Numerical analysis of gas-solidsflow hydrodynamics and heat transfer in two outlet configurationindustrial riser using mesoscale theory to predict the interfacialdrag

Se analizan numéricamente dos configuraciones de un riser del proceso FCC variando la disposición de la salida superior, usando un modelo CFD en 2 D que incluye el Modelo de los Dos Fluidos (TMF), la Teoría Cinética del Flujo Granular (KTGF) y como modelo de arrastre el modelo de la Minimización de la Energía Multi-Escala (EMMS). El modelo se resuelve a través del programa ANSYS Fluent® 14.5 solucionando las ecuaciones de balance de masa, momentum y energía; y ecuaciones constitutivas para calcular la interacción entre las fases, la fase sólida con las paredes, y las propiedades de la fase granular. El modelo propuesto en este trabajo predice adecuadamente el comportamiento del flujo gas-sólido, prediciendo diferentes patrones de flujo en las coordenadas axial y radial del riser; así como zonas concentradas y diluidas de sólidos en la parte baja y alta del riser, respectivamente. Las fluctuaciones en la concentración y las velocidades de los sólidos tanto radial como axialmente que se observan son producto del alto grado de mezclado radial que se acentúa cerca de las paredes del riser debido al arrastre considerado por el modelo utilizado. Por otro lado se observa una rápida estabilización térmica radial y axial alcanzando en poco tiempo el estado estacionario. Los perfiles obtenidos en las dos configuraciones analizadas son muy similares, lo que motiva a que en trabajos futuros se analicen otras configuraciones de salida del riser que permitan mejorar los patrones de concentración y velocidades de los sólidos.In the FCC process two configurations riser are numerically analyzed varying the upper outlet orientation using a 2 D CFD model which includes the Two Fluid Model (TFM), Kinetic Theory of Granular Flow (KTGF), and Energy Minimization Multi-Scale (EMMS) theory as drag model. This model is solved using the ANSYS Fluent® 14.5 software, solving the governing equations of mass, momentum, and energy balance; and the constitutive equations to calculate interfacial interaction, wall-solid phase interaction, and granular phase properties. The model proposed in this work properly predicts the gas-solid flow behavior, predicting different solid flow patterns in radial and axial riser directions, as well as concentrated and diluted zones at riser's top and bottom respectively. The radial and axial solids concentration and velocities profiles fluctuations observed are produced by the high radial solid mix which is higher near the riser walls due to drag force considered by the model used. On the other hand, a rapid radial and axial thermal stabilization is observed reaching the steady state rapidly. The profiles obtained from riser configurations analyzed are very similar, so in future works other riser outlets configurations will be analyzed to try to improve the solid concentration and velocity profiles.Peer Reviewe

Numerical analysis of the low velocity regions in an array of three horizontal 90° elbows conducting water

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The numerical simulation and the results analysis, of the velocity and pressure fields in a three 90º elbows horizontal array are presented in this paper. A turbulent water flow ranging in a [44000, 176000] Reynolds number was used for the simulation with Fluent®. The velocity profile and the static pressure distribution inside the pipe and the three elbows array were analyzed when the separation distance between the elbows 1 - 2, and 2 - 3 were changed. The pipe diameter used for the simulation was 44 mm, and all the elbows had an average curvature radius of 100 mm. the tested separation between the elbows (L1 and L2) was varied from 0D to 10D. Results show that there is a minimum separation distance between elbows 1 and 2 where there is no more influence on the velocity profile in the first elbow and then the lowest velocity zone could be used for metrology and separation purposes.cs201

Numerical analysis of gas-solids flow hydrodynamics and heat transfer in two outlet configuration industrial riser using mesoscale theory to predict the interfacial drag

In the FCC process two configurations riser are numerically analyzed varying the upper outlet orientation using a 2 D CFD model which includes the Two Fluid Model (TFM), Kinetic Theory of Granular Flow (KTGF), and Energy Minimization Multi-Scale (EMMS) theory as drag model. This model is solved using the ANSYS Fluent® 14.5 software, solving the governing equations of mass, momentum, and energy balance, and the constitutive equations to calculate interfacial interaction, wall-solid phase interaction, and granular phase properties. The model proposed in this work properly predicts the gas-solid flow behavior, predicting different solid flow patterns in radial and axial riser directions, as well as concentrated and diluted zones at risers top and bottom respectively. The radial and axial solids concentration and velocities profiles fluctuations observed are produced by the high radial solid mix which is higher near the riser walls due to drag force considered by the model used. On the other hand, a rapid radial and axial thermal stabilization is observed reaching the steady state rapidly. The profiles obtained from riser configurations analyzed are very similar, so in future works other riser outlets configurations will be analyzed to try to improve the solid concentration and velocity profiles