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Araya R.,Federico Santa Maria Technical University | Araus K.,Federico Santa Maria Technical University | Utria K.,Autonomous University of the Caribbean | Toledo M.,Federico Santa Maria Technical University
International Journal of Hydrogen Energy | Year: 2014

The effect of adding steam during filtration combustion of natural gas-air mixtures was studied with the aim to evaluate the optimization of hydrogen production. Temperature, velocity, chemical products of combustion waves, and conversion from fuel to H2 and CO were evaluated in the range of equivalence ratio (φ) from stoichiometric (φ = 1.0) to φ = 3.0 and steam content in the mixture from 0% to 39%, at filtration velocities from 12 to 25 cm/s. Numerical simulation was carried out using GRI-MECH 3.0. Results suggest that H2 and CO concentrations, dominant for rich and ultrarich combustion, are products from partial oxidation and steam natural gas reforming processes. Experimental and numerical results show that hydrogen yield increase with an increase of steam content in the natural gas-air mixtures. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

Archibold A.R.,University of South Florida | Archibold A.R.,Autonomous University of the Caribbean | Rahman M.M.,University of South Florida | Yogi Goswami D.,University of South Florida | Stefanakos E.K.,University of South Florida
Applied Energy | Year: 2015

The influence of radiation heat transfer during the phase change process of a storage material has been numerically analyzed in this study. Emphasis has been placed on the thermal characterization of a single constituent storage module rather than an entire storage system, in order to precisely capture the energy exchange contributions of all the fundamental heat transfer mechanisms during the melting of a phase change material (PCM) with tailored optical properties. The equations describing the conservation of mass, momentum and energy have been solved by using the control volume discretization approach, while the radiative transfer equation (RTE) was solved by the discrete ordinate method (DOM). The enthalpy-porosity method was used to track the PCM liquid/solid interface during the process. A parametric analysis has been performed in order to ascertain the effects of the optical thickness and the Planck, Grashof and Stefan numbers on the melting rate, as well as the total and radiative heat transfer rates at the inner surface of the shell. The results show that the presence of thermal radiation enhances the melting process. Correlations for the melt fraction and modified Nusselt number are developed for application in the design process of packed bed heat exchangers for latent heat thermal energy storage. © 2014 Elsevier Ltd. Source

Ibanez M.H.S.,Autonomous University of the Caribbean
Astrophysical Journal | Year: 2016

The Ertel theorem on the vorticity along the flow of adiabatic fluids is generalized for non-adiabatic flows. Several limiting cases are analyzed and the results are applied to flows behind different hydrodynamics fronts, particularly to thermal fronts (heat and cooling fronts). An important conclusion of the present analysis is that vorticity is inherent in the condensation's (or hot spots) formation by thermal instabilities in plasma flows. Implications for several astrophysical plasmas are outlined. © 2016. The American Astronomical Society. All rights reserved. Source

Gamarra Acosta M.R.,Autonomous University of the Caribbean | Velez Diaz J.C.,Universidad del Norte, Colombia | Schettini Castro N.,Universidad del Norte, Colombia
Corrosion Science | Year: 2014

This article presents an image-processing model for detection of rust zones using digital images of metals. The input image, containing a wide range of possible rusted textures, is simulated with Perlin Noise, which allows simulating extreme corrosion conditions, without waiting for these conditions to occur. Probabilistic descriptors are determined by means of discriminant analysis using Fisher indexes. A Bayesian classifier is used to identify rusted regions. Additionally, performance tests under different noise conditions and texture variations, generated with Perlin Noise, are presented. © 2014 Elsevier Ltd. Source

Archibold A.R.,University of South Florida | Archibold A.R.,Autonomous University of the Caribbean | Gonzalez-Aguilar J.,IMDEA Madrid Institute for Advanced Studies | Rahman M.M.,University of South Florida | And 3 more authors.
Applied Energy | Year: 2014

A two dimensional axisymmetric model of the heat transfer and fluid flow during the melting process inside a spherical latent heat thermal storage capsule is analyzed. A void space was provided within the capsule to take into account the volumetric expansion of the PCM. The mathematical model was solved using the finite-volume method, and the enthalpy-porosity formulation was employed to solve the energy equations in both the liquid and solid regions of the PCM. The effects of the Grashof and Stefan numbers on the thermal performance of the capsules of various diameters (20, 30, 40 and 50mm) have been investigated. It was found that increasing the Grashof number from 1.32×104 to 2. 06×105 enhances the heat transfer. Also for a constant Grashof number (9.09×104) the PCM melts at a faster rate when the Stefan number increases from 0.077 to 0.097. Finally, appropriate dimensionless variables based on a combination of the Fourier, Grashof and Stefan numbers are introduced in order to obtain a generalized correlation for the liquid mass fraction and the Nusselt number during melting of sodium nitrate. © 2013 Elsevier Ltd. Source

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