Reactor Safety Analysis Based on a Developed Two-Phase Compressible Flow Simulation

Volume 1 ◽  
2004 ◽  
Author(s):  
A. F. Nowakowski ◽  
B. V. Librovich ◽  
L. Lue
Keyword(s):  
Multiphase Flow ◽  
Compressible Flow ◽  
Fluid Model ◽  
Numerical Technique ◽  
Computational Simulation ◽  
Safety Analysis ◽  
State Equations ◽  
Pressure Relief ◽  
Two Phase ◽  
Two Phases

The direct numerical simulation of multiphase flow is a challenging research topic with various key applications. In the present work, a computational simulation of multi-phase compressible flow has been proposed for safety analysis of chemical reactors. The main objective of a pressure relief system is to prevent accidents occurring from over pressurisation of the reactor. We are particularly interested in understanding the phenomena associated with emergency pressure relief systems for batch-type reactors and storage vessels. Existence of multiphase flow is significantly influenced by the interface between the phases and the associated discontinuities across the phase. The approach, which builds on the method first introduced by Saurel and Abgrall [1], was developed for solving two-phase compressible flow problems. Each phase is separately described by conservation equations. The interactions between two phases appear in the basic equations as transfer terms across the interface. The equations are complemented by state equations for the two phases and by additional correlations for the right-hand side coupling terms. The method is able to deal with multiphase mixtures and interface problems between compressible fluids. The key difference compared to classical two-fluid model is the presence of separate pressures fields associated with phases and introduction of pressure and velocity relaxation procedures. The relaxation operators tackle the boundary conditions at the interface and consequently the model is valid for fluid mixtures, as well as for pure fluids. The numerical technique requires the system to be decomposed and involves a non-conservative hyperbolic solver, an instantaneous pressure relaxation procedure and source term operators. The solution is obtained by succession of integrators using a second-order accurate scheme. The ultimate goal of this research is to use the method for studying the venting problem in reactor systems after verifying its performance on a series of standardised test cases documented in the literature.

scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2015 ◽  
Vol 22 (1) ◽  
pp. 109-116 ◽  
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate the velocity for a debris flow.

Analysis of Centrifugal Pump Performing Under Two-Phase Flow Using Bleeding System

2001 ◽  
Author(s):  
M. A. Zaher
Keyword(s):  
Multiphase Flow ◽  
Centrifugal Pump ◽  
Fluid Model ◽  
Energy Requirement ◽  
Two Phase ◽  
Pump Test ◽  
Pump Head ◽  
Two Fluid Model ◽  
Specific Energy Requirement ◽  
Two Fluid

Abstract A one dimensional two fluid model is used to study the performance of a centrifugal pump. Pumping of two-phase products in oil/geothermal industry offered a special multiphase pump. Test with different suction void fraction was used to predict the two-phase pump head data for two scales of pumps. With the new arrangement of bleeding and correct impeller design, a radical solution is offered to handle a multiphase flow. The physical mechanism responsible for transporting multiphase flow on efficiency, specific energy requirement and flow rate were also investigated.

Effect of Pressure on Two-Phase Modeling for Viscous Potential Flow

2013 ◽  
Author(s):  
Somayeh Ahmadi
Keyword(s):  
Potential Flow ◽  
Fluid Model ◽  
Computational Stability ◽  
Two Phase ◽  
Viscous Potential Flow ◽  
Pressure Correction ◽  
Effect Of Pressure ◽  
Correction Scheme ◽  
Two Fluid Model ◽  
Two Phases

In this study, the effect of pressure on the disturbed interface for two-phase stratified regime will be discussed. It is assumed that the two phases are in potential flow condition, a pressure correction algorithm for the two-fluid model is carefully implemented to minimize its effect on numerical stability. Numerical analysis is applied using the finite difference method. Actually pressure correction scheme is employed to solve the viscous potential flow model. It is designed to increase the computational stability when the flow is near the ill-posedness condition. The viscous potential flow theory fits the only pressure experimental data for air and water well.

Assessment of Cavitation Models for Flows in Diesel Injectors With Single- and Two-Fluid Approaches

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Kaushik Saha ◽  
Xianguo Li
Keyword(s):  
Fluid Model ◽  
Injection Pressure ◽  
Experimental Results ◽  
The Other ◽  
Computational Time ◽  
Two Phase ◽  
Numerical Predictions ◽  
Mass Flow Rates ◽  
Two Phases ◽  
Two Fluid

Several recent cavitation models for the analysis of two-phase flows in diesel injectors with single- and two-fluid modeling approaches have been evaluated, including the Saha–Abu-Ramandan–Li (SAL), Schnerr–Sauer (SS), and Zwart–Gerber–Belamri (ZGB) models. The SAL model is a single-fluid model, while the other two models have been implemented with both single- and two-fluid approaches. Numerical predictions are compared with experimental results available in literature, qualitatively with experimental images of two-phase flow in an optically accessible nozzle, and quantitatively with measured mass flow rates and velocity profiles. It is found that at low injection pressure differentials there can be considerable discrepancy in the predictions of the vapor distribution from the three models considered. This discrepancy is reduced as the injection pressure differential is increased. Implementation of the SS and ZGB models with single- and two- fluid approaches yields noticeable differences in the results because of the relative velocity between the two phases, with two-fluid approach providing better agreement with experimental results. The performance of the SS and ZGB models implemented with the two-fluid approach is comparable with the SAL single-fluid model, but with significantly more computational time. Overall, the SAL single-fluid model performs comparatively better with respect to the other two models.

Design of a Chemical Pulse Reactor

1979 ◽  
Vol 34 (12) ◽  
pp. 1446-1451
Author(s):  
B. Denzel ◽  
F. F. Seelig
Keyword(s):  
Numerical Technique ◽  
Substrate Inhibition ◽  
Fixed Bed ◽  
Tubular Reactor ◽  
Fixed Bed Reactor ◽  
Low Flow ◽  
State Equations ◽  
Reactor Outlet ◽  
Catalytic Reactors ◽  
Two Phase

Abstract The general reaction X + Y + M → P + M may - due to substrate inhibition at the catalytic site M - give rise to bistability phenomena in an isothermal tubular fixed bed reactor. The parametric conditions for bistability in the single pellet are studied by a numerical technique. Solution of the steady state equations for a two phase model of the tubular reactor shows that narrow zones with high conversion are possible, similar to ignition zones in nonisothermal catalytic reactors. By a cyclic operation with alternating periods of charging the catalyst phase with substrate and discharging it by chemical reaction, pulses of high product concentration can be generated at the reactor outlet. This is demonstrated by simulation of the system assuming low flow velocity as it is characteristic for reaction columns with liquid mobile phase.

Phase Field Method for Simulation of Multiphase Flow

2011 ◽  
Author(s):  
Harish Ganapathy ◽  
Ebrahim Al-Hajri ◽  
Michael M. Ohadi
Keyword(s):  
Multiphase Flow ◽  
Phase Field ◽  
Predictive Accuracy ◽  
Fluid Model ◽  
Thin Liquid Film ◽  
Field Method ◽  
Phase Field Method ◽  
Formation Mechanisms ◽  
Two Phase ◽  
Taylor Flow

The present paper reports a comprehensive study on the numerical simulation of Taylor flow in microchannels by the phase field method. Additionally, a comparative study was also performed against an alternative volume of fluid model based on which the phase field method was found to be more advantageous in key aspects such as the absence of unphysical interfacial pressure oscillations and the ability to account for variations in the surface tension force and thus predict several bubble lengths under constant flow conditions while observing the physics of homogeneous two-phase flow. Different bubble formation mechanisms were simulated and compared against experimental findings in literature. The simulation of a thin liquid film at the channel wall was found to be a limitation of most works pertaining to Taylor flow, including the present. This was ascribed to be more likely due to limited dimensional and spatial resolution as well as inaccurate contact angle dynamics rather than limitations of the modeling approach itself. The effect of wall adhesion was studied with respect to the flow and pressure field in the channel. A validation of the model was achieved through a favorable comparison of the numerically predicted gas void fraction and bubble lengths with existing models and correlations. On the whole, the phase field method was concluded to have improved predictive accuracy with respect to certain aspects as compared to conventional multiphase flow models.

On the Simulation of Multiphase Flow Containing Hydrate Particles

2008 ◽  
Author(s):  
Jian-Kui Zhao ◽  
Jing Gong
Keyword(s):  
Liquid Phase ◽  
Multiphase Flow ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Momentum Equation ◽  
Thermodynamic Quantities ◽  
Phase Flow ◽  
Two Phase ◽  
Compositional Model ◽  
Energy Equations

The article presents a mathematical model to simulate steady multiphase flow containing hydrate particles. The approach is based on the one-dimensional two-fluid model in which the two phases consist of the gas and the mixture of the liquid and hydrate particles. That is to say the hydrate particle and liquid phase are treated as pseudo-fluid. When a compositional model is used to simulate two-phase flow, it is required to couple mass, momentum, energy equations and equation of state, then the pressure and temperature and mass transfer between gas and liquid phase along the pipeline can be simulated. In the steady condition, it’s assumed that the composition of fluid is unchangeable along the pipeline and the flow can be described by pressure and temperature. In this paper, calculation method of gas-liquid two-phase flow which required a double iterative procedure of pressure and temperature respectively was improved. Liquid holdup and pressure drop were calculated by momentum equation. Enthalpy balance equation was substituted by explicit formulation of temperature calculation which meant that the loop of temperature was not required. So the calculation speed was enhanced. With strict flash calculation the following items were determined: the amount of hydrate; phase number; the location that hydrate appeared; flow rate and molar component of gas phase and liquid phase. Then thermodynamic quantities were calculated with proper relational expressions.

scholarly journals Estimation of flow velocity for a debris flow via the two-phase fluid model

2014 ◽  
Vol 1 (1) ◽  
pp. 999-1021
Author(s):  
S. Guo ◽  
P. Xu ◽  
Z. Zheng ◽  
Y. Gao
Keyword(s):  
Debris Flow ◽  
Real World ◽  
Empirical Formula ◽  
Debris Flows ◽  
Fluid Model ◽  
Two Phase ◽  
Liquid Phases ◽  
Two Phases ◽  
Phase Fluid ◽  
Steady Velocity

Abstract. The two-phase fluid model is applied in this study to calculate the steady velocity of a debris flow along a channel bed. By using the momentum equations of the solid and liquid phases in the debris flow together with an empirical formula to describe the interaction between two phases, the steady velocities of the solid and liquid phases are obtained theoretically. The comparison of those velocities obtained by the proposed method with the observed velocities of two real-world debris flows shows that the proposed method can estimate accurately the velocity for a debris flow.

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