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Papers by Oscar Bautista
Second Law Analysis for a Mixed Electro-Osmotic and Pressure Driven Flow of a Viscoelastic Fluid in a Micro-Channel
Volume 6: Energy, Parts A and B, 2012
ABSTRACT In this work the entropy generation rate in a parallel flat plate micro-channel under mi... more ABSTRACT In this work the entropy generation rate in a parallel flat plate micro-channel under mixed electro-osmotic and pressure driven flow with a non-Newtonian fluid is analyzed. A fully-developed flow is considered and the fluid obeys a constitutive relation based in a simplified Phan-Thien-Tanner model. The temperature distributions of a conjugate heat transfer problem in the micro-channel were solved asymptotically in steady-state, then, expressions for dimensionless local and average entropy generation rate are obtained. The aim of this paper is to show the influence of dimensionless parameters involved on the entropy generation rate: the viscoelastic parameter, the ratio of pressure forces to electro-osmotic forces, the Péclet number, the normalized power generation term, the dimensionless temperature difference, the ratio of micro-channel thickness to length, the ratio of micro-channel wall thickness to length and the conjugation parameter; this set of parameters controls directly the thermal performance of this micro-channel. We can predict that the entropy generation rate is basically dominated by the Joule heating effect.
International Journal of Heat and Mass Transfer, 2015
In this work, we develop a theoretical study of the thermal and denaturation processes in a biolo... more In this work, we develop a theoretical study of the thermal and denaturation processes in a biological tissue subject to a surface heating, when coupled effects of dynamic changes of blood perfusion and temperature-dependent physical properties are taken into account. To analyze this phenomenon, the governing equations were appropriately nondimensionalized, where a suitable Damköhler number appears, which measures the competition between the denaturation time and the characteristic thermal diffusive time of tissue. In order to determine the denaturation front, situation that occurs when tissue has been completely denatured, we show the existence of a critical value of this dimensionless number for each time, which represents an eigenvalue in the mathematical model. Important results of the proposed model indicate that the denatured region, and the time required for carrying out this thermal process are substantially modified in comparison with the case of constant physical properties. In addition, the magnitude of the applied thermal energy source, the biological resistance of tissue to thermal attack and the blood perfusion are very important aspects that must be considered in those medical treatments that make use of rehabilitation therapies by thermal processes.
Second Law Analysis for a Mixed Electro-Osmotic and Pressure Driven Flow of a Viscoelastic Fluid in a Micro-Channel
Volume 6: Energy, Parts A and B, 2012
ABSTRACT In this work the entropy generation rate in a parallel flat plate micro-channel under mi... more ABSTRACT In this work the entropy generation rate in a parallel flat plate micro-channel under mixed electro-osmotic and pressure driven flow with a non-Newtonian fluid is analyzed. A fully-developed flow is considered and the fluid obeys a constitutive relation based in a simplified Phan-Thien-Tanner model. The temperature distributions of a conjugate heat transfer problem in the micro-channel were solved asymptotically in steady-state, then, expressions for dimensionless local and average entropy generation rate are obtained. The aim of this paper is to show the influence of dimensionless parameters involved on the entropy generation rate: the viscoelastic parameter, the ratio of pressure forces to electro-osmotic forces, the Péclet number, the normalized power generation term, the dimensionless temperature difference, the ratio of micro-channel thickness to length, the ratio of micro-channel wall thickness to length and the conjugation parameter; this set of parameters controls directly the thermal performance of this micro-channel. We can predict that the entropy generation rate is basically dominated by the Joule heating effect.
International Journal of Heat and Mass Transfer, 2015
In this work, we develop a theoretical study of the thermal and denaturation processes in a biolo... more In this work, we develop a theoretical study of the thermal and denaturation processes in a biological tissue subject to a surface heating, when coupled effects of dynamic changes of blood perfusion and temperature-dependent physical properties are taken into account. To analyze this phenomenon, the governing equations were appropriately nondimensionalized, where a suitable Damköhler number appears, which measures the competition between the denaturation time and the characteristic thermal diffusive time of tissue. In order to determine the denaturation front, situation that occurs when tissue has been completely denatured, we show the existence of a critical value of this dimensionless number for each time, which represents an eigenvalue in the mathematical model. Important results of the proposed model indicate that the denatured region, and the time required for carrying out this thermal process are substantially modified in comparison with the case of constant physical properties. In addition, the magnitude of the applied thermal energy source, the biological resistance of tissue to thermal attack and the blood perfusion are very important aspects that must be considered in those medical treatments that make use of rehabilitation therapies by thermal processes.