Search results for "two-phase flow"
showing 10 items of 30 documents
Hydrodynamics of two-phase flow in tubular reactor
2017
Macroscopic two-phase flow in porous media
2000
A system of macroscopic equations for two-phase immiscible displacement in porous media is presented. The equations are based on continuum mixture theory. The pairwise character of interfacial energies is explicitly taken into account. The equations incorporate the spatiotemporal variation of interfacial energies and residual saturations. The connection between these equations and relative permeabilities is established, and found to be in qualitative agreement with experiment.
Analyses of single- and two-phase flow pressure drops in helical pipes using a modified RELAP5 code
2012
Abstract Thermal fluid dynamics analyses on single- and two-phase flows in helical pipes of steam generators to be used in Generation III and IV nuclear reactors have been performed. The study concerned with experimental activities as well code simulations carried out in the framework of a collaboration between the Department of Energetics of the Polytechnic of Torino and the Department of Energy of the University of Palermo. The goal was the validation of models implemented in Relap5/Mod3.2β thermal–hydraulic advanced code to simulate the hydrodynamic behaviour of helical pipe components in spite of the one-dimensional nature of the code. It is shown that much of the experimental data obta…
A semi-empirical approach for predicting two-phase flow discharge through branches of various orientations connected to a horizontal main pipe
2010
Abstract The subdivision of two-phase flow in branching conduits consisting of a large horizontal main pipe with upward, downward, or lateral branches of reduced diameter is of great interest in various technological fields. For example, these conduits are important in light-water nuclear reactors (LWRs) in the case of a small break loss-of-coolant accident (SBLOCA) in a leg of the reactor's primary coolant loops, as well as for breaks or valve malfunctions in a large pipeline. In these kinds of circumstances, the relevant phenomenology often involves phase stratification coupled with possible liquid entrainment or gas pool-through phenomena. Therefore, these phenomena were studied in depth…
Corrigendum: Generalized Buckley–Leverett theory for two-phase flow in porous media
2012
Generalized Buckley–Leverett theory for two-phase flow in porous media
2011
Hysteresis and fluid entrapment pose unresolved problems for the theory of flow in porous media. A generalized macroscopic mixture theory for immiscible two-phase displacement in porous media (Hilfer 2006b Phys. Rev. E 73 016307) has introduced percolating and nonpercolating phases. It is studied here in an analytically tractable hyperbolic limit. In this limit a fractional flow formulation exists, that resembles the traditional theory. The Riemann problem is solved analytically in one dimension by the method of characteristics. Initial and boundary value problems exhibit shocks and rarefaction waves similar to the traditional Buckley-Leverett theory. However, contrary to the traditional th…
A comparison between simulation and experiment for hysteretic phenomena during two-phase immiscible displacement
2014
[1] The paper compares a theory for immiscible displacement based on distinguishing percolating and nonpercolating fluid parts with experimental observations from multistep outflow experiments. The theory was published in 2006 in Physica A, volume 371, pages 209–225; the experiments were published in 1991 in Water Resources Research, volume 27, pages 2113. The present paper focuses on hysteretic phenomena resulting from repeated cycling between drainage and imbibition processes in multistep pressure experiments. Taking into account, the hydraulic differences between percolating and nonpercolating fluid parts provides a physical basis to predict quantitatively the hysteretic phenomena observ…
Dimensional analysis of pore scale and field scale immiscible displacement
1996
A basic re-examination of the traditional dimensional analysis of microscopic and macroscopic multiphase flow equations in porous media is presented. We introduce a ‘macroscopic capillary number’\(\overline {Ca}\) which differs from the usual microscopic capillary number Ca in that it depends on length scale, type of porous medium and saturation history. The macroscopic capillary number\(\overline {Ca}\) is defined as the ratio between the macroscopic viscous pressure drop and the macroscopic capillary pressure.\(\overline {Ca}\) can be related to the microscopic capillary number Ca and the LeverettJ-function. Previous dimensional analyses contain a tacit assumption which amounts to setting…
A new method in investigations of bubble cluster shapes in two-phase flow
1991
Abstract In this paper a new probabilistic method is used to analyse the distribution of air bubbles in two-phase flow. So far, the method has been applied in astronomy and cosmology to investigate the distribution of galaxies. The basic idea is presented and the method applied to the photographed population of air bubbles in a liquid. The method allows the homogeneity of the flow to be evaluated qualitatively and quantitatively.
Application of the image processing methods for analysis of two-phase flow in turbomachinery
2007
The aim of this research is an application of digital image analysis for working out the method, which will allow to evaluate irregularity rate of two-phase flow across various geometry of tube bundle in aspect of the shell - and - tube heat exchanger optimization. Visualization of liquid flow in the shell — side enables an analysis of flow parameters by the use of image processing and analysis methods.