Fernando Bautista, Juan Paulo García-Sandoval, Octavio Manero
Phase diagrams out of equilibrium have been the subject of intense research. An essential concept in these diagrams is the phase definition. Currently, that definition is well established for systems at classic thermodynamic equilibrium conditions. However, such phase definition is inadequate for systems that are not at equilibrium in the classic thermodynamic sense, like fluid systems under flowing conditions. Complex fluids may exhibit instabilities like shear-banding flow and a non-equilibrium critical point where banding flow ends. At this point, the fluid undergoes a phase transition from heterogeneous to homogeneous states. An extended thermodynamic space of variables is considered to adequately address this situation, which includes non-conservative variables such as stress and shear rate. Hence, the current phase definition based on conservative variables does not apply to non-equilibrium phase diagrams. On this basis, a broader definition of phase is required. We propose that this broader definition considers the thermodynamic variables space of Extended Irreversible Thermodynamics and the mathematical conditions that ensure compatibility between equilibrium and non-equilibrium conditions for systems where phases are well described by thermodynamic potentials even out of equilibrium.
{"title":"Is there a need for an extended phase definition for systems far from equilibrium?","authors":"Fernando Bautista, Juan Paulo García-Sandoval, Octavio Manero","doi":"10.1515/jnet-2024-0063","DOIUrl":"https://doi.org/10.1515/jnet-2024-0063","url":null,"abstract":"Phase diagrams out of equilibrium have been the subject of intense research. An essential concept in these diagrams is the phase definition. Currently, that definition is well established for systems at classic thermodynamic equilibrium conditions. However, such phase definition is inadequate for systems that are not at equilibrium in the classic thermodynamic sense, like fluid systems under flowing conditions. Complex fluids may exhibit instabilities like shear-banding flow and a non-equilibrium critical point where banding flow ends. At this point, the fluid undergoes a phase transition from heterogeneous to homogeneous states. An extended thermodynamic space of variables is considered to adequately address this situation, which includes non-conservative variables such as stress and shear rate. Hence, the current phase definition based on conservative variables does not apply to non-equilibrium phase diagrams. On this basis, a broader definition of phase is required. We propose that this broader definition considers the thermodynamic variables space of Extended Irreversible Thermodynamics and the mathematical conditions that ensure compatibility between equilibrium and non-equilibrium conditions for systems where phases are well described by thermodynamic potentials even out of equilibrium.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"67 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417792","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 computationally investigates the time-dependent patterns emerging in the Soret regime for binary fluid convection in slightly inclined cylinders heated from below, with a particular focus on positive Soret coefficient thermophobic mixtures (ST > 0) and aspect ratios Γ = 5.2, Γ = 5.3, and Γ = 5.4. By varying the Rayleigh number (Ra) and smoothly adjusting its increments, we capture a range of spatio-temporal behaviours, revealing the coexistence of large-scale shear flows (LSF) and superhighway convection (SHC) patterns. SHC-like structures, characterised by a high base frequency, involve oscillating plumes arranged in adjacent lanes, moving in opposite directions along the inclination. Remarkably, this frequency remains nearly constant across different Ra values. Some of the observed coherent structures, such as periodic and modulated solutions, exhibit equivariance with respect to some elements of the D2 ${mathbb{D}}_{2}$ symmetry group inherent to the physical system. In the case of Γ = 5.4, we identify three-frequency orbits, with modulations up to two orders of magnitude smaller than the base frequency. The observed dynamics is highly sensitive to small variations of Γ, with different patterns being stabilized depending on the aspect ratio of the cell. The bifurcation scenarios are complex and case-specific, and their precise determination is computationally demanding.
{"title":"Numerical simulation of binary convection within the Soret regime in a tilted cylinder","authors":"Arantxa Alonso, Isabel Mercader, Oriol Batiste, Alvaro Meseguer","doi":"10.1515/jnet-2024-0064","DOIUrl":"https://doi.org/10.1515/jnet-2024-0064","url":null,"abstract":"This study computationally investigates the time-dependent patterns emerging in the Soret regime for binary fluid convection in slightly inclined cylinders heated from below, with a particular focus on positive Soret coefficient thermophobic mixtures (<jats:italic>S</jats:italic> <jats:sub> <jats:italic>T</jats:italic> </jats:sub> > 0) and aspect ratios Γ = 5.2, Γ = 5.3, and Γ = 5.4. By varying the Rayleigh number (<jats:italic>Ra</jats:italic>) and smoothly adjusting its increments, we capture a range of spatio-temporal behaviours, revealing the coexistence of large-scale shear flows (LSF) and superhighway convection (SHC) patterns. SHC-like structures, characterised by a high base frequency, involve oscillating plumes arranged in adjacent lanes, moving in opposite directions along the inclination. Remarkably, this frequency remains nearly constant across different <jats:italic>Ra</jats:italic> values. Some of the observed coherent structures, such as periodic and modulated solutions, exhibit equivariance with respect to some elements of the <jats:inline-formula> <jats:alternatives> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <m:msub> <m:mrow> <m:mi mathvariant=\"double-struck\">D</m:mi> </m:mrow> <m:mrow> <m:mn>2</m:mn> </m:mrow> </m:msub> </m:math> <jats:tex-math> ${mathbb{D}}_{2}$ </jats:tex-math> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_jnetdy-2024-0064_ineq_001.png\"/> </jats:alternatives> </jats:inline-formula> symmetry group inherent to the physical system. In the case of Γ = 5.4, we identify three-frequency orbits, with modulations up to two orders of magnitude smaller than the base frequency. The observed dynamics is highly sensitive to small variations of Γ, with different patterns being stabilized depending on the aspect ratio of the cell. The bifurcation scenarios are complex and case-specific, and their precise determination is computationally demanding.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"44 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143385205","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}
Entropy increase is fundamentally related to the breaking of time-reversal symmetry. By adding the ‘extra dimension’ associated with thermodynamic forces, we extend that discrete symmetry to a continuous symmetry for the dynamical fluctuations around (nonlinear) gradient flow. The latter connects macroscopic equilibrium conditions upon introducing a quasistatic protocol of control parameters. The entropy state function becomes the Noether charge. As a result, and following ideas expressed by Shin-ichi Sasa and co-workers, the adiabatic invariance of the entropy, part of the Clausius heat theorem, gets connected with the Noether theorem.
{"title":"Entropy as Noether charge for quasistatic gradient flow","authors":"Aaron Beyen, Christian Maes","doi":"10.1515/jnet-2024-0054","DOIUrl":"https://doi.org/10.1515/jnet-2024-0054","url":null,"abstract":"Entropy increase is fundamentally related to the breaking of time-reversal symmetry. By adding the ‘extra dimension’ associated with thermodynamic forces, we extend that discrete symmetry to a continuous symmetry for the dynamical fluctuations around (nonlinear) gradient flow. The latter connects macroscopic equilibrium conditions upon introducing a quasistatic protocol of control parameters. The entropy state function becomes the Noether charge. As a result, and following ideas expressed by Shin-ichi Sasa and co-workers, the adiabatic invariance of the entropy, part of the Clausius heat theorem, gets connected with the Noether theorem.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"40 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143258675","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}
According to the definition of exergy-based efficient ecological-function (EBEEF) which is proposed as product of exergy-based ecological-function (EF) and coefficient of performance (COP) in previous literature, this paper applies the EBEEF to analyze and optimize performance of endoreversible Carnot heat-pumps (ECHPs). Via the ECHP cycle model established in previous literature, EBEEF expression for ECHP cycle model is deduced, relationships among the EBEEF and heating load (HTL) and COP are researched, and performance comparison for ECHP cycle working at the maximum EBEEF and the maximum EF conditions are performed. Results show that relationships among the EBEEF and the HTL and COP are parabolic like ones and the design points of the larger COP and HTL should be selected for designing heat pumps. When the maximum EBEEF is taken as primary objective, the optimized ECHP cycle can improve its COP and reduce its entropy-generation-rate by sacrificing a small amount of its HTL. The EBEEF not only considers the trade-off between the HTL and entropy-generation-rate, but also considers the trade-off between HTL and COP.
根据以往文献中提出的基于exergy-based efficient ecological-function （EBEEF）作为exergy-based ecological-function （EF）和performance coefficient of performance （COP）的乘积的定义，本文将EBEEF应用于内可逆卡诺热泵（ecps）的性能分析和优化。通过前人建立的ECHP循环模型，推导了ECHP循环模型的EBEEF表达式，研究了EBEEF与热负荷（HTL）和COP之间的关系，并对ECHP循环在最大EBEEF和最大EF工况下的性能进行了比较。结果表明：EBEEF与热压比和热压比呈抛物线关系，设计热泵时应选择较大热压比和热压比的设计点；当以最大EBEEF为主要目标时，优化后的ECHP循环可以通过牺牲少量的html来提高COP和降低熵产率。EBEEF不仅考虑了html和熵生成率之间的权衡，而且考虑了html和COP之间的权衡。
{"title":"Efficient ecological function optimization for endoreversible Carnot heat pumps","authors":"Yiwen Su, Lingen Chen, Yanlin Ge, Huijun Feng","doi":"10.1515/jnet-2024-0061","DOIUrl":"https://doi.org/10.1515/jnet-2024-0061","url":null,"abstract":"According to the definition of exergy-based efficient ecological-function (EBEEF) which is proposed as product of exergy-based ecological-function (EF) and coefficient of performance (COP) in previous literature, this paper applies the EBEEF to analyze and optimize performance of endoreversible Carnot heat-pumps (ECHPs). Via the ECHP cycle model established in previous literature, EBEEF expression for ECHP cycle model is deduced, relationships among the EBEEF and heating load (HTL) and COP are researched, and performance comparison for ECHP cycle working at the maximum EBEEF and the maximum EF conditions are performed. Results show that relationships among the EBEEF and the HTL and COP are parabolic like ones and the design points of the larger COP and HTL should be selected for designing heat pumps. When the maximum EBEEF is taken as primary objective, the optimized ECHP cycle can improve its COP and reduce its entropy-generation-rate by sacrificing a small amount of its HTL. The EBEEF not only considers the trade-off between the HTL and entropy-generation-rate, but also considers the trade-off between HTL and COP.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"14 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925013","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 use of laser irradiation to remove contaminants from soil is an emerging soil remediation technology with broad application prospects. The mechanisms of temperature field variations, moisture transport, evaporation, and condensation under conditions with or without a carrier gas during laser soil remediation are still unclear. This paper utilizes a heat and mass transfer model under continuous wave (CW) laser irradiation, established based on local non-thermal equilibrium, to analyze the variation characteristics of the physical field within the soil, with or without introducing a carrier gas. The results show that CW laser irradiation can rapidly heat the soil to the expected remediation temperature (90 °C–560 °C). However, the gas transport speed induced solely by CW laser irradiation within the soil is very limited (on the order of 0.01 mm/s), making it ineffective at removing vapor from the soil. In contrast, using a carrier gas significantly improves gas flow (on the order of 10 mm/s), enhancing both heat and mass transfer processes and assisting in removing contaminants during laser soil remediation. This study elucidates the coupled heat and moisture transfer process in unsaturated porous media under conditions with and without a carrier gas, providing theoretical support for applying laser soil remediation.
{"title":"Study on heat and mass transfer mechanism of unsaturated porous media under CW laser irradiation: with and without carrier gas","authors":"Shao-Hui Han, Yuan Dong, Guang-Yong Jin","doi":"10.1515/jnet-2024-0025","DOIUrl":"https://doi.org/10.1515/jnet-2024-0025","url":null,"abstract":"The use of laser irradiation to remove contaminants from soil is an emerging soil remediation technology with broad application prospects. The mechanisms of temperature field variations, moisture transport, evaporation, and condensation under conditions with or without a carrier gas during laser soil remediation are still unclear. This paper utilizes a heat and mass transfer model under continuous wave (CW) laser irradiation, established based on local non-thermal equilibrium, to analyze the variation characteristics of the physical field within the soil, with or without introducing a carrier gas. The results show that CW laser irradiation can rapidly heat the soil to the expected remediation temperature (90 °C–560 °C). However, the gas transport speed induced solely by CW laser irradiation within the soil is very limited (on the order of 0.01 mm/s), making it ineffective at removing vapor from the soil. In contrast, using a carrier gas significantly improves gas flow (on the order of 10 mm/s), enhancing both heat and mass transfer processes and assisting in removing contaminants during laser soil remediation. This study elucidates the coupled heat and moisture transfer process in unsaturated porous media under conditions with and without a carrier gas, providing theoretical support for applying laser soil remediation.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"27 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142917066","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 work aimed to demonstrate that a simple modification to the previously developed rough hard-sphere-chain (RHSC) model would significantly improve the accuracy of that model for viscosities of fatty acid esters and biodiesel fuels at extended pressures up to 200 MPa and higher isotherms. The new finding of this work is the temperature dependence of the exponential factor of the roughness factor (RF) of the earlier RHSC model as the accuracy of the original model (with an average absolute relative deviation, AARD of 8.29 % for 715 data points examined) was significantly improved achieving the AARD of 3.77 % once a universal function of reduced temperature replaced the original exponential factor of 6.4 × 10−4 for RF. Besides, the predictive capability of the modified RHSC model has been compared with original RHSC model and several previously developed semi-empirical models based on friction theory and free volume theory in literature. Expanding AARD on the progress in deep learning, our research introduces Artificial Neural Network (ANN) model that is simpler than previous models while maintaining high viscosity correlation accuracy for fatty acid esters and biodiesel fuels. The refined ANN model, with a single hidden layer and sigmoid activation function, achieved an AARD% of 0.78 %. Additionally, we conducted a thorough comparison with other deep learning architectures, affirming the effectiveness of our simplified approach for viscosity correlations.
{"title":"Modeling high-pressure viscosities of fatty acid esters and biodiesel fuels based on modified rough hard-sphere-chain model and deep learning method","authors":"Sayed Mostafa Hosseini, Mariano Pierantozzi","doi":"10.1515/jnet-2024-0040","DOIUrl":"https://doi.org/10.1515/jnet-2024-0040","url":null,"abstract":"This work aimed to demonstrate that a simple modification to the previously developed rough hard-sphere-chain (RHSC) model would significantly improve the accuracy of that model for viscosities of fatty acid esters and biodiesel fuels at extended pressures up to 200 MPa and higher isotherms. The new finding of this work is the temperature dependence of the exponential factor of the roughness factor (RF) of the earlier RHSC model as the accuracy of the original model (with an average absolute relative deviation, AARD of 8.29 % for 715 data points examined) was significantly improved achieving the AARD of 3.77 % once a universal function of reduced temperature replaced the original exponential factor of 6.4 × 10<jats:sup>−4</jats:sup> for RF. Besides, the predictive capability of the modified RHSC model has been compared with original RHSC model and several previously developed semi-empirical models based on friction theory and free volume theory in literature. Expanding AARD on the progress in deep learning, our research introduces Artificial Neural Network (ANN) model that is simpler than previous models while maintaining high viscosity correlation accuracy for fatty acid esters and biodiesel fuels. The refined ANN model, with a single hidden layer and sigmoid activation function, achieved an AARD% of 0.78 %. Additionally, we conducted a thorough comparison with other deep learning architectures, affirming the effectiveness of our simplified approach for viscosity correlations.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"71 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684811","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 formal description of chemical reactions far from equilibrium is an open task. Chemical reactions are central to various phenomena in life, industry, and the environment. In this work, we use a variational principle within the framework of extended irreversible thermodynamics to obtain relaxation equations for the fast variables and close the balance equations. Our approach extends traditional local equilibrium thermodynamics by incorporating formal expressions for the unknown generalized equations of state, which we can expand in low and higher-order terms, allowing for a more comprehensive representation of non-linear and dissipative phenomena and capturing wave-like behaviours relevant to oscillatory chemical systems. The formalism aligns well with previous theoretical works and provides additional insights into the influence of diffusion fluxes on reaction rates. The resulting equations may describe velocity reactions with different relaxation times and diffusion reactions. We present a comparison of our results with experiments in the context of a particular chemical kinetics case. We emphasize the need for practical applications in areas like environmentally friendly chemical reaction systems.
{"title":"Variational approach to chemical reactions beyond local equilibrium","authors":"Filiberto Herrera-Castro, Jesus Antonio del Río","doi":"10.1515/jnet-2024-0072","DOIUrl":"https://doi.org/10.1515/jnet-2024-0072","url":null,"abstract":"The formal description of chemical reactions far from equilibrium is an open task. Chemical reactions are central to various phenomena in life, industry, and the environment. In this work, we use a variational principle within the framework of extended irreversible thermodynamics to obtain relaxation equations for the fast variables and close the balance equations. Our approach extends traditional local equilibrium thermodynamics by incorporating formal expressions for the unknown generalized equations of state, which we can expand in low and higher-order terms, allowing for a more comprehensive representation of non-linear and dissipative phenomena and capturing wave-like behaviours relevant to oscillatory chemical systems. The formalism aligns well with previous theoretical works and provides additional insights into the influence of diffusion fluxes on reaction rates. The resulting equations may describe velocity reactions with different relaxation times and diffusion reactions. We present a comparison of our results with experiments in the context of a particular chemical kinetics case. We emphasize the need for practical applications in areas like environmentally friendly chemical reaction systems.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"70 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684809","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 work investigates, using the Laplace transforms, the influence of thermal relaxation time in the piezo-thermoelastic rod under pulse heat flux. For the piezoelectric medium, the generalized piezothermoelastic fundamental equations are developed. The analytical solutions are expressed in the transformation domain using Laplace transforms. Laplace transforms are presented to solve the problem’s governing equations, removing the time impact and yielding analytical solutions for the temperature, electric field, displacement, and stresses in the Laplace domain. The time domain solutions of the variables under consideration are then found using numerical Laplace inversion and visually shown. The effects of the thermal time, pulse heating flux characteristic time, and constant heat flux are studied in a piezoelectric thermoelastic medium. The figures show that the thermal time, pulse heating flux characteristic time, and constant heat flux play significant roles in determining the values of all physical quantities.
{"title":"Generalized piezothermoelastic interactions in a piezoelectric rod subjected to pulse heat flux","authors":"Zuhur Alqahtani, Ibrahim Abbas, Alaa A. El-Bary","doi":"10.1515/jnet-2024-0077","DOIUrl":"https://doi.org/10.1515/jnet-2024-0077","url":null,"abstract":"This work investigates, using the Laplace transforms, the influence of thermal relaxation time in the piezo-thermoelastic rod under pulse heat flux. For the piezoelectric medium, the generalized piezothermoelastic fundamental equations are developed. The analytical solutions are expressed in the transformation domain using Laplace transforms. Laplace transforms are presented to solve the problem’s governing equations, removing the time impact and yielding analytical solutions for the temperature, electric field, displacement, and stresses in the Laplace domain. The time domain solutions of the variables under consideration are then found using numerical Laplace inversion and visually shown. The effects of the thermal time, pulse heating flux characteristic time, and constant heat flux are studied in a piezoelectric thermoelastic medium. The figures show that the thermal time, pulse heating flux characteristic time, and constant heat flux play significant roles in determining the values of all physical quantities.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"14 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673015","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}
Jaime Arturo de la Torre, Jesús Sánchez-Rodríguez, Pep Español
Intrinsic thermal fluctuations within a real solid challenge the rigid body assumption that is central to Euler’s equations for the motion of a free body. Recently, we have introduced a dissipative and stochastic version of Euler’s equations in a thermodynamically consistent way (European Journal of Mechanics – A/Solids 103, 105,184 (2024)). This framework describes the evolution of both orientation and shape of a free body, incorporating internal thermal fluctuations and their concomitant dissipative mechanisms. In the present work, we demonstrate that, in the absence of angular momentum, the theory predicts that the principal axes unit vectors of a body undergo an anisotropic Brownian motion on the unit sphere, with the anisotropy arising from the body’s varying moments of inertia. The resulting equilibrium time correlation function of the principal eigenvectors decays exponentially. This theoretical prediction is confirmed in molecular dynamics simulations of small bodies. The comparison of theory and equilibrium MD simulations allow us to measure the orientational diffusion tensor. We then use this information in the Stochastic Dissipative Euler’s Equations, to describe a non-equilibrium situation of a body spinning around the unstable intermediate axis. The agreement between theory and simulations is excellent, offering a validation of the theoretical framework.
{"title":"Stochastic dissipative Euler’s equations for a free body","authors":"Jaime Arturo de la Torre, Jesús Sánchez-Rodríguez, Pep Español","doi":"10.1515/jnet-2024-0029","DOIUrl":"https://doi.org/10.1515/jnet-2024-0029","url":null,"abstract":"Intrinsic thermal fluctuations within a real solid challenge the rigid body assumption that is central to Euler’s equations for the motion of a free body. Recently, we have introduced a dissipative and stochastic version of Euler’s equations in a thermodynamically consistent way (European Journal of Mechanics – A/Solids 103, 105,184 (2024)). This framework describes the evolution of both orientation and shape of a free body, incorporating <jats:italic>internal</jats:italic> thermal fluctuations and their concomitant dissipative mechanisms. In the present work, we demonstrate that, in the absence of angular momentum, the theory predicts that the principal axes unit vectors of a body undergo an anisotropic Brownian motion on the unit sphere, with the anisotropy arising from the body’s varying moments of inertia. The resulting equilibrium time correlation function of the principal eigenvectors decays exponentially. This theoretical prediction is confirmed in molecular dynamics simulations of small bodies. The comparison of theory and <jats:italic>equilibrium</jats:italic> MD simulations allow us to measure the orientational diffusion tensor. We then use this information in the Stochastic Dissipative Euler’s Equations, to describe a <jats:italic>non-equilibrium</jats:italic> situation of a body spinning around the unstable intermediate axis. The agreement between theory and simulations is excellent, offering a validation of the theoretical framework.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"68 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142580311","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}
Tubular solid oxide fuel cells (TSOFCs) generate high-grade waste heat during operation, but the existing waste heat recovery technologies designed for flat solid oxide fuel cells cannot be directly applied to TSOFC due to the geometry mismatch. To efficient harvest the waste heat, a new geometry-matching hybrid system including TSOFC and annular thermoelectric generator (ATEG) is synergistically integrated to evaluate the performance upper limit. A mathematical model is formulated and verified to describe the hybrid system by considering various thermodynamic-electrochemical irreversible effects. Key performance indicators are established to assess the potential performance. Calculations show that the peak power density and corresponding efficiency of the proposed system are enhanced by 20.39 % and 13.89 %, respectively, compared to a standalone TSOFC. Furthermore, the exergy destruction rate is reduced by 7.04 %. Extensive sensitivity analyses indicate that higher operating temperatures enhance the system’s performance, while larger electrode tortuosity negatively affects it. Additionally, various optimization paths of ATEG are explored to improve the system performance, including considerations such as the number of thermocouples, leg radial width, leg thickness, or annular shape parameter. The three-objective optimization yields an efficient design solution for the entire system, offering valuable insights for its design and operation.
{"title":"Performance prediction and manipulation strategy of a hybrid system based on tubular solid oxide fuel cell and annular thermoelectric generator","authors":"Huichao Zhu, Siyu Chen, Houcheng Zhang","doi":"10.1515/jnet-2024-0039","DOIUrl":"https://doi.org/10.1515/jnet-2024-0039","url":null,"abstract":"Tubular solid oxide fuel cells (TSOFCs) generate high-grade waste heat during operation, but the existing waste heat recovery technologies designed for flat solid oxide fuel cells cannot be directly applied to TSOFC due to the geometry mismatch. To efficient harvest the waste heat, a new geometry-matching hybrid system including TSOFC and annular thermoelectric generator (ATEG) is synergistically integrated to evaluate the performance upper limit. A mathematical model is formulated and verified to describe the hybrid system by considering various thermodynamic-electrochemical irreversible effects. Key performance indicators are established to assess the potential performance. Calculations show that the peak power density and corresponding efficiency of the proposed system are enhanced by 20.39 % and 13.89 %, respectively, compared to a standalone TSOFC. Furthermore, the exergy destruction rate is reduced by 7.04 %. Extensive sensitivity analyses indicate that higher operating temperatures enhance the system’s performance, while larger electrode tortuosity negatively affects it. Additionally, various optimization paths of ATEG are explored to improve the system performance, including considerations such as the number of thermocouples, leg radial width, leg thickness, or annular shape parameter. The three-objective optimization yields an efficient design solution for the entire system, offering valuable insights for its design and operation.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"126 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142541152","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}
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