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1.
Mathematical modelling of three-dimensional steady free convective incompressible viscous gas flows in the rooms with a heat
source is carried out within the framework of the Navier — Stokes equations with the effective viscosity determined on the
basis of the κ-ɛ turbulence model. The investigation is carried out for the case of model rooms and heat sources having the form of rectangular
parallelepipeds with square bases. The influence of the heat source power and the sizes of the room base on local and averaged
values of the air velocity and temperature in the rooms is analysed. The flow pattern in the room is shown to have a torus-like
shape. It is found that the variation of sizes of the room base rather than the capacity variation of the heat source is of
determining importance for the gas motion character in a closed volume. 相似文献
2.
In this paper, we first define a deterministic particle model for heat conduction. It consists of a chain of N identical subsystems, each of which contains a scatterer and with particles moving among these scatterers. Based on this
model, we then derive heuristically, in the limit of N → ∞ and decreasing scattering cross-section, a Boltzmann equation for this limiting system. This derivation is obtained by
a closure argument based on memory loss between collisions. We then prove that the Boltzmann equation has, for stochastic
driving forces at the boundary, close to Maxwellians, a unique non-equilibrium steady state. 相似文献
3.
Recently, in their attempt to construct steady state thermodynamics (SST), Komatsu, Nakagawa, Sasa, and Tasaki found an extension
of the Clausius relation to nonequilibrium steady states in classical stochastic processes. Here we derive a quantum mechanical
version of the extended Clausius relation. We consider a small system of interest attached to large systems which play the
role of heat baths. By only using the genuine quantum dynamics, we realize a heat conducting nonequilibrium steady state in
the small system. We study the response of the steady state when the parameters of the system are changed abruptly, and show
that the extended Clausius relation, in which “heat” is replaced by the “excess heat”, is valid when the temperature difference
is small. Moreover we show that the entropy that appears in the relation is similar to von Neumann entropy but has an extra
symmetrization with respect to time-reversal. We believe that the present work opens a new possibility in the study of nonequilibrium
phenomena in quantum systems, and also confirms the robustness of the approach by Komatsu et al. 相似文献
4.
Teruhisa S. Komatsu Naoko Nakagawa Shin-Ichi Sasa Hal Tasaki 《Journal of statistical physics》2009,134(2):401-423
Recently a novel concise representation of the probability distribution of heat conducting nonequilibrium steady states was
derived. The representation is valid to the second order in the “degree of nonequilibrium”, and has a very suggestive form
where the effective Hamiltonian is determined by the excess entropy production. Here we extend the representation to a wide
class of nonequilibrium steady states realized in classical mechanical systems where baths (reservoirs) are also defined in
terms of deterministic mechanics. The present extension covers such nonequilibrium steady states with a heat conduction, with
particle flow (maintained either by external field or by particle reservoirs), and under an oscillating external field. We
also simplify the derivation and discuss the corresponding representation to the full order. 相似文献
5.
S. N. Kallaev Z. M. Omarov R. G. Mitarov A. R. Bilalov K. Bormanis S. A. Sadykov 《Journal of Experimental and Theoretical Physics》2010,111(3):421-426
The heat capacity, thermal expansion coefficient, and deformation of the PLZT-9/65/35 compound are studied in the temperature
range 150–800 K. Diffuse anomalies are detected in the temperature dependences of the heat capacity and thermal expansion
coefficient over wide temperature ranges of 250–650 and 330–550 K, respectively. The anomalous behavior of the heat capacity
in the temperature range 250–650 K is shown to be caused by the appearance of two-level states (Schottky anomaly). The results
obtained are discussed along with the data of structural and dielectric studies. 相似文献
6.
Starting from microscopic mechanics, we derive thermodynamic relations for heat conducting nonequilibrium steady states. The extended Clausius relation enables one to experimentally determine nonequilibrium entropy to the second order in the heat current. The associated Shannon-like microscopic expression of the entropy is suggestive. When the heat current is fixed, the extended Gibbs relation provides a unified treatment of thermodynamic forces in the linear nonequilibrium regime. 相似文献
7.
The thermal physical properties (heat capacity, thermal expansion coefficient, and deformation) of a relaxor piezoelectric
ceramics based on the lead zirconate titanate PKR-7M have been studied in the temperature range 200–800 K. Diffuse anomalies
have been revealed in the temperature dependences of the heat capacity and thermal expansion over wide temperature ranges
270–650 and 450–600 K, respectively. It has been shown that the anomalous behavior of the heat capacity is due to the manifestation
of two-level states (Schottky anomalies). The results of the study have been discussed together with the data of structural
studies. 相似文献
8.
A steady state thermodynamic model for an air—cooled finned—tube condenser, used in a typical deep freezer vapour compression
system, operating with pure and refrigerant mixtures has been developed using finite difference method. The heat transfer
aspects in the condenser are treated uniquely for superheated, two—phase and subcooled regimes and studied for various heat
load, pressure, temperature, and mass flow rate. The condensation heat transfer coefficient, the tube length required for
condensation, the degree of subcooling, and the temperature glide for different ambient temperatures are estimated. The simulation
and the experimental results are in good agreement. 相似文献
9.
10.
A. G. Gamzatov A. M. Aliev K. Sh. Khizriev I. K. Kamilov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2011,53(11):2271-2274
The heat capacity of the manganite La0.87K0.13MnO3 has been measured in the temperature range 80–350 K. The nature of the ferromagnetic phase transition and the critical properties
of heat capacity near the Curie temperature have been studied. The regularities of variations in the universal critical parameters
near the phase transition point have been established. The calculated critical exponent and amplitudes of the heat capacity
with allowance for corrections on the scaling (α = −0.13 and A
+/A
− = 1.178) correspond to the critical behavior of the 3D Heizenberg model. 相似文献
11.
Shikov A. A. Panova G. Kh. Zemlyanov M. G. Parshin P. P. Kumzerov Yu. A. Naberezhnov A. A. Shaitura D. S. 《Physics of the Solid State》2011,53(12):2515-2519
The heat capacity has been studied in the temperature range 2.2–40 K and in magnetic fields up to 2 T in tin, which has been
embedded in nanometer-size pores in glass having diameter ∼7 nm, in bulk tin and in glass with empty pores. Comparison of
the properties of tin nanoparticles and bulk tin has been performed. An increase in the coefficient of electronic heat capacity
has been found in nanostructured tin as compared with the bulk tin, and also a considerable deviation of the low-temperature
lattice heat capacity from the Debye law in the temperature region T > 3 K has been found. The fact that the density of thermal vibrations in nanocrystalline tin for low energies is higher than
in bulk tin has been established using low-temperature heat capacity data. 相似文献
12.
13.
Heat capacity of Rb2ZnBr4 as a function of γ irradiation dose has been measured within the 85–300 K range by the adiabatic calorimeter technique. It is shown that, as
the irradiation dose increases, the heat capacity peak in the vicinity of the incommensurate-commensurate first-order phase
transition (PT) decreases, and the transition temperature T
c
increases. The heat capacity peak in the region of the second-order PT at T
3=112 K does not depend on γ irradiation, both in magnitude and in position, just as the heat capacity throughout the remainder of the temperature range
studied.
Fiz. Tverd. Tela (St. Petersburg) 40, 1106–1108 (June 1998) 相似文献
14.
I. K. Kamilov A. G. Gamzatov A. B. Batdalov A. S. Mankevich I. E. Korsakov 《Physics of the Solid State》2010,52(4):789-793
The magnetocaloric effect and the heat capacity of La1 − x
K
x
MnO3 (x = 0.1, 0.15, 0.175) ceramic samples have been studied at temperatures in the range 77–350 K and in magnetic fields of up
to 27 kOe. The technique for preparing the samples has been described. The heat capacity anomalies related to the ferromagnetic-paramagnetic
magnetic phase transition have been revealed and interpreted. It has been demonstrated that the change in the magnetic entropy
ΔS calculated from the data on the heat capacity C
p
and direct measurements of the magnetocaloric effect ΔT reaches values that are of practical interest. 相似文献
15.
��С��������������ѧ����î �� 《核聚变与等离子体物理》2018,38(3):329-333
为提高偏滤器的抗中子辐照能力,兼顾高热承载能力和聚变堆经济性的需要,提出了基于熔盐冷却(MSC)的偏滤器靶板结构设计。它采用FLiNaK作为冷却剂,钨镧合金为热沉材料,钨为第一壁材料。通过数值计算评估了靶板的热负荷承载能力,并完成了偏滤器冷却剂回路设计,优化了偏滤器各模块之间的流量分配。此MSC偏滤器靶板设计可以有效去除10~15MW•m-2热负荷,为适应未来聚变堆偏滤器靶板发展的需要提供了一种设计解决方案。 相似文献
16.
Ali Morsali S. Ali Beyramabadi S. Hooman Vahidi Maryam Ghorbani 《Molecular physics》2013,111(8):483-490
The curves of experimental heat capacity against density show a minimum around and below the critical temperature (Tc), but at higher temperatures, this minimum is not observed. In this study, the role of attractive and repulsive forces on excess heat capacity of Lennard–Jones (LJ) dense fluids has been investigated using a molecular dynamics simulation technique. LJ potential is divided into attractive and repulsive parts. From the molecular dynamics calculations, potential energy and heat capacities have been obtained for Argon at temperatures of 100–500?K. The repulsive forces play the main role in causing the heat capacities at temperatures greater than critical point. Around and below the critical temperature, the role of repulsion is dominant at high densities, but attraction has the main role at low densities, consequently at middle densities, a minimum is formed. 相似文献
17.
层流对流换热中的势容耗散极值与最小熵产 总被引:3,自引:0,他引:3
在一定的约束条件下,存在一个最优的速度场,它能够使得温度场和速度场的协同程度最好,从而使得对流换热的整体传热性能达到最优。目前对传热效果的评价存在熵产最小化和势容耗散取得极值两种不同的准测。分别根据这两种优化准则,用变分方法推导了在粘性耗散一定的条件下,稳态无内热源的层流对流换热的场协同方程,并对方腔内对流换热问题进行了优化。数值计算结果表明,势容耗散取得极值时的换热效果优于熵产最小的结果,因此势容耗散极值原理更适合做为对流换热的优化准则。 相似文献
18.
G. C. Ganzenmüller S. Hiermaier M. O. Steinhauser 《The European physical journal. Special topics》2012,206(1):51-60
We propose a thermodynamically consistent and energy conserving coupling scheme between the atomistic and the continuum domain.
The coupling scheme links the two domains using the DPDE (Dissipative Particle Dynamics at constant Energy) thermostat and
is designed to handle strong temperature gradients across the atomistic/continuum domain interface. The fundamentally different
definitions of temperature in the continuum and atomistic domain – internal energy and heat capacity versus particle velocity
– are accounted for in a straightforward and conceptually intuitive way by the DPDE thermostat. We verify the here proposed
scheme using a fluid, which is simultaneously represented as a continuum using Smooth Particle Hydrodynamics, and as an atomistically
resolved liquid using Molecular Dynamics. In the case of equilibrium contact between both domains, we show that the correct
microscopic equilibrium properties of the atomistic fluid are obtained. As an example of a strong non-equilibrium situation,
we consider the propagation of a steady shock-wave from the continuum domain into the atomistic domain, and show that the
coupling scheme conserves both energy and shock-wave dynamics. 相似文献
19.
We work out the non-equilibrium steady state properties of a harmonic lattice which is connected to heat reservoirs at different temperatures. The heat reservoirs are themselves modeled as harmonic systems. Our approach is to write quantum Langevin equations for the system and solve these to obtain steady state properties such as currents and other second moments involving the position and momentum operators. The resulting expressions will be seen to be similar in form to results obtained for electronic transport using the non-equilibrium Green’s function formalism. As an application of the formalism we discuss heat conduction in a harmonic chain connected to self-consistent reservoirs. We obtain a temperature dependent thermal conductivity which, in the high-temperature classical limit, reproduces the exact result on this model obtained recently by Bonetto, Lebowitz and Lukkarinen. 相似文献
20.
The heat transfer within a fuel cell at steady state conditions is considered here for one dimensional geometry. Analytical
solution for the heat transfer equation accompanied by the appropriate boundary conditions is obtained. The heat transfer
coefficient is also estimated for the case of ideal heat exchange. It was found that the geometrical characteristics of the
cell that are strongly related with its electrical ones (namely, the ohmic resistance and the current developed), are favourable
parameters for the maximization of the heat transfer.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002. 相似文献