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Entropy Generation Analysis in Near-Wall Turbulent Flow

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A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Statistical Physics".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 23127

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Prof. Dr. Amsini Sadiki

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Guest Editor

1. Department of Mechanical Engineering, Institute of Reactive Flows and Diagnostics, Technical University of Darmstadt, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany
2. Department of Mechanical Engineering, Institute of Energy and Power Plant Technology, Technical University of Darmstadt, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany
Interests: turbulence/combustion modeling; heat and mass transfer; extended thermodynamics; multiphase flows; CFD

Special Issue Information

Dear Colleagues,

With respect to both environmental sustainability and operating efficiency demands, the need for more exergy-efficient thermofluid components and devices is continuously increasing in a variety of technology sectors and energy conversion systems. Today, it is being recognized that an analysis of local entropy generation consistingof minimizing the irreversibilities in transport and physico-chemical processes can be used as an effective means to optimize the performance of current and future thermofluid-based applications and to support novel developments. The Special Issue aims to gather original contributions which deal with entropy generation analysis in near-wall turbulent flows using experiments and/or computational fluid dynamics. Potential topics may include:

The formulation of models that describe the evolving transport processes in compatibility with both the second law of thermodynamics and the design requirements;
State-of-the-art methodologies that not only allow identifying the causes of inefficiency of processes but also permit evaluating the significance (location and magnitude) of irreversibilities generated by each specific transport process;
Appropriate techniques that aid in delimiting the evolution of the processes and at the same time give access to the control and possible minimization of the irreversibilities;
Demonstrations in reacting/non-reacting flows in single-phase/multiphase environments.

Prof. Dr. Amsini Sadiki
Guest Editor

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Keywords

thermofluid components and systems
entropy generation analysis
exergy loss and irreversibilities
near-wall turbulent reacting/non-reacting flow
single phase/multiphase environments
numerical modeling/simulation
experiments
validation
optimization

Published Papers (10 papers)

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Research

20 pages, 13204 KiB

Open AccessFeature PaperArticle

Estimation of Entropy Generation in a SCR-DeNOx System with AdBlue Spray Dynamic Using Large Eddy Simulation

by Kaushal Nishad and Senda Agrebi

Entropy 2023, 25(3), 475; https://doi.org/10.3390/e25030475 - 09 Mar 2023

Viewed by 1506

Abstract

In this work, the entropy generation analysis is extended to the multi-phase fluid flow within a Large Eddy Simulation (LES) framework. The selected study case consists of a generic selective catalytic reduction (SCR) configuration in which the water/AdBlue is injected into a cross-flow of the internal combustion (IC) engine exhaust gas. The adopted numerical modules are first assessed by comparing with experimental data for film thickness in the case of AdBlue injection and then with H₂O mass fraction and temperature for water injection case. Subsequently, the impact of heat transfer, fluid flow, phase change, mixing and chemical reaction due to AdBlue injection on the entropy generation is assessed. Hence, the individual contributions of viscous and heat dissipation together with the species mixing, chemical reaction during the thermal decomposition of urea into NH₃ and dispersed phase are especially evaluated and analysed. In comparison to the shares of the viscous and mixing processes, the entropy generation is predominated by the heat, chemical and dispersed phase contributions. The influence of the operating parameters such as exhaust gas temperature, flow rate and AdBlue injection on entropy generation is discussed in details. Using a suitable measures, the irreversibility map and some necessary inferences are also provided. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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21 pages, 4414 KiB

Open AccessArticle

Experimental Study of the Influence of Different Load Changes in Inlet Gas and Solvent Flow Rate on CO₂ Absorption in a Sieve Tray Column

by Adel Almoslh, Babak Aghel, Falah Alobaid, Christian Heinze and Bernd Epple

Entropy 2022, 24(9), 1318; https://doi.org/10.3390/e24091318 - 19 Sep 2022

Viewed by 1400

Abstract

An experimental study was conducted in a sieve tray column. This study used a simulated flue gas consisting of 30% CO₂ and 70%. A 10% mass fraction of methyl diethanolamine (MDEA) aqueous solution was used as a solvent. Three ramp-up tests were performed to investigate the effect of different load changes in inlet gas and solvent flow rate on CO₂ absorption. The rate of change in gas flow rate was 0.1 Nm³/h/s, and the rate of change in MDEA aqueous solution was about 0.7 NL/h/s. It was found that different load changes in inlet gas and solvent flow rate significantly affect the CO₂ volume fraction at the outlet during the transient state. The CO₂ volume fraction reaches a peak value during the transient state. The effect of different load changes in inlet gas and solvent flow rate on the hydrodynamic properties of the sieve tray were also investigated. The authors studied the correlation between the performance of the absorber column for CO₂ capture during the transient state and the hydrodynamic properties of the sieve tray. In addition, this paper presents an experimental investigation of the bubble-liquid interaction as a contributor to entropy generation on a sieve tray in the absorption column used for CO₂ absorption during the transient state of different load changes. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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12 pages, 3081 KiB

Open AccessCommunication

Numerical Investigation of Exergy Loss of Ammonia Addition in Hydrocarbon Diffusion Flames

by Haifeng Sun, Zhongnong Zhang, Hanxiao Sun, Bin Yao and Chun Lou

Entropy 2022, 24(7), 922; https://doi.org/10.3390/e24070922 - 01 Jul 2022

Cited by 1 | Viewed by 1230

Abstract

In this paper, a theoretical numerical analysis of the thermodynamics second law in ammonia/ethylene counter-flow diffusion flames is carried out. The combustion process, which includes heat and mass transfer, as well as a chemical reaction, is simulated based on a detailed chemical reaction model. Entropy generation and exergy loss due to various reasons in ammonia/ethylene and argon/ethylene flames are calculated. The effects of ammonia addition on the thermodynamics efficiency of combustion are investigated. Based on thermodynamics analysis, a parameter, the lowest emission of pollutant (LEP), is proposed to establish a relationship between the available work and pollutant emissions produced during the combustion process. Chemical reaction paths are also analyzed by combining the chemical entropy generation, and some important chemical reactions and substances are identified. The numerical results reveal that ammonia addition has a significant enhancement on heat transfer and chemical reaction in the flames, and the total exergy loss rate increases slightly at first and then decreases with an increase in ammonia concentration. Considering the factors of thermodynamic efficiency, the emissions of CO₂ and NOx reach a maximum when ammonia concentration is near 10% and 30%, respectively. In terms of the chemical reaction path analysis, ammonia pyrolysis and nitrogen production increase significantly, while ethylene pyrolysis and carbon monoxide production decrease when ammonia is added to hydrocarbon diffusion flames. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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24 pages, 4853 KiB

Open AccessArticle

Impact of Multi-Component Surrogates on the Performances, Pollutants, and Exergy of IC Engines

by Kambale Mondo, Senda Agrebi, Fathi Hamdi, Fatma Lakhal, Amsini Sadiki and Mouldi Chrigui

Entropy 2022, 24(5), 671; https://doi.org/10.3390/e24050671 - 10 May 2022

Cited by 2 | Viewed by 2006

Abstract

Even though there is a pressing interest in clean energy sources, compression ignition (CI) engines, also called diesel engines, will remain of great importance for transportation sectors as well as for power generation in stationary applications in the foreseeable future. In order to promote applications dealing with complex diesel alternative fuels by facilitating their integration in numerical simulation, this paper targets three objectives. First, generate novel diesel fuel surrogates with more than one component. Here, five surrogates are generated using an advanced chemistry solver and are compared against three mechanisms from the literature. Second, validate the suggested reaction mechanisms (RMs) with experimental data. For this purpose, an engine configuration, which features a reacting spray flow evolving in a direct-injection (DI), single-cylinder, and four-stroke motor, is used. The RNG k-Epsilon coupled to power-law combustion models is applied to describe the complex in-cylinder turbulent reacting flow, while the hybrid Eulerian-Lagrangian Kelvin Helmholtz-Rayleigh Taylor (KH-RT) spray model is employed to capture the spray breakup. Third, highlight the impact of these surrogate fuels on the combustion properties along with the exergy of the engine. The results include distribution of temperature, pressure, heat release rate (HRR), vapor penetration length, and exergy efficiency. The effect of the surrogates on pollutant formation (

N O_{X}

C O

C O_{2}

) is also highlighted. The fifth surrogate showed 47% exergy efficiency. The fourth surrogate agreed well with the maximum experimental pressure, which equaled 85 Mpa. The first, second, and third surrogates registered 400, 316, and 276 g/kg fuel, respectively, of the total CO mass fraction at the outlet. These quantities were relatively higher compared to the fourth and fifth RMs. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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18 pages, 4549 KiB

Open AccessArticle

Impact of Spray Cone Angle on the Performances of Methane/Diesel RCCI Engine Combustion under Low Load Operating Conditions

by Fathi Hamdi, Senda Agrebi, Mohamed Salah Idrissi, Kambale Mondo, Zeineb Labiadh, Amsini Sadiki and Mouldi Chrigui

Entropy 2022, 24(5), 650; https://doi.org/10.3390/e24050650 - 05 May 2022

Cited by 8 | Viewed by 2446

Abstract

The behaviors of spray, in Reactivity Controlled Combustion Ignition (RCCI) dual fuel engine and subsequent emissions formation, are numerically addressed. Five spray cone angles ranging between 5° and 25° with an advanced injection timing of 22° Before Top Dead Center (BTDC) are considered. The objective of this paper is twofold: (a) to enhance engine behaviors in terms of performances and consequent emissions by adjusting spray cone angle and (b) to outcome the exergy efficiency for each case. The simulations are conducted using the Ansys-forte tool. The turbulence model is the Renormalization Group (RNG) K-epsilon, which is selected for its effectiveness in strongly sheared flows. The spray breakup is governed by the hybrid model Kelvin–Helmholtz and Rayleigh–Taylor spray models. A surrogate of n-heptane, which contains 425 species and 3128 reactions, is used for diesel combustion modeling. The obtained results for methane/diesel engine combustion, under low load operating conditions, include the distribution of heat transfer flux, pressure, temperature, Heat Release Rate (HRR), and Sauter Mean Diameter (SMD). An exergy balance analysis is conducted to quantify the engine performances. Output emissions at the outlet of the combustion chamber are also monitored in this work. Investigations show a pressure decrease for a cone angle θ = 5° of roughly 8%, compared to experimental measurement (θ = 10°). A broader cone angle produces a higher mass of NO_x. The optimum spray cone angle, in terms of exergy efficiency, performance, and consequent emissions is found to lie at 15° ≤ θ ≤ 20°. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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20 pages, 10177 KiB

Open AccessFeature PaperArticle

Computation of Entropy Production in Stratified Flames Based on Chemistry Tabulation and an Eulerian Transported Probability Density Function Approach

by Louis Dressler, Hendrik Nicolai, Senda Agrebi, Florian Ries and Amsini Sadiki

Entropy 2022, 24(5), 615; https://doi.org/10.3390/e24050615 - 28 Apr 2022

Cited by 4 | Viewed by 1465

Abstract

This contribution presents a straightforward strategy to investigate the entropy production in stratified premixed flames. The modeling approach is grounded on a chemistry tabulation strategy, large eddy simulation, and the Eulerian stochastic field method. This enables a combination of a detailed representation of the chemistry with an advanced model for the turbulence chemistry interaction, which is crucial to compute the various sources of exergy losses in combustion systems. First, using detailed reaction kinetic reference simulations in a simplified laminar stratified premixed flame, it is demonstrated that the tabulated chemistry is a suitable approach to compute the various sources of irreversibilities. Thereafter, the effects of the operating conditions on the entropy production are investigated. For this purpose, two operating conditions of the Darmstadt stratified burner with varying levels of shear have been considered. The investigations reveal that the contribution to the entropy production through mixing emerging from the chemical reaction is much larger than the one caused by the stratification. Moreover, it is shown that a stronger shear, realized through a larger Reynolds number, yields higher entropy production through heat, mixing and viscous dissipation and reduces the share by chemical reaction to the total entropy generated. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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18 pages, 17420 KiB

Open AccessArticle

Prediction of Heat Transfer and Fluid Flow Effects on Entropy Generation in a Monolithic Catalytic Converter Using Large-Eddy Simulation

by Yongxiang Li, Luis Felipe Rico Cortes, Hardy Hamel, Kaushal Nishad, Luigi Biondo and Florian Ries

Entropy 2022, 24(5), 602; https://doi.org/10.3390/e24050602 - 26 Apr 2022

Cited by 3 | Viewed by 1862

Abstract

In the present work, heat transfer and fluid flow and their effects on entropy generation in a realistic catalytic converter of a Lada Niva 21214 vehicle are studied using large eddy simulation. At first, the pressure drop over the catalytic converter is measured [...] Read more.

T = 298

K), different volumetric flow rates, and extrapolated to large volumetric flow rates for dry air (

T = 298

K) and for the exhaust gas under realistic engine conditions (

T = 900

K) using the Darcy–Forchheimer relation. Then, coupled heat and fluid flow phenomena inside the catalytic converter are analyzed for nonreacting isothermal conditions and nonreacting conditions with conjugate heat transfer by using the large-eddy simulation. The predicted pressure drop agrees well with the measured and extrapolated data. Based on the obtained numerical results, the characteristic flow features are identified, namely: the impinging flow with stagnation, recirculation, flow separation and laminarization within the fine ducts of the monolith, which depends on the heat transfer through temperature-dependent thermophysical properties of exhaust gas. Moreover, due to high-velocity gradients at the wall of the narrow ducts in the monolith, entropy production by viscous dissipation is observed predominantly in the monolith region. In contrast, entropy production due to heat transport is relatively small in the monolith region, while it overwhelms viscous dissipation effects in the pipe regions. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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18 pages, 4893 KiB

Open AccessArticle

The Exergy Losses Analysis in Adiabatic Combustion Systems including the Exhaust Gas Exergy

by Senda Agrebi, Louis Dreßler and Kaushal Nishad

Entropy 2022, 24(4), 564; https://doi.org/10.3390/e24040564 - 18 Apr 2022

Cited by 4 | Viewed by 6020

Abstract

The entropy generation analysis of adiabatic combustion systems was performed to quantify the exergy losses which are mainly the exergy destroyed during combustion inside the chamber and in the exhaust gases. The purpose of the present work was therefore: (a) to extend the exergy destruction analysis by including the exhaust gas exergy while applying the hybrid filtered Eulerian stochastic field (ESF) method coupled with the FGM chemistry tabulation strategy; (b) to introduce a novel method for evaluating the exergy content of exhaust gases; and (c) to highlight a link between exhaust gas exergy and combustion emissions. In this work, the adiabatic Sandia flames E and F were chosen as application combustion systems. First, the numerical results of the flow and scalar fields were validated by comparison with the experimental data. The under-utilization of eight stochastic fields (SFs), the flow field results and the associated scalar fields for the flame E show excellent agreement contrary to flame F. Then, the different exergy losses were calculated and analyzed. The heat transfer and chemical reaction are the main factors responsible for the exergy destruction during combustion. The chemical exergy of the exhaust gases shows a strong relation between the exergy losses and combustion emission as well as the gas exhaust temperature. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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18 pages, 2679 KiB

Open AccessEditor’s ChoiceArticle

Entropy Generation during Head-On Interaction of Premixed Flames with Inert Walls within Turbulent Boundary Layers

by Sanjeev Kr. Ghai, Umair Ahmed, Nilanjan Chakraborty and Markus Klein

Entropy 2022, 24(4), 463; https://doi.org/10.3390/e24040463 - 27 Mar 2022

Cited by 6 | Viewed by 1721

Abstract

The statistical behaviours of different entropy generation mechanisms in the head-on interaction of turbulent premixed flames with a chemically inert wall within turbulent boundary layers have been analysed using Direct Numerical Simulation data. The entropy generation characteristics in the case of head-on premixed flame interaction with an isothermal wall is compared to that for an adiabatic wall. It has been found that entropy generation due to chemical reaction, thermal diffusion and molecular mixing remain comparable when the flame is away from the wall for both wall boundary conditions. However, the wall boundary condition affects the entropy generation during flame-wall interaction. In the case of isothermal wall, the entropy generation due to chemical reaction vanishes because of flame quenching and the entropy generation due to thermal diffusion becomes the leading entropy generator at the wall. By contrast, the entropy generation due to thermal diffusion and molecular mixing decrease at the adiabatic wall because of the vanishing wall-normal components of the gradients of temperature and species mass/mole fractions. These differences have significant effects on the overall entropy generation rate during flame-wall interaction, which suggest that combustor wall cooling needs to be optimized from the point of view of structural integrity and thermodynamic irreversibility. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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17 pages, 5010 KiB

Open AccessArticle

Heat Transfer and Pressure Drop of Nanofluid with Rod-like Particles in Turbulent Flows through a Curved Pipe

by Wenqian Lin, Ruifang Shi and Jianzhong Lin

Entropy 2022, 24(3), 416; https://doi.org/10.3390/e24030416 - 16 Mar 2022

Cited by 6 | Viewed by 1920

Abstract

Pressure drop, heat transfer, and energy performance of ZnO/water nanofluid with rodlike particles flowing through a curved pipe are studied in the range of Reynolds number 5000 ≤ Re ≤ 30,000, particle volume concentration 0.1% ≤ Φ ≤ 5%, Schmidt number 10⁴ ≤ Sc ≤ 3 × 10⁵, particle aspect ratio 2 ≤ λ ≤ 14, and Dean number 5 × 10³ ≤ De ≤ 1.5 × 10⁴. The momentum and energy equations of nanofluid, together with the equation of particle number density for particles, are solved numerically. Some results are validated by comparing with the experimental results. The effect of Re, Φ, Sc, λ, and De on the friction factor f and Nusselt number Nu is analyzed. The results showed that the values of f are increased with increases in Φ, Sc, and De, and with decreases in Re and λ. The heat transfer performance is enhanced with increases in Re, Φ, λ, and De, and with decreases in Sc. The ratio of energy PEC for nanofluid to base fluid is increased with increases in Re, Φ, λ, and De, and with decreases in Sc. Finally, the formula of ratio of energy PEC for nanofluid to base fluid as a function of Re, Φ, Sc, λ, and De is derived based on the numerical data. Full article

(This article belongs to the Special Issue Entropy Generation Analysis in Near-Wall Turbulent Flow)

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