Thermodynamic Cycle Research Articles

Dynamics of a strongly coupled quantum heat engine-Computing bath observables from the hierarchy of pure states.

We present a fully quantum dynamical treatment of a quantum heat engine and its baths based on the Hierarchy of Pure States (HOPS), an exact and general method for open quantum system dynamics. We show how the change of the bath energy and the interaction energy can be determined within HOPS for arbitrary coupling strength and smooth time dependence of the modulation protocol. The dynamics of all energetic contributions during the operation can be carefully examined both in its initial transient phase and, also later, in its periodic steady state. A quantum Otto engine with a qubit as an inherently nonlinear work medium is studied in a regime where the energy associated with the interaction Hamiltonian plays an important role for the global energy balance and, thus, must not be neglected when calculating its power and efficiency. We confirm that the work required to drive the coupling with the baths sensitively depends on the speed of the modulation protocol. Remarkably, departing from the conventional scheme of well-separated phases by allowing for temporal overlap, we discover that one can even gain energy from the modulation of bath interactions. We visualize these various work contributions using the analog of state change diagrams of thermodynamic cycles. We offer a concise, full presentation of HOPS with its extension to bath observables, as it serves as a universal tool for the numerically exact description of general quantum dynamical (thermodynamic) scenarios far from the weak-coupling limit.

Research on multi-objective parameter optimization of split flow dual flash thermodynamic cycle

In addition to considering the intermediate pressure variables, the split flow double flash thermodynamic cycle also needs to consider the operating conditions and split flow coefficient of the cycle. Traditional algorithms require too much computation and have a longer response time. Faced with sudden operating conditions or changes in production conditions, it is difficult to quickly re-optimize the intermediate parameters of the split flow double flash thermal cycle and carry out corresponding system control. This article uses intelligent optimization algorithms instead of global search methods to optimize multi-objective parameters in a split flow double flash thermodynamic cycle. By summarizing and analyzing the characteristics of algorithms such as SIO, EA, and ANN, it is believed that the GWO algorithm in the SIO class is the most suitable for multi-objective parameter optimization of the split flow double flash thermal cycle. It is combined with the SA optimization algorithm to propose the SA-GWO algorithm with faster optimization speed and higher optimization accuracy, taking the initial position of the wolf pack as the optimization objective. Combined with the cycle thermodynamic model, a multi-objective parameter optimization model for the split flow double flash thermal cycle is established.

Study on the thermodynamic and economic performance of power generation cycle with small temperature difference

The low thermal efficiency and low economic benefits of power generation systems under small temperature difference conditions have always hindered their practical operation. In order to explore effective ways to achieve performance optimization of thermodynamic cycle electrical power generating systems under small temperature difference conditions, this study constructs a static analysis model of an organic Rankine cycle with small temperature difference, selects six different commonly used refrigerants, and investigates the influence of key parameters on the thermodynamic and economic performance of the system using difference working fluids. The outcomes indicate that key parameters such as evaporation temperature and condensation temperature play a critical role in the thermodynamic and economic performance of the power generation system. For the working fluids, R227ea provides the highest net power output, while ammonia (R717) is the best performer in regard to system thermal efficiency and economic performance.

Steady state and transient analysis of solid oxide fuel cell within the framework of thermodynamic energy cycles

The provided article comprehensively explores the modelling and analysis of solid oxide fuel cell (SOFC) systems within the context of thermodynamic energy cycles. The paper provides insight into various applications of these cells, with a specific emphasis on their role as the primary source of electrical energy in systems that work with biogas and heat recovery. The technological structure of these systems is delineated, with a focus on their principal components and the chemical reactions occurring within SOFCs. Moreover, the article incorporates a mathematical model of SOFCs and presents calculation results that illustrate the influence of air and fuel temperature on the cells’ efficiency. The research indicates that optimal SOFC efficiency is attained at higher temperatures of supplied air and fuel. The presentation of the results of calculations for the solid oxide fuel cell and its thermodynamic cycle, considering fuel supply and its thermodynamic parameters under both steady-state and transient conditions, is the main aim of the article.

6-Stroke water injection engine literature review with an introduction of heat transfer and thermodynamic analysis

AbstractInternal combustion engines have played a crucial role in the advancement of society. Consequently, there has been a persistent need to enhance their efficiency and performance. The water-injected six-stroke engine is based on conventional four-stroke engines, producing additional power by injecting water into the hot combustion products during the expansion stroke, thereby increasing the overall engine efficiency. However, a comprehensive review that consolidates existing knowledge and identifies future research opportunities in six-stroke engine technology is lacking. This study addresses this gap by thoroughly examining the thermodynamic operation of six-stroke engines and analyzing the impact of water injection on engine performance. The review covers literature from 1994 to 2023, categorizing studies based on the modeling approach, working fluid, thermodynamic cycle, and consideration of heat transfer. Among the 18 analyzed articles, predominantly published from 2015 to 2019, half utilize analytical models, while the rest employ experimental models addressing heat transfer losses. Notably, water injection exhibits a substantial influence, manifesting as a 5.18% increase in brake power and a 1.55% enhancement in thermal efficiency, particularly with acetylene as the working fluid. Finally, a literature overview of water injection in hot gas environments within the engine cylinder was conducted in addition to a preliminary thermodynamic analysis of the Otto and Diesel cycles to compare different configurations outlined in the literature. The lack of studies, experimental setups, and non-idealized models that consider factors such as heat transfer or water evaporation during injection is evident. By critically synthesizing the available literature, this study offers valuable insights into the potential advantages, limitations, and prospects of six-stroke engine studies.

3D EVALUATION OF MICROGAPS AT THE IMPLANT-ABUTMENT CONNECTION BEFORE AND AFTER THERMODYNAMIC CYCLING.

To analyze the microgap changes between hybrid-abutment crowns made of two materials and three internal taper connec9on implants with different connection designs before and after thermodynamic loading. A total of 30 implants-10 each of Straumann Bone Level Implant-RC (STR); GC AADVA Implant (AAD); and Astra-Tech OsseoSpeed EV (AST)-were included in this laboratory study. Each implant had an internal taper connection, but their designs were slightly different. Five hybrid-abutment crowns were fabricated using a lithium disilicate ceramic (LD), and five were fabricated using polymethylmethacrylate (PMMA) with CAD/CAM technologies for each implant system, providing six sample groups STR-LD, AAD-LD, AST-LD, STR-PMMA, AAD-PMMA, and ASTPMMA. The microgap volume was measured using micro-CT images obtained before and after thermodynamic loading equivalent to 4 months of clinical use. Student t test, one-way ANOVA, and Tukey test were used for comparisons. The greatest microgap volume increase was recorded (3.405% ± 1.567%) in the AST-LD group, and the lowest increase (0.45% ± 0.373%) was in the STR-PMMA group. A statistically significant difference in microgap increase was not detected among PMMA and LD groups: for STR-LD/STR-PMMA (t test: P = .273); for AAD-LD/AAD-PMMA (t test: P = .374); and for AST-LD/AST-PMMA (t test: P = .268). However, the difference in the microgap increase between the different implant systems was statistically significant. The microgap between hybrid-abutment crowns and implants increased after short-term thermodynamic cycling. Hybrid-abutment crowns with different elastic modulus showed similar microgap increase. The geometric shape of the connection influenced the microgap increase.

Insights into Activation Dynamics and Functional Sites of Inwardly Rectifying Potassium Channel Kir3.2 by an Elastic Network Model Combined with Perturbation Methods.

The inwardly rectifying potassium channel Kir3.2, a member of the inward rectifier potassium (Kir) channel family, exerts important biological functions through transporting potassium ions outside of the cell, during which a large-scale synergistic movement occurs among its different domains. Currently, it is not fully understood how the binding of the ligand to the Kir3.2 channel leads to the structural changes and which key residues are responsible for the channel gating and allosteric dynamics. Here, we construct the Gaussian network model (GNM) of the Kir3.2 channel with the secondary structure and covalent interaction information considered (sscGNM), which shows a better performance in reproducing the channel's flexibility compared with the traditional GNM. In addition, the sscANM-based perturbation method is used to simulate the channel's conformational transition caused by the activator PIP2's binding. By applying certain forces to the PIP2 binding pocket, the coarse-grained calculations generate the similar conformational changes to the experimental observation, suggesting that the topology structure as well as PIP2 binding are crucial to the allosteric activation of the Kir3.2 channel. We also utilize the sscGNM-based thermodynamic cycle method developed by us to identify the key residues whose mutations significantly alter the channel's binding free energy with PIP2. We identify not only the residues important for the specific binding but also the ones critical for the allosteric transition coupled with PIP2 binding. This study is helpful for understanding the working mechanism of Kir3.2 channels and can provide important information for related drug design.

Flexible Magnetocaloric Fiber Mats for Room-Temperature Energy Applications.

Currently, magnetocaloric refrigeration technologies are emerging as ecofriendly and more energy-efficient alternatives to conventional expansion-compression systems. However, major challenges remain. A particular concern is the mechanical properties of magnetocaloric materials, namely, their fatigue under cycling and difficulty in processing and shaping. Nevertheless, in the past few years, using multistimuli thermodynamic cycles with multicaloric refrigerants has led to higher heat-pumping efficiencies. To address simultaneously the challenges and develop a multicaloric material, in this work, we have prepared magnetocaloric-based flexible composite mats composed of micrometric electroactive (EA) polyvinylidene fluoride (PVDF) fibers with embedded magnetocaloric/strictive La(Fe,Si)13 particles by the simple and cost-effective electrospinning technique. The composite's structural characterization, using X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and measurements of the local-scale piezoresponse, revealed a cubic NaZn13-type structure of the La(Fe,Si)13 phase and the formation of the dominant polar β-phase of the PVDF polymer. The PVDF-La(Fe,Si)13 composite showed an enhancement of the longitudinal piezoelectric coefficient (effective d33) (-11.01 pm/V) compared with the single PVDF fiber matrix (-9.36 pm/V). The main magnetic properties of La(Fe,Si)13 powder were retained in the PVDF-La(Fe,Si)13 composite, including its giant magnetocaloric effect. By retaining the unique magnetic properties of La(Fe,Si)13 embedded in the electroactive piezoelectric polymer fiber mats, we have designed a flexible, easily shapeable, and multifunctional composite enabling its potential application in multicaloric heat-pumping devices and other sensing and actuating devices.

Relativistic quantum Otto engine: instant work extraction from a quantum field

In this study, we carry out a non-perturbative approach to a quantum Otto engine, employing an Unruh-DeWitt particle detector to extract work from a quantum Klein-Gordon field in an arbitrary globally hyperbolic curved spacetime. We broaden the scope by considering the field in any quasi-free state, which includes vacuum, thermal, and squeezed states. A key aspect of our method is the instantaneous interaction between the detector and the field, which enables a thorough non-perturbative analysis. We demonstrate that the detector can successfully extract positive work from the quantum Otto cycle, even when two isochoric processes occur instantaneously, provided the detector in the second isochoric process receives a signal from the first interaction. This signaling allows the detector to release heat into the field, thereby the thermodynamic cycle is completed. As a demonstration, we consider a detector at rest in flat spacetime and compute the work extracted from the Minkowski vacuum state.

Pinch, energy, and exergy analysis for a power-hydrogen cogeneration system fueled by biogas

This paper presents a combined heating, power, and hydrogen system production by utilizing biogas energy. A novel methodology is proposed to identify thermodynamic cycle conditions and reform processes by using biogas as the energy source. Biogas steam and dry reforming methods are considered based on equilibrium data employing the EES program. It is found that biogas has two principal roles for combustion and reforming processes simultaneously. The thermal energy from the combustion of biogas causes its reforming and improves the efficiency of the system by 74%. The exergy efficiency, the overall exergy destruction, and hydrogen efficiency are calculated for various electric powers ranging from 5 to 40 MW. It is found that the combustion chamber has the maximum exergy destruction of about 51%. The parametric study of the system is performed to assess the optimum conditions for producing hydrogen. The optimal condition corresponds to CO2/CH4 = 0.50–0.66, H2O/CH4 = 2–3.6, and the reforming temperature range of 965–1036 K. The conversion of methane and carbon dioxide shows the reduction of the greenhouse gases.

In-Cylinder Heat Transfer in an Ericsson Engine Prototype

An Ericsson engine is an external heat supply engine working according to a Joule thermodynamic cycle. It is based on reciprocating piston-cylinder machines. Such engines are especially interesting for low power solar energy conversion and micro-CHP from conventional fossil fuels or from biomass. An Ericsson engine prototype has been designed and realized. Due to the geometrical configuration of the compression space of this prototype, in-cylinder fluid wall heat transfer can be important. The influence of this heat transfer on the engine performance is modelled and the main results are presented. The experimental setup designed to study the in-cylinder heat transfer is presented.

Exploring the Heat of Water Intrusion into a Metal-Organic Framework by Experiment and Simulation.

Wetting of a solid by a liquid is relevant for a broad range of natural and technological processes. This process is complex and involves the generation of heat, which is still poorly understood especially in nanoconfined systems. In this article, scanning transitiometry was used to measure and evaluate the pressure-driven heat of intrusion of water into solid ZIF-8 powder within the temperature range of 278.15-343.15 K. The conditions examined included the presence and absence of atmospheric gases, basic pH conditions, solid sample origins, and temperature. Simultaneously with these experiments, molecular dynamics simulations were conducted to elucidate the changing behavior of water as it enters into ZIF-8. The results are rationalized within a temperature-dependent thermodynamic cycle. This cycle describes the temperature-dependent process of ZIF-8 filling, heating, emptying, and cooling with respect to the change of internal energy of the cycle from the calculated change in the specific heat capacity of the system. At 298 K the experimental heat of intrusion per gram of ZIF-8 was found to be -10.8 ± 0.8 J·g-1. It increased by 19.2 J·g-1 with rising temperature to 343 K which is in a reasonable match with molecular dynamic simulations that predicted 16.1 J·g-1 rise. From these combined experiments, the role of confined water in heat of intrusion of ZIF-8 is further clarified.

Moisture swing adsorption for direct air capture: Establishment of thermodynamic cycle

As a rising branch of DAC technology, moisture swing adsorption (MSA) could be regenerated through humidity regulation that can avoid such high energy consumption. However, for capture energy consumption, advantages of MSA have yet to be fully explored. Thus, a 6-step MSA thermal cycle is initially proposed in this work. Three working conditions are considered: temperature swing, moisture swing, as well as temperature and moisture co-swing. It is found that the synergic control of temperature and moisture can improve energy consumption and efficiency limits of MSA cycle due to the increase in saturated vapor pressure. Under the adsorption condition of 25 ℃ and 30% RH, it reveals that the introduction of temperature swing process effectively reduces specific energy consumption of MSA cycle by 28%, increases thermodynamic efficiency by 119%, and increases adsorbent efficiency by 30%. The findings of this cycle analysis help to guide the optimization of MSA process and promote the development of DAC.

Evaluation of Thermodynamic and Kinetic Contributions to Over-Extraction of Extractables by Nonpolar Organic Solvents in Comparison to Lipids in Exhaustive and Exaggerated Extractions of Medical Devices Based on Abraham Solvation Model and Solvent–Material Interactions Using Low-Density Polyethylene as a Representative Material

The thermodynamic and kinetic contributions to the over-extraction of extractables by nonpolar organic solvents relative to biological lipids in exhaustive and exaggerated extractions of medical devices are studied based on the Abraham solvation model and solvent–material interactions, using low-density polyethylene (LDPE) as an exemplary material. The thermodynamic effect is evaluated by the partition constant of extractables between LDPE and extraction solvents, hexane and lipids, defined as the concentration in the polymer phase divided by the concentration in the solvent phase. The Abraham solvation model is used to correlate the measured LDPE-lipid partition constant (log10Pldpe/lipid) to construct the predictive model. Similar models are also derived from the thermodynamic cycle conversion, using the system constants of LDPE-water and Lipid-water partition systems. These constructed models, together with the predictive LDPE-hexane (log10Pldpe/hexane) model established from a previous study, are used to predict and compare the ranges and values of Pldpe/s (s = lipids and hexane) for the observed LDPE extractables over a wide hydrophobicity range in log10Po/w from zero to 30. The solvent-LDPE interactions are examined by the degree of swelling of LDPE by hexane (or other nonpolar solvents) and lipids, including the solvent diffusion rates into the material. These parameters allow the evaluation of kinetic effect on the over-extraction. The extent of over-extraction is compiled directly by experimental “overall” or “specific” migration data or indirectly calculated by the diffusion coefficient of extractables when extracted by hexane or lipids. It is concluded from this study that the extractables distribution between LDPE and lipids highly favors the lipid phase thermodynamically (Pldpe/lipid<1), and the values of Pldpe/lipid are always lower than those of Pldpe/hexane, thereby indicating that the thermodynamic effect is not the cause of over-extraction. It is the kinetic effect that dominantly contributes to the over-extraction, as supported by the material swelling and solvent diffusion rates. Finally, the extent of over-extraction has been established from a few folds to over a hundred-fold, and the median value is 7. Furthermore, the methods adopted and developed in this study can be invaluable tools in other disciplines such as the reliable prediction of extractables from other device materials and environmental sampling.

Double and triple thermodynamic mutant cycles reveal the basis for specific MsbA-lipid interactions.

Structural and functional studies of the ATP-binding cassette transporter MsbA have revealed two distinct lipopolysaccharide (LPS) binding sites: one located in the central cavity and the other at a membrane-facing, exterior site. Although these binding sites are known to be important for MsbA function, the thermodynamic basis for these specific MsbA-LPS interactions is not well understood. Here, we use native mass spectrometry to determine the thermodynamics of MsbA interacting with the LPS-precursor 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)2-lipid A (KDL). The binding of KDL is solely driven by entropy, despite the transporter adopting an inward-facing conformation or trapped in an outward-facing conformation with adenosine 5'-diphosphate and vanadate. An extension of the mutant cycle approach is employed to probe basic residues that interact with KDL. We find the molecular recognition of KDL is driven by a positive coupling entropy (as large as -100 kJ/mol at 298 K) that outweighs unfavorable coupling enthalpy. These findings indicate that alterations in solvent reorganization and conformational entropy can contribute significantly to the free energy of protein-lipid association. The results presented herein showcase the advantage of native MS to obtain thermodynamic insight into protein-lipid interactions that would otherwise be intractable using traditional approaches, and this enabling technology will be instrumental in the life sciences and drug discovery.

Double and triple thermodynamic mutant cycles reveal the basis for specific MsbA-lipid interactions

Structural and functional studies of the ATP-binding cassette transporter MsbA have revealed two distinct lipopolysaccharide (LPS) binding sites: one located in the central cavity and the other at a membrane-facing, exterior site. Although these binding sites are known to be important for MsbA function, the thermodynamic basis for these specific MsbA-LPS interactions is not well understood. Here, we use native mass spectrometry to determine the thermodynamics of MsbA interacting with the LPS-precursor 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo)2-lipid A (KDL). The binding of KDL is solely driven by entropy, despite the transporter adopting an inward-facing conformation or trapped in an outward-facing conformation with adenosine 5’-diphosphate and vanadate. An extension of the mutant cycle approach is employed to probe basic residues that interact with KDL. We find the molecular recognition of KDL is driven by a positive coupling entropy (as large as –100 kJ/mol at 298 K) that outweighs unfavorable coupling enthalpy. These findings indicate that alterations in solvent reorganization and conformational entropy can contribute significantly to the free energy of protein-lipid association. The results presented herein showcase the advantage of native MS to obtain thermodynamic insight into protein-lipid interactions that would otherwise be intractable using traditional approaches, and this enabling technology will be instrumental in the life sciences and drug discovery.

Application of thermodynamics at different scales to describe the behaviour of fast reacting binary mixtures in vapour-liquid equilibrium

The use of reactive working fluids in thermodynamic cycles is currently being considered as an alternative to inert working fluids, because of the preliminarily attested higher energy-efficiency potential. The current needs to simulate their use in thermodynamic cycles, which may operate in liquid, vapour or vapour-liquid state, are an accurate real-fluid equation of state and ideal gas thermochemical properties of each molecule constituting the mixture, to calculate the equilibrium constant. To this end, the appeal to a multi-scale theoretical methodology is paramount and its definition represents the objective of the present work. This methodology is applied and validated on the system N2O4 ⇌ 2NO2. Firstly, the equations solved for simultaneous two-phase and reaction equilibrium are presented. Secondly, ideal gas thermochemical properties of N2O4 and NO2 are computed at atomic scale by quantum mechanics simulations. Then, to apply the selected cubic equation of state, pure-component properties of the species forming the reactive mixture (critical point coordinates and acentric factor) are required as input. However, these properties are not measurable, since NO2 and N2O4 do not exist in nature as pure components. To get around this difficulty, the methodology relies on molecular Monte Carlo simulations of the pure N2O4 and NO2, as well as on the reactive N2O4 ⇌ 2NO2, enabling the determination of those missing pure-component properties and thus the calculation, on a macroscopic scale, of the reactive mixture properties. Finally, the comparison of calculated mixture properties with available experimental data leads to validate the accuracy of the proposed methodology.

Thermodynamic cycle analysis of the fuel precooled multi-mode turbine engine mode transition process: Why? When? How?

The fluctuation of engine thrust during the mode transition process is a critical concern that poses a significant risk to aircraft safety. In order to address this issue, a thermodynamic model for mode transition in a dual fuel precooled multi-mode turbine engine is established, and three key issues in the mode transition process are comprehensively examined from the perspectives of steady-state analysis and dynamic process optimization: Why? When? How? Firstly, the basis for mode transition under high Mach number conditions is proposed for the first time from exergy efficiency. The engine exergy efficiency and combustion exergy efficiency in the turbofan mode decrease as the Mach number increases, while the turbojet mode exhibits superior combustion exergy efficiency. To achieve efficient operation, it is imperative to switch from the turbofan mode to the turbojet mode. Subsequently, a novel approach is proposed for determining the mode transition range based on bidirectional cyclic correction, which effectively addresses the limitation of large thrust fluctuations at the mode transition point determined by the conventional maximum state thrust continuous method. The mode transition envelope that can achieve a smooth transition between thrust and airflow rate is determined. Finally, a mode transition method is newly put forward by integrating directional adjustment and offline optimization. Throughout the entire mode transition envelope, the maximum thrust fluctuation during the process remains below 1 %, while the maximum airflow rate change stays within 3 %, which exhibits excellent efficacy in achieving smooth transitions.

Performance improvement of a fractional quantum Stirling heat engine

To investigate the impact of fractional parameters on the thermodynamic behaviors of quantum systems, we incorporate fractional quantum mechanics into the cycle of a quantum Stirling heat engine and examine the influence of fractional parameters on regeneration and efficiency. We propose a novel approach to control the thermodynamic cycle that leverages the fractional parameter structure and evaluates its effectiveness. Our findings reveal that by tuning the fractional parameter, the region of the cycle with the perfect regeneration and the Carnot efficiency can be expanded.

Performance analysis of a nitrogen-based Brayton cryocooler prototype

When very low temperatures are needed for industrial applications, reverse Brayton cryocoolers can be adopted. This paper reports the results of an energy analysis in which the performance of a Brayton cryocooler prototype was studied. The prototype is innovative in both the cycle configuration and the pressure and temperature levels. Moreover, nitrogen, an eco-friendly gas that is safe for people, was used as the working fluid.Simultaneous measurements of the pressure and temperature at the inlet and outlet of the main thermodynamic cycle components, nitrogen flow rate, and power consumption were taken during the experimental tests. The prototype was tested at design operating conditions (maximum and minimum pressure of 18.5 and 8 bar respectively, and minimum temperature of −120 °C), obtaining a cooling effect of 15.6 kW, a temperature reduction rate at the turbine outlet of 8 °C min−1, and a coefficient of performance of 0.29, which rises to 1.34 when including the waste heat (about 55 kW) that can be recovered at low temperatures (<100 °C). Also, a sensitivity analysis was carried out by testing the prototype at different maximum pressure and minimum temperature levels. The higher the maximum pressure, the higher the prototype performance is, and a minimum temperature of about −140 °C was reached. Our findings demonstrated that the tested prototype shows great promise for several industrial applications where low temperatures are required.