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Chan F.,University of Quintana Roo | Calleja H.,CENIDET
IEEE Transactions on Industrial Electronics | Year: 2011

This paper presents the reliability estimation of the power stages in three grid-connected photovoltaic systems. The circuits analyzed are an integrated topology, a two-stage configuration, and a three-stage one, all commutating in the hard-switching mode. The reliability-related parameters, such as the failure rate, are calculated following the procedure outlined in MIL-HDBK 217. A comparison between the topologies is performed, and both the components and the stress factor with the highest contribution to the failure rate are identified. The methods to calculate junction temperature variations are included. © 2006 IEEE. Source


Juarez J.O.,University of Sonora | Hinojosa J.F.,University of Sonora | Xaman J.P.,CENIDET | Tello M.P.,University of Sonora
International Journal of Thermal Sciences | Year: 2011

In this work the numerical results of heat transfer calculations in an open cavity considering natural convection and temperature-dependent fluid properties are presented. The overall continuity, momentum, and energy equations in terms of primitive variables were solved numerically using the finite-volume method. Numerical calculations were conducted for Rayleigh number (Ra) values in the range of 104-107. The temperature difference between the hot wall and the bulk fluid (ΔT) was varied between 10 and 500 K, and was represented as a dimensionless temperature difference (ε) for the purpose of generalization of the trends observed. The results show that the thickness of the hydrodynamic boundary layer in the vicinity of the hot wall increases as ε increases from 0.03 to 1.6. The average Nusselt number in the cavity (Nu) was found to increase by 807% (ε = 0.03) and 1105% (ε = 1.6) as the Ra number varied from 104 to 107. Likewise, the average Nu number in the cavity decreased by 39% (Ra = 104) and 18% (Ra = 106) as ε was varied from 0.03 to 1.6. © 2011 Elsevier Masson SAS. All rights reserved. Source


Astorga-Zaragoza C.M.,CENIDET | Theilliol D.,University of Lorraine | Ponsart J.C.,University of Lorraine | Rodrigues M.,CNRS Automation and Process Engineering Laboratory
International Journal of Adaptive Control and Signal Processing | Year: 2012

In this paper, a model-based fault estimation method for a particular class of discrete-time descriptor linear parameter-varying systems is developed. The main contribution of this work consists in the design of an observer that performs simultaneously both, the states estimation and the fault magnitude vectors, considered as unknown inputs. The conditions for the existence of such observer are given. Such conditions guarantee the observer stability and they are proved through a Lyapunov analysis combined with a linear matrix inequalities formulation. The fault estimation scheme is evaluated through numerical simulations. © 2011 John Wiley & Sons, Ltd. Source


Lvarez G.,CENIDET | Heras M.R.,CIEMAT
Journal of Solar Energy Engineering, Transactions of the ASME | Year: 2013

In this paper we present a theoretical study of a small solar chimney. The dimensions of the solar chimney channel are 1.95 m high, 1.70 m wide, and 0.24 m deep. The channel of the solar chimney has in its backside a metallic plate as a solar heat absorber, and it is attached to a concrete wall, which acts as storage and thermal insulation. On the front part of the chimney a glass cover is used to decrease the heat losses to the exterior. For this theoretical study, the steady-state energy balance equations were solved numerically for each element of the solar chimney. The results showed the temperature profiles for the glass cover, the air inside the channel, and the metallic plate. Also, the air mass flow rate was determined. When solar irradiance increases from 100 to 700 W/m 2, the maximum instantaneous efficiency of the system varies from 28 to 37, and also, the volumetric flow rate increases from 61 to 147 m 3/h. © 2012 American Society of Mechanical Engineers. Source


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. Source

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