Entropy production in flames

Arpacı, Vedat S.; Selamet, Ahmet

doi:10.1016/0010-2180(88)90022-3

Cited by 64 publications

(22 citation statements)

References 16 publications

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“…It is thus of great interest to determine the magnitudes and causes of irreversibility in this process (cf. [21,22]. Dunbar and Lior [23,24], have probably been the first to evaluate the primary causes for irreversibility,using asomewhat heuristic finite increment exergy analysis method for asimple hydrogen or methane combustor.…”

Section: Exergy Analysis In Combustion Motivationmentioning

confidence: 99%

The Exergy Fields in Processes

Lior¹,

Beretta²,

Ghoniem³

et al. 2008

AIP Conference Proceedings

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This paper is a very brief review of the method for analyzing the space and time dependent exergy and irreversibility fields in processes. It presents the basic equations, the method for their use, and three examples from the work of the author and his former graduate students: flow desiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Law analysis are used to attempt process improvement suggestions. Abstract. This paper is av ery brief reviewo ft he method for analyzing the space and time dependent exergyand irreversibility fields in processes. It presents the basic equations, the method for their use, and three examples from the work of the author and his former graduate students: 1 flowdesiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Lawanalysis are used to attempt process improvement suggestions. Law) analysis must be added to the conventional energy accounting analysis during the conception, analysis, development, and design of such systems. Most of this analysis is nowadays conducted on the system leveldevelopment, by evaluating the exergyv alues and changes of component input and output streams and energy interactions. While this can indeed identify the exergyd estruction in as ystem component, it does not deliver the detailed information about the specific process phenomena, often space and time dependent, which causes the exergyc hanges in it. The phenomena may include heat transfer,m ass transfer,fl uid mechanics, chemical and/or nuclear reactions, and the presence of fields such as gravitational, electric and magnetic. This type of detailed analysis, which we shall call "intrinsic", due in the second phase of system development, is invaluable in accelerating the evolution of the innovative systems needed to meet the difficult demands of the coming century,and is the focus of this paper. Disciplines Engineering | Mechanical Engineering APERSONAL INTRODUCTIONAlthough the objectivesofexergyorentropyanalysis appear to be obvious, it is very noteworthy to recall that the most important and useful ones are: (1) identification of the specific phenomena/processes that have large exergyl osses or irreversibilities, (2) understanding why these losses occur,(3) evaluating howtheychange with anychanges in the process parameters and configuration, and (4) as ac onsequence of all these, suggestions on howthe process could be improved. Asurprisingly large fraction of the publications in this field deal only with (1) above,and are therefore of little use, at best.We start by presenting the basic field equations needed for the intrinsic exergyanalysis, briefly survey the state of the art, and present specific examples from our work on convective desiccation and on combustion of oil droplets and of pulverized coal. THE EXERGY/ENTROPY PRODUCTION FIELD EQUATIONSThe general transient rigorous physico-chemical partial differential equations for computing the intrinsic irreversibilities and exergyd estruction ...

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Section: Exergy Analysis In Combustion Motivationmentioning

confidence: 99%

The Exergy Fields in Processes

Lior¹,

Beretta²,

Ghoniem³

et al. 2008

AIP Conference Proceedings

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“…However, the evaluation of entropy production due to radiative heat transfer in participating media has often been overlooked. Arpaci [12,13] and Arpaci and Selamet [14][15][16] evaluated the radiative entropy production by analogy to that due to conduction, which is true in the case of an optically thick medium. In their study of entropy generation due to interaction of the radiative field with solid boundaries, Wright et al [17] extended and generalized this formalism for grey and non-participating media.…”

Section: Introductionmentioning

confidence: 99%

Entropy generation through combined non-grey gas radiation and forced convection between two parallel plates

Nejma

Mazgar

Abdallah

et al. 2008

Energy

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“…From the calculated scalar fields of temperature and velocity components by using Equations (11)- (13), local entropy generation is determined by Equation (21), then total entropy generation is evaluated by numerical integration of Equation (27). Nusselt number is also calculated by Equation (17).…”

Section: Numerical Schemementioning

confidence: 99%

“…The theoretical method of entropy generation has been used in the specialized literature to treat external and internal irreversibilities. The irreversibility phenomena, which are expressed by entropy generation in a given system, are related to heat transfer, mass transfer, viscous dissipation, magnetic field, etc., Bejan [23][24][25], Bejan et al [26], Arpaci and Selamet [27,28], Arpaci [29,30], Arpaci and Esmaeeli [31], Magherbi et al [32,33] and Abbassi et al [34] have studied the influence of operating parameters on entropy generation in different flow configurations. They showed that the flow parameters might be chosen in order to minimize entropy generation inside the system.…”

Section: Introductionmentioning

confidence: 99%

Effect of an External Oriented Magnetic Field on Entropy Generation in Natural Convection

Jery

Hidouri

Magherbi³

et al. 2010

Entropy

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Abstract:The influence of an external oriented magnetic field on entropy generation in natural convection for air and liquid gallium is numerically studied in steady-unsteady states by solving the mass, the momentum and the energy conservation equations. Entropy generation depends on five parameters which are: the Prandtl number, the irreversibility coefficients, the inclination angle of the magnetic field, the thermal Grashof and the Hartmann numbers. Effects of these parameters on total and local irreversibilities as well as on heat transfer and fluid flow are studied. It was found that the magnetic field tends to decrease the convection currents, the heat transfer and entropy generation inside the enclosure. Influence of inclination angle of the magnetic field on local irreversibility is then studied.

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Entropy production in flames

Cited by 64 publications

References 16 publications

The Exergy Fields in Processes

The Exergy Fields in Processes

Entropy generation through combined non-grey gas radiation and forced convection between two parallel plates

Effect of an External Oriented Magnetic Field on Entropy Generation in Natural Convection

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