化学势在钨表面氢平衡浓度计算中的应用

化学势是热力学与统计物理中重要的物理量,能够表征系统中粒子转移的趋势.本文以钨材料表面氢平衡浓度这一实际问题为例,在氢平衡浓度计算过程中逐步引入化学势的概念,通过分析环境氢分子系统和钨表面系统中氢化学势的变化,给出不同温度、压强下钨表面的氢平衡浓度.在热力学与统计物理教学中,通过平衡浓度的计算促进学生对于化学势等概念的...     

磁场中非广延相对论费米系统的统计性质

基于广义外势中的非广延统计理论,运用理论解析与数值模拟方法,研究磁场中非广延极端相对论费米气体的热力学性质,给出总能、热容量、化学势的解析式,分析非广延参数、极端相对论效应、磁场及温度对系统热力学性质的影响机理.研究显示,非广延参数不仅对热力学性质有直接的影响,而且也影响着磁场的物理效应. 随温度的升高,非广延参数及磁场对热力学性质的影响均被放大.极端相对论效应对化学势及热容量有特别显著的影响.     

两级氨水再吸收储热系统热力学动态特性分析

本文构建了一种以氨水为工质的两级再吸收浓度差储热系统,并对该系统进行热力学动态性能分析。由于采用二元溶液吸收过程代替一元工质冷凝过程,循环的驱动热源温度能够有效降低,在热源温度为90℃时两级再吸收循环COP可达0.489.对于两级再吸收循环,研究热源温度,回水温度对储热效率的影响。储热终了时间随热源温度80℃增加为130℃从4.5 h缩短为1 h。     

Statistical Thermodynamic Properties of Linear Protein Solutions

利用统计力学理论结合格点模型,讨论了链状蛋白质分子溶液的热力学性质. 结果表明,对于稀溶液来说,溶液的吉布斯函数随蛋白质浓度的增加而降低,蛋白质分子化学势随其浓度增加而升高. 还分析了蛋白质分子链长及温度对溶液吉布斯函数和蛋白质分子化学势的影响. 并且计算讨论了几种第一类抗冻蛋白的化学势.     

有限温度下一维Hubbard模型的化学势泛函理论研究

通过数值方法求解了有限温度下一维均匀Hubbard模型的热力学Bethe-ansatz方程组,得到了在给定温度和相互作用强度情况下,比热c、磁化率χ和压缩比κ随化学势μ的变化图像.基于有限温度下一维均匀Hubbard模型的精确解,利用化学势(μ)-泛函理论研究了一维谐振势下的非均匀Hubbard模型,给出了金属态和Mott绝缘态下不同温度情况时局域粒子密度n_i和局域压缩比_κi随格点的变化情况.     

传热传质分离的绝热吸收过程实验研究

根据传热传质分离的吸收形式,设计加工了一台溴化锂绝热降膜吸收的实验装置,对溴化锂水溶液在倾斜平板上对水蒸气的吸收特性进行了实验研究,分析了预冷却温差、溶液流量及平板倾角对吸收过程的影响。实验结果表明:预冷却温差、溶液流量及平板倾角越大,溴化锂溶液对水蒸气的吸收效果越好,并认为吸收过程可以分成三个步骤,另外就热质分离吸收器的设计过程中的溴化锂溶液的最小速度提出建议。     

气相界面活性剂对溴化锂水溶液吸收水蒸气的影响

目前在溴化锂吸收式制冷机/热泵中被广泛采用的界面活性剂是2-ethyl-1-hexanol(2EH)和1-octanol。传统的界面活性剂的添加方式是,将界面活性剂以液相形式投入到溴化锂溶液中。如果在三效循环中仍采用这样的方式将2EH加入到溴化锂溶液中,由于发生器的温度较高,势必有界面活性剂被蒸发而进入冷媒系统。为探讨三效循环界面活性剂的可能添加方式,同时试图研究界面活性剂以气相形式投入对溴化锂溶液吸收水蒸气的影响,本文针对几种可能有效的界面活性剂,做了界面活性剂的气相添加对吸收速度影响的测试实验。经过对2-ethyl-1-hexanol、1-heptanol和1-hexanol等添加剂的静态池实验,结果表明,气相添加的效果与液相投入没有明显的差别,同样可以大大提高溴化锂溶液吸收水蒸气的速度。     

有限温度下一维Gaudin-Yang模型的热力学性质

本文通过数值求解有限温度下一维均匀费米Gaudin-Yang模型的热力学Bethe-ansatz方程, 研究了此模型的基本性质,得到了在给定的温度或给定的相互作用下, 化学势、相互作用、粒子密度和熵的相互变化图像. 对结果分析发现, 在给定温度和相互作用下, 熵随着化学势的变化有一个量子临界区域.     

准逆流液-液膜接触器传热传质研究

本文提出了一种准逆流平行板式膜吸收热泵(液-液膜接触器)并用于流体加热。制冷剂(水)和吸收剂(盐溶液)以逆流和错流相结合的形式(准逆流)流动,被半透膜隔开。该膜只允许水蒸气的渗透,盐溶液从水中吸收水蒸气。潜热和混合热被释放到溶液侧,使低温热量转换为可用的高温热量。为了研究膜式热泵内的热量和质量的耦合传递,选择相邻流道、两块膜及其空气隙作为研究对象建立数学模型。使用有限差分法求解动量、热量和质量传递的控制方程,得到溶液的温升。结果表明,潜热传递参数比显热传递参数对溶液温升的影响更大。     

反常磁矩对弱磁场弱相互作用费米气体热力学性质的影响

考虑费米子的反常磁矩, 运用赝势法和热力学理论, 导出弱磁场中弱相互作用费米气体自由能的解析式, 以此为基础给出高温和低温情况下系统热力学性质, 分析反常磁矩对热力学性质的影响机理. 研究表明: 反常磁矩对热力学性质的影响与温度相关, 而且这种影响随温度的上升在低温区是增大的, 在高温区是减小的; 对于系统的化学势、内能, 反常磁矩加强了磁场的影响, 弱化了相互作用的影响; 对于系统的热容量, 反常磁矩在低温区使其减小, 在高温区使其增加.     

Dilatometry of the high-temperature proton conductor Ba3Ca1.18Nb1.82O9 − δ

Firstly, the production of solid bulk specimens of the proton conductor Ba₃Ca_1.18Nb_1.82O_{9 − gd} (BCN18) of known water content up to [H^.] = n_H/n_Ba = 0.16 is described. Secondly, measuring the length change of such samples versus water content [H^.] demonstrated that the sample lengths increased linearly with a slope of (Δl/l)/[H^.] = (2.13 ±0.07) × 10⁻². Thirdly, the density of bulk samples was found to decrease linearly with water content [H^.]. This decrease was in good agreement with the above values derived from the length change. Fourthly, high temperature dilatometry showed that samples reach the thermodynamic solubility values in water vapor atmospheres only at temperatures above 700 °C. Two time scales were observed for the time-dependence of the elongation upon exposure to water vapor. A fast process occurred within minutes above 700 °C, a slow one took several hours. The fast one was identified as the chemical diffusion of the diffusion pair H^. and V_o^. which is required for the water uptake and loss of BCN18. The chemical diffusivity of water is described by the parameters D₀ = (0.022 ± 0.002) cm²/s and ΔH* = (0.79 ± 0.05) eV.     

pH值对AZ31镁合金表面植酸转化膜在模拟体液耐腐蚀性能的影响

采用沉积的方法在镁合金AZ31表面制备植酸转化膜并研究了pH值的影响. 利用极化曲线和电化学阻抗谱方法测定其耐腐蚀性能,用扫描电子显微镜观察转化膜的表面微观结构,用能谱测定转化膜的组成元素. 在理论上通过热力学的方法分析最佳pH值. 植酸转化膜可以提高镁合金AZ31的耐腐蚀性能. 当植酸溶液的pH=5时腐蚀效率达到了89.19%,此时腐蚀电位正移了156 mV,腐蚀电流密度与没有处理的试样相比减小了约一个数量级. 热力学分析表明植酸转化膜的耐腐蚀性能不仅受植酸根离子和镁离子浓度的影响,也与氢气释放的速率有关.     

Life, hierarchy, and the thermodynamic machinery of planet Earth

Throughout Earth's history, life has increased greatly in abundance, complexity, and diversity. At the same time, it has substantially altered the Earth's environment, evolving some of its variables to states further and further away from thermodynamic equilibrium. For instance, concentrations in atmospheric oxygen have increased throughout Earth's history, resulting in an increased chemical disequilibrium in the atmosphere as well as an increased redox gradient between the atmosphere and the Earth's reducing crust. These trends seem to contradict the second law of thermodynamics, which states for isolated systems that gradients and free energy are dissipated over time, resulting in a state of thermodynamic equilibrium. This seeming contradiction is resolved by considering planet Earth as a coupled, hierarchical and evolving non-equilibrium thermodynamic system that has been substantially altered by the input of free energy generated by photosynthetic life. Here, I present this hierarchical thermodynamic theory of the Earth system. I first present simple considerations to show that thermodynamic variables are driven away from a state of thermodynamic equilibrium by the transfer of power from some other process and that the resulting state of disequilibrium reflects the past net work done on the variable. This is applied to the processes of planet Earth to characterize the generation and transfer of free energy and its dissipation, from radiative gradients to temperature and chemical potential gradients that result in chemical, kinetic, and potential free energy and associated dynamics of the climate system and geochemical cycles. The maximization of power transfer among the processes within this hierarchy yields thermodynamic efficiencies much lower than the Carnot efficiency of equilibrium thermodynamics and is closely related to the proposed principle of Maximum Entropy Production (MEP). The role of life is then discussed as a photochemical process that generates substantial amounts of chemical free energy which essentially skips the limitations and inefficiencies associated with the transfer of power within the thermodynamic hierarchy of the planet. This perspective allows us to view life as being the means to transform many aspects of planet Earth to states even further away from thermodynamic equilibrium than is possible by purely abiotic means. In this perspective pockets of low-entropy life emerge from the overall trend of the Earth system to increase the entropy of the universe at the fastest possible rate. The implications of the theory are discussed regarding fundamental deficiencies in Earth system modeling, applications of the theory to reconstructions of Earth system history, and regarding the role of human activity for the future of the planet.     

The thermodynamics of electrons and the thermoelectric transport in epitaxial graphene on the size-quantized films

We investigated the thermodynamic parameters (chemical potential, heat capacity and thermodynamic potential) and a thermoelectric transport in an epitaxial graphene on the size-quantized metal and semiconductor films within the framework of simple analytical model. We considered limiting cases of high and low temperatures. We showed that the chemical potential of epitaxial graphene is smaller than the chemical potential of isolated graphene at the same carrier concentration. Conversely, the heat capacity of the epitaxial graphene is greater than the heat capacity of the isolated graphene. We investigated a conductivity and thermopower of the epitaxial graphene. We showed that in such system there are the kinks of conductivity and peaks of thermoelectric power. These peaks are several times greater than those of isolated graphene. We compared our system with cases of 2D and 3D substrates.     

A study of the optimum interaction between the working fluid and the absorbent in absorption heat pump systems

The operating efficiency of an absorption heat pump is critically dependent on the chemical, thermophysical and thermodynamic properties of the working fluid, the absorbent and their solution. The desirable properties are discussed in the light of the operating parameters and the thermodynamic limits. Deviations from ideality are considered with specific reference to water/salt systems. Plots of the heat of hydration and heat of solution against the effective ionic radius, the lowering of vapour pressure against the heat of solution and the solubility against the melting point have been made for aqueous alkali metal halide solutions. It is demonstrated that an optimisation procedure is necessary to select suitable working fluid-absorbent combinations from the hundreds of possible combinations based on the operating conditions and the field of application.     

Bubble boiling in droplets of water and lithium bromide water solution

The dynamics of growth and interaction of vapor bubbles in droplets of pure water and LiBr water solution on a horizontal wall were investigated in a wide superheating range. The growth rates of bubbles were determined both in a distillate droplet and in a salt solution droplet. The bubble growth rate in a pure water droplet at the final stage is somewhat lower than in pool boiling. The bubble growth rate in a salt solution is substantially lower than for pure water. Due to the bubble density maldistribution, the vapor flow density is appreciably higher at the droplet edges than on the droplet axis. Collective behavior of the bubbles possesses both stochastic character and elements of self-organization. The thermal measurements were carried out by means of high-speed video and blowup thermal imager.     

A field analysis of nonlinear irreversible thermodynamic processes

The generalized thermodynamic potential analysis of nonlinear irreversible processes precludes the analysis of rotational processes. The nonexistence of scalar potential functions necessitates a thermodynamic analysis of the system forces. A field analysis in the phase space of the generalized displacements and velocities treats the force components as tensors of second order that tend to deform and rotate the irreversible process, which is viewed as an elastic material. The analysis of chemical oscillatory processes involves the introduction of the thermodynamic vector potential, which is subsequently used in the formulation of a variational principle and to define an energy flux vector. The direction of energy flow elucidates the mechanism by which steady motion is maintained and it is a characteristic property of open systems. Field analyses of systems that are described by half and single degrees of freedom are contrasted.     

多孔介质对流干燥外部传热传质的非平衡热力学理论

从非平衡热力学理论出发,以广义热力学力作为传质过程驱动势,建立了描述多孔介质恒速干燥阶段外部对流传热传质过程的热力学理论模型,并进行了数值计算,计算值与已有的实验数据吻合较好;同时,还将计算结果与传统的理论进行了比较,结果表明,非平衡热力学理论更能反映过程的物理本质。