We investigate the optimal performance of the quantum Otto engine and refrigeration cycles of a time-dependent harmonic oscillator under a trade-off figure of merit for both adiabatic and nonadiabatic (sudden-switch) frequency modulations. For heat engines (refrigerators), the chosen trade-off figure of merit is an objective function defined by the product of efficiency (coefficient of performance) and work output (cooling load), thus representing a compromise between them. We obtain analytical expressions for the efficiency and coefficient of performance of the harmonic Otto cycle for the optimal performance of the thermal machine in various operational regimes. Particularly, in the sudden-switch regime, we discuss the implications of the nonadiabatic driving on the performance of the thermal machine under consideration and obtain analytic expressions for the maximum achievable efficiency and coefficient of performance of the harmonic Otto thermal machine. Particularly, we show that the quantum harmonic Otto cycle driven by sudden-switch protocol cannot work as a heat engine or refrigerator in the low-temperature limit. Finally, we show that in the high-temperature limit, the frictional effects give rise to a richer structure of the phase diagram of the harmonic Otto cycle. We identify the parametric regime for the operation of the Otto cycle as a heat engine, refrigerator, accelerator, and heater.
{"title":"Performance analysis of quantum harmonic Otto engine and refrigerator under a trade-off figure of merit","authors":"Kirandeep Kaur, Shishram Rebari, Varinder Singh","doi":"10.1515/jnet-2024-0034","DOIUrl":"https://doi.org/10.1515/jnet-2024-0034","url":null,"abstract":"We investigate the optimal performance of the quantum Otto engine and refrigeration cycles of a time-dependent harmonic oscillator under a trade-off figure of merit for both adiabatic and nonadiabatic (sudden-switch) frequency modulations. For heat engines (refrigerators), the chosen trade-off figure of merit is an objective function defined by the product of efficiency (coefficient of performance) and work output (cooling load), thus representing a compromise between them. We obtain analytical expressions for the efficiency and coefficient of performance of the harmonic Otto cycle for the optimal performance of the thermal machine in various operational regimes. Particularly, in the sudden-switch regime, we discuss the implications of the nonadiabatic driving on the performance of the thermal machine under consideration and obtain analytic expressions for the maximum achievable efficiency and coefficient of performance of the harmonic Otto thermal machine. Particularly, we show that the quantum harmonic Otto cycle driven by sudden-switch protocol cannot work as a heat engine or refrigerator in the low-temperature limit. Finally, we show that in the high-temperature limit, the frictional effects give rise to a richer structure of the phase diagram of the harmonic Otto cycle. We identify the parametric regime for the operation of the Otto cycle as a heat engine, refrigerator, accelerator, and heater.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142090068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigates the effects of using biodiesel from Mesua ferrea (BD20) and chromium oxide (Cr2O3) nanoparticles in diesel engines. The Response Surface Methodology (RSM) model and artificial neural networks (ANNs) were developed to make precise predictions of the operating parameters. The amount of Cr2O3 nanoparticles was set at 80 mg/L, and surfactant and dispersant were applied to the nanoparticles in the same amounts. The study was carried out with different compression ratios and load conditions. The parameters evaluated were engine load, fuel samples and compression ratio as inputs and BTE, BSFC, CP, NHRR, CO, UHC, NOx and smoke opacity as outputs. The addition of the QPAN80 additive at the same dosage of 80 mg/L together with the BD20 fuel blend containing Cr2O3 at a concentration of 80 mg/L resulted in a significant increase in BTE by 16.58 % and a reduction in BSFC by 0.58 %. While the NHRR increased by 85.40 %, the CP increased sharply by 24.47 %. The CO concentration decreased by 31.85 %, the UHC concentration by 22.22 %, the NOx concentration by 6.16 % and the smoke emission by 62.61 %. For each output parameter, the correlation coefficient (R2), calculated using ANNs and RSM was between 0.96 and 0.98. The observed range of values demonstrates a robust correlation between the experimental data and the predicted outcomes.
{"title":"Investigation of the operating characteristics of diesel engines with chromium oxide (Cr2O3) nanoparticles dispersed in Mesua ferrea biodiesel: an experimental and predictive approach using ANNs and RSM","authors":"Jagadish Kari, Vanthala Varaha Siva Prasad, Jaikumar Sagari","doi":"10.1515/jnet-2024-0021","DOIUrl":"https://doi.org/10.1515/jnet-2024-0021","url":null,"abstract":"This study investigates the effects of using biodiesel from <jats:italic>Mesua ferrea</jats:italic> (BD20) and chromium oxide (Cr<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>) nanoparticles in diesel engines. The Response Surface Methodology (RSM) model and artificial neural networks (ANNs) were developed to make precise predictions of the operating parameters. The amount of Cr<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanoparticles was set at 80 mg/L, and surfactant and dispersant were applied to the nanoparticles in the same amounts. The study was carried out with different compression ratios and load conditions. The parameters evaluated were engine load, fuel samples and compression ratio as inputs and BTE, BSFC, CP, NHRR, CO, UHC, NO<jats:sub> <jats:italic>x</jats:italic> </jats:sub> and smoke opacity as outputs. The addition of the QPAN80 additive at the same dosage of 80 mg/L together with the BD20 fuel blend containing Cr<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> at a concentration of 80 mg/L resulted in a significant increase in BTE by 16.58 % and a reduction in BSFC by 0.58 %. While the NHRR increased by 85.40 %, the CP increased sharply by 24.47 %. The CO concentration decreased by 31.85 %, the UHC concentration by 22.22 %, the NO<jats:sub> <jats:italic>x</jats:italic> </jats:sub> concentration by 6.16 % and the smoke emission by 62.61 %. For each output parameter, the correlation coefficient (<jats:italic>R</jats:italic> <jats:sup>2</jats:sup>), calculated using ANNs and RSM was between 0.96 and 0.98. The observed range of values demonstrates a robust correlation between the experimental data and the predicted outcomes.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents mathematical responses for the dual-phase-lag (DPL) hypothesis, which accounts for nonequilibrium heat transfer during magnetic nanoparticle hyperthermia in tumor. To get this precision, volume averaging is used for the local instantaneous energy formulation for tissues and blood. This study proposes a hybrid numerical strategy to solve this problem by combining change of variables, improved discretization techniques, and Laplace transforms. Using the Arrhenius formulas, the range of denatured proteins is used to assess the degree of heat damages to the tumor and healthy tissues. The impacts of porosity, the blood perfusion and metabolism on the temperature and the thermal injuries are studied. The numerical estimations of temperature and the resulting of thermal injuries are shown on a graph, and a comparison with earlier research establishes the results’ validity.
{"title":"Analytical solutions for nonequilibrium bioheat transfer in tumor during magnetic nanoparticles hyperthermia","authors":"Zuhur Alqahtani, Ibrahim Abbas","doi":"10.1515/jnet-2024-0035","DOIUrl":"https://doi.org/10.1515/jnet-2024-0035","url":null,"abstract":"This paper presents mathematical responses for the dual-phase-lag (DPL) hypothesis, which accounts for nonequilibrium heat transfer during magnetic nanoparticle hyperthermia in tumor. To get this precision, volume averaging is used for the local instantaneous energy formulation for tissues and blood. This study proposes a hybrid numerical strategy to solve this problem by combining change of variables, improved discretization techniques, and Laplace transforms. Using the Arrhenius formulas, the range of denatured proteins is used to assess the degree of heat damages to the tumor and healthy tissues. The impacts of porosity, the blood perfusion and metabolism on the temperature and the thermal injuries are studied. The numerical estimations of temperature and the resulting of thermal injuries are shown on a graph, and a comparison with earlier research establishes the results’ validity.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141755075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The article analyses the degree of water superheating with respect to the liquid-vapour equilibrium line in experiments on the micro-explosion of a composite droplet comprised of two immiscible liquids. The analyses were carried out for water-in-fuel drops under conditions of high-power heating. This degree is compared with the mechanical effect of droplet decay, involving the formation of daughter droplets. Our attention was drawn to the smallness of the degree of superheating preceding the decay. A model of the boiling up of such a droplet is constructed taking into account the sources of premature boiling up of water inherent in micro-explosive experiments. The dependencies of the boiling up temperature of water on the heating rate obtained in the model turned out to be in accordance with the experimental data across a wide range of heating rates. A hypothesis about the local superheating of the transition layer, which is not detected in the experiment, is formulated. Thus, a step has been taken to clarify the essence of the mismatch of the degree of superheating of water recorded by macroscopic equipment along with a completely satisfactory generation of daughter droplets serving as the basis for advanced fuel technology.
{"title":"Composite liquids under high-power heating: superheat of water in micro-explosion of water-in-fuel droplets","authors":"Alexey Melkikh, Pavel Skripov","doi":"10.1515/jnet-2024-0017","DOIUrl":"https://doi.org/10.1515/jnet-2024-0017","url":null,"abstract":"The article analyses the degree of water superheating with respect to the liquid-vapour equilibrium line in experiments on the micro-explosion of a composite droplet comprised of two immiscible liquids. The analyses were carried out for water-in-fuel drops under conditions of high-power heating. This degree is compared with the mechanical effect of droplet decay, involving the formation of daughter droplets. Our attention was drawn to the smallness of the degree of superheating preceding the decay. A model of the boiling up of such a droplet is constructed taking into account the sources of premature boiling up of water inherent in micro-explosive experiments. The dependencies of the boiling up temperature of water on the heating rate obtained in the model turned out to be in accordance with the experimental data across a wide range of heating rates. A hypothesis about the local superheating of the transition layer, which is not detected in the experiment, is formulated. Thus, a step has been taken to clarify the essence of the mismatch of the degree of superheating of water recorded by macroscopic equipment along with a completely satisfactory generation of daughter droplets serving as the basis for advanced fuel technology.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141755085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We discuss the application of the three-laser optical digital interferometry method for the determination of transport properties such as the thermodiffusion, the molecular diffusion and the Soret coefficients by the thermogravitational column technique. The primary objective of this study is to illustrate the capabilities and limitations of the method for quantifying these properties in both binary and ternary liquid mixtures from an optical viewpoint. It is concluded that the system is highly robust for the analysis of binary mixtures, with the combination of the results obtained by the three wavelengths increasing the accuracy of the measurement. The study of ternary mixtures, on the contrary, is limited to certain types of conditions. While the accuracy of a three-laser interferometer can be improved, the method may be compromised if the optical contrast factor matrices are poorly conditioned.
{"title":"Application of a three-laser optical digital interferometry in a thermogravitational analysis for binary and ternary mixtures","authors":"Ane Errarte, Antton Sanjuan, Aliaksandr Mialdun, Marcos Alonso, Imanol Andonegui, Valentina Shevtsova, M. Mounir Bou-Ali","doi":"10.1515/jnet-2023-0126","DOIUrl":"https://doi.org/10.1515/jnet-2023-0126","url":null,"abstract":"We discuss the application of the three-laser optical digital interferometry method for the determination of transport properties such as the thermodiffusion, the molecular diffusion and the Soret coefficients by the thermogravitational column technique. The primary objective of this study is to illustrate the capabilities and limitations of the method for quantifying these properties in both binary and ternary liquid mixtures from an optical viewpoint. It is concluded that the system is highly robust for the analysis of binary mixtures, with the combination of the results obtained by the three wavelengths increasing the accuracy of the measurement. The study of ternary mixtures, on the contrary, is limited to certain types of conditions. While the accuracy of a three-laser interferometer can be improved, the method may be compromised if the optical contrast factor matrices are poorly conditioned.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In many industrial applications as well as in nature, the mass transfer of CO2 at vapor-liquid interfaces in aqueous systems plays an important role. In this work, this process was studied on the atomistic level using non-equilibrium molecular dynamics simulations. In a first step, a molecular model of the system water + CO2 was developed that represents both bulk and interfacial equilibrium properties well. This system is characterized by a very large adsorption and enrichment of CO2 at the vapor-liquid interface. Then, non-equilibrium mass transfer simulations were carried out using a method that was developed recently: CO2 is inserted into the vapor phase of a simulation box which contains a liquid slab. Surprising effects are observed at the interface such as a net repulsion of CO2 particles from the interface and a complex time dependence of the amount of CO2 adsorbed at the interface.
在许多工业应用和自然界中，二氧化碳在水性体系的汽液界面上的传质都发挥着重要作用。在这项工作中，我们利用非平衡分子动力学模拟在原子水平上研究了这一过程。首先，我们建立了水 + CO2 系统的分子模型，该模型能很好地反映体液和界面的平衡特性。该系统的特点是二氧化碳在汽液界面上的大量吸附和富集。然后，使用最近开发的一种方法进行了非平衡传质模拟：在包含液态板坯的模拟箱中的气相中加入二氧化碳。在界面上观察到了令人惊讶的效应，如二氧化碳颗粒对界面的净排斥以及界面上二氧化碳吸附量的复杂时间依赖性。
{"title":"Mass transfer at vapor-liquid interfaces of H2O + CO2 mixtures studied by molecular dynamics simulation","authors":"Simon Stephan, Vilde Bråten, Hans Hasse","doi":"10.1515/jnet-2024-0010","DOIUrl":"https://doi.org/10.1515/jnet-2024-0010","url":null,"abstract":"In many industrial applications as well as in nature, the mass transfer of CO<jats:sub>2</jats:sub> at vapor-liquid interfaces in aqueous systems plays an important role. In this work, this process was studied on the atomistic level using non-equilibrium molecular dynamics simulations. In a first step, a molecular model of the system water + CO<jats:sub>2</jats:sub> was developed that represents both bulk and interfacial equilibrium properties well. This system is characterized by a very large adsorption and enrichment of CO<jats:sub>2</jats:sub> at the vapor-liquid interface. Then, non-equilibrium mass transfer simulations were carried out using a method that was developed recently: CO<jats:sub>2</jats:sub> is inserted into the vapor phase of a simulation box which contains a liquid slab. Surprising effects are observed at the interface such as a net repulsion of CO<jats:sub>2</jats:sub> particles from the interface and a complex time dependence of the amount of CO<jats:sub>2</jats:sub> adsorbed at the interface.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract From a finite-time thermodynamics perspective, a thermoeconomic analysis of a Novikov model employing a linear heat transfer law is carried out. A new component in the cost function is proposed to examine its relationship with waste management while operating in the maximum power, ecological, and efficient power regimes. The methodology consists of optimizing the profit function by including our new waste management cost function, leveraging the same method used by DeVos (“Endoreversible thermoeconomics,” Energy Convers. Manage., vol. 36, pp. 1–5, 1995) and Pacheco et al. (“Thermoeconomic optimization of an irreversible novikov plant model under different regimes of performance,” Entropy, vol. 19, p. 118, 2017). Searching for the optimal thermoeconomic efficiencies for the ecological case a novel numerical method developed by the corresponding author (A. M. Ares de Parga-Regalado, “Analytical approximation of optimal thermoeconomic efficiencies for a novikov engine with a Stefan–Boltzmann heat transfer law,” Results Phys., 2023) is used. Analytical expressions for the optimal efficiencies are obtained, and the impact of the proposed term on these values is investigated.
摘要 从有限时间热力学的角度，对采用线性传热规律的诺维科夫模型进行了热经济分析。在成本函数中提出了一个新的组成部分，以研究其与废物管理的关系，同时在最大功率、生态和高效功率状态下运行。该方法包括利用 DeVos 使用的相同方法（"Endoreversible thermoeconomics," Energy Convers.Manage.》，第 36 卷，第 1-5 页，1995 年）和 Pacheco 等人（《不同性能状态下不可逆诺维科夫工厂模型的热经济优化》，《熵》，第 19 卷，第 118 页，2017 年）所使用的方法。为寻找生态情况下的最佳热经济效率，使用了由通讯作者开发的一种新型数值方法（A. M. Ares de Parga-Regalado，"具有斯特凡-波尔兹曼传热规律的诺维科夫发动机最佳热经济效率的分析近似"，《成果物理》，2023 年）。得出了最佳效率的分析表达式，并研究了拟议项对这些值的影响。
{"title":"Thermoeconomic optimization with a dissipation cost","authors":"A. Ares de Parga-Regalado, Gonzalo Ares de Parga","doi":"10.1515/jnet-2023-0089","DOIUrl":"https://doi.org/10.1515/jnet-2023-0089","url":null,"abstract":"Abstract From a finite-time thermodynamics perspective, a thermoeconomic analysis of a Novikov model employing a linear heat transfer law is carried out. A new component in the cost function is proposed to examine its relationship with waste management while operating in the maximum power, ecological, and efficient power regimes. The methodology consists of optimizing the profit function by including our new waste management cost function, leveraging the same method used by DeVos (“Endoreversible thermoeconomics,” Energy Convers. Manage., vol. 36, pp. 1–5, 1995) and Pacheco et al. (“Thermoeconomic optimization of an irreversible novikov plant model under different regimes of performance,” Entropy, vol. 19, p. 118, 2017). Searching for the optimal thermoeconomic efficiencies for the ecological case a novel numerical method developed by the corresponding author (A. M. Ares de Parga-Regalado, “Analytical approximation of optimal thermoeconomic efficiencies for a novikov engine with a Stefan–Boltzmann heat transfer law,” Results Phys., 2023) is used. Analytical expressions for the optimal efficiencies are obtained, and the impact of the proposed term on these values is investigated.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141334949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract An extension and further development of our previous article [J. Non-equilibrium Thermodyne. 37 (2012), 119–141] is presented. We study the irreversible non-equilibrium thermodynamics (INT) properties of the exact solution to the dilute homogeneously charged gas problem with unsteady Rayleigh flow. In contrast to previous research, the charged gas flows under the influence of an external force, the flat plate oscillates, and the displacement current term is considered, leading to significant advancements in understanding natural plasma dynamics. We are solving the Boltzmann kinetic equation (BKE) Krook model supplemented by Maxwell’s equations. We used a travelling wave and moments method with an electron velocity distribution function (EVDF). To the best of our knowledge, as three new scientific achievements, we introduced a new mathematical model for calculating the thermodynamic forces, kinetic coefficients, and fluxes variables, Equations (28–40) and (50–54). Second, we determined, with reasonable accuracy, the thermodynamic equilibrium time of electrons, t equ = 26.7955, under an external force. We clarify the difference between equilibrium EVDF and perturbed EVDF and take advantage of BKE to account for non-equilibrium thermodynamic principles. For diamagnetic and paramagnetic plasmas, the extended Gibbs equation predicts ratios between various contributions to the internal energy change (IEC) is presented. A standard laboratory argon plasma model is used to apply the results.
{"title":"Kinetic and thermodynamic approach to precisely solve the unsteady Rayleigh flow problem of a rarefied homogeneous charged gas under external force influence","authors":"Taha Zakaraia Abdel Wahid, Z. M. Alaofi","doi":"10.1515/jnet-2024-0022","DOIUrl":"https://doi.org/10.1515/jnet-2024-0022","url":null,"abstract":"Abstract An extension and further development of our previous article [J. Non-equilibrium Thermodyne. 37 (2012), 119–141] is presented. We study the irreversible non-equilibrium thermodynamics (INT) properties of the exact solution to the dilute homogeneously charged gas problem with unsteady Rayleigh flow. In contrast to previous research, the charged gas flows under the influence of an external force, the flat plate oscillates, and the displacement current term is considered, leading to significant advancements in understanding natural plasma dynamics. We are solving the Boltzmann kinetic equation (BKE) Krook model supplemented by Maxwell’s equations. We used a travelling wave and moments method with an electron velocity distribution function (EVDF). To the best of our knowledge, as three new scientific achievements, we introduced a new mathematical model for calculating the thermodynamic forces, kinetic coefficients, and fluxes variables, Equations (28–40) and (50–54). Second, we determined, with reasonable accuracy, the thermodynamic equilibrium time of electrons, t equ = 26.7955, under an external force. We clarify the difference between equilibrium EVDF and perturbed EVDF and take advantage of BKE to account for non-equilibrium thermodynamic principles. For diamagnetic and paramagnetic plasmas, the extended Gibbs equation predicts ratios between various contributions to the internal energy change (IEC) is presented. A standard laboratory argon plasma model is used to apply the results.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141346297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Avramenko, I. Shevchuk, M. Kovetskaya, Y. Kovetska, A.S. Kobzar
Abstract This work focuses on the study of natural convection in a flat porous microchannel with asymmetric heating. The novelty of the work lies in the fact that for the first time the method of discrete symmetries was used to analyze the complete system of Navier–Stokes and energy equations in a two-dimensional approximation. Analytical solutions for velocity and temperature profiles have been derived based on symmetry analysis, taking into account boundary conditions such as slip and temperature jump at the channel walls. The effect of Grashof, Knudsen, Darcy, and Prandtl numbers on the flow characteristics in the microchannel and heat transfer coefficients was elucidated. At high Grashof numbers, an ascending flow near the hot wall and a descending flow near the cold wall arise. Increasing the Knudsen number leads to an increase in the velocity, temperature jump at the walls and a decrease in heat transfer coefficients. As the Darcy number increases, velocities amplify in both ascending and descending flows. The temperature jump at the hot wall grows up, while it remains unchanged at the cold wall. In the same time, the heat transfer coefficient at the hot wall decreases.
{"title":"Application of discrete symmetry to natural convection in vertical porous microchannels","authors":"A. Avramenko, I. Shevchuk, M. Kovetskaya, Y. Kovetska, A.S. Kobzar","doi":"10.1515/jnet-2024-0006","DOIUrl":"https://doi.org/10.1515/jnet-2024-0006","url":null,"abstract":"Abstract This work focuses on the study of natural convection in a flat porous microchannel with asymmetric heating. The novelty of the work lies in the fact that for the first time the method of discrete symmetries was used to analyze the complete system of Navier–Stokes and energy equations in a two-dimensional approximation. Analytical solutions for velocity and temperature profiles have been derived based on symmetry analysis, taking into account boundary conditions such as slip and temperature jump at the channel walls. The effect of Grashof, Knudsen, Darcy, and Prandtl numbers on the flow characteristics in the microchannel and heat transfer coefficients was elucidated. At high Grashof numbers, an ascending flow near the hot wall and a descending flow near the cold wall arise. Increasing the Knudsen number leads to an increase in the velocity, temperature jump at the walls and a decrease in heat transfer coefficients. As the Darcy number increases, velocities amplify in both ascending and descending flows. The temperature jump at the hot wall grows up, while it remains unchanged at the cold wall. In the same time, the heat transfer coefficient at the hot wall decreases.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":null,"pages":null},"PeriodicalIF":6.6,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141352051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fuzhang Wang, I. L. Animasaun, Dalal Matar Al Shamsi, Taseer Muhammad, Asgar Ali
Abstract The interaction between water motion efficiency, outlet control mechanisms, and energy dynamics management hinges significantly on turbulence characteristics. However, understanding the influence of input velocities and duct features on outlets remains elusive. This study employs the realizable k − ɛ viscous model and Reynolds-averaged Navier–Stokes equations (RANS equations) to explore transient water dynamics encountering a cold front through ducts leading to convergence or divergence. Using Ansys Fluent 2023R2 and the waterlight workflow, meticulous meshing of the ducts is executed to capture flow intricacies accurately. Grid independence, suitable boundary conditions, and solver settings are carefully considered to ensure reliable results for investigating four key research questions. Duct bending introduces non-uniformities in velocity distribution, impacting exit velocity and altering flow characteristics and turbulence. In Case III, centrifugal forces from a 90° bend result in higher outlet velocities at the convergent exit and secondary flow patterns like swirls and vortexes. Additionally, entrance velocities influence Reynolds numbers, affecting mixing, heat transfer coefficients, and flow regimes, thereby optimizing thermal conductivity. This comprehensive investigation sheds light on optimizing water dynamics and energy management across various duct configurations, offering valuable insights into efficient flow control and thermal performance enhancement.
摘要 水流运动效率、出水口控制机制和能量动态管理之间的相互作用在很大程度上取决于湍流特性。然而，对输入速度和风道特征对出水口的影响的理解仍很模糊。本研究采用了可实现的 k - ɛ 粘滞模型和雷诺平均纳维-斯托克斯方程（RANS 方程），以探索遇到冷锋时通过风道导致汇聚或发散的瞬态水流动力学。使用 Ansys Fluent 2023R2 和 waterlight 工作流程，对管道进行了细致的网格划分，以准确捕捉流动的复杂性。网格独立性、合适的边界条件和求解器设置都经过仔细考虑，以确保获得可靠的结果，用于研究四个关键研究问题。管道弯曲会导致速度分布不均匀，影响出口速度并改变流动特性和湍流。在案例 III 中，90° 弯曲产生的离心力导致汇聚出口处的出口速度较高，并产生漩涡和涡流等二次流动模式。此外，入口速度会影响雷诺数，从而影响混合、传热系数和流态，进而优化导热性。这项全面的研究揭示了如何在各种管道配置中优化水动力学和能源管理，为高效的流量控制和热性能提升提供了宝贵的见解。
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