Inter Phase Slip Algorithm Research Articles

Experimental and Numerical Investigations of Subcooled Boiling Heat Transfer in a Small-Diameter Tube

Abstract The boiling heat transfer for subcooled water flowing in a small-diameter tube was investigated experimentally and numerically. In the experiment, a platinum tube was used as an experimental tube (d = 1.0–2.0 mm) to conduct joule heating by direct current. The heat generation rate of the tube was controlled with an exponential function. The numerical simulation of boiling heat transfer for subcooled water flowing in the small-diameter tube was conducted using the commercial computational fluid dynamics (CFD) code, phoenics ver. 2013. The small-diameter tube was modeled in the simulation. As the boundary condition, the measured heat flux was given at the inner wall. The inlet temperature ranged from 302 to 312 K. The flow velocities of d = 1.0 mm and d = 2.0 mm were 9.29 m/s and 2.34 m/s, respectively. The three-dimensional analysis was carried out from non-boiling to the critical heat flux (CHF). Governing equations were discretized using the finite volume method in the phoenics. The semi-implicit method for pressure linked equation (SIMPLE) method was applied in the numerical simulation. For modeling boiling phenomena in the tube, the Eulerian–Eulerian two-fluid model was adopted using the interphase slip algorithm of phoenics. The surface temperature difference increased as the heat flux increased in the experiment. The numerical simulation predicted the experimental data well. When the heat flux of the experiment reached the CHF point, the predicted value of the heat transfer coefficient was approximately 3.5% lower than that of the experiment.

A Novel Multiphase Methodology Simulating Three Phase Flows in a Steel Ladle

Mixing phenomena in metallurgical steel ladles by bottom gas injection involves three phases namely, liquid molten steel, liquid slag and gaseous argon. In order to numerically solve this three-phase fluid flow system, a new approach is proposed which considers the physical nature of the gas being a dispersed phase in the liquid, while the two liquids namely, molten steel and slag are continuous phases initially separated by a sharp interface. The model was developed with the combination of two algorithms namely, IPSA (inter phase slip algorithm) where the gas bubbles are given a Eulerian approach since are considered as an interpenetrating phase in the two liquids and VOF (volume of fluid) in which the liquid is divided into two separate liquids but depending on the physical properties of each liquid they are assigned a mass fraction of each liquid. This implies that both the liquid phases (steel and slag) and the gas phase (argon) were solved for the mass balance. The Navier–Stokes conservation equations and the gas-phase turbulence in the liquid phases were solved in combination with the standard k-ε turbulence model. The mathematical model was successfully validated against flow patterns obtained experimentally using particle image velocimetry (PIV) and by the calculation of the area of the slag eye formed in a 1/17th water–oil physical model. The model was applied to an industrial ladle to describe in detail the turbulent flow structure of the multiphase system.

CFD simulation of annular oil flow wrapped with water

AbstractThe transport of heavy oil in tubes is energy intensive since the oil viscosity can reach values of 10 500 000 cP. This study focuses on the transport of oil in a piping system by an annular flow of oil wrapped with water, since this alternative reduces head loss. The piping system was comprised of horizontal tubes, curves, and vertical tubes. The assumptions for the CFD simulation were the following: 3D geometry, turbulent flow, and isothermal system as well as incompressible, steady‐state, and transient flow. A mesh convergence study was carried out. The residue for pressure and velocity dropped at least three orders of magnitude. The inter‐phase‐slip Algorithm (IPSA), algebraic slip model (ASLP), scalar equation method (SEM), and Phoenics models were applied to calculate the interaction between the phases. Turbulence was modelled with default k‐ϵ and k‐ω models and the LES strategy by using a Smagorinsky sub‐grid scale model. The density profiles generated in the CFD simulation were compared with experimental data and a resemblance was observed. The transient simulation showed a swirling flow that was experimentally observed, which was a result of synergy of multiphase flow, horizontal tube, curve, and vertical tube.

Influence of Selected Parameters on Reduction of Converter Slag - Studies with CFD Method

Abstract In this study influence of selected parameters on the process of reduction of converter slag from refining of Cu-Pb-Fe alloy was numerically examined. The process of the slag reduction is carried out in Q 80 converters of Hoboken type for copper removal. Converter slags show high concentration of lead therefore they can be seen as an important component for further processing in rotary-rocking furnaces together with other lead-bearing materials. Three-dimensional simulation was performed using the IPSA (Inter Phase Slip Algorithm) module of two-phase flow from PHOENICS package. Numerical simulations have forecasted influence of changes in the slag chemical composition and the process time on the process course.

Numerical Modeling of Copper Reduction in Fire Refining Process

Abstract Copper reduction represents one of the steps in the process of fire refining of blister copper. Process of copper reduction with natural gas as performed in the anode furnace was modeled. Numerical analysis was conducted using the IPSA (Inter- Phase-Slip Algorithm) module of PHOENICS package and standard turbulent model k - ε. The model takes into account the liquid phase - slag and phase of natural gas which is supplied through the tuyere from the bottom of the charge. Calculations were made for two different diameters of tuyeres for supply of reducer. Based on the calculations and analysis, it was found out that the gas flow which causes strong movement in the bath guarantees homogeneous composition of the liquid copper in each process stage. Application of a tuyere with a larger diameter results in a greater intensity of the reduction process and better use of the reducer.

Modelación matemática del mezclado en ollas (cucharas) de aluminio equipadas con la técnica de desgasificación rotor-inyector

In this work a fundamental Eulerian mathematical model was developed to study fluid flow and mixing phenomena in aluminum ladles equipped with impeller for deshidrogenization treatment. The effect of critical process parameters such as rotor speed, depth of immersion, gas flow rate, and type of rotor on the mixing behavior and vortex formation was analyzed with this model. The model simulates operation with and without gas injection and it was developed on the commercial CFD code PHOENICS 3.4 in order to solve all conservation equations governing the process, i.e. continuity, 3D turbulent Navier-Stokes and the k-e turbulence model for a two-phase fluid flow problem using the Inter Phase Slip Algorithm (IPSA). In order to realistically represent the process, shape of the furnace and three kinds of impellers were drawn by employing Body Fitted Coordinates (BFC). From the results it was concluded that mixing behavior is highly dependent on the rotor speed and on the rotor type. Mixing time is improved when: 1) Impeller is located at a depth of 0.229m into the aluminum bath, 2) By using high rotor speeds, 3) By using ladles with a high aspect ratio of Diameter to Height, and 4)By using an impeller with notches.

Application of CFD Models to Two-Phase Flow in Refrigerant Distributors

The goal of the work described in this paper was to identify an appropriate CFD model for refrigerant distributors and to apply the model to develop improved designs. There appears to have been no previous work applying CFD to two-phase flow in refrigerant distributors. As a first step, results of predictions using different two-phase modeling approaches available within commercial CFD codes were compared with experimental results from the literature for two-phase flow distribution with air and water as working fluids. The volume of fluid (VOF) and algebraic slip mixture (ASM) models failed to predict the experimental data available, whereas the inter-phase slip algorithm (IPSA) model predictions were in close agreement with the measurements in all cases. However, for a typical refrigerant distributor geometry and set of operating conditions, predictions of two-phase distribution and separation were quite similar for the different modeling approaches. As a result, the ASM is applicable for studying refrigerant distributor designs and was used to evaluate the performance of both existing and improved designs. In general, it is better to utilize a spherical distributor base as compared with other shapes and to locate the orifice close to the distributor base. These changes tend to improve the robustness of the distributor in terms of providing even flow and phase distribution in different outlet branches when the orifice and/or distributor are not oriented optimally. In addition, experiments were performed that tend to validate the general trends associated with the CFD results for refrigerant distributions.

Finite volume approach for solving multiphase flows in vertical pneumatic dryers

In the present study, a finite volume approach for solving two‐dimensional, two‐fluids flows with heat and mass transfer was developed for predicting the flow of particulate materials through pneumatic dryer. The model was solved for a two‐dimensional steady‐state condition and considering axial and radial profiles for the flow variables. A two‐stage drying process was implemented. The numerical procedure includes discretization of calculation domain into torus‐shaped final volumes, solving the gas phase conservation equations by a modified semi‐implicit method for pressure‐linked equations algorithm, and the conservation equations of particulate phase were solved by the explicit forward difference algorithm. The mass momentum and energy coupling between the phases were considered by principles of the Interphase slip algorithm. In order to validate the theoretical and the numerical models, the developed models were applied to simulate the drying process of wet PVC particles in a large‐scale pneumatic dryer and to the drying process of wet sand in a laboratory‐scale pneumatic dryer. The predictions of the numerical simulations were compared successfully with the results of independent numerical and experimental investigations. Following the models validation, the two‐dimensional distributions of the flow characteristics were examined.

Two-Fluid, Two-Dimensional Model for Pneumatic Drying

Pneumatic drying is a widely used process in the chemical industries and includes simultaneous conveying and heat and mass transfer between the particles and the heat gas. The increase in the use of this unit operation requires reliable mathematical models to predict processes in the industrial facilities. In the present study a Two-Fluid model has been used for modeling the flow of particulate materials through pneumatic dryer. The model was solved for a two-dimensional steady-state condition and considering axial and radial profiles for the flow variables. A two-stage drying process was implemented. In the first drying stage, heat transfer controls evaporation from the saturated outer surface of the particle to the surrounding gas. At the second stage, the particles were assumed to have a wet core and a dry outer crust; the evaporation process of the liquid from a particle is assumed to be governed by diffusion through the particle crust and by convection into the gas medium. As evaporation proceeds, the wet core shrinks while the particle dries. The numerical procedure includes discretization of calculation domain into torus-shaped final volumes, solving conservation equations by implementation of the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) algorithm and controls over coupling of phases by IPSA (Interphase Slip Algorithm). The developed model was applied to simulate a drying process of wet PVC particles in a large-scale pneumatic dryer and to a drying process of wet sand in a laboratory-scale pneumatic dryer. The numerical solutions are compared successfully with the results of independent numerical and experimental investigations. Following the model validation, the two-dimensional distributions of the flow characteristics were examined.

On the jet penetration height in fluidized beds with two vertical jets

Recent studies on jet penetration height in literature were reviewed. Double-jet penetration in fluidized beds was investigated both experimentally and numerically. The experimental investigation was performed in a 300×51 mm two-dimensional gas–solids fluidized bed with two vertical jets, and the jet penetration height was measured. Different kinds of particles were tested in turn. The numerically predicted jet penetration heights were from the solution of a hydrodynamic model describing the gas–solids fluidization. The hydrodynamic model is based on the kinetic theory for fluidization and K– ε k turbulence model for gas phase. The governing partial differential equations were solved using the modified Inter Phase Slip Algorithm (IPSA) method. The formation mechanism of jets was analyzed and the interaction of two vertical jets was reconstructed using this model. Numerical results indicated that the flow pattern of a two-jet system could be classified into three categories: isolated jets, transitional jets, and interacting jets. The criterions for those flow regions were found. The effects of jet characteristics (jet velocity, nozzle width, and the distance between two jets), particle properties (particle diameter, particle sphericity, and particle density), fluidizing gas characteristics (superficial gas velocity of bed, inlet gas density, and gas viscosity), and bed height on the jet penetration height were analyzed. It was found that the dominant factors affecting the jet penetration height are jet momentum, the drag between the two phases, entrainment near the jet neck, the distance between two jets, and the superficial gas velocity. Thus, the Froude number, Reynolds number, superficial gas velocity, the distance between the two jets, and jet nozzle width are used to propose algebraic empirical equations to estimate the jet penetration height of gas–solids fluidization at different jet regions. The empirical equations were compared with published experimental data or correlations.

Simulation of water and gas flow in fractured porous media

Abstract The porous media considered in this paper belong to gas reservoirs characterized by a low-permeability matrix, combined with a high-permeability fracture system. The transient, three-dimensional, two-phase numerical model is presented for simulating the simultaneous flow of gas and water through porous and fractured media. The specific problem to which the numerical simulation is applied assumes a single horizontal fracture perpendicular to the flow direction in a quite small geometry. The equations solved treat both fluids as incompressible and immiscible. Accounted for are the effect of capillary pressure and relative permeability. Technically, the finite volume approach is used to discretize the equations. The set of discretized and linearized equations is solved using the IPSA (inter-phase slip algorithm) method. The results of this study indicate that the multi-layer reservoir provides better estimates of post-fracture performance compared to a more conventional, single-layer reservoir description.

Efficiency of interphase coupling algorithms in fluidized bed conditions

When the coupling of phases in multi-phase flows is very tight, a special treatment of interphase coupling terms is required in order to avoid divergence of iterative sequential solvers. In this article the efficiency of these special treatments is studied in typical fluidized bed conditions, where the coupling of momentum equations is moderate. The interphase coupling algorithms studied are the partially implicit treatment, the Partial Elimination Algorithm (PEA) and the Simultaneous solution of Non-linearly Coupled Equations (SINCE). In addition to these special treatments of linearized coupling terms in momentum equations, the fundamental ideas of the SINCE are applied also to the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE (C)) type pressure correction equation in the framework of the interphase slip algorithm (IPSA). The resulting solution algorithm referred to as the Interphase Slip Algorithm-Coupled (IPSA-C) then incorporates interface couplings also into the mass balancing shared pressure correction step of the solution. It is shown that these advanced methods to treat interphase coupling terms result in a faster convergence of momentum equations despite the increased number of computational operations required by the algorithms. For solving of the entire equation set, this better solution efficiency is then almost lost partly because of the sequential structure of the IPSA and, more importantly, because of the assumption of constant volume fractions during the pressure correction step. All the computations are done in the context of a collocated multi-block control volume solver CFDS–FLOW3D.

Numerical simulation and verification of a gas-solid jet fluidized bed

From the Navier-Stokes equations and the Newtonian equations, which describe gas flow and the movement of a single particle respectively, a two-phase model describing gas-solid flow macroscopically in fluidized beds was derived by using volume averaging and the parameters of the model were determined. This general model can be reduced to several forms of simpler models reported in the literature. An improved interphase slip algorithm (IPSA) method based on finite volume approach was used in the solution of the model equations. The influences of the velocity of the central jet, height of the bed and superficial gas velocity in the bed on jet penetration height were obtained by numerical simulation. The computed flow patterns of the binary mixture were also obtained. The theoretical prediction was verified against the experiments made on a two-dimensional jet fluidized bed with both unitary and binary component materials. Under the operating conditions of an industrial ash-agglomerating coal gasifier, the arithmetical mean based upon particle number was introduced to calculate the mean diameter of the binary components. Thus the simulation of the binary components was simplified. All the computed jet penetration heights under various conditions were in good agreement with experimental and literature data.

NUMERICAL MODELLING OF CIRCULATING FLUIDIZED BEDS

ABSTRACT The development of the multi-phase flow algorithm MIPSA (Multi-InterPhase Slip-Algorithm) within a two-dimensional Computational Fluid Dynamics (CFD) code called CASCADE is summarized with its application to the modelling of lean phase circulating fluidized beds. The well-known interPhase Slip Algorithm (IPSA) technique for handling the presence of particles in an air stream is modified and extended, to handle explicitly a range of particle sizes simultaneously. The salient features of IPSA are retained; hence each size family is treated as a separate “phase” and its motion governed by its own momentum equations. The MIPSA algorithm is embedded within CASCADE, in a framework which ensures overall conservation of mass, momentum and energy. In this paper, the MIPSA algorithm is used to model the hydrodynamic behaviour of Circulating Fluidized Beds (CFB). CFB's are increasingly being employed by a wide range of process industries and their design for a specific application can be problematic. The ob...