Guillermo Ibáñez

Minimization of entropy generation by asymmetric convective cooling

The uniform internal heating of a solid slab and the viscous flow between two parallel walls, are used to illustrate the possibility of minimizing the global entropy generation rate by cooling the external surfaces convectively in an asymmetric way. The known analytic expressions for the temperature field, in the first case, and the velocity and temperature fields, in the second case, are used to calculate the global entropy generation rate explicitly. In dimensionless terms, this function depends on the dimensionless ambient temperature and convective heat transfer coefficients (Biot numbers) of each surface which, in general, are not assumed to be the same. When the Biot numbers for each surface are equal, the entropy generation rate shows a monotonic increase. However, when the Biot numbers are different this function displays a minimum for specific cooling conditions.

Optimization analysis of an alternate magnetohydrodynamic generator

The production of electric power through the oscillatory motion of an electrically conducting fluid in a continuous electrode Faraday generator is considered. The performance of this alternate magnetohydrodynamic (MHD) generator is analyzed using the conventional isotropic electrical efficiency and an overall second law efficiency, based on the global entropy generation rate. The velocity, electric current density and temperature fields for the oscillatory Hartmann flow are calculated in order to assess, in terms of the entropy generation rate, the dissipative phenomena caused by fluid friction, Joule heating and heat transfer in the MHD generator. The overall second law efficiency is used to determine optimum operation conditions that minimize process irreversibilities.

The structural transition of the Na_{309} clusters

Theoretical insights are provided for understanding why the structural changes detected by photoelectronic measurements on the canonical ensemble of clusters Na309\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}

Entropy generation minimization of a MHD (magnetohydrodynamic) flow in a microchannel

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Entropy generation analysis of a nanofluid flow in MHD porous microchannel with hydrodynamic slip and thermal radiation

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Entropy generation in MHD porous channel with hydrodynamic slip and convective boundary conditions

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