Abstract The internal heat source and reaction effects on the onset of thermosolutal convection in a local thermal non-equilibrium porous medium are examined, where the temperature of the fluid and the solid skeleton may differ. The linear instability and nonlinear stability theories of Darcy–Brinkman type with fixed boundary condition are carried out where the layer is heated and salted from below. The D 2 {D^{2}} Chebyshev tau technique is used to calculate the associated system of equations subject to the boundary conditions for both theories. Three different types of internal heat source function are considered, the first type increases across the layer, while the second decreases, and the third type heats and cools in a nonuniform way. The effect of different parameters on the Rayleigh number is depicted graphically. Moreover, the results detect that utilizing the internal heat source, reaction, and non-equilibrium have pronounced effects in determining the convection stability and instability thresholds.
{"title":"Stability Analysis of Double Diffusive Convection in Local Thermal Non-equilibrium Porous Medium with Internal Heat Source and Reaction Effects","authors":"N. Noon, S. Haddad","doi":"10.1515/jnet-2022-0047","DOIUrl":"https://doi.org/10.1515/jnet-2022-0047","url":null,"abstract":"Abstract The internal heat source and reaction effects on the onset of thermosolutal convection in a local thermal non-equilibrium porous medium are examined, where the temperature of the fluid and the solid skeleton may differ. The linear instability and nonlinear stability theories of Darcy–Brinkman type with fixed boundary condition are carried out where the layer is heated and salted from below. The D 2 {D^{2}} Chebyshev tau technique is used to calculate the associated system of equations subject to the boundary conditions for both theories. Three different types of internal heat source function are considered, the first type increases across the layer, while the second decreases, and the third type heats and cools in a nonuniform way. The effect of different parameters on the Rayleigh number is depicted graphically. Moreover, the results detect that utilizing the internal heat source, reaction, and non-equilibrium have pronounced effects in determining the convection stability and instability thresholds.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"48 1","pages":"25 - 39"},"PeriodicalIF":6.6,"publicationDate":"2022-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45973065","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}
Zhanxuan Wang, Xiulian Cheng, K. Guo, Enling Tang, Lei Li, Hui Peng, Yafei Han, Chuang Chen, Mengzhou Chang, Liping He
Abstract In actual operation, the operating environment temperature of thermoelectric devices are constantly changing and rarely remain stable, and the electrical output characteristics of thermoelectric devices are largely determined by thermoelectric materials. In response to this question, the thermoelectric properties of thermoelectric materials (p and n type Bi 2 Te 3 {mathrm{Bi}_{2}}{mathrm{Te}_{3}}) are measured under different temperature difference environments. The Seebeck coefficient, resistivity, and thermal conductivity of the specimens at T = 300 – 600 KT=300text{--}600hspace{0.1667em}text{K} were measured by CTA-4 and CLA1000 (laser flash method), respectively; the thermal and electrical output responses of the thermoelectric materials under different temperature difference conditions were collected in real time by using a self-built thermoelectric performance test platform, thermal/electrical test system with infrared thermal imager, and voltage acquisition system, respectively. The experimental results show that when the temperature difference between the two ends of the specimen increases uniformly, the electrical output signal amplitude also increases uniformly; when the temperature difference is stable, the two ends of the specimen also produce a stable electrical output signal. After stabilization, the electrical output signal amplitude also decreases uniformly when the temperature decreases at a uniform rate. In the temperature range of 298 ∼ 573 K298sim 573hspace{0.1667em}text{K}, the larger the temperature difference between the two ends of the specimen was, the larger the amplitude of the electrical output signal was after stabilization; and vice versa. The greater the loading rate of the thermal load was, the greater the rate of increase of the electrical output signal amplitude at both ends of the specimen was, and the steady-state equilibrium time required was less.
{"title":"Thermoelectric Response Characteristics of Bi2Te3 Based Semiconductor Materials","authors":"Zhanxuan Wang, Xiulian Cheng, K. Guo, Enling Tang, Lei Li, Hui Peng, Yafei Han, Chuang Chen, Mengzhou Chang, Liping He","doi":"10.1515/jnet-2022-0049","DOIUrl":"https://doi.org/10.1515/jnet-2022-0049","url":null,"abstract":"Abstract In actual operation, the operating environment temperature of thermoelectric devices are constantly changing and rarely remain stable, and the electrical output characteristics of thermoelectric devices are largely determined by thermoelectric materials. In response to this question, the thermoelectric properties of thermoelectric materials (p and n type Bi 2 Te 3 {mathrm{Bi}_{2}}{mathrm{Te}_{3}}) are measured under different temperature difference environments. The Seebeck coefficient, resistivity, and thermal conductivity of the specimens at T = 300 – 600 KT=300text{--}600hspace{0.1667em}text{K} were measured by CTA-4 and CLA1000 (laser flash method), respectively; the thermal and electrical output responses of the thermoelectric materials under different temperature difference conditions were collected in real time by using a self-built thermoelectric performance test platform, thermal/electrical test system with infrared thermal imager, and voltage acquisition system, respectively. The experimental results show that when the temperature difference between the two ends of the specimen increases uniformly, the electrical output signal amplitude also increases uniformly; when the temperature difference is stable, the two ends of the specimen also produce a stable electrical output signal. After stabilization, the electrical output signal amplitude also decreases uniformly when the temperature decreases at a uniform rate. In the temperature range of 298 ∼ 573 K298sim 573hspace{0.1667em}text{K}, the larger the temperature difference between the two ends of the specimen was, the larger the amplitude of the electrical output signal was after stabilization; and vice versa. The greater the loading rate of the thermal load was, the greater the rate of increase of the electrical output signal amplitude at both ends of the specimen was, and the steady-state equilibrium time required was less.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"355 - 373"},"PeriodicalIF":6.6,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49267425","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 A class of two finite-heat-reservoir endoreversible heat engine with the generalized models of both the reservoir thermal capacities and heat resistances is investigated. The optimality condition for cycle maximum work output is derived by applying optimal control theory, and impacts of both thermal capacity characteristics of heat reservoirs and heat transfer laws on the optimal configurations are discussed. The results obtained in some previous researches are special cases of those obtained herein, which can provide some guidelines for optimal design of actual heat engines.
{"title":"Heat Engine Cycle Configurations for Maximum Work Output with Generalized Models of Reservoir Thermal Capacity and Heat Resistance","authors":"Lingen Chen, Shaojun Xia","doi":"10.1515/jnet-2022-0029","DOIUrl":"https://doi.org/10.1515/jnet-2022-0029","url":null,"abstract":"Abstract A class of two finite-heat-reservoir endoreversible heat engine with the generalized models of both the reservoir thermal capacities and heat resistances is investigated. The optimality condition for cycle maximum work output is derived by applying optimal control theory, and impacts of both thermal capacity characteristics of heat reservoirs and heat transfer laws on the optimal configurations are discussed. The results obtained in some previous researches are special cases of those obtained herein, which can provide some guidelines for optimal design of actual heat engines.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"329 - 338"},"PeriodicalIF":6.6,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49104753","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}
L.G. Lafaurie-Ponce, F. Chejne, Luis M. Ramirez-Aristeguieta, Carlos Gomez
Abstract This work describes the nonlinear Thomson effect produced by a transient current source powering a thermoelectric cooler. The electric effect of the capacitive impedance in the semiconductors was considered in the equations as a novelty term that naturally appears by solving the Boltzmann equation to find the mathematical form of the current density. Thus, considering the new term and heath energy balances, a one-dimensional mathematical model for a thermoelectric cooler (TEC) powered by a time-dependent current was developed, finding a new nonlinear Thomson effect in the heath transfer equations. To evaluate the impact of the nonlinear effect on the thermodynamic behavior of the thermoelectric cooler, a continuous, sinusoidal and square-pulse current conditions were simulated. The temperature profile, temporal evolution, and the effective coefficient of performance (COP) were calculated. The results revealed a new thermoelectric heat transfer in addition to the Thomson flow created by virtual junctions throughout the semiconductors caused by the instantaneous change of current. This fact was evidenced by three results: the shifting of the temperature mean value due to the peak current change 0.45 A is 1.68 K1.68hspace{0.1667em}mathrm{K} and 2.56 K2.56hspace{0.1667em}mathrm{K} to sinusoidal and square current supplies, respectively; it was determined that a TEC powered by a square-pulse current signal had greater effective efficacy, having more pronounced cold side supercooling temperature peaks compared to those powered by a constant sinusoidal current signal.
{"title":"A Study of the Nonlinear Thomson Effect Produced by Changing the Current in a Thermoelectric Cooler","authors":"L.G. Lafaurie-Ponce, F. Chejne, Luis M. Ramirez-Aristeguieta, Carlos Gomez","doi":"10.1515/jnet-2022-0037","DOIUrl":"https://doi.org/10.1515/jnet-2022-0037","url":null,"abstract":"Abstract This work describes the nonlinear Thomson effect produced by a transient current source powering a thermoelectric cooler. The electric effect of the capacitive impedance in the semiconductors was considered in the equations as a novelty term that naturally appears by solving the Boltzmann equation to find the mathematical form of the current density. Thus, considering the new term and heath energy balances, a one-dimensional mathematical model for a thermoelectric cooler (TEC) powered by a time-dependent current was developed, finding a new nonlinear Thomson effect in the heath transfer equations. To evaluate the impact of the nonlinear effect on the thermodynamic behavior of the thermoelectric cooler, a continuous, sinusoidal and square-pulse current conditions were simulated. The temperature profile, temporal evolution, and the effective coefficient of performance (COP) were calculated. The results revealed a new thermoelectric heat transfer in addition to the Thomson flow created by virtual junctions throughout the semiconductors caused by the instantaneous change of current. This fact was evidenced by three results: the shifting of the temperature mean value due to the peak current change 0.45 A is 1.68 K1.68hspace{0.1667em}mathrm{K} and 2.56 K2.56hspace{0.1667em}mathrm{K} to sinusoidal and square current supplies, respectively; it was determined that a TEC powered by a square-pulse current signal had greater effective efficacy, having more pronounced cold side supercooling temperature peaks compared to those powered by a constant sinusoidal current signal.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"339 - 354"},"PeriodicalIF":6.6,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48843893","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}
E. Ragupathi, D. Prakash, M. Muthtamilselvan, Q. Al‐Mdallal
Abstract The current study is made to analyze the impact of local thermal nonequilibrium (LTNE) on the steady, incompressible, and viscous Ostwald-de-Waele nano-liquid over a rotating disk in a porous medium with the various power law index, due to many remarkable applications, such as aeronautical systems, rotating machineries, air cleaning machineries, electrical power-generating systems, heat exchangers, gas turbines, centrifugal pumps. To describe the modeling of the nano-liquid, Brownian movement and thermophoresis are employed with the passive control boundaries. Three temperature model is adopted to distinguish the temperature among the fluid, particle, and solid. The governing transport equations have been converted to a system of nonlinear coupled ordinary differential equations by employing von Karman transformation. Numerical results of the flow and heat and transfer characteristics of the fluid, particle, and solid are obtained by applying Runge–Kutta–Fehlberg method (RKF) together with the shooting technique. The numerical results in the present work are compared with the published results for the case of thermal equilibrium and found that they are in good agreement. It is observed that the temperature profile significantly varies with the fluid-particle, fluid-solid interphase heat transfer coefficients and the modified thermal capacity ratios.
摘要本研究分析了局部热非平衡（LTNE）对具有不同幂律指数的多孔介质中旋转圆盘上稳定、不可压缩和粘性的Ostwald de Waele纳米液体的影响，这些液体具有许多显著的应用，如航空系统、旋转机械、空气净化机械、发电系统，热交换器、燃气轮机、离心泵。为了描述纳米液体的建模，采用了布朗运动和热泳法以及被动控制边界。采用三温度模型来区分流体、颗粒和固体的温度。利用von Karman变换将控制输运方程转化为非线性耦合常微分方程组。采用Runge–Kutta–Fehlberg方法（RKF）和射击技术，获得了流体、颗粒和固体的流动和传热特性的数值结果。将本工作中的数值结果与已发表的热平衡情况下的结果进行了比较，发现它们非常一致。观察到，温度分布随流体颗粒、流固相间传热系数和修正的热容量比而显著变化。
{"title":"Impact of Thermal Nonequilibrium on Flow Through a Rotating Disk with Power Law Index in Porous Media Occupied by Ostwald-de-Waele Nanofluid","authors":"E. Ragupathi, D. Prakash, M. Muthtamilselvan, Q. Al‐Mdallal","doi":"10.1515/jnet-2022-0030","DOIUrl":"https://doi.org/10.1515/jnet-2022-0030","url":null,"abstract":"Abstract The current study is made to analyze the impact of local thermal nonequilibrium (LTNE) on the steady, incompressible, and viscous Ostwald-de-Waele nano-liquid over a rotating disk in a porous medium with the various power law index, due to many remarkable applications, such as aeronautical systems, rotating machineries, air cleaning machineries, electrical power-generating systems, heat exchangers, gas turbines, centrifugal pumps. To describe the modeling of the nano-liquid, Brownian movement and thermophoresis are employed with the passive control boundaries. Three temperature model is adopted to distinguish the temperature among the fluid, particle, and solid. The governing transport equations have been converted to a system of nonlinear coupled ordinary differential equations by employing von Karman transformation. Numerical results of the flow and heat and transfer characteristics of the fluid, particle, and solid are obtained by applying Runge–Kutta–Fehlberg method (RKF) together with the shooting technique. The numerical results in the present work are compared with the published results for the case of thermal equilibrium and found that they are in good agreement. It is observed that the temperature profile significantly varies with the fluid-particle, fluid-solid interphase heat transfer coefficients and the modified thermal capacity ratios.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"375 - 394"},"PeriodicalIF":6.6,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47234467","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}
F. Chejne, W. Flórez, J. Maya, Javier Ordoñez-Loza, M. García-Pérez
Abstract This paper explores the hyperbolic heat transfer effects in processes involving high heating rates. The behavior of the model is analyzed in detail under different boundary conditions and the circumstances under which a non-Fourier law could be used to describe thermal conduction processes established from physical mathematical analysis. Finally, the model developed here is coupled to a previous population balance framework to predict the bubbling phenomenon that occurs during the fast pyrolysis of biomass. We found that a transient overheating occurs in the central zone of the generated liquid phase due to the high heating rates that take place during that process.
{"title":"Physical Mathematical Modeling and Simulation Based on Hyperbolic Heat Transfer for High Heating Rate Processes in Biomass Pyrolysis","authors":"F. Chejne, W. Flórez, J. Maya, Javier Ordoñez-Loza, M. García-Pérez","doi":"10.1515/jnet-2022-0028","DOIUrl":"https://doi.org/10.1515/jnet-2022-0028","url":null,"abstract":"Abstract This paper explores the hyperbolic heat transfer effects in processes involving high heating rates. The behavior of the model is analyzed in detail under different boundary conditions and the circumstances under which a non-Fourier law could be used to describe thermal conduction processes established from physical mathematical analysis. Finally, the model developed here is coupled to a previous population balance framework to predict the bubbling phenomenon that occurs during the fast pyrolysis of biomass. We found that a transient overheating occurs in the central zone of the generated liquid phase due to the high heating rates that take place during that process.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"395 - 414"},"PeriodicalIF":6.6,"publicationDate":"2022-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47334044","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 In this study, the results of an investigation of the performance of a gas-steam combined cycle system (GSCCS) under exergetic and exergo-economical criteria are reported. The effective power (Pef), destroyed exergy (X), efficiency of exergy (ε), unit electric generation cost (Celec) and exergy-dependent economic worth of electrical energy (Cex,elec), which is novelly determined in this study, have been analyzed. The impacts of speed (N), pressure ratio of the gas cycle (λ), equivalence ratio (ϕ), the flow rate of the air mass ( m ˙ a {dot{m}_{a}}), the flow rate of the fuel mass ( m ˙ f {dot{m}_{f}}), inlet temperature of the air into the compressor ( T 1 {mathrm{T}_{1}}), steam temperature ( T 6 {mathrm{T}_{6}}) and pressure (P6) of the heat exchanger, outlet pressure (P7) of the high pressure steam turbine and condenser pressure (P9) on Pef, ε, Celec and Cex,elec have been parametrically evaluated. It was revealed that the stream and component characteristics of the system have significant influences on the performance characteristics of the GSCCS.
{"title":"Exergetic and Exergo-Economical Analyses of a Gas-Steam Combined Cycle System","authors":"G. Gonca, Bulent Guzel","doi":"10.1515/jnet-2022-0042","DOIUrl":"https://doi.org/10.1515/jnet-2022-0042","url":null,"abstract":"Abstract In this study, the results of an investigation of the performance of a gas-steam combined cycle system (GSCCS) under exergetic and exergo-economical criteria are reported. The effective power (Pef), destroyed exergy (X), efficiency of exergy (ε), unit electric generation cost (Celec) and exergy-dependent economic worth of electrical energy (Cex,elec), which is novelly determined in this study, have been analyzed. The impacts of speed (N), pressure ratio of the gas cycle (λ), equivalence ratio (ϕ), the flow rate of the air mass ( m ˙ a {dot{m}_{a}}), the flow rate of the fuel mass ( m ˙ f {dot{m}_{f}}), inlet temperature of the air into the compressor ( T 1 {mathrm{T}_{1}}), steam temperature ( T 6 {mathrm{T}_{6}}) and pressure (P6) of the heat exchanger, outlet pressure (P7) of the high pressure steam turbine and condenser pressure (P9) on Pef, ε, Celec and Cex,elec have been parametrically evaluated. It was revealed that the stream and component characteristics of the system have significant influences on the performance characteristics of the GSCCS.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"415 - 431"},"PeriodicalIF":6.6,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44861280","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 A finite source heat engine’s optimal configuration is studied. The model includes thermal resistance, heat leakage, a complex heat transfer law, and a heat source with variable temperature. The optimization objective is that the output work is the largest. The influences of factors such as the heat transfer law and heat leakage are analyzed. The results of this paper are universal and inclusive, and provide certain theoretical support for the performance improvement of actual heat engines.
{"title":"Optimal Configuration of Finite Source Heat Engine Cycle for Maximum Output Work with Complex Heat Transfer Law","authors":"Jun Li, Lingen Chen","doi":"10.1515/jnet-2022-0024","DOIUrl":"https://doi.org/10.1515/jnet-2022-0024","url":null,"abstract":"Abstract A finite source heat engine’s optimal configuration is studied. The model includes thermal resistance, heat leakage, a complex heat transfer law, and a heat source with variable temperature. The optimization objective is that the output work is the largest. The influences of factors such as the heat transfer law and heat leakage are analyzed. The results of this paper are universal and inclusive, and provide certain theoretical support for the performance improvement of actual heat engines.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"433 - 441"},"PeriodicalIF":6.6,"publicationDate":"2022-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42445471","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}
Y. Ge, Shuangshuang Shi, Lingen Chen, Difeng Zhang, H. Feng
Abstract Considering the various irreversibility conditions caused by heat transfer and working processes in a dual cycle, the power density performance is optimized by applying finite-time thermodynamics theory, and multi-objective optimization is performed by using NSGA-II. The effects of cut-off ratio, maximum cycle temperature ratio, and various losses by heat transfer and working processes on the relationships between the power density and the compression ratio and between the power density and the thermal efficiency are analyzed. The thermal efficiency and engine size obtained under the conditions of maximum power output and power density are discussed. The results show that for a dual cycle, the heat engine has a smaller size and higher thermal efficiency under the condition of maximum power density. The cycle compression ratio and cut-off ratio are selected as decision variables, and the dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density are selected as objective functions. Multi-objective optimization is performed with different objective combinations. The deviation indexes under the LINMAP, TOPSIS, and Shannon entropy approaches are discussed, and the number of generations when the genetic algorithm reaches convergence are obtained. The results show that the genetic algorithm converges at the 341st generation for the quadru-objective optimization, at the 488th generation for the tri-objective optimization, and at the 399th generation for the bi-objective optimization. When the bi-objective optimization is performed with dimensionless power output and dimensionless ecological function as the objective functions, the deviation index obtained based on the LINMAP approach is 0.1400, which is better than those obtained for other single- and multi-objective optimizations.
{"title":"Power Density Analysis and Multi-Objective Optimization for an Irreversible Dual Cycle","authors":"Y. Ge, Shuangshuang Shi, Lingen Chen, Difeng Zhang, H. Feng","doi":"10.1515/jnet-2021-0083","DOIUrl":"https://doi.org/10.1515/jnet-2021-0083","url":null,"abstract":"Abstract Considering the various irreversibility conditions caused by heat transfer and working processes in a dual cycle, the power density performance is optimized by applying finite-time thermodynamics theory, and multi-objective optimization is performed by using NSGA-II. The effects of cut-off ratio, maximum cycle temperature ratio, and various losses by heat transfer and working processes on the relationships between the power density and the compression ratio and between the power density and the thermal efficiency are analyzed. The thermal efficiency and engine size obtained under the conditions of maximum power output and power density are discussed. The results show that for a dual cycle, the heat engine has a smaller size and higher thermal efficiency under the condition of maximum power density. The cycle compression ratio and cut-off ratio are selected as decision variables, and the dimensionless power output, thermal efficiency, dimensionless ecological function, and dimensionless power density are selected as objective functions. Multi-objective optimization is performed with different objective combinations. The deviation indexes under the LINMAP, TOPSIS, and Shannon entropy approaches are discussed, and the number of generations when the genetic algorithm reaches convergence are obtained. The results show that the genetic algorithm converges at the 341st generation for the quadru-objective optimization, at the 488th generation for the tri-objective optimization, and at the 399th generation for the bi-objective optimization. When the bi-objective optimization is performed with dimensionless power output and dimensionless ecological function as the objective functions, the deviation index obtained based on the LINMAP approach is 0.1400, which is better than those obtained for other single- and multi-objective optimizations.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"289 - 309"},"PeriodicalIF":6.6,"publicationDate":"2022-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47172874","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 The formalism of the internal variable theory is applied to extend Navier-Stokes equations. The internal variable theory provides a thermodynamically consistent derivation of constitutive relations and equations of motion without a priori specifying the nature of internal variables. Both single and dual internal variables cases are thoroughly examined. The similarities and differences of the approaches are emphasized. In the single internal variable framework, the elimination of the internal variable results in Maxwell-type constitutive relations and hyperbolic equations of motion. The dual internal variable technique enables us to create even more sophisticated fluid flow models with coupled equations for fluid motion and internal variable evolution.
{"title":"Internal Variables as a Tool for Extending Navier-Stokes Equations","authors":"A. Berezovski","doi":"10.1515/jnet-2021-0089","DOIUrl":"https://doi.org/10.1515/jnet-2021-0089","url":null,"abstract":"Abstract The formalism of the internal variable theory is applied to extend Navier-Stokes equations. The internal variable theory provides a thermodynamically consistent derivation of constitutive relations and equations of motion without a priori specifying the nature of internal variables. Both single and dual internal variables cases are thoroughly examined. The similarities and differences of the approaches are emphasized. In the single internal variable framework, the elimination of the internal variable results in Maxwell-type constitutive relations and hyperbolic equations of motion. The dual internal variable technique enables us to create even more sophisticated fluid flow models with coupled equations for fluid motion and internal variable evolution.","PeriodicalId":16428,"journal":{"name":"Journal of Non-Equilibrium Thermodynamics","volume":"47 1","pages":"241 - 254"},"PeriodicalIF":6.6,"publicationDate":"2022-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47179329","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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