Basic Thermodynamic Principles Research Articles

Literature Review on Thermodynamic and Kinetic Limitations of Thermal Decomposition of Methane

The state of the art in methane pyrolysis does not yet provide a definitive answer as to whether the concept of an elementary reaction is universally applicable to the apparently simple process of methane dissociation. Similarly, the literature currently lacks a comprehensive and unambiguous description of the methane pyrolysis process and, in particular, a single model that would well represent its course at both the micro and macro scales. Given the wide range of conditions under which this reaction can occur—whether thermal or thermo-catalytic, in solid or fluidized bed reactors—it is crucial to evaluate the usefulness of different kinetic models and their compatibility with basic thermodynamic principles and design assumptions. To address these research gaps, the authors analysed the thermodynamic and kinetic dependencies involved in the thermal decomposition of methane, using the synthesis of methane from its elemental components and its reversibility as a basis for exploring suitable kinetic models. Using experimental data available in the literature, a wide range of kinetic models have been analysed to determine how they all relate to the reaction rate constant. It was found that regardless of whether the process is catalytic or purely thermal, for temperatures above 900 °C the reversibility of the reaction has a negligible effect on the hydrogen yield. This work shows how the determined kinetic parameters are consistent with the Kinetic Compensation Effect (KCE) and, by incorporating elements of Transition State Theory (TST), the possibility of the existence of Entropy–Enthalpy Compensation (EEC). The indicated correspondence between KCE and EEC is strengthened by the calculated average activation entropy at isokinetic temperature (∆SB=−275.0 J·(mol·K)−1). Based on these results, the authors also show that changes in the activation energy (E=20–421 kJ·mol−1) can only serve as an estimate of the optimal process conditions, since the isoconversion temperature (Tiso=1200−1450 K>Teq) is shown to depend not only on thermodynamic principles but also on the way the reaction is carried out, with temperature (T) and pressure (P) locally compensating each other.

Thermodynamic dissipation does not bound replicator growth and decay rates

In a well-known paper, Jeremy England derived a bound on the free energy dissipated by a self-replicating system [J. L. England, “Statistical physics of self-replication,” J. Chem. Phys. 139, 121923 (2013)]. This bound is usually interpreted as a universal relationship that connects thermodynamic dissipation to replicator per-capita decay and growth rates. We argue from basic thermodynamic principles against this interpretation. In fact, we suggest that such a relationship cannot exist in principle, because it is impossible for a thermodynamically consistent replicator to undergo both per-capita growth and per-capita decay back into reactants. Instead, replicator may decay into separate waste products, but in that case, replication and decay are two independent physical processes, and there is no universal relationship that connects their thermodynamic and dynamical properties.

KnowTD─An Actionable Knowledge Representation System for Thermodynamics.

We demonstrate that thermodynamic knowledge acquired by humans can be transferred to computers so that the machine can use it to solve thermodynamic problems and produce explainable solutions with a guarantee of correctness. The actionable knowledge representation system that we have created for this purpose is called KnowTD. It is based on an ontology of thermodynamics that represents knowledge of thermodynamic theory, material properties, and thermodynamic problems. The ontology is coupled with a reasoner that sets up the problem to be solved based on user input, extracts the correct, pertinent equations from the ontology, solves the resulting mathematical problem, and returns the solution to the user, together with an explanation of how it was obtained. KnowTD is presently limited to simple thermodynamic problems, similar to those discussed in an introductory course in Engineering Thermodynamics. This covers the basic theory and working principles of thermodynamics. KnowTD is designed in a modular way and is easily extendable.

Contrail or chemtrail? Challenges and opportunities for educators

Debunking conspiracy theories is a never-ending battle. These theories often suggest that the condensation trails left by jet aircraft are, in fact, chemical or biological agents intentionally dispersed for various purposes. Although any discussion with supporters of conspiracy theories is pointless, this paper outlines several potential strategies for incorporating this theory into physics education. Specifically, the concept of ‘chemtrails’ can be leveraged to introduce basic principles of thermodynamics, facilitate the construction of atmospheric models, analyze readily available data, and, importantly, underscore the significance of critical and scientific thinking, which is so important for students these days.

Effect of salinity on the effective stress of compacted bentonites

Adopting a double-porosity macroscopic modelling framework, a general formulation of the effective stress in compacted bentonites is derived from basic thermodynamic principles. The formulation indicates that, when there is equilibrium between macrostructural and microstructural water, the effect of salinity is affected by a factor that is equal to the ratio of the overall bulk modulus of the soil to that of the aggregates. The analysis of many well-tested salinisation experiments has shown that it is advisable to account for this factor. In double porosity systems, this factor represents how the effect of salinity is attenuated as the increment of intra-aggregate porosity stabilises, and the increase in total porosity becomes almost equal to the increase in macrostructural porosity.

Asymptotic and Finite-Time Semistability for Nonlinear Discrete-Time Systems With Application to Network Consensus

This article focuses on semistability and finite-time semistability analysis and synthesis of discrete-time dynamical systems having a continuum of equilibria. Semistability is the property whereby the solutions of a dynamical system converge to Lyapunov stable equilibrium points determined by the system initial conditions. In this article, we build on the theories of semistability and finite-time semistability for continuous-time dynamical systems to develop a rigorous framework for discrete semistability and discrete finite-time semistability. Specifically, Lyapunov and converse Lyapunov theorems for semistability and finite-time semistability are developed, and the regularity properties of the Lyapunov function establishing finite-time semistability are shown to be related to the settling time function capturing the finite settling time behavior of the dynamical system. These results are then used to develop a general framework for designing semistable and finite-time semistable consensus protocols for discrete dynamical networks for achieving multiagent coordination tasks asymptotically and in finite time. The proposed controller architectures involve the exchange of generalized energy state information between agents guaranteeing that the closed-loop dynamical network is semistable to an equipartitioned equilibrium representing a state of consensus consistent with basic thermodynamic principles.

Viscoelastic Cahn–Hilliard models for tumor growth

We introduce a new phase field model for tumor growth where viscoelastic effects are taken into account. The model is derived from basic thermodynamical principles and consists of a convected Cahn–Hilliard equation with source terms for the tumor cells and a convected reaction–diffusion equation with boundary supply for the nutrient. Chemotactic terms, which are essential for the invasive behavior of tumors, are taken into account. The model is completed by a viscoelastic system consisting of the Navier–Stokes equation for the hydrodynamic quantities, and a general constitutive equation with stress relaxation for the left Cauchy–Green tensor associated with the elastic part of the total mechanical response of the viscoelastic material. For a specific choice of the elastic energy density and with an additional dissipative term accounting for stress diffusion, we prove existence of global-in-time weak solutions of the viscoelastic model for tumor growth in two space dimensions [Formula: see text] by the passage to the limit in a fully-discrete finite element scheme where a CFL condition, i.e. [Formula: see text], is required. Moreover, in arbitrary dimensions [Formula: see text], we show stability and existence of solutions for the fully-discrete finite element scheme, where positive definiteness of the discrete Cauchy–Green tensor is proved with a regularization technique that was first introduced by Barrett and Boyaval [Existence and approximation of a (regularized) Oldroyd-B model, Math. Models Methods Appl. Sci. 21 (2011) 1783–1837]. After that, we improve the regularity results in arbitrary dimensions [Formula: see text] and in two dimensions [Formula: see text], where a CFL condition is required. Then, in two dimensions [Formula: see text], we pass to the limit in the discretization parameters and show that subsequences of discrete solutions converge to a global-in-time weak solution. Finally, we present numerical results in two dimensions [Formula: see text].

Development of a statistical model for calculating the carbon diffusion parameters in iron and steels

Carbon diffusion in metals has received a lot of attention and has been the subject of intensive theoretical investigations in recent years. The purpose of this work is development a simple statistical model of the carbon atoms diffusion in the crystal lattice of metals and its application for calculating the diffusion coefficients of carbon atoms in iron and steel. The relationship between the diffusion flux of atoms and the gradient of their chemical potential, as required by non-equilibrium thermodynamics, is obtained from the basic principles of statistical thermodynamics. For a real solid solution of impurity atoms in a metal, an expression is found for the diffusion coefficient, the value of which depends on physical constants, the atomic weight of the solute, the square of the temperature and activity i-element in solid solution. The calculations have a good agreement with the known experimental data on the diffusion of carbon atoms in iron and steels and is higher than in classical atomic diffusion models. The activation energy of carbon diffusion in γ- phase of various steels has values close to 120 kJ. Proposed formula well describes the deviation of the carbon diffusion coefficient from the Arrhenius law at medium and high temperature.

Quantum heat engine based on a spin-orbit- and Zeeman-coupled Bose-Einstein condensate

We explore the potential of a spin-orbit coupled Bose-Einstein condensate for thermodynamic cycles. For this purpose we propose a quantum heat engine based on a condensate with spin-orbit and Zeeman coupling as a working medium. The cooling and heating are simulated by contacts of the condensate with an external magnetized media and demagnetized media. We examine the condensate ground state energy and its dependence on the strength of the synthetic spin-orbit and Zeeman couplings and interatomic interaction. Then we study the efficiency of the proposed engine. The cycle has a critical value of spin-orbit coupling related to the engine maximum efficiency.

Energy and Entropy in Open and Irreversible Chemical Reaction–Diffusion Systems with Asymptotic Stability

Abstract This work proposes a novel approach for the study of open systems described by completely irreversible reaction mechanisms in non-homogeneous systems and subject to non-equilibrium boundary conditions. Using the non-equilibrium thermodynamics framework, we consider that in an autonomous system of reaction–diffusion equations, the thermodynamic potentials can be constructed from a Lyapunov function that depends directly on the eigenvalues and eigenvectors of the linearized problem. By interpreting this Lyapunov function as the free energy and redefining the chemical potentials, we were able to demonstrate the local stability properties of non-equilibrium stationary states, i. e., states that do not change with time due to a complex equilibration of internal and external flows. We demonstrate the consistency of our hypotheses with basic thermodynamic principles such as the spectral decomposition of entropy production and the Glansdorff–Prigogine evolution criterion. We discuss how our approach allows us to understand thermodynamic systems without assuming equilibrium or any kind of reversibility.

Energy and exergy analysis of NH3/CO2 cascade refrigeration system with subcooling in the low-temperature cycle based on an auxiliary loop of NH3 refrigerants

This paper proposes a NH3/CO2 cascade refrigeration system that sets an auxiliary refrigeration loop in the high-temperature cycle to increase the subcooling degree in the low-temperature cycle (CRSS). Based on the basic principles of thermodynamics, a mathematical model is established and theoretical simulation is carried out to obtain the influence of key parameters on the cycle performance. Compared with the conventional cascade refrigeration system (CCRS), the conclusions find that there exists an optimal condensation temperature of low-temperature cycle (TMC.opt) to maximize COP. The maximum COP of CRSS is 4.58% higher than that of CCRS when the subcooling degree is 10 °C. The maximum exergy efficiency is 0.391, increasing by 4.40%. With the increase of the subcooling degree, both the COP and the TMC.opt of CRSS increase. When the subcooling degree increases from 5 °C to 15 °C, the performance increment increases from 2.73% to 6.00%. When the evaporation temperature of the system changes, both the COP and exergy efficiency decreases slightly and it is found that the performance is better when the evaporation temperature is lower when condensation temperature is kept constant. Besides, the discharge temperature of the NH3 compressor in CRSS can be reduced by 9.9 °C when the evaporation temperature is −30 °C.

Symmetry-breaking, motion and bistability of active drops through polarization-surface coupling.

Cell crawling crucially depends on the collective dynamics of the acto-myosin cytoskeleton. However, it remains an open question to what extent cell polarization and persistent motion depend on continuous regulatory mechanisms and autonomous physical mechanisms. Experiments on cell fragments and theoretical considerations for active polar liquids have highlighted that physical mechanisms induce motility through splay and bend configurations in a nematic director field. Here, we employ a simple model, derived from basic thermodynamic principles, for active polar free-surface droplets to identify a different mechanism of motility. Namely, active stresses drive drop motion through spatial variations of polarization strength. This robustly induces parity-symmetry breaking and motility even for liquid ridges (2D drops) and adds to splay- and bend-driven pumping in 3D geometries. Intriguingly, then, stable polar moving and axisymmetric resting states may coexist, reminiscent of the interconversion of moving and resting keratocytes by external stimuli. The identified additional motility mode originates from a competition between the elastic bulk energy and the polarity control exerted by the drop surface. As it already breaks parity-symmetry for passive drops, the resulting back-forth asymmetry enables active stresses to effectively pump liquid and drop motion ensues.

Flows of Linear Polymer Solutions and Other Suspensions of Rod-like Particles: Anisotropic Micropolar-Fluid Theory Approach.

We formulate equations governing flows of suspensions of rod-like particles. Such suspensions include linear polymer solutions, FD-virus, and worm-like micelles. To take into account the particles that form and their rotation, we treat the suspension as a Cosserat continuum and apply the theory of micropolar fluids. Anisotropy of suspensions is determined through the inclusion of the microinertia tensor in the rheological constitutive equations. We check that the model is consistent with the basic principles of thermodynamics. In addition to anisotropy, the theory also captures gradient banding instability, coexistence of isotropic and nematic phases, sustained temporal oscillations of macroscopic viscosity, shear thinning and hysteresis. For the flow between two planes, we also establish that the total flow rate depends not only on the pressure gradient, but on the history of its variation as well.

Moisture uptake in nanocellulose: the effects of relative humidity, temperature and degree of crystallinity

Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods.Graphic abstract

Comments on the Experimental Study of the Combustion and Emission Characteristics of Lower Alcohols in a Constant Volume Vessel

We point out significant deficiencies in the article by Shao et al. (Shao, Z.; Han, Y.; Yang, H.; Wang, J.; Tian, J.; Xu, Y.; Zhang, L.; Ren, X.; Xu, C. Experimental study of the combustion and emission characteristics of lower alcohols in a constant volume vessel. Energy Fuels 2020, 34 (3), 3649−3660. DOI: 10.1021/acs.energyfuels.9b02834). Regrettably, the experimental findings reported in the article by Shao et al. violate the laws of thermodynamics. We demonstrate that, using the basic principles of thermodynamics, results presented in the article do not obey the conservation of mass and energy.

Nonlinear Analysis of a Quasi-Zero Stiffness Air Suspension Based on the Cell-Mapping Method

The quasi-zero stiffness system has the characteristics of low dynamic stiffness and high static stiffness, which can bring a better driving experience and lower road dynamic load at high speed on irregular roads. This paper studies a type of interconnected quasi-zero stiffness air suspension system, which has two states, namely, the non-interconnected quasi-zero stiffness air suspension and the interconnected quasi-zero stiffness air suspension, to meet the performance requirements under different loads and vehicle speed. First, the mathematical model of the nonlinear system is established based on the basic principles of fluid mechanics and thermodynamics. Then, the stability of the equilibrium point is analyzed using the Lyapunov first method, where the quantitative analysis of the attractive region of the system is conducted through the bifurcation diagram and phase diagram. By using the Taylor series expansion, cell-mapping theory and domain map of attraction, the attractive region of the system is quantitatively analyzed to obtain the parametric feasible domain under stable conditions. Finally, the performance of the quasi-zero stiffness suspension system with the selected parameters under the stability constraint is verified by simulation analysis and experiment. The results show that the system represented in this paper provides higher suspension comfort and stability.

Quantitative analysis of mitochondrial ATP synthesis

We present a computational framework for analyzing and simulating mitochondrial ATP synthesis using basic thermodynamic and kinetic principles. The framework invokes detailed descriptions of the thermodynamic driving forces associated with the processes of the electron transport chain, mitochondrial ATP synthetase, and phosphate and adenine nucleotide transporters. Assembling models of these discrete processes into an integrated model of mitochondrial ATP synthesis, we illustrate how to analyze and simulate in vitro respirometry experiments and how models identified from in vitro experimental data effectively explain cardiac respiratory control in vivo. Computer codes for these analyses are embedded as Python scripts in a Jupyter Book to facilitate easy adoption and modification of the concepts developed here. This accessible framework may also prove useful in supporting educational applications. All source codes are available on at https://beards-lab.github.io/QAMAS_book/.

A thermodynamic description for physiological transmembrane transport.

A general formulation for both passive and active transmembrane transport is derived from basic thermodynamical principles. The derivation takes into account the energy required for the motion of molecules across membranes and includes the possibility of modeling asymmetric flow. Transmembrane currents can then be described by the general model in the case of electrogenic flow. As it is desirable in new models, it is possible to derive other well-known expressions for transmembrane currents as particular cases of the general formulation. For instance, the conductance-based formulation for current turns out to be a linear approximation of the general formula for current. Also, under suitable assumptions, other formulas for current based on electrodiffusion, like the constant field approximation by Goldman, can be recovered from the general formulation. The applicability of the general formulations is illustrated first with fits to existing data, and after, with models of transmembrane potential dynamics for pacemaking cardiocytes and neurons. The general formulations presented here provide a common ground for the biophysical study of physiological phenomena that depend on transmembrane transport.

PRELIMINARY DEVELOPMENT OF A CONCEPTUAL MODEL OF MATRIX HEAT EXCHANGER

While the basic principles of thermodynamics have remained the same, the necessity for heat exchangers to have good effectiveness in a small volume is constantly growing. Heat exchangers type Matrix Heat Exchanger (MHE), which can meet these requirements, does not have an optimal design variant for its use. These heat exchangers have been approached for 60 years, by many researchers, currently offering only an overview of the process. The mechanism of heat transfer in a matrix heat exchanger is complex, having three different thermal convection paths as well as thermal conduction through two different surfaces. This paper presents the simulations performed in ANSYS Workbench, combining all these heat transfer modes, for developing an optimal model of a perforated plate matrix heat exchanger, used for the pre-cooling of a hydrogen isotopes stream mixture, for purification purposes, as well as, for preparing the inlet temperature in cryogenic distillation columns of hydrogen isotopes.

Thermal atomic layer etching: A review

This article reviews the state-of-the art status of thermal atomic layer etching of various materials such as metals, metal oxides, metal nitrides, semiconductors, and their oxides. We outline basic thermodynamic principles and reaction kinetics as they apply to these reactions and draw parallels to thermal etching. Furthermore, a list of all known publications is given organized by the material etched and correlated with the required reactant for each etch process. A model is introduced that describes why in the nonsaturation mode etch anisotropies may occur that can lead to unwanted performance variations in high aspect ratio semiconductor devices due to topological constraints imposed on the delivery of reactants and removal of reactant by-products.