Thermodynamic System Research Articles

Order Degree and Centrality Analysis of Advanced Fighter Environmental Control System and Thermal Management System

As fighter aircraft become more advanced, traditional air cycle systems have fallen short of meeting the complex environmental control requirements. Advanced fighters such as the F-22 Raptor have responded to these challenges by adopting integrated thermal management systems. These systems feature complex thermodynamic processes and intricate information transmission pathways among various components, creating a sophisticated network structure. To unravel the complexity of such systems, this paper employs a blend of thermodynamics and information theory. We conduct multi-level analysis using structure entropy method and centrality algorithms to explore the information transmission characteristics within these thermodynamic systems. At the system level, we find that variation in environmental parameters have only a 1% impact on order degree, whereas the influence from the system's own structure is more pronounced. At the component level, within the whole system, the varies components in AFT PAO and fuel loops emerge as critical hubs for information transmission. Among these components, the PAO/Fuel stands out as the most important, with closeness and betweenness centrality exceeding that of all other components by at least 11.5% and 29.1%. This study offers a theoretical foundation for the optimization of thermodynamic system structure and layout, viewed through the lens of information theory.

Phase transitions, shadows, and microstructure of Reissner-Nordström-Anti-de-Sitter black holes from a geometrothermodynamic perspective

We study the thermodynamic properties of the Reissner-Nordström black hole with cosmological constant, expressed in terms of the curvature radius, using the approach of shadow thermodynamics and the formalism of geometrothermodynamics. We derive explicit expressions for the shadow radius in terms of the horizon, photon sphere, and observer radii. The phase transition structure turns out to strongly depend on the value of the curvature radius, including configurations with zero, one, or two phase transitions. We also analyze the black hole's microscopic structure and find differences between the approaches of thermodynamic geometry and geometrothermodynamics, which are due to the presence of the curvature radius. We impose the important condition that the black hole is a quasi-homogeneous thermodynamic system to guarantee the consistency of the geometrothermodynamic approach.

Schottky Anomaly of the Kalb-Ramond-de Sitter Spacetime

In the theory of gravity, the spontaneous breaking of Lorentz symmetry due to the non-minimal coupling between the Kalb-Ramond field and Einstein gravity results in the existence of exactly static and spherically symmetric black hole solutions related to the Lorentz violating parameter. Based on the consideration of the interaction between the black hole and cosmological horizons, this paper studies the thermodynamic properties of Kalb-Ramond-de Sitter (KR-dS) spacetime. The Smarr relation expressed by equivalent thermodynamic quantities is found, and it is proved that the equivalent thermodynamic quantities of the KR-dS spacetime satisfy the universal Euler's theorem. It is discovered that the heat capacity of the KR-dS spacetime with respect to the ratio of the two horizons and the variation curve of the heat capacity with effective temperature possess the characteristics of Schottky specific heat. Moreover, the black hole and the cosmological horizon in the equivalent thermodynamic system are regarded as two different energy levels, and the heat capacity of the KR-dS spacetime is discussed using the general form given by the ordinary two-level system. It is found that the heat capacity of KR-dS spacetime described by equivalent thermodynamic quantities not only conforms to the characteristics of Schottky specific heat but also is consistent with the heat capacity of the ordinary two-level system. This result reflects that when the cosmological constant and the charged carried in the KR-dS spacetime remain unchanged, the heat capacity of the system can be represented by a universal two-level system. By comparing the maximum value of the heat capacity curves, the number of microscopic particles between the two horizons can be estimated, which reflects the quantum properties of the KR-dS spacetime. These studies will open a new perspective to probe the thermodynamics of black holes.

Development of an electrochemically approximated simulation model and a hardware substitution cell approach for thermal management battery system tests

AbstractBattery tests require a high degree of safety-related preparation and constant monitoring of the operating parameters to guarantee the smooth running of tests without incidents or exceptional events such as a thermal runaway. As the handling before, during, and especially after the tests is relatively complex and sometimes just as costly, it is important to reduce these risks and costs as well as to find an alternative to conventional battery tests. Such an approach is being developed by the T-cell project of the Institute of Thermodynamics and Sustainable Propulsion Systems at Graz University of Technology, founded by the Austrian Research Promotion Agency (FFG). A thermal substitution cell, which resembles a battery cell on the outside, is to reflect the surface temperature distribution of a chemical cell without there being any cell chemistry inside the substitution cell. Rather, the interior should not be part of the observation and the thermal requirements should be provided by an internal heating option. Such a measurement approach requires, among other things, a control and regulation unit, without which it would not be possible to transfer the thermal behavior of a battery cell to the substitution cell. Together with the electronic structure of the substitution cell and a circuit environment including a battery simulation model established at a later date, this control/regulation module forms an overall package that considerably facilitates investigations at cell, module, and pack level by substitution of a certain amount of cells using system symmetry advantages. A suitable simulation model was constructed and parameterized for this purpose from an electrochemical and a thermal network. As a first step, the data, which were partly determined empirically but also derived from real cell measurements in the literature, were adapted to the requirements of the simulation environment, so that the real cell used could be simulated thermally in principle. The simulation observations represent the state of the art of the model and are continuously improved by measurements carried out at the institute, thus building up the overall system in more detail.

Equivalent Circuits for Exergy Flow in Thermodynamic Systems

Abstract The second law of thermodynamics explains the nature of all spontaneous processes, and it imposes a limit on the performance of all technologies, from heat engines to refrigerators. These limits are well described as early as Sadi Carnot's 1824 publication that established the field of thermodynamics; researchers later developed the concept of exergy, or the available work, that a thermodynamic system can produce when interacting with a specified environment. In this work, we describe a resistance analogy for thermodynamic systems, in which the need to remove entropy forces some amount of energy to leave the system as heat rejection. Specifically, it is the inverse temperature of the heat sink that resists energy flowing out of the system as heat rejection. An equivalent circuit can be drawn for any thermodynamic system, with energy flowing through different branches of the circuit. The different paths correspond to different energy and exergy flows, including the energy that must flow out of the system as heat rejection and, therefore, cannot contribute to the exergy content of the system. After establishing this equivalent circuit, it is applied to a natural gas combined cycle example problem, a desalination example problem, and a transient heating problem.

Superstatistical functions of modified shifted Morse potential for diatomic molecules

The application of the molecular potential model to the study of different thermodynamic systems has been a focus of interest in recent time due to its importance in molecular and chemical physics. Hence, the asymptotic iteration method and the Laguerre polynomials are employed to obtain the eigensolutions of the Schrödinger equation with the modified shifted Morse potential model. Vibrational energy results for different diatomic molecules have been presented numerically, and these results are compared with experimental data and other results from available literature. The variation of normalised wave function and probability density of modified shifted Morse potential for some selected diatomic molecules at the ground- and first-excited states have been considered. Results obtained show that the equally spaced sinusoidal wave curves and varying nodes depend on the level of electron concentrations in the diatomic molecules considered. Partition function and other superstatistical function expressions of modified shifted Morse potential for some diatomic molecules within the modified Dirac delta distribution are obtained, using the Poisson summation formula. The superstatistical plots show a high level of dependence on the temperature parameter, maximum vibrational quantum number and deformation parameter. The superstatistical functions for a deformation parameter of zero correspond to the conventional thermodynamic functions.

Investigation of an Ammonia-Fueled SOFC-mGT Hybrid System: Performances Analysis and Comparison With Natural Gas-Based System

Abstract Hybrid systems (HS) are highly attractive in power generation due to their potential for higher power outputs and efficiencies by integrating different technologies. Among solid oxide fuel cell (SOFC) plants, the SOFC-Micro-Gas Turbine (mGT) system is particularly innovative. In this setup, the SOFC replaces the mGT combustion chamber, with an afterburner completing fuel combustion before the expander. Various configurations and control systems have been explored over the years, and prototypes have demonstrated satisfactory efficiency. However, these systems have predominantly used NG and Biogas, which do not achieve zero carbon emissions. The growing global demand for carbon-free energy production is increasing, highlighting the importance of alternative fuels in the power generation sector: among them, thanks to its chemical and physical properties, ammonia is gaining more and more interest. This work investigates an innovative ammonia-to-power system based on an SOFC-mGT HS, focusing on thermodynamic parameters, system features, and technical and environmental challenges. A MATLAB/Simulink model, built on a validated HS model fueled by NG, was developed to analyze the new system configuration. This configuration replaces the SOFC prereformer with an ammonia cracker, allowing for the exploration of anode gas recirculation effects and optimal system design. Key operating parameters such as anodic recirculation factor, fuel utilization, performance, and gas turbine characteristics are discussed. Finally, a comparison is made between hybrid systems and mGTs powered by methane, biogas, and ammonia.

The concept of creating a maneuverable power plant based on a small modular reactor

Purpose. To develop a maneuverable power plant (MPP) based on the NuScale small modular reactor (SMR) by selecting a thermal scheme structure for a steam turbine installation using minimal additional equipment and ensuring its operation in both nominal and peak modes with maximum efficiency. This also includes ensuring its maneuverability through the use of hydrogen technologies for generating, storing, and returning energy to the steam turbine cycle. Methodology. The study employed the method of mathematical modeling of thermodynamic cycles of thermal schemes of steam turbine installations (STI) with concentrated parameters, which makes it possible to describe the dynamics of systems consisting of discrete elements that are thermodynamic systems. Findings. Various structural options for the thermal scheme of the MPP based on the NuScale SMR for nominal operation were developed and mathematically modeled, followed by a comparative analysis of their energy efficiency. As a result, a scheme and operational parameters were selected with the highest electrical efficiency (net), which allows increasing the net efficiency of the NuScale SMR-based power plant from the developers’ announced 28 to 32.8 %. A thermal scheme for the MPP based on the SMR with an energy storage system was proposed. Applying this scheme allows increasing the net efficiency of a power plant based on NuScale SMR in peak mode to 34.8 %. Originality. A concept for creation and schematic solution for a prospective MPP based on an SMR capable of accumulating electrical energy was proposed. The main innovative solution regarding the structure of the technological scheme of the MPP based on the SMR is the organization of its operation in nominal and peak modes, which fundamentally differ in the thermodynamic cycle. In the nominal mode, the steam turbine installation operates on a thermodynamic cycle with steam separation, and in the peak mode without it, by increasing the temperature of fresh steam as a result of burning hydrogen and oxygen. Hydrogen and oxygen are produced in an electrolyzer during the power plant’s operation in the nominal mode by using the generated electricity “excess”. Practical value. Small modular reactors are currently mainly in the development stage. Additionally, the non-nuclear part of the SMR-based power plant, namely the STI, has not received sufficient attention, as evidenced by the literature. However, it plays a crucial role in the overall efficiency of the installation. The study focuses on the highly relevant issue of improving the efficiency of an SMR-based power plant by developing the structure of the STI thermal scheme involving hydrogen technologies. This will help reduce dependence on fossil hydrocarbons in the total volume of primary fuel and enable sustainable functioning of the Ukrainian energy system, as well as contribute to the preservation and improvement of the environmental state.

Not All Fluctuations Are Created Equal: Spontaneous Variations in Thermodynamic Function

We identify macroscopic functioning arising during a thermodynamic system’s typical and atypical behaviors, thereby describing system operations over the entire set of fluctuations. We show how to use the information processing second law to determine functionality for atypical realizations and how to calculate the probability of distinct modalities occurring via the large-deviation rate function, extended to include highly correlated, memoryful environments and systems. Altogether, the results complete a theory of functional fluctuations for complex thermodynamic nanoscale systems operating over finite periods. In addition to constructing the distribution of functional modalities, one immediate consequence is a cautionary lesson: ascribing a single, unique functional modality to a thermodynamic system, especially one on the nanoscale, can be misleading, likely masking an array of simultaneous, parallel thermodynamic transformations that together may also be functional. In this way, functional fluctuation theory alters how we conceive of the operation of biological cellular processes, the goals of engineering design, and the robustness of evolutionary adaptation.

Entropy Engineering of 2D Materials.

Entropy, a measure of disorder or uncertainty in the thermodynamics system, has been widely used to confer desirable functions to alloys and ceramics. The incorporation of three or more principal elements into a single sublattice increases the entropy to medium and high levels, imparting these materials a mélange of advanced mechanical and catalytic properties. In particular, when scaling down the dimensionality of crystals from bulk to the 2D space, the interplay between entropy stabilization and quantum confinement offers enticing opportunities for exploring new fundamental science and applications, since the structural ordering, phase stability, and local electronic states of these distorted 2D materials get significantly reshaped. During the last few years, the large family of high-entropy 2D materials is rapidly expanding to host MXenes, hydrotalcites, chalcogenides, metal-organic frameworks (MOFs), and many other uncharted members. Here, the recent advances in this dynamic field are reviewed, elucidating the influence of entropy on the fundamental properties and underlying elementary mechanisms of 2D materials. In particular, their structure-property relationships resulting from theoretical predictions and experimental findings are discussed. Furthermore, an outlook on the key challenges and opportunities of such an emerging field of 2D materials is also provided.

Non-linear charged dS spacetime and its thermodynamics and Schottky Anomaly

Abstract In this paper, firstly, the conditions and existence region for the coexistence of the black hole and cosmological horizons in Non-linear charged dS (NLC-dS) spacetime are discussed, subsequently, the thermodynamic quantities for which the boundary conditions are satisfied in spacetime in the coexistence region of the two horizons are discussed, and the effective thermodynamic quantities in the NLC-dS spacetime in the coexistence region with two horizons are presented. Based on these, the heat capacity in the coexistence region with two horizons is addressed, the behavior of the heat capacity in the NLC-dS spacetime in the aforementioned region is found to exhibit the characteristics of Schottky specific heat. In order to investigate the intrinsic reason of the heat capacity in spacetime, we regard the two horizons in the NLC-dS spacetime as two distinct energy levels, consequently, the microscopic particles at different horizons exhibit disparate energies. Using the heat capacity relationship between the two-energy levels in an ordinary thermodynamic system, the heat capacity in dS spacetime is discussed, it is observed that the behavior of the heat capacity is analogous to that of the two-energy levels in an ordinary thermodynamic system. The number of microscopic particles in the two-energy-level system are approximated by comparing the maximum value of the heat capacity of the system with the maximum value obtained by treating the two horizons in the NLC-dS spacetime as a two-energy-level system of two distinct energies. This conclusion reflects the quantum properties of the coexistence region with two horizons in the NLC-dS spacetime. It provides a new avenue for further study of the thermodynamic properties of black holes and the quantum properties of de Sitter spacetime.

Theory of Space Quantization and the Quantum Level Understanding of the True Logics of the Principles of Thermodynamics and Heat Engines

The recently discovered Topological Theory of Quantum Gravity (TTQG) is basically a Theory of Space Quantization (TSQ) and in this article first of all it has been substantiated that though the laws of thermodynamics, the well-known thermodynamic principles, the operations of heat engines are very much intuitive but they, in their conventional representations, miserably lack the harmony to the quantized ‘space -time’ of the universe. The well-known thermodynamic parameters, e.g., pressure (P), volume (V), heat content (H), internal energy (U), entropy (S), Gibbs free energy (G),....etc. and the related physical variables like ‘time’ (t)and ‘mass’ (m) do exist in the form of ‘quantum’ or ‘packets’(referred as Gravitons in TTQG) and those are continuously being exchanged between the so called ‘thermodynamic systems’ and the ‘space-time’. It has been shown in this article that a ‘thermodynamic system’ and the above said ‘space quantums’ are very much complimentary and ‘part and parcel’ to each other and a quantum level ‘space-time’ rich understanding has been made through the TSQ of the true logic behind the standing of the thermodynamic laws and the operations of the heat engines.

Phase transitions and thermal properties of the charged Acoustic black hole

In this article, we analyze the thermal properties and phase transition of the acoustic black hole. We investigate the equilibrium and modified thermodynamical quantities through thermal fluctuations. Notably, thermal fluctuations affect entropy, which is important for understanding physical behavior and phase space. The black hole mass, Hawking temperature, heat capacity and numerous potentials are computed to evaluate thermodynamic stability. Significantly, the outcomes for large and small black holes are used to examine the effects of correction and coupling terms on the thermodynamic system.

Evaluation of the Second Virial Coefficient for the Mie Potential Using the Method of Brackets

The second virial coefficient for the Mie potential is evaluated using the method of brackets. This method converts a definite integral into a series in the parameters of the problem, in this case this is the temperature T. The results obtained here are consistent with some known special cases, such as the Lenard-Jones potential. The asymptotic properties of the second virial coefficient in molecular thermodynamic systems and complex fluid modeling are described in the limiting cases of T → 0 and T → ∞ .

Phenomenological models of ferroelastics with a fully symmetric order parameter: classification by methods of equivariant catastrophe theory

Using the methods of the catastrophe theory, which take into account the symmetry of the thermodynamic system, phenomenological models of phase transitions in proper and pseudo-proper ferroelastics have been constructed for interacting order parameters, one of which is fully symmetric, invariant with respect to all symmetry transformations of the crystal. A classification of models based on the number of control parameters, which depend on external thermodynamic conditions, has been carried out. A phase diagram of one of the models has been constructed, and the theoretical temperature dependence of the heat capacity has been calculated. The comparison of theoretical and experimental data showed satisfactory qualitative agreement.

Evaluation of thermal destratification performance and optimization of jetting parameters in a spray-bar thermodynamic vent system

Future operations in space exploration require the spray-bar thermodynamic vent system (TVS) to control self-pressurization in the cryogenic propellant tank. The submerged buoyant jetting, which is followed by thermal destratification due to mixing, leads to a decrease in tank pressure. In this study, a three-dimensional (3D) numerical model is developed to study the mixing and cooling characteristics induced by submerged buoyant jets in a fully filled, thermally stratified cryogenic propellant tank. The finite volume method is employed to perform transient simulations, solving the governing equations and turbulence models. The SIMPLEC algorithm is applied for pressure–velocity coupling, and the pressure terms are discretized spatially using the PRESTO! technique. Subsequently, dynamic response studies for various parameters are carried out. The results reveal that as the jetting cryogenic energy increases from 5.5 W to 88 W, both the average and maximum temperatures decrease by 0.8 K and 0.4 K, respectively. Adjusting the jetting angle to an upward 45° is beneficial in reducing the maximum temperature by approximately 0.2 K. Moreover, the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) is integrated with the Entropy Weight Method (EWM) to derive a comprehensive evaluation index that includes the average temperature, maximum temperature, temperature standard deviation, and jetting cryogenic energy. Additionally, by correlating dimensionless jetting parameters with the evaluation index, it is identified that an inlet Reynolds number of 158 and a Grashof number of 19,161 correspond to the optimal thermal destratification performance. This study offers significant insights for the design and improvement of the TVS.

Signatures of substorm onset in thermodynamic model of geomagnetic tail

Earlier, an entropy switch model (ESM) for substorm onset as a result of the development of localized inner magnetospheric interchange-ballooning instability, was suggested. Shown observations testify that the substorm onset is accompanied by the reversal and strong fluctuations in key magnetospheric parameters such as total magnetic field strength, plasma pressure, entropy, and some others. Independently, similar behavior was attributed to a thermodynamic theory, where the onset of a substorm is regarded as a consequence of global energy development in the geomagnetic tail. In the latter, the geomagnetic tail is taken as an open thermodynamic system with an infinite number of conserved energy links (CEL) to the external space environment, and the shaping of the substorm profile is ultimately controlled by the system properties of the tail. A comparison between the signatures of substorm onset in the ESM and CEL models is conducted, and correspondence between experimental data and theoretical results is discussed.

Active phase and amplitude temperature control method for cryostat: A case in the thermodynamic temperature international comparison system

Achieving highly stable temperature control is essential for cryostats. However, the cryocooler used in cryostats, such as the pulse tube cryocooler, produces regular sinusoidal temperature fluctuations due to its inherent working principles. To establish a highly stable temperature environment, an active phase and amplitude control method for suppressing temperature fluctuation is proposed in this paper, by which the optimal phase and amplitude can be predicted in theory. To validate this approach, a thermal response model was developed based on experiments conducted in the thermodynamic temperature international comparison cryostat at approximately 3.7 K. Based on this model, we conducted both single-stage and multi-stage active temperature control experiments. The results demonstrate that the temperature control effect is the best when the active temperature control current is added at the second cold head, the fluctuation of the comparison copper block from 3.3mK to 0.166mK with 94.9 % suppression rate. The multi-stage joint temperature control reduced the temperature fluctuation with an attenuation rate of 95.4 %. These findings offer significant potential for improving temperature stability in future thermodynamic temperature comparison experiments.

Projected climatic exposure and velocities of precipitation extremes over India and its biogeographic zones

AbstractClimate change is leading to alterations in the dynamic and thermodynamic climate systems worldwide, including the Indian summer monsoon (ISM), which supports more than a billion population and drives the Indian economy. The anthropogenic climate change induces unprecedented transformations in the natural and ecological systems, such as the increased probability of precipitation extremes, changes in their frequency, duration and spatial variabilities. This current study aims to project the regional landscape‐based metric, velocity of climate change (VoCC) and associated climatic exposure regarding precipitation extremes (PEs) for India and its different biogeographic zones. The climate velocities of mean precipitation, 95th, 99.5th and 99.9th percentiles of precipitation for the ISM season are presented for the historical and three projected time slices under the RCP8.5 scenario. ROM, a state‐of‐the‐art regional earth system model over the CORDEX‐South Asia domain, was used in the study. It was observed that the intense and very intense rainfall (95th, 99.5th and 99.9th percentiles) was enhanced over most of the study region in the near‐ and mid‐future compared to the far‐future. The intense rainfall exhibited higher climate velocity than the mean and very intense precipitation in the near‐future. The southern part of the Indian subcontinent usually displayed positive VoCC values for the historical and near‐future time slices compared to the northern part of the Indian peninsula, particularly the intense and very intense precipitation. The climatic exposure for all‐India was also higher in the near‐ and mid‐future compared to the far‐future, especially for the intense rainfall followed by the mean and very intense rainfall. These results suggest the need for focusing the adaptation and mitigation measures towards managing the near‐term impacts of PEs in relation to the long‐term impacts, especially on the country's diverse flora.

Methods of Thermal Energy Storage by Using Smart Heat Pumps

Abstract To address energy problems in thermodynamic installations, the authors of the paper propose a working methodology in which the determining role of the exergetic aspects of the processes is especially emphasized. One of these energy problems, addressed in many papers in recent years, is of particular importance in the fight to reduce chemical and thermal pollution of the environment: the problem of storing excess energy and energy from renewable or residual sources. Approaching this issue as well from this point of view, the authors propose a series of solutions by which they seek to use the most of the exergy extracted from the available energy sources. The solutions proposed here are based on the use of an own invention, the isothermalizer, a particularly powerful tool, able to bring highly effective solutions to many of the problems that concern researchers determined to create a cleaner planet. Designers and users of thermodynamic systems now have the possibility of an initial choice and subsequent changes (with the change of external conditions), of their energy and exergetic efficiency, as well as the possibility of calculating the material and energy costs necessary to achieve the proposed objective. In any gas compression/expansion problem, the energy efficiency is established precisely, by choosing the isothermal speed of the process (so of the isothermal temperature), and the power density, by choosing the total surface of the thermal sponge, the flow rate and the mode of distribution of the cooling agent. As the isothermalizer is equipped with a processor that controls and modifies the isothermal speed in such a way that the exergy consumption is optimized, the energy storage processes become processes of extracting thermal energy from a tank and transferring it to another tank, a process accompanied by consumption/supply of mechanical energy.