrial scale bioprocessing. Recently their ability to be readily scaled and interface easily in single-use, flexible biomanufacturing has led to industrial re-evaluation of ATPSs. The purpose of this review is to perform a SWOT analysis that includes a discussion of: (i) strengths of ATPS partitioning as an effective and simple platform for biomolecule purification; (ii) weaknesses of ATPS partitioning in regard to intrinsic problems and possible solutions; (iii) opportunities related to biotechnological challenges that ATPS partitioning may solve; and (iv) threats related to alternative techniques that may compete with ATPS in performance, economic benefits, scale up and reliability. This approach provides insight into the current status of ATPS as a bioprocessing technique and it can be concluded that most of the perceived weakness towards industrial implementation have now been largely overcome, thus paving the way for opportunities in fermentation feed clarification, integration in multi-stage operations and in single-step purification processes. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Reda, D.C.; Eaton, R.R.
1981-01-01
A facility-development effort is currently underway at Sandia National Laboratories in order to create an experimental capability for the study of two-phase, steam/water flows through a variety of porous media. The facility definition phase of this project is described. Equations are derived for the steady, adiabatic, macroscopically-linear two-phase flow of a single-component fluid through a porous medium, including energy transfer both by convection and conduction. These equations are then solved to give relative permeabilities for the steam and water phases as functions of known and/or measurable quantities. A viable experimental approach was thereby formulated, leading to the definition of facility components and instrumentation requirements, including the application of gamma-beam densitometry for the measurement of liquid-saturation distributions in porous media. Finally, a state-of-the-art computer code was utilized to numerically simulate the proposed experiments, providing an estimate of the facility operating envelope
International Nuclear Information System (INIS)
Sauter, H.; Meyder, R.; Philipp, P.; Samstag, M.
1995-01-01
The NOVA program was continued with turbulent, vertical, upward two-phase flow experiments. The development of a local gas distribution along the test section was visualized by X-ray tomography. (orig.)
Falabella, Steven; Meyer, Glenn A; Tang, Vincent; Guethlein, Gary
2014-06-10
A two-phase mixed media insulator having a dielectric fluid filling the interstices between macro-sized dielectric beads packed into a confined volume, so that the packed dielectric beads inhibit electro-hydrodynamically driven current flows of the dielectric liquid and thereby increase the resistivity and breakdown strength of the two-phase insulator over the dielectric liquid alone. In addition, an electrical apparatus incorporates the two-phase mixed media insulator to insulate between electrical components of different electrical potentials. And a method of electrically insulating between electrical components of different electrical potentials fills a confined volume between the electrical components with the two-phase dielectric composite, so that the macro dielectric beads are packed in the confined volume and interstices formed between the macro dielectric beads are filled with the dielectric liquid.
Ross, Michelle; Wakefield, Jon
2015-10-01
Two-phase study designs are appealing since they allow for the oversampling of rare sub-populations which improves efficiency. In this paper we describe a Bayesian hierarchical model for the analysis of two-phase data. Such a model is particularly appealing in a spatial setting in which random effects are introduced to model between-area variability. In such a situation, one may be interested in estimating regression coefficients or, in the context of small area estimation, in reconstructing the population totals by strata. The efficiency gains of the two-phase sampling scheme are compared to standard approaches using 2011 birth data from the research triangle area of North Carolina. We show that the proposed method can overcome small sample difficulties and improve on existing techniques. We conclude that the two-phase design is an attractive approach for small area estimation.
Reversible, on-demand generation of aqueous two-phase microdroplets
Collier, Charles Patrick; Retterer, Scott Thomas; Boreyko, Jonathan Barton; Mruetusatorn, Prachya
2017-08-15
The present invention provides methods of on-demand, reversible generation of aqueous two-phase microdroplets core-shell microbeads, microparticle preparations comprising the core-shell microbeads, and drug delivery formulation comprising the microparticle preparations. Because these aqueous microdroplets have volumes comparable to those of cells, they provide an approach to mimicking the dynamic microcompartmentation of biomaterial that naturally occurs within the cytoplasm of cells. Hence, the present methods generate femtoliter aqueous two-phase droplets within a microfluidic oil channel using gated pressure pulses to generate individual, stationary two-phase microdroplets with a well-defined time zero for carrying out controlled and sequential phase transformations over time. Reversible phase transitions between single-phase, two-phase, and core-shell microbead states are obtained via evaporation-induced dehydration and water rehydration.
Prediction of two-phase choked-flow through safety valves
International Nuclear Information System (INIS)
Arnulfo, G; Bertani, C; De Salve, M
2014-01-01
Different models of two-phase choked flow through safety valves are applied in order to evaluate their capabilities of prediction in different thermal-hydraulic conditions. Experimental data available in the literature for two-phase fluid and subcooled liquid upstream the safety valve have been compared with the models predictions. Both flashing flows and non-flashing flows of liquid and incondensable gases have been considered. The present paper shows that for flashing flows good predictions are obtained by using the two-phase valve discharge coefficient defined by Lenzing and multiplying it by the critical flow rate in an ideal nozzle evaluated by either Omega Method or the Homogeneous Non-equilibrium Direct Integration. In case of non-flashing flows of water and air, Leung/Darby formulation of the two-phase valve discharge coefficient together with the Omega Method is more suitable to the prediction of flow rate.
Single and two-phase flow pressure drop for CANFLEX bundle
Energy Technology Data Exchange (ETDEWEB)
Park, Joo Hwan; Jun, Ji Su; Suk, Ho Chun [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Dimmick, G R; Bullock, D E [Atomic Energy of Canada Limited, Ontario (Canada)
1999-12-31
Friction factor and two-phase flow frictional multiplier for a CANFLEX bundle are newly developed and presented in this paper. CANFLEX as a 43-element fuel bundle has been developed jointly by AECL/KAERI to provide greater operational flexibility for CANDU reactor operators and designers. Friction factor and two-phase flow frictional multiplier have been developed by using the experimental data of pressure drops obtained from two series of Freon-134a (R-134a) CHF tests with a string of simulated CANFLEX bundles in a single phase and a two-phase flow conditions. The friction factor for a CANFLEX bundle is found to be about 20% higher than that of Blasius for a smooth circular pipe. The pressure drop predicted by using the new correlations of friction factor and two-phase frictional multiplier are well agreed with the experimental pressure drop data of CANFLEX bundle within {+-} 5% error. 11 refs., 5 figs. (Author)
A Rotational Pressure-Correction Scheme for Incompressible Two-Phase Flows with Open Boundaries
Dong, S.; Wang, X.
2016-01-01
Two-phase outflows refer to situations where the interface formed between two immiscible incompressible fluids passes through open portions of the domain boundary. We present several new forms of open boundary conditions for two-phase outflow simulations within the phase field framework, as well as a rotational pressure correction based algorithm for numerically treating these open boundary conditions. Our algorithm gives rise to linear algebraic systems for the velocity and the pressure that involve only constant and time-independent coefficient matrices after discretization, despite the variable density and variable viscosity of the two-phase mixture. By comparing simulation results with theory and the experimental data, we show that the method produces physically accurate results. We also present numerical experiments to demonstrate the long-term stability of the method in situations where large density contrast, large viscosity contrast, and backflows occur at the two-phase open boundaries. PMID:27163909
Identification of two-phase flow regimes by time-series modeling
International Nuclear Information System (INIS)
King, C.H.; Ouyang, M.S.; Pei, B.S.
1987-01-01
The identification of two-phase flow patterns in pipes or ducts is important to the design and operation of thermal-hydraulic systems, especially in the nuclear reactor cores of boiling water reactors or in the steam generators of pressurized water reactors. Basically, two-phase flow shows some fluctuating characteristics even at steady-state conditions. These fluctuating characteristics can be analyzed by statistical methods for obtaining flow signatures. There have been a number of experimental studies conducted that are concerned with the statistical properties of void fraction or pressure pulsation in two-phase flow. In this study, the authors propose a new technique of identifying the patterns of air-water two-phase flow in a vertical pipe. This technique is based on analyzing the statistic characteristics of the pressure signals of the test loop by time-series modeling
A New Appraoch to Modeling Immiscible Two-phase Flow in Porous Media
DEFF Research Database (Denmark)
Yuan, Hao; Shapiro, Alexander; Stenby, Erling Halfdan
In this work we present a systematic literature review regarding the macroscopic approaches to modeling immiscible two-phase flow in porous media, the formulation process of the incorporate PDE based on Film Model(viscous coupling), the calculation of saturation profile around the transition zone...... to modeling immiscible two-phase flow in porous media. The suggested approach to immiscible two-phase flow in porous media describes the dispersed mesoscopic fluids’ interfaces which are highly influenced by the injected interfacial energy and the local interfacial energy capacity. It reveals a new...... possibility of modeling two-phase flow through energy balance. The saturation profile generated through the suggested approach is different from those through other approaches....
Development of One Dimensional Hyperbolic Coupled Solver for Two-Phase Flows
International Nuclear Information System (INIS)
Kim, Eoi Jin; Kim, Jong Tae; Jeong, Jae June
2008-08-01
The purpose of this study is a code development for one dimensional two-phase two-fluid flows. In this study, the computations of two-phase flow were performed by using the Roe scheme which is one of the upwind schemes. The upwind scheme is widely used in the computational fluid dynamics because it can capture discontinuities clearly such as a shock. And this scheme is applicable to multi-phase flows by the extension methods which were developed by Toumi, Stadtke, etc. In this study, the extended Roe upwind scheme by Toumi for two-phase flow was implemented in the one-dimensional code. The scheme was applied to a shock tube problem and a water faucet problem. This numerical method seems efficient for non oscillating solutions of two phase flow problems, and also capable for capturing discontinuities
Development of One Dimensional Hyperbolic Coupled Solver for Two-Phase Flows
Energy Technology Data Exchange (ETDEWEB)
Kim, Eoi Jin; Kim, Jong Tae; Jeong, Jae June
2008-08-15
The purpose of this study is a code development for one dimensional two-phase two-fluid flows. In this study, the computations of two-phase flow were performed by using the Roe scheme which is one of the upwind schemes. The upwind scheme is widely used in the computational fluid dynamics because it can capture discontinuities clearly such as a shock. And this scheme is applicable to multi-phase flows by the extension methods which were developed by Toumi, Stadtke, etc. In this study, the extended Roe upwind scheme by Toumi for two-phase flow was implemented in the one-dimensional code. The scheme was applied to a shock tube problem and a water faucet problem. This numerical method seems efficient for non oscillating solutions of two phase flow problems, and also capable for capturing discontinuities.
Experimental on two sensors combination used in horizontal pipe gas-water two-phase flow
International Nuclear Information System (INIS)
Wu, Hao; Dong, Feng
2014-01-01
Gas-water two phase flow phenomenon widely exists in production and living and the measurement of it is meaningful. A new type of long-waist cone flow sensor has been designed to measure two-phase mass flow rate. Six rings structure of conductance probe is used to measure volume fraction and axial velocity. The calibration of them have been made. Two sensors have been combined in horizontal pipeline experiment to measure two-phase flow mass flow rate. Several model of gas-water two-phase flow has been discussed. The calculation errors of total mass flow rate measurement is less than 5% based on the revised homogeneous flow model
Development of an Enhanced Two-Phase Production System at the Geysers Geothermal Field; FINAL
International Nuclear Information System (INIS)
Steven Enedy
2001-01-01
A method was developed to enhance geothermal steam production from two-phase wells at THE Geysers Geothermal Field. The beneficial result was increased geothermal production that was easily and economically delivered to the power plant
A Variational Model for Two-Phase Immiscible Electroosmotic Flow at Solid Surfaces
Shao, Sihong; Qian, Tiezheng
2012-01-01
We develop a continuum hydrodynamic model for two-phase immiscible flows that involve electroosmotic effect in an electrolyte and moving contact line at solid surfaces. The model is derived through a variational approach based on the Onsager
Single and two-phase flow pressure drop for CANFLEX bundle
Energy Technology Data Exchange (ETDEWEB)
Park, Joo Hwan; Jun, Ji Su; Suk, Ho Chun [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Dimmick, G. R.; Bullock, D. E. [Atomic Energy of Canada Limited, Ontario (Canada)
1998-12-31
Friction factor and two-phase flow frictional multiplier for a CANFLEX bundle are newly developed and presented in this paper. CANFLEX as a 43-element fuel bundle has been developed jointly by AECL/KAERI to provide greater operational flexibility for CANDU reactor operators and designers. Friction factor and two-phase flow frictional multiplier have been developed by using the experimental data of pressure drops obtained from two series of Freon-134a (R-134a) CHF tests with a string of simulated CANFLEX bundles in a single phase and a two-phase flow conditions. The friction factor for a CANFLEX bundle is found to be about 20% higher than that of Blasius for a smooth circular pipe. The pressure drop predicted by using the new correlations of friction factor and two-phase frictional multiplier are well agreed with the experimental pressure drop data of CANFLEX bundle within {+-} 5% error. 11 refs., 5 figs. (Author)
Two-phase flow boiling in small channels: A brief review
Indian Academy of Sciences (India)
fer coefficients, reduced inventory requirements, low capital cost etc. ... lot of work has been done to understand the fundamental aspects of two-phase flow and ... occurrence would facilitate optimal and safe operation of the involved systems.
Numerical simulation of multi-dimensional two-phase flow based on flux vector splitting
Energy Technology Data Exchange (ETDEWEB)
Staedtke, H.; Franchello, G.; Worth, B. [Joint Research Centre - Ispra Establishment (Italy)
1995-09-01
This paper describes a new approach to the numerical simulation of transient, multidimensional two-phase flow. The development is based on a fully hyperbolic two-fluid model of two-phase flow using separated conservation equations for the two phases. Features of the new model include the existence of real eigenvalues, and a complete set of independent eigenvectors which can be expressed algebraically in terms of the major dependent flow parameters. This facilitates the application of numerical techniques specifically developed for high speed single-phase gas flows which combine signal propagation along characteristic lines with the conservation property with respect to mass, momentum and energy. Advantages of the new model for the numerical simulation of one- and two- dimensional two-phase flow are discussed.
A new treatment of capillarity to improve the stability of IMPES two-phase flow formulation
Kou, Jisheng; Sun, Shuyu
2010-01-01
In this paper, we present an efficient numerical method for two-phase immiscible flow in porous media with different capillarity pressures. In highly heterogeneous permeable media, the saturation is discontinuous due to different capillary pressure
Two-phase gas bubble-liquid boundary layer flow along vertical and inclined surfaces
International Nuclear Information System (INIS)
Cheung, F.B.; Epstein, M.
1985-01-01
The behavior of a two-phase gas bubble-liquid boundary layer along vertical and inclined porous surfaces with uniform gas injection is investigated experimentally and analytically. Using argon gas and water as the working fluids, a photographical study of the two-phase boundary layer flow has been performed for various angles of inclination ranging from 45 0 to 135 0 and gas injection rates ranging from 0.01 to 0.1 m/s. An integral method has been employed to solve the system of equations governing the two-phase motion. The effects of the gas injection rate and the angle of inclination on the growth of the boundary layer have been determined. The predicted boundary layer thickness is found to be in good agreement with the experimental results. The calculated axial liquid velocity and the void fraction in the two-phase region are also presented along with the observed flow behavior
Simultaneous thermal and optical imaging of two-phase flow in a micro-model.
Karadimitriou, N K; Nuske, P; Kleingeld, P J; Hassanizadeh, S M; Helmig, R
2014-07-21
In the study of non-equilibrium heat transfer in multiphase flow in porous media, parameters and constitutive relations, like heat transfer coefficients between phases, are unknown. In order to study the temperature development of a relatively hot invading immiscible non-wetting fluid and, ultimately, approximate heat transfer coefficients, a transparent micro-model is used as an artificial porous medium. In the last few decades, micro-models have become popular experimental tools for two-phase flow studies. In this work, the design of an innovative, elongated, PDMS (polydimethylsiloxane) micro-model with dimensions of 14.4 × 39 mm(2) and a constant depth of 100 microns is described. A novel setup for simultaneous thermal and optical imaging of flow through the micro-model is presented. This is the first time that a closed flow cell like a micro-model is used in simultaneous thermal and optical flow imaging. The micro-model is visualized by a novel setup that allowed us to monitor and record the distribution of fluids throughout the length of the micro-model continuously and also record the thermal signature of the fluids. Dynamic drainage and imbibition experiments were conducted in order to obtain information about the heat exchange between the phases. In this paper the setup as well as analysis and qualitative results are presented.
The hydrodynamics of segmented two-phase flow in a circular tube with rapidly dissolving drops.
Leary, Thomas F; Ramachandran, Arun
2017-05-03
This article discusses boundary integral simulations of dissolving drops flowing through a cylindrical tube for large aspect ratio drops. The dynamics of drop dissolution is determined by three dimensionless parameters: λ, the viscosity of the drop fluid relative to the suspending fluid; Ca, the capillary number defining the ratio of the hydrodynamic force to the interfacial tension force; and k, a dissolution constant based on the velocity of dissolution. For a single dissolving drop, the velocity in the upstream region is greater than the downstream region, and for sufficiently large k, the downstream velocity can be completely reversed, particularly at low Ca. The upstream end of the drop travels faster and experiences greater deformation than the downstream end. The film thickness, δ, between the drop and the tube wall is governed by a delicate balance between dissolution and changes in the outer fluid velocity resulting from a fixed pressure drop across the tube and mass continuity. Therefore, δ, and consequently, the drop average velocity, can increase, decrease or be relatively invariant in time. For two drops flowing in succession, while low Ca drops maintain a nearly constant separation distance during dissolution, at sufficiently large Ca, for all values of k, dissolution increases the separation distance between drops. Under these conditions, the liquid segments between two adjacent drops can no longer be considered as constant volume stirred tanks. These results will guide the choices of geometry and operating parameters that will facilitate the characterization of fast gas-liquid reactions via two-phase segmented flows.
Pulsed neutron measurement of single and two-phase liquid flow
International Nuclear Information System (INIS)
Kehler, P.
1978-01-01
Use of radioactive tracers for flow velocity measurements is well developed and documented. Measurement techniques involving pulsed sources of fast (14 MeV) neutrons for in-situ production of tracers can be considered as extensions of the old methods. Improvements offered by these Pulsed Neutron Activation (PNA) techniques over conventional radioisotope techniques are (1) non-intrusion into the system, (2) easier introduction and better mixing of the tracer, and (3) no requirement to handle large amounts of relatively long lived radioactive materials. Just as in conventional tracer techniques, flow velocity measurements by PNA methods can be based on the transit-time or the total-count method. A very significant difference of the PNA technique from conventional methods is that the induced activity is proportional to the density of the fluid, and that PNA techniques can be used for density measurements (of two-phase flows) in addition to flow velocity measurement. Original equations were derived that relate experimental data to the mass flow velocity and the average density. The accuracy of these equations is not effected by the flow regime. Experimental results are presented for tests performed on liquid sodium loops, on air--water loops, on the EBR-II reactor and on the LOFT reactor. Current instrumentation development programs (detectors, pulsed neutron sources) are discussed
Design of a welltest for determining two-phase hydraulic properties
International Nuclear Information System (INIS)
Finsterle, S.
1995-01-01
This report describes the design of a well test to determine two-phase hydraulic properties of a low permeability, low porosity formation. Estimation of gas-related parameters in such formations is difficult using standard pumping tests mainly because of the strong fluctuations in the pressure and flow rate data which are a consequence of gas bubbles evolving in the test interval. Even more important is the fact that the data do not allow distinguishing among alternative conceptual models. The estimated parameters are therefore uncertain, highly correlated, and ambiguous. In this study we examine a test sequence that could be appended to a standard hydraulic testing program. It is shown that performing a series of water and gas injection tests significantly reduces parameter correlations, thus decreasing the estimation error. Moreover, the extended test sequence makes possible the identification of the model that describes relative permeabilities and capillary pressures. This requires, however, that data of high accuracy are collected under controlled test conditions. The purpose of this report is to describe the modeling approach, assumptions and limitations of the procedure, and to provide practical recommendations for future testing
International Nuclear Information System (INIS)
Easterday, O.T.; Wang, C.Y.; Cheng, P.
1995-01-01
Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental interest for a number of engineering applications. Examples include thermal technologies for remediation of contaminated subsurfaces, the extraction of geothermal energy from vapor-dominated reservoirs, and the assessment of high-level nuclear waste repositories. A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while the latter creates a relative motion between the phases in the vertical direction. Experiments are also performed to measure temperature distributions and to visualize the two-phase flow patterns. Qualitative agreement between experiments and numerical predictions is achieved. Overall, this combined experimental and numerical study has provided new insight into conjugate single- and two-phase flow and heat transfer in porous media, although future research is required if accurate modeling of these complex problems is to be accomplished
Kou, Jisheng
2017-12-09
A general diffuse interface model with a realistic equation of state (e.g. Peng-Robinson equation of state) is proposed to describe the multi-component two-phase fluid flow based on the principles of the NVT-based framework which is an attractive alternative recently over the NPT-based framework to model the realistic fluids. The proposed model uses the Helmholtz free energy rather than Gibbs free energy in the NPT-based framework. Different from the classical routines, we combine the first law of thermodynamics and related thermodynamical relations to derive the entropy balance equation, and then we derive a transport equation of the Helmholtz free energy density. Furthermore, by using the second law of thermodynamics, we derive a set of unified equations for both interfaces and bulk phases that can describe the partial miscibility of multiple fluids. A relation between the pressure gradient and chemical potential gradients is established, and this relation leads to a new formulation of the momentum balance equation, which demonstrates that chemical potential gradients become the primary driving force of fluid motion. Moreover, we prove that the proposed model satisfies the total (free) energy dissipation with time. For numerical simulation of the proposed model, the key difficulties result from the strong nonlinearity of Helmholtz free energy density and tight coupling relations between molar densities and velocity. To resolve these problems, we propose a novel convex-concave splitting of Helmholtz free energy density and deal well with the coupling relations between molar densities and velocity through very careful physical observations with a mathematical rigor. We prove that the proposed numerical scheme can preserve the discrete (free) energy dissipation. Numerical tests are carried out to verify the effectiveness of the proposed method.
Experimental and analytical study of two-phase pressure drops during evaporation in horizontal tubes
Moreno Quibén, Jesús; Thome, John Richard
2007-01-01
Two-phase flow of gases and liquids or vapors and liquids in pipes, channels, equipment, etc. is frequently encountered in industry and has been studied intensively for many years. The reliable prediction of pressure drop in two-phase flow is thereby an important aim. Because of the complexity of these types of flow, empirical or semiempirical relationships are only of limited reliability and pressure drops predicted using leading methods may differ by up to 100%. In order to improve predicti...
Personal view of educating two-phase flow and human resource development as a nuclear engineer
International Nuclear Information System (INIS)
Hotta, Akitoshi
2010-01-01
As an engineer who has devoted himself in the nuclear industry for almost three decades, the author gave a personal view on educating two-phase flow and developing human resources. An expected role of universities in on-going discussions of collaboration among industry-government-academia is introduced. Reformation of two-phase flow education is discussed from two extreme viewpoints, the basic structure of physics and the practical system analysis. (author)
Experimental investigation on passive heat transfer by long closed two-phase thermosiphons
Energy Technology Data Exchange (ETDEWEB)
Grass, Claudia; Kulenovic, Rudi; Starflinger, Joerg [Stuttgart Univ. (Germany). Inst. fuer Kernenergetik und Energiesysteme (IKE)
2017-07-15
The removal of decay heat from spent fuel pools is presently realized by active cooling systems. In case of a station black out, a passive heat removal based on closed two-phase thermosiphons can contribute to the power plant safety. In this paper, the basic laboratory setup for closed two-phase thermosiphons and first experimental results are presented. Depending on the driving temperature difference and the heat input, steady-state and pulsating operation of the thermosiphons are investigated.
Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code
International Nuclear Information System (INIS)
Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.
1992-01-01
FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime
Water property lookup table (sanwat) for use with the two-phase computational code shaft
International Nuclear Information System (INIS)
Sherman, M.P.; Eaton, R.R.
1980-10-01
A lookup table for water thermodynamic and transport properties (SANWAT) has been constructed for use with the two-phase computational code, SHAFT. The table, which uses density and specific internal energy as independent variables, covers the liquid, two-phase, and vapor regions. The liquid properties of water are contained in a separate subtable in order to obtain high accuracy for this nearly incompressible region that is frequently encountered in studies of the characteristics of nuclear-waste repositories
Treatment technologies of liquid and solid wastes from two-phase olive oil mills
Borja Padilla, Rafael; Raposo Bejines, Francisco; Rincón, Bárbara
2006-01-01
Over the last 10 years the manufacture of olive oil has undergone important evolutionary changes in the equipment used for the separation of olive oil from the remaining components. The latest development has been the introduction of a two-phase centrifugation process in which a horizontally-mounted centrifuge is used for a primary separation of the olive oil fraction from the vegetable solid material and vegetation water. Therefore, the new two-phase olive oil mills produce three ident...
Treatment technologies of liquid and solid wastes from two-phase olive oil mills
Rincón, Bárbara; Raposo, Francisco; Borja, Rafael
2006-01-01
Over the last 10 years the manufacture of olive oil has undergone important evolutionary changes in the equipment used for the separation of olive oil from the remaining components. The latest development has been the introduction of a two-phase centrifugation process in which a horizontally-mounted centrifuge is used for a primary separation of the olive oil fraction from the vegetable solid material and vegetation water. Therefore, the new two-phase olive oil mills produce three identifiabl...
Bioconversion of apigenin-7-O-β-glucoside in aqueous two-phase system
Directory of Open Access Journals (Sweden)
Ilić Sanja M.
2005-01-01
Full Text Available The study is concerned with the conversion of apigenin-7-O-β-glucoside into apigenin in polyethylene glycol 6000 / dextran 20000 aqueous two-phase system by β-glucosidase. Apigenin was separated from apigenin-7-O-β-glucoside and β-glucosidase by their partition into opposite phases. In 14% PEG / 22.5% DEX aqueous two-phase system obtained yield of apigenin in top phase was 108%.
Determination of drift-flux velocity as a function of two-phase flow patterns
International Nuclear Information System (INIS)
Austregesilo Filho, H.
1986-01-01
A method is suggested for the calculation of drift-flux velocity as a function of two-phase flow patterns determined analytically. This model can be introduced in computer codes for thermal hydraulic analyses based mainly on homogeneous assumptions, in order to achieve a more realis tic description of two-phase flow phenomena, which is needed for the simulation of accidents in nuclear power plants for which phase separation effects are dominant, e.g., small break accidents. (Author) [pt
Measurement of local two-phase flow parameters of nanofluids using conductivity double-sensor probe.
Park, Yu Sun; Chang, Soon Heung
2011-04-04
A two-phase flow experiment using air and water-based γ-Al2O3 nanofluid was conducted to observe the basic hydraulic phenomenon of nanofluids. The local two-phase flow parameters were measured with a conductivity double-sensor two-phase void meter. The void fraction, interfacial velocity, interfacial area concentration, and mean bubble diameter were evaluated, and all of those results using the nanofluid were compared with the corresponding results for pure water. The void fraction distribution was flattened in the nanofluid case more than it was in the pure water case. The higher interfacial area concentration resulted in a smaller mean bubble diameter in the case of the nanofluid. This was the first attempt to measure the local two-phase flow parameters of nanofluids using a conductivity double-sensor two-phase void meter. Throughout this experimental study, the differences in the internal two-phase flow structure of the nanofluid were identified. In addition, the heat transfer enhancement of the nanofluid can be resulted from the increase of the interfacial area concentration which means the available area of the heat and mass transfer.
Numerical study for two phase flow in the near nozzle region of turbine combustors
International Nuclear Information System (INIS)
Pervez, K.; Mushtaq, S.
1999-01-01
In the present study flow conditions in the near nozzle region of the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion zone largely depends on the spray field in the near nozzle region the studies are conducted to determined the effects of multi jets on the flow pattern in the near nozzle region The phase doppler particle analyzer (PDPA) has been used to measure the velocities and sizes of the droplets. The flow field of two-phase liquid drop-air jets is formed from three injectors arranged in t line. Furthermore the two-phase flow field has been analyzed numerically also. The numerical analysis consists of two computational models, namely (i) 3 non-evaporating two-phase jets, (II) 3 evaporating two phase jets. The Eulerian-Eulerian approach in incorporated in both the numerical models. Since the flow is turbulent, a two-equation model (k-Epsilon) is implemented in the numerical analysis. Numerical solution of the conservation equation is obtained using PHOENICS computer code. Boundary conditions are provided from the experimental measurements. Numerical domain for the two models of the analysis starts at some distance (about 10 diameters of the injector orifice) where the atomization process is complete and droplet size and velocity could be measured experimentally. (author)
Application of non-equilibrium thermodynamics to two-phase flows with a change of phase
International Nuclear Information System (INIS)
Delhaye, J.M.
1969-01-01
In this report we use the methods of non-equilibrium thermodynamics in two-phase flows. This paper follows a prior one in which we have studied the conservation laws and derived the general equations of two-phase flow. In the first part the basic ideas of thermodynamics of irreversible systems are given. We follow the classical point of view. The second part is concerned with the derivation of a closed set of equations for the two phase elementary volume model. In this model we assume that the elementary volume contains two phases and that it is possible to define a volumetric local concentration. To obtain the entropy balance we can choose either the reversibility of the barycentric motion or the reversibility of each phase. We adopt the last assumption and our derivation is the same as this of I.Prigogine and P. Mazur about the hydrodynamics of liquid helium. The scope of this work is not to find a general solution to the problems of two phase flows but to obtain a new set of equations which may be used to explain some characteristic phenomena of two-phase flow such as wave propagation or critical states. (author) [fr
Two-phase flow regimes for counter-current air-water flows in narrow rectangular channels
International Nuclear Information System (INIS)
Kim, Byong Joo; Sohn, Byung Hu; Jeong, Si Young
2001-01-01
A study of counter-current two-phase flow in narrow rectangular channels has been performed. Two-phase flow regimes were experimentally investigated in a 760 mm long and 100 mm wide test section with 2.0 and 5.0 mm gap widths. The resulting flow regime maps were compared with the existing transition criteria. The experimental data and the transition criteria of the models showed relatively good agreement. However, the discrepancies between the experimental data and the model predictions of the flow regime transition became pronounced as the gap width increased. As the gap width increased the transition gas superficial velocities increased. The critical void fraction for the bubbly-to-slug transition was observed to be about 0.25. The two-phase distribution parameter for the slug flow was larger for the narrower channel. The uncertainties in the distribution parameter could lead to a disagreement in slug-to-churn transition between the experimental findings and the transition criteria. For the transition from churn to annular flow the effect of liquid superficial velocity was found to be insignificant
International Nuclear Information System (INIS)
Feng Qixi; Feng Quanke; Takeshi, K.
2008-01-01
The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008. In this paper, we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the tube were obtained using the MCNP code without influence of γ-ray and electronic-noise. The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated. The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI. The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques. And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI. (authors)
International Nuclear Information System (INIS)
Roshani, G.H.; Nazemi, E.; Roshani, M.M.
2017-01-01
In this paper, a novel method is proposed for predicting the density of liquid phase in stratified regime of liquid-gas two phase flows by utilizing dual modality densitometry technique and artificial neural network (ANN) model of radial basis function (RBF). The detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors for registering transmitted and scattered photons. At the first step, a Monte Carlo simulation model was utilized to obtain the optimum position for the scattering detector in dual modality densitometry configuration. At the next step, an experimental setup was designed based on obtained optimum position for detectors from simulation in order to generate the required data for training and testing the ANN. The results show that the proposed approach could be successfully applied for predicting the density of liquid phase in stratified regime of gas-liquid two phase flows with mean relative error (MRE) of less than 0.701. - Highlights: • Density of liquid phase in stratified regime of two phase flows was predicted. • Combination of dual modality densitometry technique and ANN was utilized. • Detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors. • MCNP simulation was done to obtain the optimum position for the scattering detector. • An experimental setup was designed to generate the required data for training the ANN.
Ziegler, C.; Gerteisen, D.
A dynamic two-phase model of a proton exchange membrane fuel cell with respect to the gas diffusion layer (GDL) is presented and compared with chronoamperometric experiments. Very good agreement between experiment and simulation is achieved for potential step voltammetry (PSV) and sine wave testing (SWT). Homogenized two-phase models can be categorized in unsaturated flow theory (UFT) and multiphase mixture (M 2) models. Both model approaches use the continuum hypothesis as fundamental assumption. Cyclic voltammetry experiments show that there is a deterministic and a stochastic liquid transport mode depending on the fraction of hydrophilic pores of the GDL. ESEM imaging is used to investigate the morphology of the liquid water accumulation in the pores of two different media (unteflonated Toray-TGP-H-090 and hydrophobic Freudenberg H2315 I3). The morphology of the liquid water accumulation are related with the cell behavior. The results show that UFT and M 2 two-phase models are a valid approach for diffusion media with large fraction of hydrophilic pores such as unteflonated Toray-TGP-H paper. However, the use of the homgenized UFT and M 2 models appears to be invalid for GDLs with large fraction of hydrophobic pores that corresponds to a high average contact angle of the GDL.
Multi-scale diffuse interface modeling of multi-component two-phase flow with partial miscibility
Kou, Jisheng; Sun, Shuyu
2016-08-01
In this paper, we introduce a diffuse interface model to simulate multi-component two-phase flow with partial miscibility based on a realistic equation of state (e.g. Peng-Robinson equation of state). Because of partial miscibility, thermodynamic relations are used to model not only interfacial properties but also bulk properties, including density, composition, pressure, and realistic viscosity. As far as we know, this effort is the first time to use diffuse interface modeling based on equation of state for modeling of multi-component two-phase flow with partial miscibility. In numerical simulation, the key issue is to resolve the high contrast of scales from the microscopic interface composition to macroscale bulk fluid motion since the interface has a nanoscale thickness only. To efficiently solve this challenging problem, we develop a multi-scale simulation method. At the microscopic scale, we deduce a reduced interfacial equation under reasonable assumptions, and then we propose a formulation of capillary pressure, which is consistent with macroscale flow equations. Moreover, we show that Young-Laplace equation is an approximation of this capillarity formulation, and this formulation is also consistent with the concept of Tolman length, which is a correction of Young-Laplace equation. At the macroscopical scale, the interfaces are treated as discontinuous surfaces separating two phases of fluids. Our approach differs from conventional sharp-interface two-phase flow model in that we use the capillary pressure directly instead of a combination of surface tension and Young-Laplace equation because capillarity can be calculated from our proposed capillarity formulation. A compatible condition is also derived for the pressure in flow equations. Furthermore, based on the proposed capillarity formulation, we design an efficient numerical method for directly computing the capillary pressure between two fluids composed of multiple components. Finally, numerical tests
Multi-scale diffuse interface modeling of multi-component two-phase flow with partial miscibility
Kou, Jisheng
2016-05-10
In this paper, we introduce a diffuse interface model to simulate multi-component two-phase flow with partial miscibility based on a realistic equation of state (e.g. Peng-Robinson equation of state). Because of partial miscibility, thermodynamic relations are used to model not only interfacial properties but also bulk properties, including density, composition, pressure, and realistic viscosity. As far as we know, this effort is the first time to use diffuse interface modeling based on equation of state for modeling of multi-component two-phase flow with partial miscibility. In numerical simulation, the key issue is to resolve the high contrast of scales from the microscopic interface composition to macroscale bulk fluid motion since the interface has a nanoscale thickness only. To efficiently solve this challenging problem, we develop a multi-scale simulation method. At the microscopic scale, we deduce a reduced interfacial equation under reasonable assumptions, and then we propose a formulation of capillary pressure, which is consistent with macroscale flow equations. Moreover, we show that Young-Laplace equation is an approximation of this capillarity formulation, and this formulation is also consistent with the concept of Tolman length, which is a correction of Young-Laplace equation. At the macroscopical scale, the interfaces are treated as discontinuous surfaces separating two phases of fluids. Our approach differs from conventional sharp-interface two-phase flow model in that we use the capillary pressure directly instead of a combination of surface tension and Young-Laplace equation because capillarity can be calculated from our proposed capillarity formulation. A compatible condition is also derived for the pressure in flow equations. Furthermore, based on the proposed capillarity formulation, we design an efficient numerical method for directly computing the capillary pressure between two fluids composed of multiple components. Finally, numerical tests
Forced convection flow boiling and two-phase flow phenomena in a microchannel
Na, Yun Whan
2008-07-01
) technique. The effects of different constant heat fluxes and different channel heights on the boiling mechanisms were investigated. The effects of liquid velocity on the bubble departure diameter were analyzed. The obtained results showed that the wall superheats at the position of nucleate boiling are relatively independent of the mass flow rates at the same channel height. The obtained results, however, showed that the heat flux at the onset of nucleate boiling strongly depends on the channel height. With a decrease of the channel height and an increase of the liquid velocity at the channel inlet, the departure diameter of a bubble was smaller. The periodic flow patterns, such as the bubbly flow, elongated slug flow, and churn flow were observed in the microchannel. Flow instabilities of two-phase flow boiling in a trapezoidal microchannel using a three-dimensional model were investigated. Fluctuation behaviors of flow boiling parameters such as wall temperature and inlet pressure caused by periodic flow patterns were studied at different heat fluxes and mass fluxes. The numerical results showed large amplitude and short period oscillations for wall temperature and inlet pressure fluctuations. Stable and unstable flow boiling regime with short period oscillations were investigated. Those flow boiling regimes were not listed in stable and unstable boiling regime map proposed by Wang et al. (2007).
Retinoid production using metabolically engineered Escherichia coli with a two-phase culture system.
Jang, Hui-Jeong; Yoon, Sang-Hwal; Ryu, Hee-Kyung; Kim, Jung-Hun; Wang, Chong-Long; Kim, Jae-Yean; Oh, Deok-Kun; Kim, Seon-Won
2011-07-29
Retinoids are lipophilic isoprenoids composed of a cyclic group and a linear chain with a hydrophilic end group. These compounds include retinol, retinal, retinoic acid, retinyl esters, and various derivatives of these structures. Retinoids are used as cosmetic agents and effective pharmaceuticals for skin diseases. Retinal, an immediate precursor of retinoids, is derived by β-carotene 15,15'-mono(di)oxygenase (BCM(D)O) from β-carotene, which is synthesized from the isoprenoid building blocks isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Retinoids are chemically unstable and biologically degraded via retinoic acid. Although extensive studies have been performed on the microbial production of carotenoids, retinoid production using microbial metabolic engineering has not been reported. Here, we report retinoid production using engineered Escherichia coli that express exogenous BCM(D)O and the mevalonate (MVA) pathway for the building blocks synthesis in combination with a two-phase culture system using a dodecane overlay. Among the BCM(D)O tested in E. coli, the synthetic retinoid synthesis protein (SR), based on bacteriorhodopsin-related protein-like homolog (Blh) of the uncultured marine bacteria 66A03, showed the highest β-carotene cleavage activity with no residual intracellular β-carotene. By introducing the exogenous MVA pathway, 8.7 mg/L of retinal was produced, which is 4-fold higher production than that of augmenting the MEP pathway (dxs overexpression). There was a large gap between retinal production and β-carotene consumption using the exogenous MVA pathway; therefore, the retinal derivatives were analyzed. The derivatives, except for retinoic acid, that formed were identified, and the levels of retinal, retinol, and retinyl acetate were measured. Amounts as high as 95 mg/L retinoids were obtained from engineered E. coli DH5α harboring the synthetic SR gene and the exogenous MVA pathway in addition to dxs overexpression, which
A single-reciprocating-piston two-phase thermofluidic prime-mover
International Nuclear Information System (INIS)
Taleb, Aly I.; Timmer, Michael A.G.; El-Shazly, Mohamed Y.; Samoilov, Aleksandr; Kirillov, Valeriy A.; Markides, Christos N.
2016-01-01
We explore theoretically a thermodynamic heat-engine concept that has the potential of attaining a high efficiency and power density relative to competing solutions, while having a simple construction with few moving parts and dynamic seals, allowing low capital and operating costs, and long lifetimes. Specifically, an unsteady heat-engine device within which a working fluid undergoes a power cycle featuring phase-change, termed the ‘Evaporative Reciprocating-Piston Engine’ (EPRE) is considered as a potential prime mover for use in combined heat and power (CHP) applications. Based on thermal/fluid-electrical analogies, a theoretical ERPE device is conceptualized initially in the electrical-analogy domain as a linearized, closed-loop active electronic circuit model. The circuit-model representation is designed to potentially exhibit high efficiencies compared to similar, existing two-phase unsteady heat engines. From the simplified circuit model in the electrical domain, and using the thermal/fluid-electrical analogies, one possible configuration of a corresponding physical ERPE device is derived, based on an early prototype of a device currently under development that exhibits some similarities with the ERPE, and used as a physical manifestation of the proposed concept. The corresponding physical ERPE device relies on the alternating phase change of a suitable working-fluid (here, water) to drive a reciprocating displacement of a single vertical piston and to produce sustained oscillations of thermodynamic properties within an enclosed space. Four performance indicators are considered: the operational frequency, the power output, the exergy efficiency, and the heat input/temperature difference imposed externally on the device's heat exchangers that is necessary to sustain oscillations. The effects of liquid inertia, viscous drag, hydrostatic pressure, vapour compressibility and two-phase heat transfer in the various engine components/compartments are
Spectral Cascade-Transport Turbulence Model Development for Two-Phase Flows
Brown, Cameron Scott
Turbulence modeling remains a challenging problem in nuclear reactor applications, particularly for the turbulent multiphase flow conditions in nuclear reactor subchannels. Understanding the fundamental physics of turbulent multiphase flows is crucial for the improvement and further development of multiphase flow models used in reactor operation and safety calculations. Reactor calculations with Reynolds-averaged Navier-Stokes (RANS) approach continue to become viable tools for reactor analysis. The on-going increase in available computational resources allows for turbulence models that are more complex than the traditional two-equation models to become practical choices for nuclear reactor computational fluid dynamic (CFD) and multiphase computational fluid dynamic (M-CFD) simulations. Similarly, increased computational capabilities continue to allow for higher Reynolds numbers and more complex geometries to be evaluated using direct numerical simulation (DNS), thus providing more validation and verification data for turbulence model development. Spectral turbulence models are a promising approach to M-CFD simulations. These models resolve mean flow parameters as well as the turbulent kinetic energy spectrum, reproducing more physical details of the turbulence than traditional two-equation type models. Previously, work performed by other researchers on a spectral cascade-transport model has shown that the model behaves well for single and bubbly twophase decay of isotropic turbulence, single and two-phase uniform shear flow, and single-phase flow in a channel without resolving the near-wall boundary layer for relatively low Reynolds number. Spectral models are great candidates for multiphase RANS modeling since bubble source terms can be modeled as contributions to specific turbulence scales. This work focuses on the improvement and further development of the spectral cascadetransport model (SCTM) to become a three-dimensional (3D) turbulence model for use in M
A dual-porosity model for two-phase flow in deforming porous media
Shu, Zhengying
Only recently has one realized the importance of the coupling of fluid flow with rock matrix deformations for accurately modeling many problems in petroleum, civil, environmental, geological and mining engineering. In the oil industry, problems such as reservoir compaction, ground subsidence, borehole stability and sanding need to be simulated using a coupled approach to make more precise predictions than when each process is considered to be independent of the other. Due to complications associated with multiple physical processes and mathematical representation of a multiphase now system in deformable fractured reservoirs, very few references, if any, are available in the literature. In this dissertation, an approach, which is based on the dual-porosity concept and takes into account rock deformations, is presented to derive rigorously a set of coupled differential equations governing the behavior of fractured porous media and two-phase fluid flow. The finite difference numerical method, as an alternative method for finite element, is applied to discretize the governing equations both in time and space domains. Throughout the derived set of equations, the fluid pressures and saturations as well as the solid displacements are considered as the primary unknowns. The model is tested against the case of single-phase flow in a 1-D consolidation problem for which analytical solutions are available. An example of coupled two-phase fluid flow and rock deformations for a scenario of a one-dimensional, fractured porous medium is also discussed. The numerical model and simulator, RFIA (Rock Fluid InterAction), developed in this dissertation can be a powerful tool to solve difficult problems not only in petroleum engineering such as ground subsidence, borehole stability and sand control, but also in civil engineering such as groundwater flow through fractured bedrock and in environmental engineering such as waste deposit concerns in fractured and unconsolidated formations
Debris bed coolability using a 3-D two phase model in a porous medium
Energy Technology Data Exchange (ETDEWEB)
Bechaud, C.; Duval, F.; Fichot, F. [CEA Cadarache, Inst. de Protection et de Surete Nucleaire13 - Saint-Paul-lez-Durance (France); Quintard, M. [Institut de Mecanique des Fluides de Toulouse, 31 (France); Parent, M. [CEA Grenoble, Dept. de Thermohydraulique et de Physique, 38 (France)
2001-07-01
During a severe nuclear accident, a part of the molten corium resulting from the core degradation may relocate in the lower plenum of the reactor vessel. In order to predict the safety margin of the reactor under such conditions, the coolability of this porous heat-generating medium is evaluated in this study and compared with other investigations. In this work, conservation equations derived for debris beds are implemented in the three dimensional thermal-hydraulic module of the CATHARE code. The coolant flow is a two phase flow with phase change. The momentum balance equation for each fluid phase is an extension of Darcy's law. This extension takes into account the capillary effects between the two phases, the relative permeabilities and passabilities of each phase, the interfacial drag force between liquid and gas, and the porous bed configuration (porosity, particle diameter,... ). The model developed is three-dimensional which is important to better predict the flow in configuration such as counter-current flow or to emphasize preferential ways induced by porous geometry. The energy balance equations of the three phases (liquid, gas and solid phase) are obtained by a volume averaging process of the local conservation equations. In this method, the local thermal non-equilibrium between the three phases is considered and the heat exchanges, the phase change rate as well as the thermal dispersion coefficients are calculated as a function of the local geometry of the porous medium. Such a method allows the numerical estimation of these thermal properties which are very difficult to determine experimentally. This feature is a great advantage of this approach. After a brief description of the thermal-hydraulic model, one-dimensional predictions of critical dryout fluxes are presented and compared with results from the literature. Reasonable agreement is obtained. Then a two-dimensional calculation is presented and shows the influence of the porous medium
Measurement of Two-Phase Flow and Heat Transfer Parameters using Infrared Thermometry
Kim, Tae-Hoon; Kommer, Eric; Dessiatoun, Serguei; Kim, Jungho
2012-01-01
A novel technique to measure heat transfer and liquid film thickness distributions over relatively large areas for two-phase flow and heat transfer phenomena using infrared (IR)thermometry is described. IR thermometry is an established technology that can be used to measure temperatures when optical access to the surface is available in the wavelengths of interest. In this work, a midwave IR camera (3.6-5.1 microns) is used to determine the temperature distribution within a multilayer consisting of a silicon substrate coated with a thin insulator. Since silicon is largely transparent to IR radiation, the temperature of the inner and outer walls of the multilayer can be measured by coating selected areas with a thin, IR opaque film. If the fluid used is also partially transparent to IR, the flow can be visualized and the liquid film thickness can be measured. The theoretical basis for the technique is given along with a description of the test apparatus and data reduction procedure. The technique is demonstrated by determining the heat transfer coefficient distributions produced by droplet evaporation and flow boiling heat transfer.
Air-lift pumps characteristics under two-phase flow conditions
International Nuclear Information System (INIS)
Kassab, Sadek Z.; Kandil, Hamdy A.; Warda, Hassan A.; Ahmed, Wael H.
2009-01-01
Air-lift pumps are finding increasing use where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids in nuclear applications must be handled and when a compressed air is readily available as a source of a renewable energy for water pumping applications. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters. For this purpose, an air-lift pump was designed and tested. Experiments were performed for nine submergence ratios, and three risers of different lengths with different air injection pressures. Moreover, the pump was tested under different two-phase flow patterns. A theoretical model is proposed in this study taking into account the flow patterns at the best efficiency range where the pump is operated. The present results showed that the pump capacity and efficiency are functions of the air mass flow rate, submergence ratio, and riser pipe length. The best efficiency range of the air-lift pumps operation was found to be in the slug and slug-churn flow regimes. The proposed model has been compared with experimental data and the most cited models available. The proposed model is in good agreement with experimental results and found to predict the liquid volumetric flux for different flow patterns including bubbly, slug and churn flow patterns
Investigation of vertical slug flow with advanced two-phase flow instrumentation
International Nuclear Information System (INIS)
Mi, Y.; Ishii, M.; Tsoukalas, L.H.
2001-01-01
Extensive experiments of vertical slug flow were carried out with an electromagnetic flowmeter and an impedance void-meter in an air-water two-phase experimental loop. The basic principles of these instruments in vertical slug flow measurements are discussed. Time series of the liquid velocity and the impedance were separated into two parts corresponding to the Taylor bubble and the liquid slug. Characteristics of slug flow, such as the void fractions, probabilities and lengths of the Taylor bubble and liquid slug, slug unit velocity, area-averaged liquid velocity, and liquid film velocity of the Taylor bubble tail, etc., were obtained. For the first time, the area-averaged liquid velocity of slug flow was revealed by the electromagnetic flowmeter. It is realized that the void fraction of the liquid slug is determined by the turbulent intensity due to the relative liquid motion between the Taylor bubble tail region and its wake region. A correlation of the void fraction of the liquid slug is developed based on experimental results obtained from a test section with 50.8 mm i.d. The results of this study suggest a promising improvement in understanding of vertical slug flow
Study on spectral entropy of two-phase flow density wave instability
International Nuclear Information System (INIS)
Zhang Zuoyi
1992-05-01
By using mathematic proof, spectral entropy calculations for simple examples and a practical two-phase flow system, it has been proved that under the same stochastic input, the output spectral entropy of a stable linear system is in maximum, while for an unstable linear system, its entropy is in relative lower level. Because the spectral entropy describes the output uncertainty of a system and the second law of thermodynamics rules the direction of natural tendency, the spontaneous process can develop only toward the direction of uncertainty increasing, and the opposite is impossible. It seems that the physical mechanism of the stability of a system can be explained as following: Any deviation from its original state of a stable system will reduce the spectral entropy and violate the natural tendency so that the system will return to original state. On the contrary, the deviation from its original state of an unstable system will increase the spectral entropy that will enhance the deviation and the system will be further away from its original state
Comparison of simplified models in the prediction of two phase flow in pipelines
Jerez-Carrizales, M.; Jaramillo, J. E.; Fuentes, D.
2014-06-01
Prediction of two phase flow in pipelines is a common task in engineering. It is a complex phenomenon and many models have been developed to find an approximate solution to the problem. Some old models, such as the Hagedorn & Brown (HB) model, have been highlighted by many authors to give very good performance. Furthermore, many modifications have been applied to this method to improve its predictions. In this work two simplified models which are based on empiricism (HB and Mukherjee and Brill, MB) are considered. One mechanistic model which is based on the physics of the phenomenon (AN) and it still needs some correlations called closure relations is also used. Moreover, a drift flux model defined in steady state that is flow pattern dependent (HK model) is implemented. The implementation of these methods was tested using published data in the scientific literature for vertical upward flows. Furthermore, a comparison of the predictive performance of the four models is done against a well from Campo Escuela Colorado. Difference among four models is smaller than difference with experimental data from the well in Campo Escuela Colorado.
Numerical and dimensional analysis of nanoparticles transport with two-phase flow in porous media
El-Amin, Mohamed
2015-04-01
In this paper, a mathematical model and numerical simulation are developed to describe the imbibition of nanoparticles-water suspension into two-phase flow in a porous medium. The flow system may be changed from oil-wet to water-wet due to nanoparticles (which are also water-wet) deposition on surface of the pores. So, the model is extended to include the negative capillary pressure and mixed-wet relative permeability correlations to fit with the mixed-wet system. Moreover, buoyancy and capillary forces as well as Brownian diffusion and mechanical dispersion are considered in the mathematical model. An example of countercurrent imbibition in a core of small scale is considered. A dimensional analysis of the governing equations is introduced to examine contributions of each term of the model. Several important dimensionless numbers appear in the dimensionless equations, such as Darcy number Da, capillary number Ca, and Bond number Bo. Throughout this investigation, we monitor the changing of the fluids and solid properties due to addition of the nanoparticles using numerical experiments.
Hot-film anemometer measurements in adiabatic two-phase flow through a vertical duct
International Nuclear Information System (INIS)
Trabold, T.A.; Moore, W.E.; Morris, W.O.
1997-06-01
A hot-film anemometer (HFA) probe was used to obtain local measurements of void fraction and bubble frequency in a vertically oriented, high aspect ratio duct containing R-134a under selected adiabatic two-phase flow conditions. Data were obtained along a narrow dimension scan over the range 0.03 ≤ bar Z ≤ 0.80, where bar Z is the distance from the wall normalized with the duct spacing dimension. The void fraction profiles displayed large gradients in the near-wall regions and broad maxima near the duct centerline. The trends in the bubble frequency data generally follow those for the local void fraction data. However, the relatively large number of bubbles at higher pressure implies a larger magnitude of the interfacial area concentration, for the same cross-sectional average void fraction. For the two annular flow conditions tested, analysis of the HFA output voltage signal enabled identification of three distinct regions of the flow field; liquid film with dispersed bubbles, interfacial waves, and continuous vapor with dispersed droplets
Local measurement of interfacial area, interfacial velocity and liquid turbulence in two-phase flow
International Nuclear Information System (INIS)
Hibiki, T.; Hogsett, S.; Ishii, M.
1998-01-01
Double sensor probe and hotfilm anemometry methods were developed for measuring local flow characteristics in bubbly flow. The formulation for the interfacial area concentration measurement was obtained by improving the formulation derived by Kataoka and Ishii. The assumptions used in the derivation of the equation were verified experimentally. The interfacial area concentration measured by the double sensor probe agreed well with one by the photographic method. The filter to validate the hotfilm anemometry for measuring the liquid velocity and turbulent intensity in bubbly flow was developed based on removing the signal due to the passing bubbles. The local void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter, liquid velocity, and turbulent intensity of vertical upward air-water flow in a round tube with inner diameter of 50.8 mm were measured by using these methods. A total of 54 data sets were acquired consisting of three superficial gas flow rates, 0.039, 0.067, and 0.147 m/s, and three superficial liquid flow rates, 0.60, 1.00, and 1.30 m/s. The measurements were performed at the three locations: L/D=2, 32, and 62. This data is expected to be used for the development of reliable constitutive relations which reflect the true transfer mechanisms in two-phase flow. (author)
A simplified approach for the computation of steady two-phase flow in inverted siphons.
Diogo, A Freire; Oliveira, Maria C
2016-01-15
Hydraulic, sanitary, and sulfide control conditions of inverted siphons, particularly in large wastewater systems, can be substantially improved by continuous air injection in the base of the inclined rising branch. This paper presents a simplified approach that was developed for the two-phase flow of the rising branch using the energy equation for a steady pipe flow, based on the average fluid fraction, observed slippage between phases, and isothermal assumption. As in a conventional siphon design, open channel steady uniform flow is assumed in inlet and outlet chambers, corresponding to the wastewater hydraulic characteristics in the upstream and downstream sewers, and the descending branch operates in steady uniform single-phase pipe flow. The proposed approach is tested and compared with data obtained in an experimental siphon setup with two plastic barrels of different diameters operating separately as in a single-barrel siphon. Although the formulations developed are very simple, the results show a good adjustment for the set of the parameters used and conditions tested and are promising mainly for sanitary siphons with relatively moderate heights of the ascending branch. Copyright © 2015 Elsevier Ltd. All rights reserved.
An alternating direction algorithm for two-phase flow visualization using gamma computed tomography.
Xue, Qian; Wang, Huaxiang; Cui, Ziqiang; Yang, Chengyi
2012-12-01
In order to build high-speed imaging systems with low cost and low radiation leakage, the number of radioactive sources and detectors in the multiphase flow computed tomography (CT) system has to be limited. Moreover, systematic and random errors are inevitable in practical applications. The limited and corrupted measurement data have made the tomographic inversion process the most critical part in multiphase flow CT. Although various iterative reconstruction algorithms have been developed based on least squares minimization, the imaging quality is still inadequate for the reconstruction of relatively complicated bubble flow. This paper extends an alternating direction method (ADM), which is originally proposed in compressed sensing, to image two-phase flow using a low-energy γ-CT system. An l(1) norm-based regularization technique is utilized to treat the ill-posedness of the inverse problem, and the image reconstruction model is reformulated into one having partially separable objective functions, thereafter a dual-based ADM is adopted to solve the resulting problem. The feasibility is demonstrated in prototype experiments. Comparisons between the ADM and the conventional iterative algorithms show that the former has obviously improved the space resolution in reasonable time.
"Hypothetical" Heavy Particles Dynamics in LES of Turbulent Dispersed Two-Phase Channel Flow
Gorokhovski, M.; Chtab, A.
2003-01-01
The extensive experimental study of dispersed two-phase turbulent flow in a vertical channel has been performed in Eaton's research group in the Mechanical Engineering Department at Stanford University. In Wang & Squires (1996), this study motivated the validation of LES approach with Lagrangian tracking of round particles governed by drag forces. While the computed velocity of the flow have been predicted relatively well, the computed particle velocity differed strongly from the measured one. Using Monte Carlo simulation of inter-particle collisions, the computation of Yamamoto et al. (2001) was specifically performed to model Eaton's experiment. The results of Yamamoto et al. (2001) improved the particle velocity distribution. At the same time, Vance & Squires (2002) mentioned that the stochastic simualtion of inter-particle collisions is too expensive, requiring significantly more CPU resources than one needs for the gas flow computation. Therefore, the need comes to account for the inter-particle collisions in a simpler and still effective way. To present such a model in the framework of LES/Lagrangian particle approach, and to compare the calculated results with Eaton's measurement and modeling of Yamamoto is the main objective of the present paper.