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On small local equilibrium systems 关于局部小平衡系统
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-03-02 DOI: 10.1515/jnet-2022-0074
H. C. Öttinger
Abstract Even for large nonequilibrium systems, local equilibrium subsystems in the presence of strong inhomogeneities may be very small. Such situations typically arise either in the presence of large gradients of temperature, velocity or pressure, or in transition zones between different phases. For small thermodynamic systems, the Euler equation of macroscopic thermodynamics does not hold. One less equation implies one additional degree of freedom, which is the hallmark of small thermodynamic systems. I would like to offer some remarks on the description and role of small local equilibrium subsystems in nonequilibrium thermodynamics.
摘要即使对于大型非平衡系统,在存在强不均匀性的情况下,局部平衡子系统也可能非常小。这种情况通常出现在存在大的温度、速度或压力梯度的情况下,或者出现在不同相之间的过渡区中。对于小的热力学系统,宏观热力学的欧拉方程不成立。少一个方程式意味着多一个自由度,这是小型热力学系统的标志。我想对小局部平衡子系统在非平衡热力学中的描述和作用发表一些看法。
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引用次数: 1
A practical upper-bound efficiency model for solar power plants 一种实用的太阳能发电厂效率上限模型
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-02-27 DOI: 10.1515/jnet-2022-0080
Eduardo González-Mora, R. Poudel, M. D. Durán-García
Abstract A generalized model for the maximum work rate extractable from the Sun is developed considering a reversible and an endoreversible system to define a more practical upper-bound efficiency for the conversion of solar radiation into work and power. This model is based on a photo-thermal work extractor in communication with a high-temperature radiation reservoir and a low-temperature heat sink. Following the model, a parametric analysis of the concentration acceptance product (ξ) and thermal conductance is performed to identify the interdependence of variables for the solar exergy. The results are compared with existing models to provide a practical baseline of work and power extractable from concentrated solar power plants (CSP) technologies. Therefore, it is possible to quantify the irreversibilities of an idealized thermodynamic system operating between the Sun and the absorber (via radiative transfer) and the environment (via convective transfer).
摘要考虑可逆系统和内可逆系统,建立了太阳可提取最大功率的广义模型,以定义将太阳辐射转换为功和功率的更实用的上限效率。该模型基于与高温辐射库和低温散热器通信的光热功提取器。根据该模型,对浓度可接受乘积(ξ)和热导率进行了参数分析,以确定太阳能火用变量的相互依赖性。将结果与现有模型进行比较,以提供可从聚光太阳能发电厂(CSP)技术中提取的功和功率的实用基线。因此,可以量化在太阳和吸收器(通过辐射传递)和环境(通过对流传递)之间运行的理想化热力学系统的不可逆性。
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引用次数: 4
Multiscale theory 多尺度理论
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-02-25 DOI: 10.1515/jnet-2022-0092
M. Grmela
Abstract Boltzmann kinetic equation is put into the form of an abstract time evolution equation representing links connecting autonomous mesoscopic dynamical theories involving varying amount of details. In the chronological order we present results that led to the abstract time equation evolution in both state space and the space of vector fields. In the final section we list some open problems.
摘要将玻尔兹曼动力学方程转化为抽象的时间演化方程,表示包含不同数量细节的自主介观动力学理论之间的联系。我们按时间顺序给出了导致抽象时间方程在状态空间和向量场空间演化的结果。在最后一节,我们列出了一些尚未解决的问题。
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引用次数: 1
Energy production in one-qubit quantum Agrawal machines 单量子位量子Agrawal机的能量产生
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-24 DOI: 10.1515/jnet-2022-0081
Julio J. Fernández
Abstract We obtain the power and Ω-function of one-qubit Agrawal quantum heat engines solving the Lindbland equation and using the tools of Finite Time Thermodynamics. We prove that these two thermodynamic functions have their maximum values for efficiencies different to zero and the Carnot efficiency. Finally, analyzing the high temperature limit of AQHEs we discover the range of temperatures for which the quantum behaviour is valid.
摘要利用有限时间热力学的工具,求解Lindbland方程,得到了单量子比特Agrawal量子热机的功率和Ω函数。我们证明了这两个热力学函数对于不同于零的效率和卡诺效率具有它们的最大值。最后,通过分析AQHEs的高温极限,我们发现了量子行为有效的温度范围。
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引用次数: 5
The optimization of heat transfer in thermally convective micropolar-based nanofluid flow by the influence of nanoparticle’s diameter and nanolayer via stretching sheet: sensitivity analysis approach 纳米颗粒直径和拉伸片纳米层对微极流体热对流传热的影响:灵敏度分析方法
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-24 DOI: 10.1515/jnet-2022-0064
L. Ali, Pardeep Kumar, Zahoor Iqbal, S. Alhazmi, S. Areekara, M. M. Alqarni, A. Mathew, R. Apsari
Abstract The proposed study demonstrates the flow phenomenon and thermo-variation of a magnetized stretching sheet induced-radiative nanofluid flow. By incorporating the response surface methodology, the heat transfer rate of the thermally convective flow of nanofluid is optimized. The graphene nanomaterial is used in the water-based nanofluid. A dynamic magnetic field, thermal radiation, and the Cattaneo–Christov heat flux model have used to represent the thermal behavior of the nanofluid. The simulation utilizes experimentally estimated values for the nanomaterial’s thermal conductivity and viscosity. To further reveal the thermal enhancement of the flow, the impact of nanoparticle diameter and the solid-liquid interfacial layer is proposed at the molecular level. The response surface methodology and the sensitivity analysis has used to examine the effects of the nanoparticle volume fraction, Biot number, and magnetic parameter on the rate of heat transfer statistically. A set of equations is formed from the governing partial differential equations by implementing suitable similarity transformations. The bvp4c approach is used to solve the problem numerically. The effect of various parameters has displayed through tables, graphs, and surface plots on heat transfer, mass transfer, and the local Nusselt number. It is discovered that as the Biot number increases, so does the concentration and temperature profile. An excellent accord between the present and previously existing solutions is establishing the validity of the achieved results.
摘要所提出的研究证明了磁化拉伸片诱导的辐射纳米流体流动的流动现象和热变化。通过结合响应面方法,优化了纳米流体热对流的传热速率。石墨烯纳米材料用于水性纳米流体中。动态磁场、热辐射和Cattaneo–Christov热通量模型已用于表示纳米流体的热行为。该模拟利用了纳米材料的热导率和粘度的实验估计值。为了进一步揭示流动的热增强,在分子水平上提出了纳米颗粒直径和固液界面层的影响。响应面方法和灵敏度分析已用于从统计学上检查纳米颗粒体积分数、Biot数和磁性参数对传热速率的影响。通过执行适当的相似性变换,由控制偏微分方程形成一组方程。bvp4c方法用于数值求解该问题。通过表格、图表和表面图显示了各种参数对传热、传质和局部努塞尔数的影响。研究发现,随着Biot数的增加,浓度和温度分布也会增加。目前的解决方案和以前存在的解决方案之间的一个极好的一致性是确定所取得的结果的有效性。
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引用次数: 11
A simplified analysis of the Feynman pallet and ratchet mechanism considering different forms of generated power 考虑不同发电形式的费曼托盘和棘轮机构的简化分析
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-18 DOI: 10.1515/jnet-2022-0098
D. Ladino-Luna, J. C. Chimal-Eguía, J. C. Pacheco-Paez, R. Páez-Hernández
Abstract In this paper, we analyze the advanced Feynman’s mechanism from the well-known Feynman’s Lectures on Physics, under the maximum power output, maximum efficient power, and maximum power density criterion. Considering this mechanism like a thermal engine, and using a simplified model, the physical existence regions for these objective functions are shown. We also show their comparison for given values of a defined dimensionless parameter. The behavior for each case of both the general and the normalized forms of the objective functions is compared graphically and the existence of certain intervals of values for the variable parameter used, in which the relation of these objective functions change, is determined. Additionally, it is shown that as the numerical value of the mentioned variable parameter used approaches zero, the area of the region of physical existence of the objective functions is greater. The results of the mentioned comparison are discussed, and appropriate conclusions are included.
摘要本文从著名的《费曼物理学讲义》中,在最大功率输出、最大有效功率和最大功率密度准则下,分析了先进的费曼机制。将这种机制视为热机,并使用简化模型,显示了这些目标函数的物理存在区域。我们还展示了它们对于定义的无量纲参数的给定值的比较。以图形方式比较目标函数的一般形式和归一化形式的每种情况下的行为,并确定所使用的变量参数的某些值区间的存在性,其中这些目标函数的关系发生变化。此外,还表明,当所使用的变量参数的数值接近零时,目标函数的物理存在区域的面积就越大。讨论了上述比较的结果,并得出了适当的结论。
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引用次数: 4
Conservatively perturbed equilibrium in multi-route catalytic reactions 多路催化反应的保守微扰平衡
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-12 DOI: 10.1515/jnet-2022-0054
Vitaliy R. Trishch, G. Yablonsky, D. Constales, Y. Beznosyk
Abstract The phenomenon of conservatively perturbed-equilibrium (CPE) in multi-route catalytic reactions was studied in the plug-flow reactor (PFR). The following multi-route mechanisms were chosen for studying, i.e., the two-route mechanism with the single common intermediate, the three-route mechanism with some common steps, and the two-route mechanism with the single common step and two common intermediates. All mentioned mechanisms exhibit the CPE-phenomenon. At given rate coefficients, the mechanism with the single common intermediate showed the greater CPE-effect than the mechanism with the common steps. A special computer experiment was performed in which the kinetic characteristics of non-catalytic and catalytic reactions have been compared. In this experiment, both non-catalytic and catalytic reactions have the same overall-reactions with the given equilibrium constant. It was shown that the absolute values of extreme concentrations at the CPE-point are almost the same. In this case, it is possible to estimate the concentrations at the CPE-values for complex reactions based on similar characteristics of the corresponding simple ones.
摘要在塞流反应器(PFR)中研究了多途径催化反应中的保守扰动平衡现象。选择了以下多途径机制进行研究,即具有单个共同中间体的双途径机制、具有一些共同步骤的三途径机制以及具有单个共同步骤和两个共同中间体的两途径机制。所有提到的机制都表现出CPE现象。在给定的速率系数下,采用单一通用中间体的机理比采用通用步骤的机理表现出更大的CPE效应。进行了一个专门的计算机实验,比较了非催化反应和催化反应的动力学特性。在这个实验中,在给定的平衡常数下,非催化反应和催化反应都有相同的总反应。结果表明,CPE点的极端浓度的绝对值几乎相同。在这种情况下,可以基于相应简单反应的相似特性来估计复杂反应的CPE值下的浓度。
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引用次数: 0
Natural convection of a viscoelastic Cattaneo–Christov fluid bounded by thick walls with finite thermal conductivity 热导率有限的厚壁粘弹性Cattaneo-Christov流体的自然对流
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-09 DOI: 10.1515/jnet-2022-0051
L. Dávalos-Orozco, Jose Antonio Ruiz Díaz
Abstract The linear natural convection of a Maxwell viscoelastic fluid with Cattaneo–Christov heat flux constitutive equation, between two thick walls with finite thermal conductivity is investigated. The viscoelastic fluid and the heat flux have different relaxation times. The main interest is on the curves of criticality for different thicknesses ratio D and thermal conductivities ratio X. In the middle range of log X the curves of criticality stabilize depending on the other parameters of the problem. It is revealed that for some Prandtl numbers the curves of criticality remain higher for small X and lower for large X. However, increasing the Prandtl number this behavior is reversed. It is shown that this has important consequences in the order of the criticality curves when the heat flux relaxation time is increased. Depending on the Prandtl number, an increase of this relaxation time may decrease (destabilize) the curves of criticality until a minimum is reached, after which the curves start to increase (stabilize) again. For two different magnitudes of the viscoelastic relaxation time, the critical Rayleigh number, wavenumber and frequency of oscillation are plotted against log X for different magnitudes of D and the heat flux relaxation time.
采用Cattaneo-Christov热流本构方程,研究了具有有限导热系数的厚壁间Maxwell粘弹性流体的线性自然对流问题。粘弹性流体和热流具有不同的松弛时间。主要关注的是不同厚度比D和热导率比X的临界曲线。在log X的中间范围内,临界曲线随问题的其他参数而趋于稳定。结果表明,对于某些普朗特数,小X的临界曲线仍然较高,大X的临界曲线仍然较低。然而,增加普朗特数,这种行为是相反的。结果表明,随着热流弛豫时间的增加,这对临界曲线的顺序有重要影响。根据普朗特数的不同,这个松弛时间的增加可能会降低(破坏)临界曲线,直到达到最小值,之后曲线又开始增加(稳定)。对于两种不同大小的粘弹性松弛时间,对不同大小的D和热流松弛时间,用log X绘制了临界瑞利数、波数和振荡频率。
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引用次数: 1
Impact of wavy porous layer on the hydrodynamic forces and heat transfer of hybrid nanofluid flow in a channel with cavity under the effect of partial magnetic field 部分磁场作用下波浪状多孔层对带腔通道内混合纳米流体流体动力及传热的影响
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-06 DOI: 10.1515/jnet-2022-0070
S. Hussain, M. A. Qureshi, Sameh E. Ahmed
Abstract This computational analysis focuses on the effects of porous layer on the flow dynamics, heat transfer and hydrodynamic forces of hybrid nanofluid in a channel having an open cavity fixed with bottom wall in the presence of partial magnetic field. The set of PDEs governing the dynamics has been transformed to dimensionless form and simulated using higher order finite element method. In particular, P 3 / P 2 ${mathbb{P}}_{3}/{mathbb{P}}_{2}$ finite element pair is employed for the spatial discretization and Crank–Nicolson approach is utilized for the temporal discretization. The obtained equations has been linearized with adaptive Newtons method and linearized systems have been computed using the geometric multi-grid technique. The impact of parameters, for instance, Richardson number, thickness of porous layer and nanoparticle fraction is analyzed in the presence of partial magnetic field and porous layer on the hydrodynamic forces like lift and drag forces on the submerged bodies, being the important part of the fluid flow and heat transfer are also be analysed. It is noticed that the drag and lift coefficients are reduced as the nanoparticle fraction is altered while the local- and average-Nusselt number get higher values.
摘要本文研究了局部磁场作用下,多孔层对混合纳米流体在开孔固定底壁通道中的流动动力学、换热和水动力的影响。将控制动力学的偏微分方程集合转化为无量纲形式,并用高阶有限元方法进行了仿真。其中空间离散采用p3 / p2 ${mathbb{P}}_{3}/{mathbb{P}}_{2}$有限元对,时间离散采用Crank-Nicolson方法。用自适应牛顿法对得到的方程进行线性化处理,并用几何多网格技术对线性化系统进行计算。分析了在局部磁场和多孔层存在的情况下,理查德森数、多孔层厚度和纳米颗粒分数等参数对流体流动和传热的重要组成部分——沉体的升力和阻力等水动力的影响。随着纳米颗粒分数的改变,阻力系数和升力系数减小,局部努塞尔数和平均努塞尔数增大。
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引用次数: 4
The Onsager–Machlup theory of fluctuations and time-dependent generalized normal distribution Onsager–Machlup涨落理论与含时广义正态分布
IF 6.6 3区 工程技术 Q1 MECHANICS Pub Date : 2023-01-05 DOI: 10.1515/jnet-2022-0071
S. I. Serdyukov
Abstract Generalization of the variational formulation of the Onsager–Machlup thermodynamic theory of fluctuation is considered. Within the framework of variational theory, we introduce the time-dependent generalized normal distribution and Hamilton–Jacobi equation. The family of higher-order partial differential equations, which generalize classical Fokker–Planck equation, is considered. It is shown that proposed theory can be used for describing anomalous diffusion.
摘要考虑了Onsager–Machlup涨落热力学理论变分公式的推广。在变分理论的框架内,我们引入了含时广义正态分布和Hamilton–Jacobi方程。研究了高阶偏微分方程族,它推广了经典的Fokker–Planck方程。结果表明,该理论可用于描述异常扩散。
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引用次数: 0
期刊
Journal of Non-Equilibrium Thermodynamics
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