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Special Issue "Entropy Generation Minimization"

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A special issue of Entropy (ISSN 1099-4300).

Deadline for manuscript submissions: closed (31 August 2011)

Special Issue Editor

Guest Editor
Prof. Dr. Heinz Herwig (Website)

Hamburg University of Technology, Institute of Thermo-Fluid Dynamics, M-21, Denickestr. 17, D-21071 Hamburg, Germany
Fax: ++49 (0)40-42878-4169
Interests: enhancement of heat and mass transfer (fundamental investigations and development of adapted sanctions); critical use of commercial CFD-Software; evaluation of transport phenomena by entropy production considerations; influence of heat transfer on flow stability; fundamental investigations of momentum-, heat- and mass-transfer in components of micro fluid devices; LDV measurements in turbulent separated flows

Special Issue Information

Dear Colleagues,

In almost all technical applications momentum, heat, and/or mass transfer occurs. These transfer processes are subject to "losses", which from a thermodynamic point of view can be identified as losses of exergy (available work). A second law analysis (SLA) is appropriate to identify and to quantify these losses by determining the entropy generation involved. Whenever exergy losses are disadvantageous and should be avoided as far as possible it comes to an "Entropy Generation Minimization". The special issue of Entropy collects studies that account for the entropy generation in this sence in various fields.

Heinz Herwig
Guest Editor

Keywords

  • second law analysis
  • loss of exergy
  • loss of available work
  • optimization

Published Papers (9 papers)

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Research

Open AccessArticle Entropy Generation During the Interaction of Thermal Radiation with a Surface
Entropy 2012, 14(4), 717-735; doi:10.3390/e14040717
Received: 15 February 2012 / Revised: 27 March 2012 / Accepted: 27 March 2012 / Published: 11 April 2012
Cited by 5 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
The entropy calculation for radiation fluxes is reviewed and applied to simple radiation-surface interactions. A plate interacting with radiation from a hot object in the zenith of the hemisphere surrounded by a colder atmosphere is analyzed in detail. The entropy generation rate [...] Read more.
The entropy calculation for radiation fluxes is reviewed and applied to simple radiation-surface interactions. A plate interacting with radiation from a hot object in the zenith of the hemisphere surrounded by a colder atmosphere is analyzed in detail. The entropy generation rate upon absorption and reflection of the incoming radiation is calculated and discussed. The plate is adiabatic in a first version (thermal equilibrium), then its temperature is fixed by allowing a heat flux to or from the plate. This analysis prepares the way towards an entropy generation minimization analysis of more complex radiation settings. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Open AccessArticle Effects of Radiation Heat Transfer on Entropy Generation at Thermosolutal Convection in a Square Cavity Subjected to a Magnetic Field
Entropy 2011, 13(12), 1992-2012; doi:10.3390/e13121992
Received: 1 June 2011 / Revised: 27 June 2011 / Accepted: 21 July 2011 / Published: 28 November 2011
PDF Full-text (2620 KB) | HTML Full-text | XML Full-text
Abstract
Thermosolutal convection in a square cavity filled with a binary perfect gas mixture and submitted to an oriented magnetic field taking into account the effect of radiation heat transfer is numerically investigated. The cavity is heated and cooled along the active walls [...] Read more.
Thermosolutal convection in a square cavity filled with a binary perfect gas mixture and submitted to an oriented magnetic field taking into account the effect of radiation heat transfer is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined for laminar flow by solving numerically: The continuity, momentum energy and mass balance equations, using a Control Volume Finite-Element Method. The structure of the studied flows depends on five dimensionless parameters which are: The Grashof number, the buoyancy ratio, the Hartman number, the inclination angle of the magnetic field and the radiation parameter. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Open AccessArticle Entropy Generation Analysis of Desalination Technologies
Entropy 2011, 13(10), 1829-1864; doi:10.3390/e13101829
Received: 5 September 2011 / Revised: 27 September 2011 / Accepted: 27 September 2011 / Published: 30 September 2011
Cited by 46 | PDF Full-text (297 KB)
Abstract
Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on [...] Read more.
Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Figures

Open AccessArticle Spectral Entropy in a Boundary-Layer Flow
Entropy 2011, 13(9), 1555-1583; doi:10.3390/e13091555
Received: 15 July 2011 / Revised: 20 August 2011 / Accepted: 23 August 2011 / Published: 26 August 2011
Cited by 6 | PDF Full-text (2206 KB) | HTML Full-text | XML Full-text
Abstract
This article presents a comparison of the entropy production in a laminar and transitional boundary layer flow with the spectral entropy produced in a region of instability induced by an imposed periodic disturbance. The objective of the study is exploratory in nature [...] Read more.
This article presents a comparison of the entropy production in a laminar and transitional boundary layer flow with the spectral entropy produced in a region of instability induced by an imposed periodic disturbance. The objective of the study is exploratory in nature by computing a boundary-layer environment with well-established computer techniques and comparing the predictions of the maximum rate of entropy production in the wall shear layer with the deterministic prediction of the spectral entropy growth within an inceptive instability in the inner region of the upstream boundary-layer flow. The deterministic values of the spectral entropy within the instability are brought into agreement with the computed rate of entropy production inversely along the shear flow with the assumption that the instability is of a span-wise vortex form and that the spectral entropy components are transported into the wall shear layer by vortex down sweep and are processed into thermodynamic entropy in the boundary-layer wall region. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Figures

Open AccessArticle Second Law Analysis for Variable Viscosity Hydromagnetic Boundary Layer Flow with Thermal Radiation and Newtonian Heating
Entropy 2011, 13(8), 1446-1464; doi:10.3390/e13081446
Received: 6 May 2011 / Revised: 3 July 2011 / Accepted: 16 July 2011 / Published: 5 August 2011
Cited by 22 | PDF Full-text (5658 KB) | HTML Full-text | XML Full-text
Abstract
The present paper is concerned with the analysis of inherent irreversibility in hydromagnetic boundary layer flow of variable viscosity fluid over a semi-infinite flat plate under the influence of thermal radiation and Newtonian heating. Using local similarity solution technique and shooting quadrature, [...] Read more.
The present paper is concerned with the analysis of inherent irreversibility in hydromagnetic boundary layer flow of variable viscosity fluid over a semi-infinite flat plate under the influence of thermal radiation and Newtonian heating. Using local similarity solution technique and shooting quadrature, the velocity and temperature profiles are obtained numerically and utilized to compute the entropy generation number. The effects of magnetic field parameter, Brinkmann number, the Prandtl number, variable viscosity parameter, radiation parameter and local Biot number on the fluid velocity profiles, temperature profiles, local skin friction and local Nusselt number are presented. The influences of the same parameters and the dimensionless group parameter on the entropy generation rate in the flow regime and Bejan number are calculated, depicted graphically and discussed quantitatively. It is observed that the peak of entropy generation rate is attained within the boundary layer region and plate surface act as a strong source of entropy generation and heat transfer irreversibility. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Open AccessArticle Diffuser and Nozzle Design Optimization by Entropy Generation Minimization
Entropy 2011, 13(7), 1380-1402; doi:10.3390/e13071380
Received: 10 June 2011 / Revised: 1 July 2011 / Accepted: 15 July 2011 / Published: 20 July 2011
Cited by 8 | PDF Full-text (998 KB) | HTML Full-text | XML Full-text
Abstract
Diffusers and nozzles within a flow system are optimized with respect to their wall shapes for a given change in cross sections. The optimization target is a low value of the head loss coefficient K, which can be linked to the overall [...] Read more.
Diffusers and nozzles within a flow system are optimized with respect to their wall shapes for a given change in cross sections. The optimization target is a low value of the head loss coefficient K, which can be linked to the overall entropy generation due to the conduit component. First, a polynomial shape of the wall with two degrees of freedom is assumed. As a second approach six equally spaced diameters in a diffuser are determined by a genetic algorithm such that the entropy generation and thus the head loss is minimized. It turns out that a visualization of cross section averaged entropy generation rates along the flow path should be used to identify sources of high entropy generation before and during the optimization. Thus it will be possible to decide whether a given parametric representation of a component’s shape only leads to a redistribution of losses or (in the most-favored case) to minimal values for K. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Figures

Open AccessArticle Application of the EGM Method to a LED-Based Spotlight: A Constrained Pseudo-Optimization Design Process Based on the Analysis of the Local Entropy Generation Maps
Entropy 2011, 13(7), 1212-1228; doi:10.3390/e13071212
Received: 22 April 2011 / Revised: 5 June 2011 / Accepted: 15 June 2011 / Published: 27 June 2011
Cited by 3 | PDF Full-text (5560 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the entropy generation minimization (EGM) method is applied to an industrial heat transfer problem: the forced convective cooling of a LED-based spotlight. The design specification calls for eighteen diodes arranged on a circular copper plate of 35 mm diameter. [...] Read more.
In this paper, the entropy generation minimization (EGM) method is applied to an industrial heat transfer problem: the forced convective cooling of a LED-based spotlight. The design specification calls for eighteen diodes arranged on a circular copper plate of 35 mm diameter. Every diode dissipates 3 W and the maximum allowedtemperature of the plate is 80 °C. The cooling relies on the forced convection driven by a jet of air impinging on the plate. An initial complex geometry of plate fins is presented and analyzed with a commercial CFD code that computes the entropy generation rate. A pseudo-optimization process is carried out via a successive series of design modifications based on a careful analysis of the entropy generation maps. One of the advantages of the EGM method is that the rationale behind each step of the design process can be justified on a physical basis. It is found that the best performance is attained when the fins are periodically spaced in the radial direction. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Figures

Open AccessArticle Entropy Generation at Natural Convection in an Inclined Rectangular Cavity
Entropy 2011, 13(5), 1020-1033; doi:10.3390/e13051020
Received: 10 February 2011 / Revised: 29 March 2011 / Accepted: 4 April 2011 / Published: 23 May 2011
Cited by 13 | PDF Full-text (2107 KB) | HTML Full-text | XML Full-text
Abstract
Natural convection in an inclined rectangular cavity filled with air is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls of the cavity are adiabatic. Entropy generation due to heat transfer and fluid friction [...] Read more.
Natural convection in an inclined rectangular cavity filled with air is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls of the cavity are adiabatic. Entropy generation due to heat transfer and fluid friction has been determined in transient state for laminar natural convection by solving numerically: the continuity, momentum and energy equations, using a Control Volume Finite Element Method. The structure of the studied flows depends on four dimensionless parameters which are: the thermal Grashof number, the inclination angle, the irreversibility distribution ratio and the aspect ratio of the cavity. The obtained results show that entropy generation tends towards asymptotic values for lower thermal Grashof number values, whereas it takes an oscillative behavior for higher values of thermal Grashof number. Transient entropy generation increases towards a maximum value, then decreases asymptotically to a constant value that depends on aspect ratio of the enclosure. Entropy generation increases with the increase of thermal Grashof number, irreversibility distribution ratio and aspect ratio of the cavity. Bejan number is used to measure the predominance of either thermal or viscous irreversibility. At local level, irreversibility charts show that entropy generation is mainly localized on bottom corner of the left heated wall and upper corner of the right cooled wall. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)
Open AccessArticle Analysis of the Magnetic Field Effect on Entropy Generation at Thermosolutal Convection in a Square Cavity
Entropy 2011, 13(5), 1034-1054; doi:10.3390/e13051034
Received: 10 February 2011 / Revised: 5 April 2011 / Accepted: 19 April 2011 / Published: 23 May 2011
Cited by 3 | PDF Full-text (2100 KB) | HTML Full-text | XML Full-text
Abstract
Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are [...] Read more.
Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined in transient state for laminar flow by solving numerically the continuity, momentum energy and mass balance equations, using a Control Volume Finite—Element Method. The structure of the studied flows depends on four dimensionless parameters which are the Grashof number, the buoyancy ratio, the Hartman number and the inclination angle. The results show that the magnetic field parameter has a retarding effect on the flow in the cavity and this lead to a decrease of entropy generation, Temperature and concentration decrease with increasing value of the magnetic field parameter. Full article
(This article belongs to the Special Issue Entropy Generation Minimization)

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