Entropy Generation in Nonisothermal Flows: Influence of Boundary Condition Type and Intensity

2019 ◽  
Vol 33 (4) ◽  
pp. 1085-1095
Author(s):  
J. M. Avellaneda ◽  
A. Toutant ◽  
G. Flamant ◽  
P. Neveu ◽  
F. Bataille
Keyword(s):  
Boundary Condition ◽  
Entropy Generation ◽  
Nonisothermal Flows

Lower Entropy Generation in Microchannels With Laminar Single Phase Flow

2010 ◽  
Author(s):  
E. Galvis ◽  
J. R. Culham
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Channel Geometry ◽  
Micro Channels ◽  
Optimum Channel

In this study the entropy generation minimization method is used to find the optimum channel dimensions in micro heat exchangers with a uniform heat flux. With this approach, pressure drop and heat transfer in the micro channels are considered simultaneously during the optimization analysis. A computational model is developed to find the optimum channel depth knowing other channel geometry dimensions and coolant inlet properties. The flow is assumed laminar and both hydrodynamically and thermally fully developed and incompressible. However, to take into account the effect of the developing length in the friction losses, the Hagenbach’s factor is introduced. The micro channels are assumed to have an isothermal or isoflux boundary condition, non-slip flow, and fluid properties have dependency on temperature accordingly. For these particular case studies, the pressure drop and heat transfer coefficient for the isoflux boundary condition is higher than the isothermal case. Higher heat transfer coefficient and pressure drop were found when the channel size decreased. The optimum channel geometry that minimizes the entropy generation rate tends to be a deep, narrow channel.

Entropy Generation Analysis in Nonlinear Convection Flow of Thermally Stratified Fluid in Saturated Porous Medium With Convective Boundary Condition

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
B. Vasu ◽  
Ch. RamReddy ◽  
P. V. S. N. Murthy ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Boundary Condition ◽  
Porous Medium ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Local Similarity ◽  
Surface Boundary ◽  
Thermal Dispersion ◽  
Partial Differential

This article emphasizes the significance of entropy generation analysis and nonlinear temperature density relation on thermally stratified viscous fluid flow over a vertical plate embedded in a porous medium with a thermal dispersion effect. In addition, the convective surface boundary condition is taken into an account. By using the suitable transformations, the governing flow equations in dimensional form are converted into set of nondimensional partial differential equations. Then the local similarity and nonsimilarity procedures are applied to transform the set of nondimensional partial differential equations into set of ordinary differential equations and then the resulting system of equations are solved by Chebyshev spectral collocation method along with the successive linearization. The effect of pertinent parameters, namely, Biot number, mixed convection parameter, and thermal dispersion on velocity, temperature, entropy generation rate, and heat transfer rate are displayed graphically and the salient features are explored in detail.

Analysis of Heat Transfer and Entropy Generation in a Channel Partially Filled With N-Layer Porous Media

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Kun Yang ◽  
Hao Chen ◽  
Jiabing Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Porous Medium ◽  
Porous Media ◽  
Entropy Generation ◽  
Entropy Generation Rate ◽  
Free Fluid ◽  
Bejan Number ◽  
Stress Jump

Convective heat transfer in a channel partially filled with porous medium has received a lot of attention due to its wide engineering applications. However, most researches focused on a channel partially filled with single layer porous medium. In this paper, we will analyze the heat transfer and entropy generation inside a channel partially filled with N-layer porous media. The flow and the heat transfer in the porous region are described by the Darcy–Brinkman model and the local thermal nonequilibrium model, respectively. At the porous-free fluid interface, the momentum and the heat transfer are described by the stress jump boundary condition and the heat flux jump boundary condition, respectively; while at the interface between two different porous layers, the momentum and the heat transfer are described by the stress continuity boundary condition and the heat flux continuity boundary condition, respectively. The analytical solutions for the velocity and temperature in the channel are derived and used to calculate the overall Nusselt number, the total entropy generation rate, the Bejan number, and the friction factor. Furthermore, the performances of the flow and heat transfer of a channel partially filled with third-layer porous media are studied.

Effect of Temperature Jump on Nonequilibrium Entropy Generation in a MOSFET Transistor Using Dual-Phase-Lagging Model

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Fraj Echouchene ◽  
Hafedh Belmabrouk
Keyword(s):  
Boundary Condition ◽  
Entropy Production ◽  
Entropy Generation ◽  
Temperature Jump ◽  
Oxide Semiconductor ◽  
Effect Of Temperature ◽  
Dual Phase ◽  
Conduction Model ◽  
Nonequilibrium Entropy ◽  
Effect Transistor

This paper investigates the effect of temperature-jump boundary condition on nonequilibrium entropy production under the effect of the dual-phase-lagging (DPL) heat conduction model in a two-dimensional sub-100 nm metal-oxide-semiconductor field effect transistor (MOSFET). The transient DPL model is solved using finite element method. Also, the influences of the governing parameters on global entropy generation for the following cases—(I) constant applied temperature, (II) temperature-jump boundary condition, and (III) a realistic MOSFET with volumetric heat source and adiabatic boundaries—are discussed in detail and depicted graphically. The analysis of our results indicates that entropy generation minimization within a MOSFET can be achieved by using temperature-jump boundary condition and for low values of Knudsen number. A significant reduction of the order of 85% of total entropy production is observed when a temperature-jump boundary condition is adopted.

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