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Cazarez-Candia O.,Mexican Institute of Petroleum | Cazarez-Candia O.,Zacatepec Institute of Technology | Benitez-Centeno O.C.,National Research Center y Desarrollo Tecnologico | Espinosa-Paredes G.,Metropolitan Autonomous University
International Journal of Heat and Fluid Flow | Year: 2011

In this work it is presented a transient, one-dimensional, adiabatic model for slug flow simulation, which appears when liquid (mixture of oil and water) and gas flow simultaneously through pipes. The model is formed by space and time averaged conservation equations for mass, momentum and energy for each phase, the numerical solution is based on the finite difference technique in the implicit scheme. Velocity, pressure, volumetric fraction and temperature profiles for both phases were predicted for inclination angles from the horizontal to the vertical position (unified model) and ascendant flow. Predictions from the model were validated using field data and ten correlations commonly used in the oil industry. The effects of gas heating or cooling, due to compression and expansion processes, on the predictions and numerical stability, were studied. It was found that when these effects are taken into account, a good behavior of temperature predictions and numerical stability are obtained. The model presents deviations lower than 14% regarding field data and it presents better predictions than most of the correlations. © 2011 Elsevier Inc.

Sanchez-Rivera M.M.,National Polytechnic Institute of Mexico | Almanza-Benitez S.,Zacatepec Institute of Technology | Bello-Perez L.A.,National Polytechnic Institute of Mexico | Mendez-Montealvo G.,National Polytechnic Institute of Mexico | And 3 more authors.
Carbohydrate Polymers | Year: 2013

The effect of iodine concentration on the acetylation of starches with low and moderate degree of substitution (DS < 0.5) and its impact on the physicochemical feature and structural features was evaluated. The acetylated starches were prepared with 0.03 mol anhydroglucose unit, 0.12 mol of anhydride acetic, and 0.6, 0.9 or 1.4 mM of molecular iodine as catalyst in a sealed Teflon vessel using microwave heating (600 W/2 min). Pasting profile and rheological properties were obtained under steady flow; dynamic oscillatory test was used. Structural features were obtained by HPSEC-RI. In acetylated starches, DS and acetyl groups increased when the iodine concentration increased, corn starch showed higher values than banana starch. The viscosity of acetylated starches decreased relative to unmodified starches while, acetylated corn starch had lower value than acetylated banana starch. In the flow curves, a non-Newtonian pattern (shear-thinning) was shown in the pastes of native and modified starches. Storage modulus (G') and loss modulus (G") showed low dependence on frequency (G' α ω0.1; G" α ω0.2) on frequency sweep test, which is characteristic of a viscoelastic gel. Debranched native banana and corn starches presented trimodal chain-length distribution. The pattern was maintained in the acetylated starches, but with different level of short and long chains. The structural differences in native and acetylated samples explain the rheological characteristics in both starches. © 2012 Elsevier Ltd.

Romero Ugalde H.M.,CNRS Systems and Information Sciences Lab LSIS | Romero Ugalde H.M.,CENIDET | Carmona J.-C.,CNRS Systems and Information Sciences Lab LSIS | Alvarado V.M.,CENIDET | Reyes-Reyes J.,Zacatepec Institute of Technology
Neurocomputing | Year: 2013

In this paper a dedicated recurrent neural network design and a model reduction approach are proposed in order to improve the balance between complexity and quality of black box nonlinear system identification models. The proposed neural network design, based on a three-layers architecture, helps to reduce the number of parameters of the model after the training phase without any significant loss of estimation accuracy. Nevertheless, the proposed architecture remains sufficiently general to provide a wide range of models among the most encountered in the literature. This reduction, achieved by a convenient choice of the activation functions and the initial conditions of the synaptic weights, is developed in two steps. The first step is to train the proposed architecture under two reasonable assumptions. Then the recurrent three-layers neural network is transformed into a representation of two-layer with less number of neurons, that is, a significant reduced number of parameters. The constructed architecture provided models with reasonable reduced number of parameters with a convenient estimation accuracy. To validate the proposed approach, we identify the Wiener-Hammerstein benchmark nonlinear system proposed in SYSID2009 [1]. © 2012 Elsevier B.V.

Alvarado-Juarez R.,CENIDET | Alvarez G.,CENIDET | Xaman J.,CENIDET | Hernandez-Lopez I.,CENIDET | Hernandez-Lopez I.,Zacatepec Institute of Technology
Desalination | Year: 2013

Double-diffusive natural convection and surface thermal radiation in an inclined cavity that simulates a solar still device is studied numerically. The parameters considered were 103≤RaT (RaM)≤106, 8≤A≤16 and 15°≤θ≤35°. The steady state 2-D governing equations have been solved by the finite volume method. Streamlines, isotherms, isolines of water vapor, mass flow rate of distillate and average Nusselt and Sherwood numbers as a function of Rayleigh number for different inclination angle are presented. The results show that surface thermal radiation modifies the fluid flow from one-cell to multi-cellular pattern due to the surface thermal radiation increases the velocity near the walls, as a consequence the average convective Nusselt number, the total Nusselt number and the Sherwood number were increased about 25%, 175% and 15%, respectively. The mass flow rate of distillate increases as A, Ra and θ increase. The most suitable case for a solar still device is that for RaT=106, A=16 and θ≤25°. © 2013 Elsevier B.V.

Lopez-Chavez R.,National Autonomous University of Mexico | Lopez-Chavez R.,Zacatepec Institute of Technology | Cuentas-Gallegos A.K.,National Autonomous University of Mexico
Journal of New Materials for Electrochemical Systems | Year: 2013

In the present work we show results related with the influence of the binder type used to elaborate active electrodes made of activated carbon (DLC) for the assembly of supercapacitor cells. A Nafion 5%w solution and/or Kinar Flex (Polyvinylidene fluoride, PVDF) were used as binders at different concentrations, using DLC carbon as the active material to make the electrodes by aerography, and carbon paper as support and current collector. Thickness of the electrodes was controlled by the weight of active material (DLC carbon). Cyclic voltammetry technique was used to investigate the intrinsic capacitive nature of these electrodes, increasing this value from 120 F/g to 245 F/g at 20 mV/s just by improving the type and amount of binder, and the thickness of the electrode. Symmetric 2-electrode cells assembled with binder-free electrodes were electrochemically characterized by galvanostatic cycling, showing capacitance values of 38F/g and a stable behavior during 7000 charge-discharge cycles. © J. New Mat. Electrochem. Systems.

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