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We investigated the optimal performance of an irreversible Stirling-like heat engine described by both overdamped and underdamped models within the framework of stochastic thermodynamics. By establishing a link between energy dissipation and Wasserstein distance, we derived the upper bound of maximal power that can be delivered over a complete engine cycle for both models. Additionally, we analytically developed an optimal control strategy to achieve this upper bound of maximal power and determined the efficiency at maximal power in the overdamped scenario. [ABSTRACT FROM AUTHOR]

Carnot treats Heat as a Force of Nature, with its typical fundamental characteristics of intensity and thermal tension (temperature and temperature difference), extension (amount of heat, i.e., caloric), and power. To suggest how the three aspects are related, he applies the imagery of waterfalls to causative thermal processes: heat powers motion in a heat engine just as falling water does when activating rotation in a water wheel. We understand Carnot's waterfall imagery as an archetype of human reasoning—as an embodiment of how we experience and understand causative (agentive) phenomena. We project it onto the macroscopic phenomena identified in physical science and so unlock the power of analogical structure mapping between theories of fluids, electricity and magnetism, heat, substances, gravity, and linear and rotational motion. In particular, the notion of (motive) power of a waterfall lets us create imaginative explanations of the interactions of Forces of Nature and helps us construct a generalized energy principle. Two-hundred years after Carnot made us aware of it, his Waterfall Analogy is a powerful example of theory construction with roots deep in how we experience phenomena as caused by natural agents. [ABSTRACT FROM AUTHOR]

Entropy and energy had not yet been introduced to physics by the time Carnot wrote his seminal Réflexions. Scholars continue to discuss what he really had in mind and what misconceptions he might have had. Actually, his work can be read as a correct introduction to the physics of heat engines when the term calorique is replaced by entropy and entropy is used as the other fundamental thermal quantity besides temperature. Carnot's concepts of falling entropy as an analogy to the waterfall, and the separation of real thermal processes into reversible and irreversible processes are adopted. Some details of Carnot's treatise are ignored, but the principal ideas are quoted and assumed without modification. With only two thermal quantities, temperature and entropy, modern heat engines can be explained in detail. Only after the principal function of heat engines is developed is energy introduced as physical quantity in order to compare thermal engines with mechanical and electrical engines and, specifically, to calculate efficiency. [ABSTRACT FROM AUTHOR]

Quantum heat engines (QHEs) are established by applying the principles of quantum thermodynamics to small−scale systems, which leverage quantum effects to gain certain advantages. In this study, we investigate the quantum Otto cycle by employing the dipole−dipole coupled polar molecules as the working substance of QHE. Here, the molecules are considered to be trapped within an optical lattice and located in an external electric field. We analyze the work output and the efficiency of the quantum Otto heat engine (QOHE) as a function of various physical parameters, including electric field strength, dipole−dipole interaction and temperatures of heat baths. It is found that by adjusting these physical parameters the performance of the QOHE can be optimized effectively. Moreover, we also examine the influences of the entanglement and relative entropy of coherence for the polar molecules in thermal equilibrium states on the QOHE. Our results demonstrate the potential of polar molecules in achieving QHEs. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the onset conditions of a thermoacoustic Stirling engine loaded with a commercially available audio loudspeaker. The thermoacoustic engine converts supplied heat power into mechanical power in the form of sound, without any mechanical moving parts. The simplicity of the acoustical heat engine holds great promise for high reliability and low cost. By utilizing a readily available electromagnetic device, the engine can serve as a durable solution for practical applications. In this study, we assembled a commercially available moving-coil loudspeaker as a low-cost linear alternator for the thermoacoustic Stirling engine, enabling electric generation from supplied heat. We modeled the loudspeaker using linear control equations and experimentally calibrated its acoustic impedances to estimate the acoustic load. For the part of the thermoacoustic engine, we estimated its acoustic characteristics within the framework of the linear thermoacoustic theory. By solving the characteristic equation resulting from the engine loaded with the audio speaker, we estimated the operational point of self-sustained oscillations excited by the coupling of the loudspeaker and the thermoacoustic engine system. To validate the estimations, we tested a prototype of the combined system, comprising the loudspeaker and the thermoacoustic engine. The results highlight the necessity of precise calibration and accounting for complex geometries within the acoustic load for accurate theoretical estimations, especially when incorporating a commercially available loudspeaker into a thermoacoustic engine. [ABSTRACT FROM AUTHOR]

The document "Grand challenges in heat engines" published in the Frontiers in Thermal Engineering Journal discusses the historical impact, scientific challenges, and future directions of heat engines. It highlights key challenges such as reducing pollutant emissions, increasing thermal efficiency, and decarbonization through the use of alternative fuels like biofuels and e-fuels. The document emphasizes the importance of research and development efforts to address these challenges and improve the sustainability and efficiency of heat engines for various applications. [Extracted from the article]

Unlike traditional free-piston Stirling heat engines or heat pumps, the free piston Stirling air conditioning (FPSAC) is specifically designed for electric vehicle air conditioning under ambient room temperature conditions. In the FPSAC system, the displacer and the power piston are coupled through gas forces, emphasizing the importance of investing the thermodynamic–kinetic coupling characteristics. This study analyzed the damping terms within the dynamic equations of the FPSAC model and solved these equations to reveal system dynamics. By linearizing the working chamber's pressure, the study examined the machine's dynamic behavior, presenting solutions for amplitude and phase angle. Derived expressions for the displacement and acceleration of both the power piston and the displacer further support this analysis. The research evaluates the influence of driving force on amplitude and phase angle, alongside the impact of damping coefficients, thereby isolating thermodynamic–dynamic coupling characteristics. Control equations integrating dynamics and thermodynamics were developed, and a comprehensive system model was constructed using MATLAB(2020a)/Simulink to simulate acceleration and displacement variation in the pistons. Key findings include: (1) a positive correlation between driving force and displacer, where increased force leads to higher amplitudes; (2) a frequency of 65 Hz reveals a singularity occurs in displacer amplitude, resulting in system instability; (3) phase angle between pistons reduces to below 10° when the driving force exceeds 150 N; and (4) the power piston's amplitude decreases with an increase in damping C1, while changes in damping C2 primarily affect the displacer's singularity position around 65 Hz, with higher C2 values shifting the singularity to lower frequencies. [ABSTRACT FROM AUTHOR]

The maritime industry, central to global trade, faces critical challenges related to energy efficiency and environmental sustainability due to significant energy loss from waste heat in marine engines. This review investigates the potential of waste heat recovery (WHR) technologies to enhance operational efficiency and reduce emissions in marine systems. By analyzing major WHR methods, such as heat exchangers, Organic Rankine Cycle (ORC) systems, thermoelectric generators, and combined heat and power (CHP) systems, this work highlights the specific advantages, limitations, and practical considerations of each approach. Unique to this review is an examination of WHR performance in confined marine spaces and compatibility with existing ship components, providing essential insights for practical implementation. Findings emphasize WHR as a viable strategy to reduce fuel consumption and meet environmental regulations, contributing to a more sustainable maritime industry. [ABSTRACT FROM AUTHOR]

The pre-cooler is a key component of the pre-cooled turbine combined cycle engine, and its performance significantly impacts the overall engine performance. To clarify the flow and heat transfer characteristics of the pre-cooler and the effects of its key structural parameters on engine performance, the pre-cooler of the SABRE engine (Synergetic Air-Breathing Rocket Engine) was analyzed using numerical simulation methods to investigate the influences of air crossflow tube bundles and tube spacing on pre-cooler performance. The results indicate that increasing the number of air crossflow tubes significantly enhances heat transfer capacity; however, it also leads to an increase in the total pressure drop. Specifically, as the number of air crossflow tubes increases from 24 to 48, the overall heat transfer capacity improves by 42.1%, while the total pressure loss coefficient nearly doubles. Additionally, increasing tube spacing reduces the overall pressure drop, but this comes at the cost of decreasing heat transfer capacity and structural compactness. When the total pressure loss coefficient was reduced by approximately 29.8%, the overall heat transfer capacity decreased by 4.9%. Notably, the impact of tube spacing on flow resistance is greater than its effect on heat transfer, suggesting that the total pressure loss can be minimized by optimizing tube spacing. Therefore, both performance and structural integrity must be considered in pre-cooler design. Finally, selecting appropriate structural parameters based on operating conditions is essential to optimize heat transfer efficiency and overall design quality. [ABSTRACT FROM AUTHOR]

Earth's tropics are characterized by quasi‐steady precipitation with small oscillations about a mean value, which has led to the hypothesis that moist convection is in a state of quasi‐equilibrium (QE). In contrast, very warm simulations of Earth's tropical convection are characterized by relaxation‐oscillator‐like (RO) precipitation, with short‐lived convective storms and torrential rainfall forming and dissipating at regular intervals with little to no precipitation in between. We develop a model of moist convection by combining a zero‐buoyancy model of bulk‐plume convection with a QE heat engine model, and we use it to show that QE is violated at high surface temperatures. We hypothesize that the RO state emerges when the equilibrium condition of the convective heat engine is violated, that is, when the heating rate times a thermodynamic efficiency exceeds the rate at which work can be performed. We test our hypothesis against one‐ and three‐dimensional numerical simulations and find that it accurately predicts the onset of RO convection. The proposed mechanism for RO emergence from QE breakdown is agnostic of the condensable, and can be applied to any planetary atmosphere undergoing moist convection. To date, RO states have only been demonstrated in three‐dimensional convection‐resolving simulations, which has made it seem that the physics of the RO state requires simulations that can explicitly resolve the three‐dimensional interaction of cloudy plumes and their environment. We demonstrate that RO states also exist in single‐column simulations of radiative‐convective equilibrium with parameterized convection, albeit in a different surface temperature range and with much longer storm‐free intervals. Plain Language Summary: Earth's tropics are characterized by steady rainfall, indicating that moist convection is a continuous process. However, in simulations of very warm conditions, a form of episodic convection emerges that is characterized by short bursts of intense rainfall followed by longer rain‐free intervals. We construct a simple model that represents convection as a heat engine, and use it to show that steady convection must break down in very warm conditions. We hypothesize that the essential condition for steady convection is the balanced conversion of heat into work, which is violated at high surface temperatures. We test our hypothesis against climate model simulations of increasing complexity—the first parameterizes convection and the second actually resolves it—and found that it accurately predicts when the steady climate state transitions to the episodic state. The simple model of convection isn't limited to Earth, and could be applied to planets with different atmospheric compositions. Finally, while it has seemed that episodic precipitation could only be obtained from model simulations that resolve convection, we've shown here that it can also occur in simpler climate models with parameterized convection. Key Points: A transition from quasi‐equilibrium (QE) to relaxation‐oscillator (RO) convection occurs at high surface temperatures on EarthQE breakdown is predicted by a simple model of a convective heat engine in radiative‐convective equilibrium where plumes have zero buoyancyQE breaks down when the equilibrium condition of the heat engine is violated, and this leads to RO emergence [ABSTRACT FROM AUTHOR]

The reverse electrodialysis heat engine (REDHE) represents a transformative innovation that converts low-grade thermal energy into salinity gradient energy (SGE). This crucial form of energy powers reverse electrodialysis (RED) reactors, significantly changing wastewater treatment paradigms. This comprehensive review explores the forefront of this emerging field, offering a critical synthesis of key discoveries and theoretical foundations. This review begins with a summary of various oxidation degradation methods, including cathodic and anodic degradation processes, that can be integrated with RED technology. The degradation principles and characteristics of different RED wastewater treatment systems are also discussed. Then, this review examines the impact of several key operational parameters, degradation circulation modes, and multi-stage series systems on wastewater degradation performance and energy conversion efficiency in RED reactors. The analysis highlights the economic feasibility of using SGE derived from low-grade heat to power RED technology for wastewater treatment, offering the dual benefits of waste heat recovery and effective wastewater processing. [ABSTRACT FROM AUTHOR]

Biofuels are the most essential types of alternative fuels, which currently have significant potential to reduce CO2 emissions compared to fossil fuels. Methanol is a more efficient fuel than petrol due to its physicochemical properties, such as a higher latent heat of vaporization, research octane number, and heat of combustion of the fuel–air mixture. Also, biomethanol is cheaper than traditional petrol and diesel fuel for agricultural countries. The authors have proposed a new approach to improve the characteristics and efficiency of methanol diesel engines by using biomethanol mixed with hydrogen instead of pure biomethanol. Using a hydrogen–biomethanol mixture in modern engines is an effective method because hydrogen is a carbon-free, low-ignition, highest-flame-rate, high-octane fuel. A small quantity of hydrogen added to biomethanol and its combustion in an engine with a heat exchanger increases the combustion temperature and heat release, increases engine power, and reduces fuel consumption. This article presents experimental results of methanol combustion and a hydrogen-in-methanol mixture if hydrogen was retained due to the utilization of the heat of the exhaust gases. The tests were carried on a single-cylinder experimental engine with an injection of liquid methanol and gaseous hydrogen mixtures. The experiments showed that green hydrogen generated onboard the car due to the utilization of heat significantly reduced fuel costs of engines of vehicles and technological installations. It was established a hydrogen gaseous mixture addition of up to 5% by mass to methanol requires a corresponding change in the coefficient of excess air to λ = 1.25. Also, using an additional hydrogen mixture requires adjustment at the ignition moment in the direction of its decrease by 4–5 degrees of the engine crankshaft. Hydrogen gas mixture addition reduced methanol consumption, reaching a maximum reduction of 24%. The maximum increase in power was 30.5% based on experimental data. The reduction in the specified fuel consumption, obtained after experimental tests of the methanol research engine on the stand, can be implemented on the vehicle engines and technological installations equipped with an onboard heat recovery system. Such a system, due to the utilization of heat and the supply of additional hydrogen, can be implemented for engines that work on any alternative or traditional fuels. [ABSTRACT FROM AUTHOR]

The item under test was the engine without its standard facility-based cooling systems, the lack of which makes it impossible to operate as a power unit of a vehicle in a great majority of experimental research of internal combustion engines at high altitudes. The findings may create a wrong impression of the range of power ratings and economic parameters of the engine when operating at high altitudes because changes in atmospheric conditions exert an effect on the running efficiency of its standard systems as well. It is established that the efficiency loss of the cooling system may cause a forced power limitation of the engine as a result of the experimental research of the diesel engine equipped with all standard facility-based systems at very high altitudes. Thus, the shortage of power may significantly exceed the power loss of the engine due to air density reduction at high altitudes. [ABSTRACT FROM AUTHOR]

Typical textbook analyses of heat engines assume that the temperatures of thermal reservoirs do not change; that is, the reservoirs have infinite heat capacity. Several authors have investigated the performance of reversible heat engines for which reservoirs have finite heat capacities and thus the reservoir temperatures do change with time. We find that previous studies have been too restrictive in that they assumed that the reservoir temperature change per cycle is infinitesimal and that the engine ceases operation when the hot reservoir cools to match the temperature of the cold reservoir. We model a Carnot-like engine and show that (1) the problem can be solved exactly with no requirement for infinitesimal temperature changes and (2) there is nothing special about the instant when the temperatures converge, with the device transitioning smoothly from a heat engine to a refrigerator. We find explicit expressions for the limiting reservoir temperature and the total efficiency. Editor's Note: Most textbook thermodynamics problems assume thermal reservoirs of infinite heat capacity and consequently unchanging temperatures. Analyses involving engines operating between finite reservoirs are not unknown, but they typically assume that the temperature change per cycle is infinitesimal and that the engine stops operating when the hot reservoir has come to the temperature of the cold reservoir. This paper considers a Carnot-like engine operating between a finite hot reservoir and an infinite cold one, showing that the problem can be solved exactly with no requirement for infinitesimal changes and also that when the reservoir temperatures converge, the device simply transitions from being a heat engine to a refrigerator. Explicit expressions are developed for the limiting initially-hot reservoir temperature and the total efficiency. Appropriate for upper-level thermodynamics courses. [ABSTRACT FROM AUTHOR]

Over 50% of an engine's energy dissipates via the exhaust and cooling systems, leading to considerable energy loss. Effectively harnessing the waste heat generated by the engine is a critical avenue for enhancing energy efficiency. Traditional exhaust heat recovery systems are limited to real-time recovery of exhaust heat primarily for engine warm-up and fail to fully optimize exhaust heat utilization. This paper introduces a novel exhaust heat recovery system leveraging thermal battery technology, which utilizes phase change materials for both heat storage and reutilization. This innovation significantly minimizes the engine's cold start duration and provides necessary heating for the cabin during start-up. Dynamic models and thermal management system models were constructed. Parameter optimization and calculations for essential components were conducted, and the fidelity of the simulation model was confirmed through experiments conducted under idle warm-up conditions. Four distinct operational modes for engine warm-up are proposed, and strategies for transitioning between these heating modes are established. A simulation analysis was performed across four varying operational scenarios: WLTC, NEDC, 40 km/h, and 80 km/h. The results indicated that the thermal battery-based exhaust heat recovery system notably reduces warm-up time and fuel consumption. In comparison to the cold start mode, the constant speed condition at 40 km/h showcased the most significant reduction in warm-up time, achieving an impressive 22.52% saving; the highest cumulative fuel consumption reduction was observed at a constant speed of 80 km/h, totaling 24.7%. This study offers theoretical foundations for further exploration of thermal management systems in new energy vehicles that incorporate heat storage and reutilization strategies utilizing thermal batteries. [ABSTRACT FROM AUTHOR]

The methods of increasing the efficiency of internal combustion engines through heat utilization are examined. A proposed classification of heat utilization systems for mobile energy vehicles is presented. External utilization harnesses the heat generated by a diesel engine to fulfill the needs of consumers not directly related to the engine, such as interior heating and air conditioning systems. Internal recycling focuses on enhancing the power, environmental performance, and economic performance of an engine and its related systems. Various heat utilization schemes are compared. For the economic conditions of the European Union (EU), a turbocompounding diesel engine is acceptable if its agricultural tractor rated power is more than 275 kW and its combine harvester rated power is more than 310 kW. Steam injection into the combustion chamber is utilized to improve the technical and economic performance of gas turbine engines. This technology is also produced in Ukraine and is proposed for use in internal combustion engines. It is suggested to inject water vapor into a turbocharger turbine. This approach reduces the number of components in the heat recovery system, thereby lowering its cost. A recycling chiller can be employed to cool the air after it passes through the air cleaner, enhance the efficiency of the air cooler, and improve the performance of the thermoelectric generators. This device is particularly effective at relatively high air temperatures and can be recommended for agricultural machinery that operates in such conditions, such as combines. With the application of this new technology, it is possible to increase the power of diesel engines by 15...20% and reduce fuel consumption by up to 14%. Further research will focus on substantiating the parameters of recycling systems for different classes of vehicles. Developing a methodology to justify the effective application of heat utilization systems in agricultural mobile energy vehicles is advisable. [ABSTRACT FROM AUTHOR]

There continues to be considerable research on the adverse effect of photovoltaic (PV) panel temperature on its power production. Aside from attempting to minimize heating up of the panel by providing heat sinks and the like, several studies looked into using the unconverted heat as an input to a Thermoelectric generator residing below the PV panel and questionably generating additional power. Using simple steady energy balances, simplified steady thermal models of PV panels, individually or thermally-in-series coupled to heat engines are studied. The nodal energy equations are solved to ascertain resulting temperatures and efficiencies under different insolations. After establishing a simplified model for a lone PV panel, a PV panel with an added thermoelectric generator attached to its back side is studied. Solving the associated steady energy equations, the photovoltaic-thermoelectric system is found to have a smaller than expected advantage in net power, no more than 4.15 %, over the lone PV panel and then only at high insolation's and concentrations. The implication of this work is that hybridizing a PV panel by bottoming it with a thermoelectric generator is not quite attractive except possibly at higher solar concentrations. The margin to Increase the overall efficiency of a photovoltaic-thermoelectric hybrid by improving the thermoelectric-figure-of-merit does not appear to be significant although further consideration of thermoelectric materials may be required. [ABSTRACT FROM AUTHOR]

The Camellia oleifera fruit harvester, a specialized agricultural device, is engineered for efficient operation within the densely planted C. oleifera groves of China's undulating terrains. Its design features a notably small footprint to navigate the constrained spaces between trees. With the enhancement of the functionality and power of the harvester, the engine compartment becomes even more congested. This, while beneficial for performance, complicates heat dissipation and reduces harvesting efficiency. In this study, experiments were initially conducted to collect temperature data from the main heat-generating components and parts susceptible to high temperatures within the harvester's engine compartment. Subsequently, a 3D model was developed for numerical simulations, leading to the proposal of optimization schemes for the engine compartment's structure and the validation of these schemes' feasibility. A comparison of the experimental data, both before and after optimization, revealed a significant reduction in the surface temperatures of components within the engine compartment following optimization. As a result, the heat dissipation of the engine compartment has been greatly optimized. The harvester has demonstrated prolonged normal operation, enhancing the reliability and economy of the harvester. [ABSTRACT FROM AUTHOR]

Modern information theory pioneered by Shannon provides the mathematical foundation of information transmission and compression. However, the physical (and especially the energetic) nature of the information has been elusive. While the processing of information incurs inevitable energy dissipation, it is possible for communication systems to harness information to perform useful work. In this article, we prove that the thermodynamic cost (that is, the entropy production of the communication system) is at least equal to the information transmitted. Based on this result, a model of a communication heat engine is proposed, which can extract work from the heat bath by utilizing the transmission of information. The communication heat engine integrates the manipulation of both energy and information so that both information and power may be transmitted in parallel. The information transmission rate and the information power of the communication heat engine are derived from a pure thermodynamics argument. We find that the information power of the communication heat engine can be increased by increasing the number of communication channels, but the absolute energy efficiency of the heat engine first increases and then decreases after the number of channels of the system exceeds a threshold. The proposed model and definitions provide a new way to think of a classical communication system from a thermodynamic perspective. [ABSTRACT FROM AUTHOR]

Electric vehicle (EV) is more environmental-friendly than gasoline vehicle because the main power is not petrol. For the heating system, the waste heat generated by engines is recycled to heat the cabin of gasoline ones, while the EV need extra electric energy consumption for heating the cabin which decreases the driving range. Personal comfort system (PCS) has been reported that it is an alternative technique to improve occupant thermal comfort and indirectly save building heating energy. This study aims to investigate the occupants' thermal sensation under four heating modes in the EV cabin in winter, including no heating, only PCS, only air conditioning, and both air conditioning and PCS. The field survey is conducted in a parked EV with 12 subjects. Three thermal comfort indexes (PMV, SET*, and operative temperature Top) are used and assessed for their applicability in the thermal environment of the EV. Results show that the thermal environment in the cabin is non-uniform and dynamic with the air conditioning mode, while the PCS mode just slightly affects the temperature differences inside. Meanwhile, the subjects' thermal sensations cannot maintain neutral or warmer under the PCS mode only. The results of PMV are lower than the subjects' actual thermal sensation votes (TSV), while the results of SET* and Top show significant linear relationships with the TSV for the correlation coefficients above 0.80. Compare to the air conditioning mode, the neutral SET* and neutral Top are decreased by 2.7 °C and 1.6 °C under the mode with PCS and air conditioning, respectively. The findings indicate that PCS not only has a positive effect on improving the cabin environment and occupant's thermal sensation but also has the potential to lower the setting temperature of air conditioner of EVs in winter. [ABSTRACT FROM AUTHOR]

The high demand for natural gas (NG) worldwide has led to an increase in the size of the LNG carrier fleet. However, the heat losses from this type of ship's engines are not properly managed, nor is the excess boil-off gas (BOG) effectively utilised when generation exceeds the ship's power demand, resulting in significant energy losses dissipated into the environment. This article suggests storing the lost energy into green H2 for subsequent use. This work compares three different electrolysis technologies: solid oxide (SOEC), proton exchange membrane (PEME), and alkaline (AE). The energy required by the electrolysis processes is supplied by both the LNG's excess BOG and engine waste heat through an organic Rankine cycle (ORC). The results show that the SOEC consumes (743.53 kW) less energy while producing more gH2 (21.94 kg/h) compared to PEME (796.25 kW, 13.96 kg/h) and AE (797.69 kW, 10.74 kg/h). In addition, both the overall system and SOEC stack efficiencies are greater than those of PEME and AE, respectively. Although the investment cost required for AE (with and without H2 compression consideration) is cheaper than SOEC and PEME in both scenarios, the cost of the H2 produced by the SOEC is cheaper by more than 2 USD/kgH2 compared to both other technologies. [ABSTRACT FROM AUTHOR]

We have now identified two thermodynamically distinct types (A and B) of energetic processes naturally occurring on Earth. Type-A energy processes, such as classical heat engines, apparently well follow the second law of thermodynamics; Type-B energy processes, such as the newly discovered thermotrophic function that isothermally utilizes environmental heat energy to perform useful work in driving ATP synthesis, follow the first law of thermodynamics (conservation of mass and energy) but do not have to be constrained by the second law, owing to their special asymmetric functions. Several Type-B energy processes such as asymmetric function-gated isothermal electricity production and epicatalysis have been created through human efforts. The innovative efforts in Type-B processes to enable isothermally utilizing endless environmental heat energy could help to liberate all peoples from their dependence on fossil fuel energy, thus helping to reduce greenhouse gas CO2 emissions and control climate change towards a sustainable future for humanity on Earth. In addition to the needed support for further research, development, and commercialization efforts, currently, better messaging and education on Type-B energetic processes are also highly needed to achieve the mission. [ABSTRACT FROM AUTHOR]

The problem of formulating thermodynamics in a relativistic scenario remains unresolved, although many proposals exist in the literature. The challenge arises due to the intrinsic dynamic structure of spacetime as established by the general theory of relativity. With the discovery of the physical nature of information, which underpins Landauer's principle, we believe that information theory should play a role in understanding this problem. In this work, we contribute to this endeavour by considering a relativistic communication task between two partners, Alice and Bob, in a general Lorentzian spacetime. We then assume that the receiver, Bob, reversibly operates a local heat engine powered by information, and seek to determine the maximum amount of work he can extract from this device. As Bob cannot extract work for free, by applying both Landauer's principle and the second law of thermodynamics, we establish a bound on the energy Bob must spend to acquire the information in the first place. This bound is a function of the spacetime metric and the properties of the communication channel. [ABSTRACT FROM AUTHOR]

Currently, a significant number of automobiles are equipped with internal combustion engines. In urban areas, a significant number of transportation methods have detrimental environmental effects through the release of pollutants resulting from the combustion of fossil fuels. In addition to the emission of toxic pollutants, internal combustion engines experience significant energy losses through exhaust emissions. Advanced technological applications have the potential to recover of a portion of the waste heat from exhaust ducts. Evaluations conducted by scholars across several disciplines highlight diverse perspectives on the recycling of thermal energy from exhaust gases as a means of mitigating pollution sources. However, this review focuses on the utilization of thermoelectric generators for harvesting a fraction of the aforementioned dissipated energy. The energy harvesting system is comprised of three components: the heat exchanger, which serves as the heat source; the cooler, which functions as the heat sink; and the thermoelectric generators, which act as the heat engine sandwiched between the heat exchanger and the cooler. This review examines the diverse exterior designs of heat exchangers and coolers and categorizes them accordingly. Additionally, it identifies the optimal installation locations for harvesting systems and explores the impact of design variations, choice of metals for manufacturing, and internal topography on the generation of electrical power. The primary findings of this review emphasize the significance of prioritizing the design of heat exchangers over coolers. This is because the uniformity of the temperature distribution within the heat exchanger plays a crucial role in governing the overall performance. Moreover, the installation of the system on petrol engines was seen as more cost-effective in comparison to its installation on diesel engines, primarily due to the higher magnitude of energy emitted from the exhaust gases of the former as opposed to the latter. To the best of the author's knowledge, this review classification has never been performed before. This can be considered a brief path map and a starting point for future work by researchers and investigators in designing heat exchangers and coolers and choosing the locations of TEG system installations. Then profitable investment from the data that has been prepared and summarized. [ABSTRACT FROM AUTHOR]

Biodiesel is a promising alternative fuel derived from renewable feedstocks like vegetable oils and animal fats. However, biodiesel usage in compression ignition (CI) engines reduces performance and increases NOx emissions compared to petroleum diesel. This study aims to improve the efficiency of juliflora methyl ester (JFME) biodiesel and simultaneously reduce NOx emissions by converting a CI engine into low heat rejection (LHR) mode and adding natural and synthetic antioxidants. The transesterification process produced JFME biodiesel from Juliflora seeds. A 20% blend of JFME biodiesel with diesel (JFME20) was optimal based on fuel property analysis. The CI engine was coated with lanthanum oxide to create a LHR engine. Natural (Albizia lebbeck leaf extract) and synthetic antioxidants were added to JFME20 at 0.01% concentration. Engine tests showed that JFME20 with natural antioxidants in LHR mode decreased NOx by 15.4% and smoking by 5.48% compared to baseline diesel in a normal CI engine at full load. The brake thermal efficiency of the LHR engine with natural antioxidants increased by 1.8%. CO and HC emissions reduced by 30.76 and 36.95%, respectively. The synthetic antioxidant was less effective than the natural one. In summary, the antioxidant-enriched JFME20 biodiesel blend in the LHR engine demonstrated superior performance over baseline diesel while substantially reducing NOx and other emissions. [ABSTRACT FROM AUTHOR]

Heat engines are key devices that convert thermal energy into usable energy. Strong thermoelectricity, at the basis of electrical heat engines, is present in superconducting spin tunnel barriers at cryogenic temperatures where conventional semiconducting or metallic technologies cease to work. Here we realize a superconducting spintronic heat engine consisting of a ferromagnetic insulator/superconductor/insulator/ferromagnet tunnel junction (EuS/Al/AlOx/Co). The efficiency of the engine is quantified for bath temperatures ranging from 25 mK up to 800 mK, and at different load resistances. Moreover, we show that the sign of the generated thermoelectric voltage can be inverted according to the parallel or anti-parallel orientation of the two ferromagnetic layers, EuS and Co. This realizes a thermoelectric spin valve controlling the sign and strength of the Seebeck coefficient, thereby implementing a thermoelectric memory cell. We propose a theoretical model that allows describing the experimental data and predicts the engine efficiency for different device parameters. An electrical heat engine has been realized at sub-Kelvin temperatures. It consists of a superconducting spin-selective tunnel junction of EuS/Al/AlOx/Co. The efficiency of the engine is quantified for different magnetic configurations. [ABSTRACT FROM AUTHOR]

Quantum revival phenomena, wherein the wave function of a quantum system periodically returns to its initial state after evolving in time, are investigated in this study. Focusing on electrons confined within a quantum box with an impurity, both weak- and strong-coupling regimes are explored, revealing intricate relationships between impurity parameters and temporal dynamics. This investigation considers the influence of impurity position, impurity strength, and external factors such as aluminum concentration, temperature and hydrostatic pressure on classical periods and revival times. Through analytical derivations and graphical analyses, this study elucidates the sensitivity of quantum revivals to these parameters, providing valuable insights into the fundamental aspects of quantum mechanics. While no specific physical applications are discussed, the findings offer implications for quantum heat engines and other quantum-based technologies, emphasizing the importance of understanding quantum revivals in confined quantum systems. [ABSTRACT FROM AUTHOR]

The impact of fossil fuel utilisation in different combustion systems on climate change due to greenhouse gas accumulation in the atmosphere is rather evident. A part of these gases comes from the large engines used for propulsion in marine applications. In the continuous global effort made by engine manufacturers to mitigate this negative impact, one way is represented by the utilisation of alternative fuels such as biodiesel and methanol, based on dedicated research to fulfil the more stringent regulations concerning pollutant emissions issued by piston heat engines. In this study, a numerical investigation was conducted on a four-stroke large marine diesel engine (ALCO 16V 251C) at several engine speeds and full load conditions. Different blends of diesel–methanol and biodiesel B20–methanol with methanol mass fractions of 10% and 20% were considered for theoretical analysis in two techniques of methanol supply: direct injection mode of a blend of base fuel diesel/biodiesel B20 with methanol and injection of methanol after the intercooler, and direct injection of the base fuel. The results show that, if 10% in power loss can be acceptable, then for diesel–methanol 10%, in the direct injection technology, the NOx emission can be reduced up to 19%, but with a compromise of an 8% increase in SOOT emission, while for biodiesel B20–methanol 10%, with the same direct injection method, the NOx emissions increase by up to 58% with the benefit of reducing SOOT by up to 23% relative to the original diesel fuel operation. For a 20% methanol fraction in blend fuel, the drop in power is more than 10% regardless of the method of methanol supply and the base fuel, diesel, or B20 used. [ABSTRACT FROM AUTHOR]

The interest in combined heat and solar power (CHP) systems has increased due to the growing demand for sustainable energy with low carbon emissions. An effective technical solution to address this requirement is using a parabolic trough solar collector (PTC) in conjunction with a Rankine cycle (RC) heat engine. The solar-powered Rankine cycle (SPRC) system is a renewable energy technology that can be relied upon for its high efficiency and produces clean energy output. This study describes developing a SPRC system specifically for electricity generation in Aden, Yemen. The system comprises parabolic trough collectors, a thermal storage tank, and a Rankine cycle. A 4E analysis of this system was theoretically investigated, and the effects of various design conditions, namely the boiler's pinch point temperature and steam extraction from the high-pressure turbine, steam extraction from the intermediate-pressure turbine, and condenser temperature, were studied. Numerical simulations showed that the system produces a 50 MW net. The system's exergetic and energy efficiencies are 30.7% and 32.4%. The planned system costs 2509 USD/h, the exergoeconomic factor is 79.43%, and the system's energy cost is 50.19 USD/MWh. The system has a 22.47 kg/MWh environmental carbon footprint. It is also observed that the performance of the cycle is greatly influenced by climatic circumstances. Raising the boiler's pinch point temperature decreases the system's performance and raises the environmental impact. [ABSTRACT FROM AUTHOR]

Due to the rapidly increasing energy demand, the world needs to focus more on identifying alternative energy sources like biofuels and energy conservation techniques that enhance the efficiency of various systems. A cogeneration (CHP) system is one of the most emerging techniques for achieving the goal of energy conservation by providing useful power (electricity) and heating simultaneously. So the current study proposes a diesel engine-driven CHP system that is fueled with different blends of biodiesel. The objective of the current study is to investigate the impact of Eureka Sativa oil biodiesel on waste heat recovery, performance, and emission characteristics of diesel engine driven combined heating and power generation system. The cogeneration unit is developed by connecting the exhaust pipe of a single-cylinder, four-stroke diesel engine with a heat exchanger. The pure diesel, along with 10%, 15%, 20%, and 25% by volume of biodiesel, was used as fuel for the cogeneration unit. The AVL Di-Gas 444N multi-gas analyzer was utilized to evaluate the engine exhaust gas emissions. Diesel fuel has the highest brake thermal efficiency and the lowest brake specific fuel consumption (BSFC). B20 has the highest brake thermal efficiency and the lowest BSFC among all blends of biodiesel. Also, B20 has better emission characteristics than all other blends of biodiesel. The exhaust gas temperature and waste heat recovery increase with the percentage of biodiesel in the blends. The B25 has the highest overall efficiency (38.49%) among all blends, which is 1.93 % lower than pure diesel. However, result analysis revealed that B20 is the best fuel among all biodiesel blends in terms of engine performance and emission formation. Whereas B25 is a better fuel in terms of WHR and overall cogeneration unit efficiency. [ABSTRACT FROM AUTHOR]

In this work, we lay the foundations for computing the behavior of a quantum heat engine whose working medium consists of an ensemble of non-harmonic quantum oscillators. In order to enable this analysis, we develop a method based on the Schrödinger picture. We investigate different possible choices on the basis of expanding the density operator, as it is crucial to select a basis that will expedite the numerical integration of the time-evolution equation without compromising the accuracy of the computed results. For this purpose, we developed an estimation technique that allows us to quantify the error that is unavoidably introduced when time-evolving the density matrix expansion over a finite-dimensional basis. Using this and other ways of evaluating a specific choice of basis, we arrive at the conclusion that the basis of eigenstates of a harmonic Hamiltonian leads to the best computational performance. Additionally, we present a method to quantify and reduce the error that is introduced when extracting relevant physical information about the ensemble of oscillators. The techniques presented here are specific to quantum heat cycles; the coexistence within a cycle of time-dependent Hamiltonian and coupling with a thermal reservoir are particularly complex to handle for the non-harmonic case. The present investigation is paving the way for numerical analysis of non-harmonic quantum heat machines. [ABSTRACT FROM AUTHOR]

Though CO2 power cycles are preferred for diesel engine waste heat recovery, a very high operating pressure of the CO2 power cycle is an issue of concern. To address this issue, in the present study, CO2-propane and CO2-R152a mixtures with various CO2 mass fractions are proposed as the working fluid of a regenerative transcritical power cycle recovering waste heat of a diesel power plant. To reduce the possibility of accidental fire hazard; the minimum permissible CO2 mass fraction is restricted to 0.3. It is observed that reducing CO2 mass fraction ensures higher output power and lesser levelized electricity cost (LEC), specifically at a lower turbine inlet pressure. Between two considered CO2-based mixture pairs, the transcritical cycle exhibits a superior performance with CO2-R152a-based mixtures. The LEC of the presented CO2-propane-based optimized cycle is about 6.36% lower compared to that of the optimized supercritical CO2 power cycle. For the CO2-R152a mixture-based cycle, the corresponding achievable reduction in LEC is about 15.20%. Turbine inlet pressures corresponding to the minimum LECs of the optimized CO2-propane and CO2-R152a mixture-based cycles are, respectively, close to 33% and 39% lower than that of the optimized supercritical CO2 power cycle. As R152a is less flammable than propane, an R152a-based mixture working fluid also ensures a safer operation compared to a propane-based mixture. [ABSTRACT FROM AUTHOR]

The objective of this study is to design a heat-recovery boiler for a 1 MW-class gas engine-based cogeneration system intended to recover heat from engine exhaust gas. To accommodate high-pressure applications, a water tube-type boiler is selected. For ensuring effective water circulation within the boiler, an innovative modular-type boiler based on the mini-boiler concept is developed. This boiler comprises finned tube-type risers, and their heat-transfer characteristics are measured and compared with the conventional correlation used in the design process. Additionally, an inlet guide vane is developed to address the temperature nonuniformity resulting from the shape mismatch between the gas engine outlet and heat-recovery boiler inlet. The performance of the proposed boiler was evaluated by integrating it into an experimental rig. The diamond-shaped inlet guide vane, which was designed by computational fluid dynamics, facilitated a uniform temperature distribution. However, the temperature became nonuniform downstream owing to the influence of a downcomer. Although the modular heat-recovery boiler effectively produced steam from gas engine exhaust gasses, its heat-transfer performance in the downstream section was lower than expected, necessitating additional heat-transfer area. [ABSTRACT FROM AUTHOR]

Near-field radiative heat transfer has recently attracted increasing interests for its applications in energy technologies, such as thermophotovoltaics. Existing works, however, are restricted to time-independent systems. Here, we explore near-field radiative heat transfer between two bodies under time modulation by developing a rigorous fluctuational electrodynamics formalism. We demonstrate that time modulation can result in the enhancement, suppression, elimination, or reversal of radiative heat flow between the two bodies, and can be used to create a radiative thermal diode with an infinite contrast ratio, as well as a near-field radiative heat engine that pumps heat from the cold to the hot bodies. The formalism reveals a fundamental symmetry relation in the radiative heat transfer coefficients that underlies these effects. Our results indicate the significant capabilities of time modulation for managing nanoscale radiative heat flow. [ABSTRACT FROM AUTHOR]

In order to increase the comfort of vehicle passengers in specific vehicle categories, the heating of the passenger compartment is not provided by the heat from the engine driving the vehicle but by an additional heating device. The study examines the effect of auxiliary heaters that use liquid fuels to heat the passenger compartment of vehicles. The device was operated during the test with two different mixtures containing bioethanol (E30, E100) and the original motor gasoline (E10). It aimed to understand the effects of different fuels, particularly heating performance, operating time and emissions. Based on the results, as the ethanol content increases, the temperature of the device's flame and heating air decreases. The experiments showed that in the case of E100 bioethanol, the average temperature measured in stable operating conditions was significantly lower than in the case of E10 motor gasoline. That suggests that an increase in the ethanol content reduces the heating performance. Another significant result of the study was that in the case of mixtures containing ethanol, a longer operating time is required to achieve the same amount of heat, which leads to additional fuel consumption. In addition, when using E100 bioethanol, the amount of harmful gases that are emitted increases significantly during the longer operating time. This observation can be important for evaluating the environmental impact and efficiency of vehicles. [ABSTRACT FROM AUTHOR]

Atoms falling into a black hole (BH) through a cavity are shown to enable coherent amplification of light quanta powered by the BH-gravitational vacuum energy. This process can harness the BH energy towards useful purposes, such as propelling a spaceship trapped by the BH. The process can occur via transient amplification of a signal field by falling atoms that are partly excited by Hawking radiation reflected by an orbiting mirror. In the steady-state regime of thermally equilibrated atoms that weakly couple to the field, this amplifier constitutes a BH-powered quantum heat engine. The envisaged effects substantiate the thermodynamic approach to BH acceleration radiation. [ABSTRACT FROM AUTHOR]

The study aims to improve the waste thermal energy retrieval from flue gas of an internal combustion engine (ICE). The recovered waste heat energy was used for distillation by using a thermal distillation system. The performance of the thermal distillation unit was investigated by varying the evaporator (boiler) type and engine load (25, 50, 75 %). Four different types of boilers were used including one smooth copper tube and other three were two, three and four axial finned copper tube evaporators. The impact of boiler type and engine load on the net retrieved energy and exergy, net energy and exergy efficiency, and distillate yield rate of thermal distillation unit was also examined. The results showed that the net extracted heat energy and exergy for axial finned tube evaporator was approximately 26.823 - 45.513 % and 7.614 - 25.203 W higher than that of smooth tubes evaporator at 25 and 75 % engine load, respectively. The distillation yield was found to be ~ 2.35 liter/hour in the case of four axial finned tube boiler at 75 % engine load. [ABSTRACT FROM AUTHOR]

We consider an autonomous heat engine in simultaneous contact with a hot and a cold reservoir and describe it within a linear irreversible framework. In a tight-coupling approximation, the rate of entropy generation is effectively written in terms of a single thermal flux that is a homogeneous function of the hot and cold fluxes. The specific algebraic forms of the effective flux are deduced for scenarios containing internal and external irreversibilities for the typical example of a thermoelectric generator. [ABSTRACT FROM AUTHOR]

The non-stationary mode of movement of the working fluid flow in the Stirling engine causes serious difficulties in the design of heat exchangers. In most cases, the operation of conventional commercial heat exchangers is considered under steady-state flow conditions with relatively slowly varying parameters. Another situation is observed in Stirling engines, where the working fluid flow mode is characterized by significant changes in pressure, density and flow rate, the direction of which changes twice per cycle. These circumstances significantly complicate the design of regenerators and other heat exchangers for Stirling engines. The results of a theoretical and experimental study of recuperative heat exchangers in the Stirling engine system and possible ways to improve the efficiency of heat transfer in order to increase power and efficiency are considered in this article. A method of comparative evaluation of heat exchange surfaces efficiency is proposed under conditions of their operation in the engines with external heat supply system. [ABSTRACT FROM AUTHOR]

This article provides a comprehensive overview of the performance evaluation of looped tube thermoacoustic power generators using numerical and experimental analysis. The study focuses on small-scale generators operating at atmospheric pressure and utilizing low-cost linear alternators. The analysis considers factors such as temperature variation, pressure fluctuation, volume flow rate, and acoustic power distribution. The results show that the generators produce maximum acoustic power at a frequency of 78 Hz, with an overall thermal to electric efficiency of approximately 8.3%. The article also includes references to other research papers and articles that cover various aspects of thermoacoustic engines and generators, providing valuable insights into the field. [Extracted from the article]

This article introduces a new, physically-based Lyapunov function definition that can be used as acoustic energy for finite-amplitude pressure oscillations in reacting systems, especially in combustion chambers. Reacting flow is seen as an open, non-equilibrium (parameters are distributed unevenly locally) thermodynamic system. This Lyapunov function is defined as the maximum mechanical work that could be extracted by a heat engine from the studied system if this system were disconnected from the inlet and outlet and from any other surrounding environment and the engine could transfer to the surrounding environment only mechanical work. [ABSTRACT FROM AUTHOR]

Effective treatment of breast cancer relies heavily on early detection. Routine annual mammography is a widely accepted screening technique that has resulted in significantly improving the survival rate. However, it suffers from low sensitivity resulting in high false positives from screening. To overcome this problem, adjunctive technologies such as ultrasound are employed on about 10% of women recalled for additional screening following mammography. These adjunctive techniques still result in a significant number of women, about 1.6%, who undergo biopsy while only 0.4% of women screened have cancers. The main reason for missing cancers during mammography screening arises from the masking effect of dense breast tissue. The presence of a tumor results in the alteration of temperature field in the breast, which is not influenced by the tissue density. In the present paper, the IRI-Numerical Engine is presented as an adjunct for detecting cancer from the surface temperature data. It uses a computerized inverse heat transfer approach based on Pennes's bioheat transfer equations. Validation of this enhanced algorithm is conducted on twenty-three biopsy-proven breast cancer patients after obtaining informed consent under IRB protocol. The algorithm correctly predicted the size and location of cancerous tumors in twenty-four breasts, while twenty-two contralateral breasts were also correctly predicted to have no cancer (one woman had bilateral breast cancer). The tumors are seen as highly perfused and metabolically active heat sources that alter the surface temperatures that are used in heat transfer modeling. Furthermore, the results from this study with twenty-four biopsy-proven cancer cases indicate that the detection of breast cancer is not affected by breast density. This study indicates the potential of the IRI-Numerical Engine as an effective adjunct to mammography. A large scale clinical study in a statistically significant sample size is needed before integrating this approach in the current protocol. [ABSTRACT FROM AUTHOR]

Thermodynamics of non-flat Amended Friedmann–Robertson–Walker (AFRW) universe with cosmological constant as thermodynamic pressure is studied. The unified first law of thermodynamics, the Clausius relation and the gravity equations yield entropy on the dynamic apparent horizon. Temperature, volume, pressure, enthalpy, Gibb's free energy and Helmholtz's free energies, and specific heat capacity with constant pressure of the universe are calculated in terms of surface area of dynamic apparent horizon. The study shows a non-negative Joule–Thomson coefficient, indicating the cooling nature of the AFRW universe. Inversion pressure and inversion temperature are expressed in terms of the surface area of the apparent horizon. Finally, the thermodynamical AFRW universe is considered as a heat engine. Work done for the Carnot engine is derived with maximum efficiency, and a new engine is also considered for which the work done, and its efficiency are calculated for AFRW universe. [ABSTRACT FROM AUTHOR]

This paper presents a continuation of the Chambadal model optimization of the irreversible Carnot engine. We retrieved the results presented in the Special Issue "Carnot Cycle and Heat Engine Fundamentals and Applications II" and enriched them with new contributions that allowed comparing two points of view: (1) the now classical one, centered on entropy production in the four processes of the cycle, which introduces the action of entropy production, with several sequential optimizations; (2) the new one that is relative to an energy degradation approach. The same démarche of sequential optimization was used, but the results were slightly different. We estimate that the second approach is more representative of physics by emphasizing the energy conservation and the existence on an upper and a lower bound in the mechanical energy and power output of the engine. [ABSTRACT FROM AUTHOR]

Motor vehicle exhaust is an important cause of atmospheric pollution. Nowadays, mainstream exhaust emission aftertreatment technologies, such as TWC, DOC, SCR, and DPF, usually require sufficient temperature to perform good purification or maintain normal working conditions. Compared with exhaust gas heating technologies such as engine enrichment and fuel injection, electric heating technology can quickly increase the temperature of exhaust gas aftertreatment devices without adverse effects on engine operating conditions. This article introduces the research and progress of electric heating technology combined with traditional aftertreatment devices on major types of vehicles, such as gasoline vehicles, diesel vehicles, motorcycles, and hybrid vehicles, to improve exhaust purification efficiency and its accompanying fuel consumption impact. In addition, the common structure and characteristics of electric heaters, as well as the current status and development trend of electric heating unit technologies such as electric heating power supply are introduced. [ABSTRACT FROM AUTHOR]

The article focuses on the development of decarbonized marine power systems, consisting of solid oxide fuel cells (SOFC) and gas turbines (GT), aiming to provide high economic and environmental performance. Currently, the potential of such systems is not fully realized due to issues related to the insufficient reliability and durability of the fuel cells themselves, as well as suboptimal heat utilization processes in the gas turbine section of the power plant. In contrast to previous research, this study demonstrates the prospects of using the steam-injected gas turbine (STIG) cycle and overexpanded turbine to improve the heat recovery conditions of exhaust gasses from fuel cells, enhance the efficiency of the power system, and increase the longevity of its key components. To achieve this, a corresponding mathematical model was developed, and optimization calculations for the proposed system cycle were conducted. Adopting the proposed cycle with a steam-injected gas turbine resulted in a 4.4 % increase in efficiency compared to traditional schemes. Such a system could be utilized in the design of advanced marine power system for the next generation.