Thermodynamic irreversibilities and exergy balance in combustion processes

Som, S. K.; Datta, Amitava

doi:10.1016/j.pecs.2007.09.001

Cited by 233 publications

(103 citation statements)

References 54 publications

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“…Som et al [9] reviewed the earliest studies on thermodynamic irreversibility and exergy analysis in the process of the combustion of gaseous, liquid and solid fuels. In natural and mixed convection system flow, Oztop et al [10] reviewed the entropy generation exploitation, while other authors focused on laminar and turbulent forced convection (see [11]).…”

Section: Introductionmentioning

confidence: 99%

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

Ries

Janicka

Sadiki

2017

Entropy

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Abstract:In the present paper, thermal transport and entropy production mechanisms in a turbulent round jet of compressed nitrogen at supercritical thermodynamic conditions are investigated using a direct numerical simulation. First, thermal transport and its contribution to the mixture formation along with the anisotropy of heat fluxes and temperature scales are examined. Secondly, the entropy production rates during thermofluid processes evolving in the supercritical flow are investigated in order to identify the causes of irreversibilities and to display advantageous locations of handling along with the process regimes favorable to mixing. Thereby, it turned out that (1) the jet disintegration process consists of four main stages under supercritical conditions (potential core, separation, pseudo-boiling, turbulent mixing), (2) causes of irreversibilities are primarily due to heat transport and thermodynamic effects rather than turbulence dynamics and (3) heat fluxes and temperature scales appear anisotropic even at the smallest scales, which implies that anisotropic thermal diffusivity models might be appropriate in the context of both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) approaches while numerically modeling supercritical fluid flows.

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Section: Introductionmentioning

confidence: 99%

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

Ries

Janicka

Sadiki

2017

Entropy

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“…Nishida et al [8] analysed entropy generation mechanisms in laminar hydrogen-air and methane-air premixed flames based on detailed chemistry based simulations and demonstrated the effects of equivalence ratio on the entropy generation in premixed flames. Different mechanisms of entropy generation in multi-component reacting systems have been identified in a number of previous analyses [8][9][10][11][12][13][14][15] on premixed and non-premixed combustion. Interested readers are referred to [15] for an extensive review of entropy generation in reactive system.…”

Section: Introductionmentioning

confidence: 99%

“…Different mechanisms of entropy generation in multi-component reacting systems have been identified in a number of previous analyses [8][9][10][11][12][13][14][15] on premixed and non-premixed combustion. Interested readers are referred to [15] for an extensive review of entropy generation in reactive system. It has been found that viscous dissipation, thermal conduction, mass diffusion and irreversible chemical reaction give rise to generation of entropy in reacting flows.…”

Section: Introductionmentioning

confidence: 99%

A Direct Numerical Simulation-Based Analysis of Entropy Generation in Turbulent Premixed Flames

Farran

Chakraborty

2013

Entropy

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A compressible single step chemistry Direct Numerical Simulation (DNS) database of freely propagating premixed flames has been used to analyze different entropy generation mechanisms. The entropy generation due to viscous dissipation within the flames remains negligible in comparison to the other mechanisms of entropy generation. It has been found that the entropy generation increases significantly due to turbulence and the relative magnitudes of the augmentation of entropy generation and burning rates under turbulent conditions ultimately determine the value of turbulent second law efficiency in comparison to the corresponding laminar values. It has been found that the entropy generation mechanisms due to chemical reaction, thermal conduction and mass diffusion in turbulent flames strengthen with decreasing global Lewis number in comparison to the corresponding values in laminar flames. The ratio of second law efficiency under turbulent conditions to its corresponding laminar value has been found to decrease with increasing global Lewis number. An increase in heat release parameter significantly augments the entropy generation due to thermal conduction, whereas other mechanisms of entropy generation are marginally affected. However, the effects of augmented entropy generation due to thermal conduction at high values of heat release parameter are eclipsed by the increased change in availability due to chemical reaction, which leads to an increase in the second law efficiency with increasing heat release parameter for identical flow conditions. The combustion regime does not have any major influence on the augmentation of entropy generation due to chemical reaction, thermal conduction and mass diffusion in turbulent flames in comparison to corresponding laminar flames, whereas the extent of augmentation of entropy generation due to viscous dissipation in turbulent conditions in comparison to OPEN ACCESSEntropy 2013, 15 1541 corresponding laminar flames, is more significant in the thin reaction zones regime than in the corrugated flamelets regime. However, the ratio of second law efficiency under turbulent conditions to its corresponding laminar value does not get significantly affected by the regime of combustion, as viscous dissipation plays a marginal role in the overall entropy generation in premixed flames.

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“…Hence, this paper assesses the thermodynamic irreversibilities of HTAC. Such irreversibilities cause entropy generation which limits fuel energy conversion into useful work [7].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Entropy Generation in Diffusion HTAC Processes

Makhanlall¹,

Jiang²

2014

IJAPM

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Abstract-Thermodynamic irreversibility significantly limits fuel energy conversion into useful work. Hence, the evaluation of thermodynamic irreversibility is an important aspect in the development of combustion techniques for better fuel utilization. This evaluation is performed for the HTAC (high-temperature air combustion) process through entropy generation analysis. The primary irreversible processes of HTAC are determined and the influence of key operating parameters such as the combustion air temperature, and oxygen-dilution are studied.

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Thermodynamic irreversibilities and exergy balance in combustion processes

Cited by 233 publications

References 54 publications

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

Thermal Transport and Entropy Production Mechanisms in a Turbulent Round Jet at Supercritical Thermodynamic Conditions

A Direct Numerical Simulation-Based Analysis of Entropy Generation in Turbulent Premixed Flames

Analysis of Entropy Generation in Diffusion HTAC Processes

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