Antonio Gilson Barbosa de Lima

Drying of Lentil Including Shrinkage: A Numerical Simulation

Abstract This article presents a theoretical study about drying of lentil including shrinkage. The two-dimensional unsteady-state diffusion modeling written in the oblate spheroidal coordinates system considers the volume variation effect, convective boundary condition at the surface of the solid, and variable thermo-physical properties. The governing equation was discretized using the finite-volume method and the linear equations system was solved by Gauss-Siedel iterative method. To validate the model, numerical results of the average moisture content were compared with experimental data from eight experiments and a good agreement was obtained. The diffusion coefficients for all drying experiments are determined using the least square error technique.

Numerical Analysis of Heat and Mass Transfer in Porous Media

Numerical Analysis of Mass Transfer around a Sphere Buried in Porous Media: Concentration Contours and Boundary Layer Thickness.- Unsaturated-Saturated Flow in Porous Media under Centrifugation.- Applying Computational Analysis in Studies of Resin Transfer Moulding.- Mass Transport in Growing Porous Media.- Modeling the Pore Level Fluid Flow in Porous Media using the Immersed Boundary Method.- Computer Simulation of Nanoparticles Deposition.- A Comparison of Thermal Dispersion Behaviour in High-Conductivity Porous Media of Various Pore Geometries.- Assessment of Heat Affected Zone of Submerged Arc Welding Process through Digital Image Processing.- Study of diffusion in a one-dimensional lattice-gas model of zeolites: The analytical approach and kinetic Monte Carlo simulations.- Contaminant transport in partially saturated porous.- Three-dimensional diffusion in arbitrary domain using generalized coordinates for the boundary condition of the first kind.- Convection and heat transfer of viscoelastic fluids saturated a porous medium.- Unsteady Heat Conduction from Spheroids.

Three-Dimensional Diffusion in Arbitrary Domain Using Generalized Coordinates for the Boundary Condition of the First Kind: Application in Drying

This work presents a three-dimensional numerical solution for the diffusion equation in transient state, in an arbitrary domain. For this end, the diffusion equation was discretized using the finite volume method with a fully implicit formulation and generalized coordinates, for the equilibrium boundary condition. For each time step, the system of equations obtained for a given structured mesh was solved by the Gauss-Seidel method. The computational code was developed in FORTRAN, using the CFV 6.6.0 Studio, in a Windows platform. The proposed solution was validated using analytical and numerical solutions of the diffusion equation for different geometries (orthogonal and non-orthogonal meshes). The analysis and comparison of the results showed that the proposed solution provides correct results for the cases investigated. The developed computational code was applied in the simulation of the drying of ceramic roof tiles for the following temperature: 55.6 °C. The analysis of the results makes it possible to affirm that the developed numerical solution satisfactorily describes the drying processes in this temperature.

Numerical Simulation of the Vibration Behavior of Curved Carbon Nanotubes

Several zigzag and armchair single-walled carbon nanotubes (CNTs) were modeled by a commercial finite element package and their vibrational behavior was studied. Numerous computational tests with different boundary conditions and different bending angles were performed. Both computational and analytical results were compared. It was shown that the computational results are in good agreement with the analytical calculations in the case of straight tubes. In addition, it was concluded that the natural frequency of straight armchair and zigzag CNTs increases by increasing the chiral number of both armchair and zigzag CNTs. It was also revealed that the natural frequency of CNTs with higher chirality decreases by introducing bending angles. Nevertheless, the influence of increasing bending angle on the natural frequency of armchair and zigzag CNTs with lower chiral number is almost negligible.

Numerical Study of Heavy Oil Flow on Horizontal Pipe Lubricated by Water

This chapter reports information related to multiphase flow with emphasis to core-annular flow. Industrial application has been given to transient water-heavy ultraviscous oil two-phase flow in horizontal pipe. The high viscosity heavy oil transportation is one of the main technological challenges for the oil industry. This fact is related with the high pressure drop due to the viscous effects during the flow. Different techniques for the heavy oil transportation have been cited in the literature, core-flow is one. In this technique, water is injected in the pipe and flows as an annular film near the wall while oil moves in the core region. This way, a smallest amount of energy is required for heavy oil pumping. Mathematical formulation to describe transient and isothermal two-phase flow (water-heavy oil) is presented. Results of the velocity, pressure and volume fraction distributions of the phases were obtained and analyzed. A large reduction of pressure drop by comparison with single phase heavy oil flow (around 59 times) was verified and shows the efficiency of the technique applied to production and transportation of heavy oils.

CONTINUOUS AND INTERMITTENT DRYING (TEMPERING) OF OBLATE SPHEROIDAL BODIES: MODELING AND SIMULATION

Abstract In this work, modeling of continuous and intermittent drying of oblate spheroidal bodies is presented. The model considers the liquid diffusion as the only process of mass transfer inside the body, constant diffusion coefficient and equilibrium conditions at the surface of the solid. The diffusion equation is described in the oblate spheroidal coordinates system and it was discretized using the finite-volume method. Formulation was applied to predict drying of lentil grains. Several cases of intermittent drying for lentils were simulated: using a same time of tempering (time of rest), beginning in different drying time and for two or more drying passes (time steps) along the process. For a same useful time of the dryer, it was observed that the intermittent drying always increases the efficiency of the process. Another outstanding result is the improvement of the final quality of the product due to the absence of large moisture content gradients inside of the product during the drying process after tempering.

Numerical Simulation Of Heavy Oil Flows InPipes Using The Core-annular Flow Technique

The importance of heavy oils in the world market for petroleum has increased very quickly in the last years. The reserves of heavy oils in the world are estimated at 3 trillion barrels, while reserves of light oils have reduced progressively in the last decade. The high oil viscosity creates major problems in the production and transportation of the oil. This situation leads to the high pressure and power required for its flow, overloading and damaging the equipment, increasing the cost of production. Due to the need to develop new alternatives that will make the production and transport of heavy oil economically viable, this work has the objective to study, numerically, the behavior of isothermal multiphase flow (heavy oil and water), type “core flow”, in pipelines, using the software CFX 3D. The pressure drop was determinated to a core-flow in a pipe with 7 in. diameter, 2.7 Pa.s oil viscosity and water at environment temperature. Results of the pressure, velocity and volume fraction distributions of the phases are presented and analyzed. It was verified that the pressure drop was reduced 58 times when compared to that obtained with oil flow alone in the pipe.

Resin transfer molding process: a numerical and experimental investigation

Resin Transfer Molding (RTM) is one of the composite manufacturing technique that consists in injecting a resin pre-catalysed thermosetting in a closed mold containing a dry fiber preform, where the resin is impregnated. In this sense, the aim of this research is to study theoretically and experimentally the RTM process. Experimental and simulations of the rectilinear infiltration of polyester resin (filled and non filled with CaCO 3 ) in mold with glass fiber preform were performed in cavity with dimensions 320 · 150 · 3.6 mm. Numerical results of the filling time and fluid front position over time were assessed by comparison with experimental data and good accuracy was obtained. It was verified that, the CaCO 3 content affect resin velocity during filling, the permeability of the reinforcement and resin viscosity, thus the filling time is affected strongly.

Resin Transfer Molding Process: Fundamentals, Numerical Computation and Experiments

Resin Transfer Molding (RTM) is one of the most widely known composite manufacturing technique of the liquid molding family, being extensively studied and used to obtain advanced composite materials comprised of fibers embedded in a thermoset polymer matrix. The fibrous reinforcement is considered a porous medium regarding its infiltration by the polymer resin. In this sense, this chapter aims to briefly discuss multiphase flow and heat transfer theory in RTM process, focusing on a multifluid model and the Control Volume/Finite Element (CV/FE) method. Finally, computational analysis was developed on the basis of ANSYS CFX® and PAM-RTM commercial software’s for the investigation of the fluid flow in RTM composite molding. In order to show the versatility and performance of the commercial codes, RTM experiments were carried under distinct injection pressure and fiber volume fraction conditions using plain-weave glass fiber cloth as the porous media. The transient numerical simulations provided information about volume fraction, pressure and velocity distribution of the phases (resin and air) inside the porous media.

Theoretical/Experimental Study of an Upflow Anaerobic Sludge Blanket Reactor Treating Domestic Wastewater

This work reports a theoretical and experimental study to evaluate the fluid dynamic of an Upflow Anaerobic Sludge Blanket reactor (UASB), treating domestic wastewater in a pilot scale. Simulations were developed using the Ansys CFX 10.0. For validating the numerical results, an experimental study was conducted by monitoring the total concentration of suspended solids in the effluent and pressure along the reactor. The comparative analysis between the numerical and experimental results of the pressure and sludge concentration in the outlet of the reactor presented few differences, being considered satisfactory.