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Transport of heat in combustion engines, burners and consumption of energy via nuclear explosions is remarkably effected by magnetize nanofluid and radiation. Present attempt is relevant to the current Engineering applications; as design of heat exchangers, systems of renewable energy, and Nanotechnology. Therefore, main concern of the study is explored the radiative flux in Micropolar nanofluid flow under the Lorentz force and gravity modulation. The impacts of cross diffusion is also included in flow field. The mathematical model governing the flow are transformed into ODEs via similarity variables. The Keller box approach is utilized for numerical outcomes. A comprehensive analysis of the physical parameters is carried out, and numerical outcomes are displayed in graphical and tabular form. Obtained outcomes are compared with results that have already been published and found a good match. It has been found that temperature profile and concentration profile have a direct relation against Soret and Dufour respectively. Temperature profile and concentration profile has a direct relation against Dufour and Soret effects. Thermal field grows by enhancing radiation, Brownian motion and thermophoresis parameter. Furthermore, the skin friction.increases as the inclination factor grows up, but Nusselt and Sherwood numbers decline. [ABSTRACT FROM AUTHOR]

Reactivity-controlled compression ignition engines have garnered significant interest for their potential to deliver enhanced performance, particularly in environmental aspects. This study investigates the performance of such engines within a co-generation framework for simultaneous power and cooling production. Low reactivity fuel for the engine is derived from solar steam reforming of methanol, with waste heat recovered through a supercritical CO 2 cycle and an absorption refrigeration cycle. The designed configuration undergoes comprehensive analysis encompassing thermodynamic, economic, and exergoenvironmental assessments, including parametric analysis. Optimal engine performance is evaluated through computational fluid dynamics, thermodynamic, and exergoenvironmental analyses across various syngas compositions and reforming conditions. Results indicate that a syngas portion of 60% at a reforming temperature and CH3OH to H2O ratio of 200 °C and 1.2 yields optimal engine performance. Besides, the inlet temperature of the CO 2 turbine exhibits the greatest impact on co-generation performance. At the optimal state, co-generation's power and cooling load generation reach 467.8 kW and 225 kW, with a unit cost of 53.89 $/GJ, an exergy efficiency of 38.14%, a sustainability index of 1.622, and an exergoenvironmental impact index of 1.607. • A RCCI engine's performance is investigated in a co-generation. • The LRF is supplied by a steam reforming of methanol. • The engine's best performance is achieved at syngas portion of 60%. • The optimal exergy efficiency, SI, and EII are attained 38.14%, 1.622, and 1.607. [ABSTRACT FROM AUTHOR]

Engines are systems and devices that convert one form of energy into another, typically into a more useful form that can perform work. In the classical setup, physical, chemical, and biological engines largely involve the conversion of heat into work. This energy conversion is at the core of thermodynamic laws and principles and is codified in textbook material. In the quantum regime, however, the principles of energy conversion become ambiguous, since quantum phenomena come into play. As with classical thermodynamics, fundamental principles can be explored through engines and refrigerators, but, in the quantum case, these devices are miniaturized and their operations involve uniquely quantum effects. Our work provides a broad overview of this active field of quantum engines and refrigerators, reviewing the latest theoretical proposals and experimental realizations. We cover myriad aspects of these devices, starting with the basic concepts of quantum analogs to the classical thermodynamic cycle and continuing with different quantum features of energy conversion that span many branches of quantum mechanics. These features include quantum fluctuations that become dominant in the microscale, non-thermal resources that fuel the engines, and the possibility of scaling up the working medium's size, to account for collective phenomena in many-body heat engines. Furthermore, we review studies of quantum engines operating in the strong system–bath coupling regime and those that include non-Markovian phenomena. Recent advances in thermoelectric devices and quantum information perspectives, including quantum measurement and feedback in quantum engines, are also presented. • Quantum Engines link quantum phenomena with nonequilibrium thermodynamics. • The role of quantum fluctuations, non-Markovianity, and strong coupling in energy conversion. • Many-body systems and non-thermal baths are building blocks of Quantum Engines. • Recent developments in thermoelectric devices open new experimental possibilities. • Quantum correlation measurements and feedback can serve as resources for work extraction and cooling. [Display omitted] [ABSTRACT FROM AUTHOR]

Compact heat-driven cryocoolers can harness the thermal energy produced by burning a small quantity of natural gas to accomplish liquefaction. This addresses the requirements of distributed natural gas stations in remote locations. This paper introduces a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler designed for natural gas liquefaction. It conducts a comparative analysis of the mechanical and electrical systems, focusing on the acoustic field, available energy loss, and performance. Simulation results indicate that the optimized mechanical configuration system achieves peak performance with a piston area ratio of 0.84 and a piston phase angle of 90°. It yields a cooling power of 1964 W@130 K when driven by an 873 K heat source, resulting in an overall system efficiency of 28.3%. This marks a notable enhancement compared to current thermoacoustic systems. While the electrical configuration provides superior stability, the performance is constrained by significant losses in acoustic-electric conversion of linear alternators and compressors. To further enhance efficiency, it is worthwhile to establish direct power transfer between the pistons, for example, by aligning the expansion piston and compression piston coaxially. The evolved duplex configuration eliminates the loss from electrical energy conversion, leading to a remarkable 64.7% increase in overall efficiency. Simultaneously, this evolutionary approach offers a new perspective to elucidate the inherent connections among Stirling heat engines of Franchot double-acting and duplex. It provides valuable theoretical insights for the subsequent analysis and design of Stirling heat-driven refrigerators or cryocoolers. • A Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler is proposed. • A notable enhancement compared to current thermoacoustic systems. • The electrical configuration provides stability but limited by energy conversion losses. • The evolved duplex configuration eliminates the loss of energy conversion. [ABSTRACT FROM AUTHOR]

A hydrogen-fueled free-piston engine generator (FPEG) with a mechanical-pressurized structure is adopted to enable the prototype to operate at high frequency while improving the combustion efficiency. However, in the actual experiment, the prototype cannot run stably due to the low output power and the large cyclic combustion variations of pure hydrogen. In order to solve this problem, firstly, the radius of the air-spring is parameterized to maintain the high operating frequency of the prototype while reducing the bidirectional current flow. Secondly, the current in the expansion stroke is adjusted multiple times based on the ideal displacement, not only based on the maximum pressure in the cylinder, to ensure that the prototype can maintain high dead center control accuracy under large cyclic combustion variations. Finally, the control strategy is tested by simulating the combustion variations through the modification of the combustion parameters in the mathematical model, and the simulation results show that the control accuracy of inner dead center (IDC) can be within 0.2 mm and outer dead center (ODC) within 0.5 mm under the heat engine condition of ODC 38 mm and IDC 1 mm, which has accumulated valuable experience for the next-generation prototype as well as for experiments. • The pure hydrogen combustion variations during the experiments is analyzed. • An optimization scheme based on current bidirectional flow is proposed. • More comprehensive combustion variations is simulated by mathematical model. • The control accuracy of IDC and ODC reaches 0.2 mm and 0.5 mm, respectively. • The prototype can run stably under large combustion variations through simulation. [ABSTRACT FROM AUTHOR]

Ammonia is a carbon-free, promising fuel for hydrogen carriers. It is a liquid fuel under low-pressure conditions (8.62 bars) and can be easily stored. Many researchers have tried to apply it in engines because there are no carbon dioxide emissions when combusting it. However, ammonia is a low cetane number fuel and is difficult to ignite. It can be used in a dual fuel mode in compression ignition (CI) engines, i.e., a fuel such as diesel, n-heptane, dimethyl ether, hydrogen etc., is used as a pilot fuel to ignite the ammonia. In this work, n-heptane was used as the pilot fuel and ammonia was used as the primary fuel in a light-duty CI engine. The engine's heat release rate (HRR), cylinder pressure, ignition delay and indicated efficiency were investigated experimentally at 80 %, 89 %, 95 % and 98 % ammonia fuel energy proportion. In order to investigate the ignition and combustion characteristics of the dual fuel engine, a multi-zone combustion model for n-heptane and a flame propagation model for the ammonia fuel were developed. In this work, it is found that the combustion process of n-heptane/ammonia can be simulated in most cases by a multi-zone evaporative combustion model combined with a flame propagation model. This work also found that the ignition performance of n-heptane is more affected by the long chemical ignition delay. Eventually, it was found that the more minor the discrepancy between the simulated and experimental ignition delays, the more insignificant the discrepancy between the simulated heat release rates and cylinder pressures and the experimental ones. The HRR, cylinder pressure, physical and chemical ignition delays and indicated efficiency of the engine were then simulated. The simulation showed good agreement with experimental results for the 89 %, 95 % and 98 % ammonia fuel energy proportion cases. The simulated physical ignition delay was 1.45–2.37 CA deg, the chemical ignition delay was 7.21–8.88 CA deg, and the indicated efficiency was 39.84%–42.80 % (for the three cases with 89 %, 95 % and 98 % ammonia fuel energy proportions). A detailed analysis of each parameter was conducted. • The n-heptane multi-zone model and flame propagation model for ammonia were jointly developed. • Combined theoretical and experimental analysis of combustion processes. • Analysis of the heat release rate and cylinder pressure of ammonia fuels with different energy proportions. • Prediction deviation in ignition delay largely determines prediction deviation in HHR and cylinder pressure. • Chemical ignition delay dominates the ignition performance. [ABSTRACT FROM AUTHOR]

Owing to contamination of air and environmental hazards, the demand for sustainable fuels in power plants and other heat engines has climbed undeniably. Aluminum metal is classified among high energy density and low carbon content, which can be reacted with water and repeatedly released a large amount of heat and hydrogen. Since hydrogen is one of the zero-carbon and clean fuels, aluminum can be exploited as a promising energy-carrying and renewable source of energy. This paper is dedicated to the customization of two novel schemes of the combined cycle of power generation systems. The main components of the proposed integrated installations include a hydrogen turbine, gas turbine, multi pressure steam turbines, condenser, heat recovery steam generator and aluminum-water reactor, in which pressurized water absorbs produced heat of the reactor then superheated steam expands in steam turbines. Direct supplied hydrogen, which is generated from the Al-water reaction, expands in the hydrogen turbine and subsequently burns in the combustion chamber of the gas turbine. Hydrogen properties, consumed heat of reactor, generated powers, effects of streams pressure, energetic and exergetic productivity variation of both schemes were evaluated comparatively to ensure the best system performance along with the high net efficiency. According to the numerical analysis of the thermodynamic characteristics in steady state regime using EES software, the energy and energy efficiencies of scheme A were calculated to be 40.72% and 38.36%, besides in scheme B were 39.6% and 37.3%, respectively. [Display omitted] • Demands for environmentally friendly fuels have been raised exponentially. • Aluminum water reaction can release repeatedly heat and hydrogen. • Hydrogen as zero-carbon fuel burns in combustion chamber. • Stream of steam can absorb produced heat in Al-water reaction. • Performance of reheat cycle is better than cycle without reheat. [ABSTRACT FROM AUTHOR]

This study focused on improving the energy demand of conventional large-scale natural gas to methanol flow sheet where even a small efficiency improvement has significant economics and carbon emissions benefits. A conventional flow sheet, case A, was based on best available literature information. A case B where the conventional cryogenic air separation unit (ASU) is replaced with the novel ion transport membrane (ITM) oxygen unit was developed. The ITM oxygen is also heat integrated into the autothermal reformer (ATR) process. A case C where the methanol synthesis process is configured into a gas turbine cycle was developed from further modifying case B. The flow sheets were constructed and modelled in Aspen Plus V10 and, heat and material balance results are reported. To our knowledge, the integration of ITM oxygen membranes into the ATR-based methanol process has not been assessed previously. Energy and exergy results are generated and analysed. It was found that is it possible to replace the cryogenic ASU with the ITM oxygen for oxygen production in the ATR process. There is enough process syngas heat available to provide the ITM oxygen unit heating requirement and to generate process steam feed to the ATR. Case A was found to consume only 12 % natural gas as utility fuel which is lower than typical SMR-based methanol processes. This reduced to about 5 % in case B and C. Power production improved by 47 % in case B and 68 % in case C compared to case A. A thermal efficiency definition suitable for combined process steam, power and oxygen production was proposed. This showed that integration of a high temperature gas power cycle enables combined steam (heat) and power configuration which has a higher efficiency compared to single cycles, such as the steam cycles. The overall plant exergy losses decreased by up to 21 %. • Cryogenic air separation processes consume large amounts of energy for air compression. • Autothermal reforming technology is preferred for large scale methanol production from gas. • Ion transport membrane (ITM) technology is an alternative to cryogenic air separation. • Integration of ITM with methanol production creates opportunities to improve efficiency, and reduce exergy losses. • Adequate heat is available from the hot synthesis gas stream to provide to the ITM process. [ABSTRACT FROM AUTHOR]

In this research work, N-Isopropyl-N-Phenyl-p-phenylenediamine (IPPD) and N,N′-Diphenyl-p-phenylenediamine (DPPD) are used as antioxidants for oxides of nitrogen (NO x) mitigation in a biodiesel-diesel blend run in a dual-fuelled compression (CI) engine. Five different antioxidant concentrations are selected for doping JME20, from 0 ppm to 2000 ppm at an interval of 500 ppm. A 4.4 kW rated power at 1500 rpm, four-stroke, single-cylinder, CI engine is modified to operate as a low heat rejection (LHR) engine. The LHR engine is formed by replacing the conventional piston with a YSZ + CeO 2 thermal barrier coated (TBC) piston. The combined effects of the antioxidant-doped biodiesel-diesel blend with oxy-hydrogen gas (HHO) gas are experimentally investigated on the LHR engine to study engine combustion, performance, and emission characteristics. The dual-fuelled LHR engine's combustion and performance characteristics are enhanced with the help of hydrogen combustion as compared to diesel data. The results of the engine run on the antioxidant-doped biodiesel-diesel blend reveal that a 3.13%, 6.24%, and 9.8% reduction in BSEC, EGT and NO emissions, respectively are noticed with JME20D 4 +HHO operation compared to JME20+HHO operation. [Display omitted] • This research work presents a characterization of amine antioxidants (IPPD and DPPD) and their usage in the LHR engine. • The doping of antioxidant additives to biodiesel-diesel blends results in a reduction of prompt NO emissions. • DPPD is determined as a potential amine antioxidant additive for the reduction of NO emissions. [ABSTRACT FROM AUTHOR]

Heat integration is a well-admitted technology to reuse the waste of different engines in different arrangements, relying on the principal needs. Considering the heat capacity of the flow released from the engine of a ship during maritime travel, heat integration is a promising tool to maintain the marine environment, along with processing some energy-related needs of the ship. This is a technology that is being developed based on which this study presents a new structure. In this regard, an innovative combined cooling and power (CCP) scheme using a dual-stage coolant production technology (bi-evaporator) for air-conditioning and freezing purposes is arranged and integrated into the engine. The proposed technology, which can provide one of the basic needs of a ship during maritime travel, i.e., freezing, has not been studied and optimized for a ship in previous studies. In addition, the arranged structure uses a multi-effect desalination coupled with the engine for cascade heat integration. First, the most suitable working fluid of the designed CCP was investigated using a comparative study. Afterward, based on the selected working fluid, the entire process was simulated and scrutinized in the engineering equation solver (EES) software from the viewpoints of thermodynamics, environment, economics, and sustainability. Eventually, this structure is optimized using a NSGA-II optimization method in the MATLAB environment. Here, the most suitable working fluid determined by the TOPSIS approach is R236ea, and the optimal unit cost of products and sustainability index are found as 0.7326 $/GJ and 1.335, respectively. [Display omitted] • An innovative heat integration for a 1-MW marine diesel engine. • Arranging a CCP-desalination process using bi-evaporator technology and MED. • Comparative study to distinguish the most suitable working fluid for the CCP unit. • R236ea is determined as the efficient working fluid by TOPSIS method. • The optimal SI total and TUCP are found at 1.335 and 0.7326 $/GJ by NSGA-II+TOPSIS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined effects of ZnO and 2nd generation biodiesel on diesel engine attributes. • The addition of ZnO compensated for poor combustion characteristic of biodiesel. • ZnO nanoparticles improved the performance characteristics of diesel engine. • Biodiesel blends can be increased through the addition of ZnO nanoparticles. • Employing sustainability assessment tools in the context of bioproducts and fuel additives is essential. To improve the fuel properties and enhance the overall characteristics of a diesel engine, the current work assesses the performance and combustion attributes of a diesel engine fueled by different blends of diesel, second generation biodiesel, and zinc oxide (ZnO) nanoparticles. The biodiesel was prepared using the transesterification of waste cooking vegetable oil. Zinc oxide nanoparticles were dispersed in diesel and biodiesel fuel blends at one dosage level of 50 ppm using ultrasonication process to prevent their agglomeration in the base liquid. The experiments were performed at different engine speeds (1700, 2000, 2300, 2600, 2900) RPM and full load operating conditions. The experimental results revealed that the addition of ZnO compensated for the poor combustion characteristic of biodiesel and hence promoted diesel engine performance and combustion attributes. The engine torque improved by 6.74, 4.9 and 3.69% while the BSFC reduced by 5.6, 6.44 and 2.5% for B0ZnO, B20ZnO and B40ZnO fuel blends compared to B0, B20 and B40 respectively at 2300 RPM. In addition, the engine heat release rate, ignition delay period and in-cylinder pressure were promoted. ZnO nanoparticles additives could be an effective approach for improving the combustion and performance characteristics in diesel engine applications. [ABSTRACT FROM AUTHOR]

Compression ignition (CI)-powered alternative energy sources are currently the main focus due to the constantly rising worldwide demand for energy and the growing industrialization of the automotive sector. Due to their difficulty of disposal, non-degradable plastics contribute significantly to solid waste and pollution. The waste plastics were simply dropped into the sea, wasting no energy in the process. Attempts have been made to convert plastic waste into usable energy through recycling. Waste plastic oil (WPO) is produced by pyrolyzing waste plastic to produce a fuel that is comparable to diesel. Initially, a standard CI engine was utilized for testing with diesel and WPO20 (20% WPO+80% diesel). When compared to conventional fuel, the brake thermal efficiency (BTE) of WPO20 dropped by 3.2%, although smoke, carbon monoxide (CO), and hydrocarbon (HC) emissions were reasonably reduced. As a result, nitrogen oxide (NOx) emissions decreased while HC and CO emissions marginally increased in subsequent studies utilizing WPO20 with the addition of 5% water. When combined with WPO20 emulsion, nanoadditives have the potential to significantly cut HC and CO emissions without impacting performance. The possibility of incorporating nanoparticles into fuel to improve performance and lower NOx emissions should also be explored. In order to reduce heat loss through the coolant, prevent heat transfer into the cylinder liner, and increase combustion efficiency, the thermal barrier coating (TBC) material is also coated inside the combustion chamber surface. In this work, low heat rejection (LHR) engines powered by emulsion WPO20 containing varying percentages of carbon nanotubes (CNT) are explored. The LHR engine was operated with a combination of 10 ppm, 20 ppm, and 30 ppm CNT mixed with WPO20. It was shown that while using 20 ppm of CNT with WPO20, smoke, hydrocarbons, and carbon monoxide emissions were reduced by 11.9%, 21.8%, and 22.7%, respectively, when compared to diesel operating in normal mode. The LHR engine achieved the greatest BTE of 31.7% as a result of the improved emulsification and vaporization induced by CNT-doped WPO20. According to the study's findings, WPO20 with 20 ppm CNT is the most promising low-polluting fuel for CI engines. [ABSTRACT FROM AUTHOR]

In this paper, the impact of the combustion chamber wall heat loss on the performance of the hydrogen-fueled precooled combined cycle Scimitar engine is investigated. Overall and exergy efficiencies, coefficient of ecological performance and coefficient of emission based ecological performance (C E E P) are considered as the performance indicators to analyze the effects of wall heat loss flux, chamber length, chamber contraction area ratio, throat area and nozzle convergent half angle. A multiobjective optimization is carried out to find the optimum values of hydrogen and air mass flow rates, cruise speed and altitude and core nozzle outlet area. It is found that a wall heat loss flux of 10 MW/m2 decreases the overall efficiency by 1.1% and causes an increase of 2 kJ/gNO x in C E E P. Multiobjective optimization revealed that increasing the hydrogen mass flow rate, decreasing the cruise speed and air mass flow rate improve the overall performance while the optimum values of cruise altitude and core nozzle outlet area are 23 km and 4.94 m2, respectively. The optimized design has a 20.35% better emission performance than the base design with a compromise of a 3.38% reduction in the overall efficiency. • Impact of combustion chamber wall heat loss on the engine's performance and multiobjective optimization is investigated. • A heat flux of 10 MW/m2 decreases overall efficiency by 1.1% and increases emission based performance by 2 kJ/gNO x. • Increasing hydrogen flow rate and decreasing air flow rate and cruise speed improve the engine's performance. • Optimum cruise altitude and core nozzle outlet area are 23 km and 4.94 m2. • Optimized design has 20.35% lower NO x emissions than the base design. [ABSTRACT FROM AUTHOR]

Intercooler heat exchangers (IHE) are used to improve engine charge air temperature, which enhances engine efficiency and reduces emissions. The current study introduces a novel intercooler heat exchanger designed to improve combustion and engine performance by providing cold intake air. Lamella heat exchanger is proposed, based on space availability in existing engines, operated as an evaporator utilizing a refrigeration unit, the same used for vehicle compartment cooling. A numerical investigation is carried out for a 1.496 L naturally aspirated engine at rpm 4000, 5000, and 6000. The intake air temperature is taken as 45 °C to examine the proposed four models: model A, model B, model C & model D bearing aspect ratios of 21.6 mm, 27 mm, 36 mm & 43.2 mm, respectively. The study aims to obtain high heat transfer with minimal pressure loss. For that, the evaluation criteria for all models are heat transfer, temperature drop, number of transfer units, logarithmic mean temperature difference, and pressure drop. As a result, all models under consideration are ranked from high to low; model D, model C, model B, and model A. The maximum heat transfer of 1.55 KW and the maximum temperature drop of 24.06 °C are observed for model D at rpm of 6000 and 4000, respectively. Likewise, the maximum pressure drop is recorded for model D at all rpm ranges; still, the pressure drop for model D is less than 28 % of the reference model used in this study at 6000 rpm. The simulated results indicate that all evaluation parameters except LMTD are directly proportional to the aspect ratio of the lamella. Due to their compactness, the proposed heat exchanger designs offer more surface area per unit volume, resulting in higher thermal capacity than the other conventional intercooler heat exchangers. [ABSTRACT FROM AUTHOR]

Quantum thermal machines are powerful platforms to investigate how quantum effects impact the energy flow between different systems. We here investigate a two-stroke cycle in which spin squeezing effects are intrinsically switched on during all the operation time. By using Kitagawa and Ueda's parameter and the ℓ 1 -norm to compute the degree of spin squeezing and the quantum coherence, we first show that the greater the spin squeezing effect, the greater the amount of coherence in the energy basis. Then, we investigate the engine performance given the amount of spin squeezing into the system. Our results show that even assuming an always-on spin squeezing, which is directly associated with the amount of entropy production in the cycle, it is possible to find a better set of efficiency and extracted power for the engine provided a high level of control over the relevant parameters, i.e., the operation time and the squeezing intensity. • A two-stroke engine is investigated from the spin squeezing point of view. • The best performance depends on the control on the squeezing degree. • The amount of quantum coherence along the cycle is related to the spin squeezing. [ABSTRACT FROM AUTHOR]

We study the behavior of a single spin in the presence of a time-varying magnetic field utilizing Glauber dynamics. We engineer the system to function as an engine by changing the magnetic field according to specific protocols. Subsequently, we analyze the engine's performance using various protocols and stochastic thermodynamics to compute average values of crucial quantities for quantifying engine performance. In the longtime limit of the engine cycle, we derive exact analytical expressions for work, heat, and efficiency in terms of a generalized protocol. We then analyze the model in terms of optimization of efficiency and power. Additionally, we use different protocols and employ a gradient descent algorithm to best fit those to obtain optimal efficiency and then optimal power for a finite cycle time. All the protocols converge to the piece-wise constant protocol during efficiency optimization. We then explore a more general approach using the variational principle to determine the optimal protocols for optimizing power and efficiency. During the optimization process for both power and efficiency, the net entropy production decreases, which enhances the engine's performance. This approach demonstrates the superior optimization of efficiency and power in this system compared to the gradient descent algorithm. • Microscopic heat engine. • Detailed Analytical study using Stochastic thermodynamics. • Optimization of power and efficiency. • Variational Optimization technique for optimal protocols. • Comparison of different optimization procedures. [ABSTRACT FROM AUTHOR]

• Phase-change heat transfer is comprehensively studied by molecular dynamics simulations and molecular level insights are provided. • The heat transfer coefficient is improved by 113 % via applying the external electrostatic field and modifying the surface with functional groups. • Low activation energy (∼10.0 kcal/mol) and high interfacial thermal conductance (∼99.0 MW/m2⋅K) collaboratively boost evaporative heat transfer. Understanding the mechanism behind phase-change heat transfer and designing new strategies to improve the heat transfer coefficient is crucial for numerous applications, such as heat engines, cooling, and steam generators. Here, we demonstrate the heat transfer coefficient at the Au surface can be improved by 113 % utmost via applying an external electric field (EEF) and modifying the surface with functional groups (FGs). This enhancement is found to be resulting from the fast vapor-liquid transition and high thermal conductance across the solid-liquid interface. On the one hand, the EEF decreases water-vapor phase transition activation energy and therefore increases the evaporation rate. On the other hand, introducing the FGs at the Au surface increases the interfacial adhesion and bridges the interfacial inter-medium vibrational couplings, leading to an increasing thermal conductance of Au/water interfaces. The vibrational coupling between water and the FGs is further increased by the EEF which complements the decreased influence of EFF on the water-vapor phase transition activation energy at high temperatures. Our work here provides a collaborative strategy to enhance phase-change heat transfer on surfaces which could be beneficial to its related applications. [ABSTRACT FROM AUTHOR]

Solar dish collector system are inevitably subjected to wind load leading to structural deformation, which will deteriorate its flux distribution and optical performance, how to realize the optical performance maintenance is particularly important. The methods of tracking compensation and receiver translational compensation are proposed for realizing the optical performance maintenance of dish collector systems (includes horn-cavity receiver for Stirling heat engine and cylindrical cavity receiver) under the combined action of self-weight and wind loads, and the maintenance effect is evaluated in detail using a large solar dish/Stirling system with 17.7 0 m diameter constructed by authors as a case study. Furthermore, the optical-thermal performance of a cylindrical cavity receiver before and after compensation is also comparatively analyzed. The results show that both compensation methods can significantly eliminate the unfavorable problems of local high flux, non-uniform circumferential energy distribution and optical intercept loss under service load, and the optical/thermal performance is very close to the ideal optical condition, which achieves excellent maintenance effect. Using the two compensation methods, the energy distribution maintenance factor E e of the cylindrical cavity receiver is significantly reduced from 0.12 to 0.17 to 0.01–0.06; for the horn-cavity receiver, the E e is reduced from 0.41 to 0.62 to 0.04–0.19, and the maximum energy difference within the four-quadrant region is reduced from 27.83 kW to only 4.86 kW at most unfavorable 45°–180° condition, which can effectively guarantee the safe and smooth operation of the Stirling heat engine. • Two compensation methods for optical performance maintenance under loads was proposed. • Optical/thermal performance indexes before and after compensation was analyzed. • Two compensation methods to bring optics/thermal close to ideal optical conditions. • Energy variance in horn-receiver reduce from 27.83 to 4.86 kW at worst condition. • Receiver output temperature increased 125 °C and wall temperature reduced 297 °C. [ABSTRACT FROM AUTHOR]

Hypersonic vehicles flying at high Mach numbers face severe aerodynamic heating on their outer surfaces. Active cooling is an effective thermal protection method. Convection cooling shows the best application prospects but lacks comprehensive research on its impact on vehicle performance. We propose a scramjet engine using ammonia-aviation kerosene dual fuels. Liquid ammonia's high heat sink efficiently cools the aircraft wall, and the recovered heat improves engine propulsion. In order to comprehensively evaluate the cooling effect and propulsion performance of the dual-fuel engine, a thermodynamic model of the dual-fuel scramjet engine was established, and the system performance when aviation kerosene, liquid ammonia, liquid hydrogen and water were used as coolants was also compared and analyzed. Results show the ammonia-kerosene dual-fuel engine has the highest specific thrust and total efficiency, with thermal protection second only to low-temperature liquid hydrogen. At the optimal blending ratio, the specific thrust is increased by 2–25 %; the cooling effect is improved by 15–35 %; and the required generalized heat exchange area is reduced by 40–60 %. In summary, the calculation shows that the dual-fuel engine with convection cooling has significant quality advantages and system-level advantages. The research results provide insights for the subsequent research direction of active convection cooling. • A dual-fuel scramjet engine/wall thermal protection coupling model was established. • Convective cooling has obvious quality advantages and system-level advantages. • The cooling effect of ammonia fuel is better than that of aviation kerosene. • Ammonia-kerosene dual-fuel engine have the highest specific thrust, total efficiency. • Active cooling can increase the maximum flight Mach number of the aircraft. [ABSTRACT FROM AUTHOR]

Heat pipe micro-reactors (HPMRs) with Stirling engines for power conversion are emerging as a promising surface power technology. We developed a comprehensive multi-physics solver using the open-source finite-volume code OpenFOAM to perform high-fidelity analysis of HPMR systems' steady-state and dynamic performance. The solver couples a 3D coarse-mesh multi-group neutron diffusion model with a 3D fine-mesh thermal conduction model using a mapping approach to accurately simulate multi-physics phenomena in the reactor core. Additionally, it integrates a 2D high-temperature heat pipe model as boundary conditions for heat transfer in the core, a 1D Stirling engine model for energy conversion, and a lumped parameter radiator model for heat dissipation. Applied to the HOMER-15 reactor system, the solver aided to identify the optimal working point of the system, achieving 3 kW of electric power with a conversion efficiency of 25.2 % under 20-Hz Stirling engine frequency and 3.34-MPa pressure. The transient full-scope simulation with the solver shows that the load-follow strategy based on gas charging and venting in Stirling engines is capable to accommodate 35 % step increase of external load. When the unexpected reactivity insertion is within 0.1$, the peak temperature in the reactor core is below the allowable limit temperature. Analysis of single failure of Stirling engines indicates that the system safety and reliability can be enhanced by either incorporating an appropriate number of engines or enhancing heat transfer between Stirling engine channels. • A high-fidelity full-scope solver is developed for HPMR with Stirling engines. • The optimal working point is identified based on steady-state analysis. • Dynamic analysis is performed for transient and accident conditions. [ABSTRACT FROM AUTHOR]

Freshwater serves as a vital energy source for ships, underscoring the paramount importance of research into desalination systems in facilitating diverse and reliable energy supply for maritime vessels. Aiming at numerous waste heat of marine engines and the shortage of freshwater resources on board, this paper designs an innovative waste heat recovery (WHR) system. It includes an organic Rankine cycle, a compression refrigeration cycle, and a humidification-dehumidification (HDH) desalination system to recover waste heat from exhaust gases in cascades, which can effectively produce power, cooling, and freshwater, respectively. A parametric study of the co-generation system in terms of the freshwater production, gained output ratio (GOR), cost per unit of freshwater production, net power output, and per unit of output power cost, are conducted to identify the key operating parameters. A set of operating parameters is determined for the HDH system with a temperature of the humidifier outlet of 358.15 K and a mass flow rate ratio (MR) of seawater to humid air of 4.5. The effect of the relative humidity and temperature of the humid air, as well as the salinity and temperature of the seawater, on the performance of the HDH subsystem are analyzed. And the optimal operating conditions of the co-generation system are obtained through multi-objective cuckoo search optimization. The results demonstrate that the co-generation system can produce an output-power of 1479.8 kW, 500 kW, and 0.49 kg/s for cooling and freshwater production by using the working-fluid R365mfc/Cyclopentane with a mixing ratio of 33:67 under optimal conditions. The GOR and cost per unit of HDH subsystem are 1.62 and 1.70 $/m3, with a capital payback period of 4.18 years. The equivalent output-power of the co-generation system is 9.5 % higher than that of an ORC system. [Display omitted] • Power, freshwater and cooling co-generation system are designed and optimization. • Productivity, GOR, and unit freshwater cost analysis of HDH systems are performed. • The performance of eighteen working-fluids is analyzed and compared. • Multi-objective cuckoo search algorithm is performed to find the optimal condition. [ABSTRACT FROM AUTHOR]

The energy-saving capabilities and efficient operation of marine low-speed diesel engines (MLDE) is a key emphasis for the main power source for ocean transportation. The purpose of the supercritical carbon dioxide recompression Brayton cycle (SCRBC) is to capture and utilise waste heat emitted by the engine's exhaust gas. However, the SCRBC performance will be severely affected by the large temperature fluctuations of ocean-going vessels during operation and high ambient temperatures in the cabin. A SCRBC model was built using the exhaust gas test data as the boundary conditions and validated using the Sandia National Laboratory (SNL) test data. The physical characteristics of the working fluids were evaluated by adding other fluids to CO 2 in specific proportions to modify the critical point and increase cycle efficiency. The results demonstrated that employing CO 2 -based binary working fluids with low alkane and hydrogen sulfide (H 2 S) enhanced the recovery power, with the most significant increase obtained by the addition of 16.48 % H 2 S, which increased the power by 9.72 kW and improved the Brayton cycle efficiency by 3.31 %. Compared to the MLDE at 100 % load, the total efficiency increased by 1.77 % and the BSFC decreased by 6.76 (g kW−1 h−1) using CO 2 -H 2 S as the working fluid. The analysis of the SCRBC system component exergy losses showed that the cooler had the highest exergy losses. Adding other fluids to CO 2 reduced the exergy losses of each component with the SCRBC system exergy losses decreasing from 162.97 to 129.90 kW and the exergy loss efficiency decreasing from 24.24 % to 22.65 %. The use of CO 2 -based binary working fluids specifically designed for ambient temperature may be expanded to other engines to enhance the efficiency of waste heat recovery. • Optimizing the SCRBC for marine low-speed engines by adding CO 2 -based mixing medium. • The compressor inlet temperature is controlled by the CO 2 -based binary mixed working fluids. • The composition of CO 2 -based binary mixture was selected optimize the cycle efficiency. • With 16.48 % H 2 S added, the Brayton cycle efficiency was improved by 3.31 % in 310K. • The exergy losses of each component were reduced by the addition of other fluids to the CO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Green hydrogen integration via wind power for commercial greenhouse. • Transitioning cogeneration from natural gas to hydrogen for electricity generation. • Nine scenarios analyzed for hydrogen production, transportation, blending and usage. • Evaluated levelized cost of hydrogen, IRR, payback, and discounted payback. • 10% hydrogen blend reduces levelized cost; 100% blend improves IRR and payback. This study investigates the feasibility of using green hydrogen technology produced via Proton Exchange Membrane (PEM) electrolysis powered by a 200 MW wind farm for a commercial Greenhouse in Ontario, Canada. Nine different scenarios are analyzed, exploring various approaches to hydrogen (H 2) production, transportation, and utilization for electricity generation. The aim is to transition from using natural gas to using varying combinations of H 2 and natural gas that include 10 %, 20 %, and 100 % of H 2 with 90 %, 80 %, and 0 % of natural gas, to generate 13.3 MW from Combined Heat and Power (CHP) engines. The techno-economic parameters considered for the study are the levelized cost of hydrogen (LCOH), payback period (PBT), internal rate of return (IRR), and discounted payback period (DPB). The study found that a 10 % H 2 -Natural Gas blend using existing wired or transmission line (W-10H 2) with 5 days of storage capacity and 2,190 h of CHP operation per year had the lowest cost with a LCOH of USD 3.69/kg. However, 100 % of H 2 using existing wired or transmission line (W-100H 2) with the same storage and operation hours revealed better PBT, IRR, and DPB with values of 6.205 years, 15.16 % and 7.993 years respectively. It was found impractical to build a new pipeline or transport H 2 via tube trailer from wind farm site to greenhouse. A sensitivity analysis was also conducted to understand what factors affect the LCOH value the most. [ABSTRACT FROM AUTHOR]

The increasing demand for sustainable energy solutions has driven research into improving the efficiency and emission profiles of biodiesel-powered engines. This study aimed to enhance the performance and emission characteristics of a low heat rejection (LHR) engine by incorporating a natural antioxidant (NA) additive derived from Albizia lebbeck leaves into a soybean methyl ester (SBME20) biodiesel blend. The primary objective was to determine the optimal concentration of NA that would improve engine efficiency while reducing harmful emissions. The NA was prepared through a process of drying, grinding, and solvent extraction, and then blended with SBME20 biodiesel at concentrations of 500 ppm, 1000 ppm, 1500 ppm, and 2000 ppm. The physical properties of these blends, such as viscosity, calorific value, density, cetane number, flashpoint, and fire point, were measured according to ASTM standards. Performance and emissions testing was conducted using a single-cylinder, four-stroke diesel engine equipped with partially stabilized zirconia (PSZ)-coated components to assess various loads. The results revealed that the blend with 1000 ppm NA achieved the best overall performance, exhibiting the lowest brake-specific fuel consumption (BSFC) at 0.38 kg/kWh and the highest brake thermal efficiency (BTE) at 32 %. Furthermore, the exhaust gas temperature (EGT) was reduced, indicating more efficient combustion. Emission measurements showed a 15 % reduction in carbon monoxide (CO), a 10 % decrease in hydrocarbon (HC) emissions, a 12 % reduction in nitrogen oxide (NOx) emissions, and a 20 % decrease in smoke opacity when compared with the base SBME20 blend. The novelty of this research lies in the application of a natural antioxidant additive from Albizia lebbeck to enhance biodiesel's performance and emission characteristics in LHR engines. Incorporating 1000 ppm NA in SBME20 biodiesel offers a sustainable and efficient alternative for compression ignition engines. Further research is suggested to evaluate long-term effects and scalability for broader industrial applications. [Display omitted] • Optimal 1000 ppm NA blend in SBME20 improves engine efficiency and reduces emissions. • 1000 ppm NA blend achieves lowest BSFC of 0.38 kg/kWh and highest BTE of 32 %. • CO emissions reduced by 15 %, HC by 10 %, NOx by 12 %, and smoke opacity by 20 %. • Enhanced combustion efficiency and stability observed with PSZ coating in LHR engine. • Further research suggested the long-term effects and scalability of NA additives. [ABSTRACT FROM AUTHOR]

This paper presents the results of simulations of a supercritical CO2 system integrated with a 180 kW nominal power piston engine. The sCO2 system consists of a compressor, expander, and four heat exchangers. The analysis delivered the optimum operating point of the system, where the sCO2 system generates an extra 18.03 kW. The main research was oriented into generation of off-design characteristics of the system, where sCO2 system were subjected to varying engine load and the system response was analyzed. The results of the calculations refer to the nominal point of the system and are given as maps of parameter changes normalized to the nominal point. The supercritical CO2 system itself is not controlled (only the speed of the turbomachinery is kept constant), while the power of this system depends on the current state of the reciprocating engine and directly influences the amount and temperature of the exhaust gases fed to the heater. The study revealed that the sCO2-biogas piston engine hybrid system would benefit from extra power generated by sCO2 when the engine operates with at least 60 % of its nominal power. [Display omitted] • Integration of sCO2 Cycle with Reciprocating Engine: The study investigates the integration of a supercritical CO2 cycle with a 180 kW reciprocating engine for waste heat recovery. • Off-Design Performance Analysis: Detailed simulations are conducted to evaluate the system's off-design performance, focusing on varying engine loads and biogas composition. • Energy Recovery Efficiency: The sCO2 system is shown to recover approximately 10 % of the engine's nominal power output, demonstrating its effectiveness in energy recovery. • Sensitivity to Operational Conditions: The study reveals that system performance is significantly affected by engine load and the methane content of the biogas, offering insights for optimization. • Implications for Sustainable Energy: The research contributes to the development of sustainable energy technologies by providing a novel approach to enhancing energy efficiency in existing power systems. [ABSTRACT FROM AUTHOR]

As the greenhouse effect intensifies, ammonia is garnering increasing attention as a carbon-free fuel. In the transport sector, ammonia-diesel dual-fuel (ADDF) engines are regarded as an effective means of reducing carbon emissions. The objective of this study is to investigate the combustion and emission optimization of an ADDF engine under high load conditions. To this end, an experimental optimization study of different start of diesel injection timing (SODI) and exhaust gas recirculation (EGR) rates was conducted at a load of 18 bar and an ammonia energy ratio of 80 %. The mechanism of heat capacity, dilution, and chemical effects of EGR was also revealed by numerical simulation based on the separated variables method. It was demonstrated that advancing SODI is effective in enhancing combustion efficiency. However, this approach is limited by the upper limit of in-cylinder pressure and results in higher nitrogen oxides (NO x) emissions, which can be mitigated by the EGR. The heat capacity effect of EGR increases the specific heat capacity and decreases the average temperature. The suppression of the combustion process leads to a reduction in thermal and fuel NO x , but an increase in nitrous oxide (N 2 O) emissions. The dilution effect of EGR results in insufficient oxygen, which decreases the heat release rate and combustion efficiency. Additionally, the NO x and N 2 O are significantly reduced. The chemical effect of EGR affects reactive groups and unburned components that accelerate heat release rate and increase accumulated heat release, resulting in significantly higher NO x. The comprehensive effect of EGR results in a decrease in N 2 O emissions and a significant reduction in thermal and fuel NO x. The EGR and further optimization of SODI enabled the ADDF engine to achieve a gross indicated thermal efficiency of 48.5 % with a load of 18 bar and an ammonia energy ratio of 80 %. In addition, NO emissions were reduced by 32.8 percent and greenhouse gas emissions by 63.3 percent. • Under high loads and high RAE, ADDF engines are limited by maximum pressure. • Heat capacity, dilution and chemical effects of EGR were investigated. • The effect of EGR on thermal-NO x and fuel-NO x was analyzed. • The higher the EGR rate, the greater the range of SODI optimization. [ABSTRACT FROM AUTHOR]

• A splitting organic Rankine cycle prototype is established. • Experiment proof that there is a splitting ratio that maximizes the performance. • Compared to single-loop ORC, splitting ORC's performance increases by 8.3%. • Splitting configuration has been proven feasible in improving system performance. The organic Rankine cycle (ORC) is an effective method for internal combustion engines' waste heat recovery. The waste heat from internal combustion engines primarily includes exhaust gas and engine cooling water. However, single-loop preheating and dual-loop ORC configurations are difficult to balance the recovery efficiency of the dual heat sources and the complexity of the equipment. The splitting ORC, as an effective method for enhancing the utilization of waste heat sources, has been proposed. This study developed for the first time a test bench for a splitting ORC with a recuperator (SR-ORC) for internal combustion engines' waste heat recovery, aiming to verify the enhancement effect of the system's performance by splitting the working fluid into two branches to recover the engine cooling water and exhaust gas waste heat respectively. The research results indicate that there exists an optimal working fluid pump speed and splitting ratio to maximize the net output power and efficiency of the system. Moreover, under the engine condition of rotating speed of 1100 rpm and torque of 600 N·m, the system achieves a maximum net power output of 2.81 kW, a maximum internal combustion engine efficiency improvement of 1.6 %, and a maximum thermal efficiency of 10.1 % at the maximum heat source safety operating range. Compared to the non-splitting mode of this test bench with the same engine and heat source condition, these values represent a relative improvement of 8.3 %, 9.6 %, and 27.9 %, respectively. [ABSTRACT FROM AUTHOR]

This study investigates acoustic impedance matching between a thermoacoustic Stirling heat engine and a branch liquid column, using multiple regenerators. We characterize acoustic impedances at both the engine and liquid column load ends using thermoacoustic theory, expressed as functions of frequency and temperature differences across regenerators. The intersection points of these functions indicate matched impedances, critical for evaluating the engine's operating points. Notably, this study emphasizes the impact of a vibrating membrane on the system's acoustic impedance, highlighting its significant role in modulating acoustic states and facilitating self-sustained oscillations. To verify our theoretical models, we conducted experiments with the proposed fluidyne engine under various liquid column volumes. The verifications confirmed our simple calibrations for characterizing a vibrating membrane clamped in the engine and the oscillating liquid columns. Significantly, the acoustic compliance and inertance effects respectively introduced by the membrane and liquid columns enable us to modulate the engine's acoustic states. The proposed configuration is named a thermoacoustic Stirling fluidyne. This fluidyne, a heat engine that outputs work power using a liquid piston, achieves a markedly higher acoustic impedance than the pure gas case while maintaining traveling wave phasing for the regenerators. • Introducing a flexible design in the fluidyne-style thermoacoustic Stirling engine. • Utilization of a vibrating membrane coupled with oscillating liquid columns for improved acoustic modulation. • Attainment of remarkably high acoustic impedance, while efficiently preserving the traveling wave phasing within regenerators. [ABSTRACT FROM AUTHOR]

This study presents calculations of a multiparticle system within the framework of fractional quantum mechanics. We specifically explore the energy levels of a bosonic system with repulsive interactions confined in a hard-wall box. The impacts of fractional parameters on the system's thermodynamic properties are meticulously analyzed. Furthermore, utilizing this model, we construct a quantum Otto cycle and discover that the system exhibits Bose–Fermi duality under varying fractional parameters. Intriguingly, the introduction of fractional parameters enables to optimize the performance of the quantum heat engine, edging it closer to the Carnot efficiency. • A method is discovered to solve multiparticle systems in fractional quantum mechanics. • Thermodynamic behavior of fractional Bose gas is analyzed under varying fractional parameters. • An Otto heat engine is built, showcasing Bose-Fermi duality in fractional systems. • Fine-tuning fractional parameters greatly enhances the Otto heat engine's efficiency. [ABSTRACT FROM AUTHOR]

With ever increasing fossil fuel price and growing demands in cutting emissions, waste heat recovery (WHR) appears as a promising pathway to improve propulsion system performance, which can be potentially achieved by incorporating a recuperator. This paper explores the advantages and potentiality of further recovering exhaust heat from recuperated turboshaft engine through the concept of organic Rankine cycle (ORC) to improve fuel economy and thermal efficiency. For the intended application, working fluid selection is conducted after systematic consideration of thermophysical properties, environmental impact, health and safety issues. Furthermore, parametric analysis is carried out from the viewpoint of thermodynamics, and the genetic algorithm is also employed to obtain the maximum net power output. Targeting the implicit coupling between recuperator effectiveness and ORC performance, the potential advantages of the combined engine-ORC system are comprehensively evaluated at different operational regimes. The influence of flight condition is also discussed through sensitivity simulations for different altitudes. Results reveal that the combination of the recuperated engine with ORC cycle operated using acetone generally offers the greatest benefits, significantly reducing specific fuel consumption by 46%–59 % relative to the baseline simple-cycle engine, depending on the availability of heat source. This analytical work contributes to provide valuable insights into WHR technologies in the aviation industry. • ORC is proposed to recover exhaust heat from turboshaft engine with a recuperator. • Working fluid selection procedure suitable for aeroengine is conceived and applied. • Parametric investigation is conducted and GA is employed for optimization. • System performance is comprehensively evaluated at different operational regimes. [ABSTRACT FROM AUTHOR]

Triggered by the pressing need to enhance the power conversion efficiency of photovoltaic systems, this work introduces a novel hybrid system that combines a concentrated photovoltaic cell (CPV) with a thermolytic pressure retarded osmosis heat engine (PRO). This innovative integration allows for the efficient recovery and conversion of waste heat from CPV into additional electricity, addressing the challenge of high-output dependence on lower operating temperatures. A detailed theoretical model of the system is developed to ultimately derive and analyze the mathematical expressions for key performance indicators. Numerical analysis confirms that the novel system achieves a maximum power density, energy efficiency, and exergy efficiency of 239.28 W m−2, 13.9 %, and 14.6 %, respectively, which are improved by 13.06 % over a sole concentrated photovoltaic cell. Comprehensive sensitivity analysis is conducted to obtain optimal selection criteria for crucial parameters including inlet concentration, concentration ratio, operating temperature, and diode ideality factor, which have a significant impact on overall performance. Comparative analysis shows that the CPV-PRO system outperforms existing CPV hybrids in terms of lower operational temperatures and enhanced economic viability, making it a superior choice for sustainable energy production. • Proposing a novel CPV-driven thermolytic PRO heat engine. • Mathematical formulation of performance indicators for the coupled system. • Achieving energy and exergy efficiencies of 13.9 % and 14.6 %, respectively. • Realizing a 13.06 % efficiency improvement over the standalone CPV system. • Conducting in-depth sensitivity analysis of key performance parameters. [ABSTRACT FROM AUTHOR]

• Laminar combustion characteristics of propyl acetate were studied. • The burning flux increased with increasing initial pressures and temperatures. • Empirical correlations were established to predict the burning velocity at elevated conditions. • Burning velocity at 8 bar and 534 K were obtained for propyl acetate. Since propyl acetate has the potential to be used as a biofuel in heat engines, it is necessary to ascertain and comprehend its combustion properties. Using equivalence ratios of 0.7–1.4, the laminar burning velocity of propyl acetate was studied in the constant volume combustion vessel at the initial pressures of 1, 2, and 4 bar and initial temperatures of 390 K, 420 K, and 450 K. The constant volume method was used to determine the burning velocity via extrapolations at the initial condition. In addition, a ten-fitted empirical correlation was formulated to calculate the burning velocity for pressures and temperatures as high as 8 bar and 534 K, respectively. The extrapolated burning velocity showed good agreement with the numerical simulation burning velocity, and the correlated burning velocity agreed well with the extrapolated burning velocity. The laminar burning flux was also investigated and was ascertained that laminar burning flux increases as the initial pressure and temperature increase. The fuel mixture density significantly influences the burning flux as the initial pressure rises, whereas the laminar burning velocity has a notable impact on the burning flux as the initial temperature rises. In summary, this study advances our knowledge of propyl acetate combustion, particularly concerning its flame propagation at higher pressures and temperatures and its potential application in combustion engines, and the data are of great engineering value for developing and understanding the combustion science of propyl acetate. [ABSTRACT FROM AUTHOR]

The control system is an important component of a gas engine-driven heat pump (GHP). Recent studies conducted on GHPs focus on the model construction and optimization, while neglecting the control system. This study proposes an embedded control system to monitor GHP cold–hot water equipment (GHPW). The accuracy of the control system and strategy was verified. Additionally, the operational characteristics of GHPW system based on the control system were discussed through cooling and heating experiments. The experimental results demonstrated that double closed-loop control of the engine speed and evaporator superheat via the main controller ensured stable and accurate outlet water temperature control in the GHPW system. The heating capacity of the heat pump was increased from 42.37 to 75.2 kW in the heating mode with a gradual increase in the engine speed from 1200 to 2400 rpm, while the heating capacity of the experimental system was increased from 56.18 to 105.87 kW. The waste heat recovery of the engine significantly improved the system heating capacity and primary energy ratio (ratio of GEHP heating capacity to natural gas consumption power). Additionally, the GHPW system improved energy saving. The circuits and control strategy proposed in this study are simple and easy to implement. The control system improved the performance of GHPs and reduced the peak power load during summer. [ABSTRACT FROM AUTHOR]

In this study, a novel marine diesel engine waste heat recovery layout is designed and thermodynamically analyzed for hydrogen production, electricity generation, water desalination, space heating, and cooling purposes. The integrated system proposed in this study utilizes waste heat from a marine diesel engine to charge an organic Rankine and an absorption refrigeration cycle. The condenser of the Organic Rankine Cycle (ORC) provides the heat for the single stage flash distillation unit (FDU) process, which uses seawater as the feedwater. A portion of the produced freshwater is used to supply the Polymer Electrolyte Membrane (PEM) electrolyzer array. This study aims to store the excess desalinated water in ballast tanks after an Ultraviolet (UV) treatment. Therefore it is expected to preclude the damage of ballast water discharge on marine fauna. The integrated system's thermodynamic analysis is performed using the Engineering Equation Solver software package. All system components are subjected to performance assessments based on their energy and exergy efficiencies. Additionally, the capacities for power generation, freshwater production, hydrogen production, and cooling are determined. A parametric study is conducted to evaluate the impacts of operating conditions on the overall system. The system's overall energy and exergy efficiencies are calculated as 25% and 13%, respectively, where the hydrogen production, power generation, and freshwater production capacities are 306.8 kg/day, 659 kW, and 0.536 kg/s, respectively. Coefficient of Performance (COP) of the absorption refrigeration cycle is calculated as 0.41. • A novel onboard multigeneration WHR system for ships is proposed. • The freshwater is stored in ballast tanks after thermal treatment to preserve marine fauna. • The effects of different parameters on the system outputs are investigated. • Over 300 kgH 2 /day production capacity is achieved for H 2 added fuel use. [ABSTRACT FROM AUTHOR]

Osmotic heat engines have attracted increasing attention in harvesting ultra-low temperature waste heat. In order to fill the gap in the high-throughput computational screening of adsorbent-aqueous salt solution working pairs for adsorption-driven osmotic heat engines, an experimental water adsorption isotherm database is constructed and eight common salt-water solutions are selected to identify the high-performance work pairs with system energy efficiency as evaluation indicator. The relationship between adsorbent properties, adsorbent structure characteristics and system performance is systematically analyzed. Results revealed that high working capacity and moderate adsorption enthalpy of adsorbents and large osmotic coefficients of salts are beneficial to energy efficiency. Adsorbents with larger accessible surface area, moderate available pore volume and critical pore diameter are favorable. Furthermore, regression machine learning is employed for achieving fast and accurate prediction of the system energy efficiency to accelerate screening. Genetic algorithm is adopted to search for the best-performing working pair properties. [ABSTRACT FROM AUTHOR]

Conventional submarines produced to date can be more easily detected and exposed to attacks due to their visible, infrared, and radar signatures. Diesel-electric submarines need to come to a close surface at certain time intervals to charge their batteries and power their diesel generators with snorting systems. This situation causes submarines to face threats from land, sea, and air war elements. In order to reduce these threats, it is clear that there is a need for an innovative system in which the need for submarines to the surface is minimized and the timing of emergence is more flexible. To ensure this situation, air-independent propulsion systems have come to the fore from past to present and have gained more and more strategic importance. These air-independent systems significantly improve silent underwater time, and maneuverability and greatly contribute to maintaining the submarine's military stealth strategy. In this context, in this study, six different power system alternatives used as air-independent propulsion (AIP) submarine systems were evaluated, their advantages and disadvantages were compared, and alternatives were sorted by five experts in terms of nine important technical and economic criteria with the fuzzy VIKOR method. It has been seen that the propulsion power with the fuel cell system comes to the fore. The choice of a high power density fuel cell system for a submarine AIP system can allow for superior underwater range and durability and a minimal rate of instability and thermal signature than would be achievable from any heat engine. This will greatly expand the strategic advantage of AIP submarines. In this respect, this article can be a guide in understanding the critical technical features of submarines and in deciding between alternatives in submarine system selection. • Emphasis was placed on the importance of air-independent propulsion systems for submarines. • Six different air-independent submarine power systems are introduced and evaluated. • Nine important technical and economic criteria were examined with the help of five experts in the field. • The optimal air-independent propulsion system was selected as the fuel cell system. [ABSTRACT FROM AUTHOR]

To reuse the exhaust heat produced by molten hydroxide direct carbon fuel cells (MHDCFCs), a new combined system mainly composed of an MHDCFC, a regenerator, and a Stirling heat engine (SHE) is theoretically integrated for fuel-to-power efficiency enhancement. Mathematical formulas of the performance indicators for the combined system are derived based on the first and second laws of thermodynamics, from which the feasibility and effectiveness of the combined system are evaluated from both energetic and exergetic viewpoints. Moreover, the optimum working regions of the combined system are further specified by using a multi-objective function paying equal attention to both efficiency and power output. Results show that SHEs can be effectively acted as bottoming cycles for MHDCFC for additional mechanical power production. Numerical calculations indicate that the maximum power density and its corresponding energy efficiency and exergy efficiency of the proposed system are, respectively, about 97.6%, 97.1% and 99.2% greater than that of the single MHDCFC. Furthermore, extensive parametric studies show that increasing working temperature, volume ratio, hot-side working substance temperature or mean pressure is beneficial for the overall system performance, while increasing reactor compartment width may degrade the overall system performance. [ABSTRACT FROM AUTHOR]

• A fine powder increases the specific surface area of the powder and the laser absorptivity, thus reducing the minimum energy required to melt the pure copper powder. • The ultimate tensile strength is 18 % higher than the highest ultimate tensile strength that has been reported so far. • Precise control of process parameters, especially laser power and hatch spacing, can significantly enhance the mechanical properties of pure copper parts, with the optimal specimens exhibiting an average grain size of 3.6 µm. Pure copper is widely used in motor windings, heat exchangers and aerospace engines because of its high electrical and thermal conductivity. High-strength laser powder bed fusion (HS-LPBF) not only allows rapid production of components with complex geometry and high spatial resolution, but also offers various advantages such as small focal spot diameter, fine powder, and small layer thickness, providing advantages for forming complex structural parts in fields such as engines and heat exchangers. A single factor single layer experiment was performed by varying the hatch spacing (H), and the range of hatch spacing was determined according to the overlap rate. The degree of influence of process parameters on the relative density of pure copper specimens was analyzed using an orthogonal experiment, and a comparative study of the phase composition, microstructure and mechanical properties of pure copper specimens was carried out by varying the laser power. The characteristics of pure copper formed by HS-LPBF were analyzed. In addition, the effect of heat treatment on the microstructure and mechanical properties of pure copper specimens was investigated, and the fracture morphology of the specimens was observed comparatively. The results show that the HS-LPBF technique can effectively increase the energy density and improve the specific surface area of the powder and the laser absorptivity due to its small focal spot diameter, fine powder and layer thickness, thus reducing the minimum energy required to melt pure copper powder. The optimum process parameters were obtained by orthogonal experiment with a relative density of 98.1 % of the specimen. The highest hardness, ultimate tensile strength and elongation were obtained at a laser power of 260 W with 84 HV, 320 MPa and 17.8 %, respectively. This ultimate tensile strength is 18 % higher than the highest ultimate tensile strength that has been reported so far. In addition, the average grain size of the optimal specimens was 3.6 µm. Mechanical properties such as hardness, tensile strength and elongation of pure copper parts can be significantly improved by precisely controlling the process parameters, in particular laser power and hatch spacing. [ABSTRACT FROM AUTHOR]

At extremely high Mach number (Ma ≥8), kerosene is faced with issues of cracking with a limited heat sink for regenerative cooling. Supercritical CO 2 can be used as additional cooling method for regenerative cooling because of its excellent heat and mass transfer capability and it can easily convert heat into electricity for the engine electric system. In this study, pin-fins are applied to a regenerative cooling channel using sCO 2 to further enhance heat transfer at extremely high heat flux. Heat transfer and fluid flow are analyzed by the k-ω SST model considering effects of pitch ratio, solid materials and accelerations. From this study, compared with a smooth cooling channel, the pin-fin channel (Case 3) obtains a heat transfer enhancement of 3.08, a friction factor of 4.66, thermal performance enhancement of 1.84, and the maximum temperature of the heated surface is decreased by 36 % at Re = 45,000. The maximum velocity is found at the near-wall regions determined by the combined effects of temperature difference and accelerations. When the channel material is Cu with the high thermal conductivity, the maximum temperature is decreased by 37 % compared with a steel channel and the temperature distribution also becomes more uniform. • Supercritical CO2 is introduced to regenerative cooling. • Pin-fin structures are applied further enhance heat transfer. • Heat transfer enhancement by 3.08 and maximum temperature decreased by 36 %. [ABSTRACT FROM AUTHOR]

Coupling advanced systems with carbon dioxide (CO 2) capture and CO 2 -to-methanol technologies is a possible solution for both greenhouse gas emissions and low-carbon use of fossil energy. In view of this, this study further develops an advanced molten carbonate fuel cell (MCFC)/steam turbine (ST) hybrid system. The existing single pressurized liquefaction for storing CO 2 is expanded to co-exist with liquid methanol synthesis for storing CO 2. In detail, the valid thermodynamic models are presented, and the evaluation criteria for energy conversion are described. The case study shows that the energy efficiency of the referenced MCFC/ST system reaches about 62.60 %, without cutting down this performance, the photovoltaic methanol efficiency is in the range of about 54 %–63 %, which is at a current leading level. This study also investigates the effect of oxygen purity in cryogenic air separation unit (ASU), hydrogen production pressure of proton membrane electrolytic cells (PEMEC), and incident irradiation on CO 2 -to-methanol conversion. The results indicate that O 2 purity of 0.97 in ASU, H 2 production pressure of 13.6 bar in PEMEC and a dual-axis tracking method is recommended. These findings provide theoretical guidance for improving the CO 2 -to-methanol performance and providing a possible solution to the storage of intermittent renewable electricity. • Solar-driven CO 2 -to-methanol process couples carbon capture with carbon sequestration. • Solar methanol efficiency of 54 %–63 % is gained without reducing fuel performance. • Combining PEMEC and MCFC/ST system gives a solution to store intermittent solar power. • A new approach to purifying methanol is proposed by using low-grade steam extraction. • More or all captured CO 2 can be liquid methanol rather than pressurized liquefaction. [ABSTRACT FROM AUTHOR]

Traditional windows have poor thermal insulation performance, resulting in significant indoor heat loss in winter and outdoor heat entry in summer. Thermochromic smart windows can effectively block solar radiant heat by automatically adjusting light transmittance, thereby reducing air conditioning loads and leading to significant energy savings. In this study, the poly N-isopropyl acrylamide (PNIPAm)-based thermochromic hydrogel, modified MXene nanoparticles, and Ni Ti shape memory alloy (SMA) are integrated to endow the smart window with heat storage, temperature control, and ventilation. The smart window achieves 88.6% visible light transmission and 70% solar modulation. The inclusion of MXene nanoparticles further enhances photothermal response efficiency, while the ventilation system ensures efficient and fresh indoor air circulation. Compared to the common glass, the smart window reduces the indoor temperature by 8 °C, demonstrating its excellent temperature regulation ability. Simulation results indicate that in Shanghai, Cairo, Singapore, and Kuwait, the employment of thermochromic smart windows can reduce heating, ventilation, and air conditioning energy consumption (HVAC) by 32.6%, 49.9%, 42.7%, and 34.1%, respectively. This versatile thermochromic smart window is expected to significantly improve building efficiency and occupant comfort, offering a sustainable solution for future building designs. • PAA/PEG/MXene increased the smart window temperature by 8.3°C. • Intelligent windows enable ventilation, thermoregulation and heat storage. • The solar modulation function is realized to reduce indoor temperature effectively. • Intelligent window systems effectively reduce building energy consumption. • The combination of a heat engine and thermochromic intelligent windows was realized. [ABSTRACT FROM AUTHOR]

Earth's climate underwent secular structural evolution and cooling since the Pliocene Warmth, punctuated by increasing thermal gradients between the Western Pacific Warm Pool (WPWP) and the surrounding cooler regions of Eastern Pacific Cold Tongue and extra-tropics. One key mechanism for deciphering the climate evolution since Pliocene is the shoaling of the ocean thermocline, but much remains unknown about the upper-water structure of the western Pacific Warm Pool, the heat engine of the climate system, and its linkage to global ocean circulations. Here, by a newly made series of millennial-resolved δ18O and δ13C records of paired mixed-layer and thermocline dwelling planktonic foraminifera from IODP Site U1489 drilled in the center of WPWP, the trends of cooling and respired carbon content decreasing in the WPWP thermocline since ∼4 Ma are revisited and diagnosed. Our data allows us to propose that, the tropical Pacific upper-water circulation cell had shoaled and shrunk and the vertical mixing from deeper waters may have increased, since the Pliocene. Development towards a modern-style Warm Pool was initially onset at ∼3.1 and finalized at ∼0.7 Ma, respectively. • The Western Equatorial Pacific thermocline shoaled and cooled since the Pliocene Warmth. • Key shifts of the Western Equatorial Pacific thermocline structure at ∼3.1 and ∼0.7 Ma. • The Pacific Shallow meridional overturning circulation shrunk and shifted equatorward since Pliocene. [ABSTRACT FROM AUTHOR]

Absorption carbon capture is currently the most commercialized technology and deemed as the vital solution to balance continued use of fossil fuels and carbon emission reduction. Nevertheless, its high energy cost remains the major concern for wide-scale application. Consequently, it is of great significance to address this issue by analyzing the underlying energy conversion mechanism, answering the pivotal question "What characteristics lead to a superior absorbent?", and developing more efficient absorbent. In this paper, an irreversible decoupling model of absorption carbon capture system, consisting of a heat engine and a chemical pump, is innovatively established. Accordingly, key performance indicators are analytically derived and the optimal operation strategies of the system are explicitly determined. Notably, the matching of two subsystems leads to a novel insight into the heat and mass transfer interaction of absorbent, according to which the simulated results and the question concerning the best absorbent are thermodynamically interpreted and addressed, respectively. Additionally, the comparisons between the calculated optimal energy conversion efficiencies with experimental and simulated results are presented and discussed. Our findings may indicate the efficient pathway for developing advanced absorbent and provide instructing information for the design and operation of practical carbon capture systems. [Display omitted] • An irreversible decoupling model of absorption carbon capture system is established. • Optimal energy conversion efficiency and parameters are analytically derived. • A new insight into the heat and mass transfer interaction of absorbent is provided. • Theoretical answer to the pivotal question concerning optimum absorbent is obtained. • Optimal absorbent selection criteria and operation regions are determined. [ABSTRACT FROM AUTHOR]

The present work focuses on vessel engine waste heat recovery (WHR) architectures for cooling, heating and power production based on the combination of an Organic Rankine Cycle (ORC) and a thermally assisted ejector cooling cycle-vapor compression cycle (EVCC), integrated into an ORC-EVCC. Their advantages and disadvantages are analyzed and their performance is evaluated using numerical models developed according to boundary conditions corresponding to a vessel diesel engine WHR micro-scale (100 kW th thermal input) application considering R1233zd(E), R1234yf and R1234ze as working fluids. Ultimately, a parallel ORC- parallel/serial EVCC layout operating with R1233zd(E) is determined as the most promising configuration, considering its superior thermodynamic performance and practical aspects (simplicity, space and weight requirements and cost). The ORC and EVCC are integrated in parallel and operate with the same fluid. Furthermore, the EVCC compressor and ejector are connected in a parallel/serial layout. Under the design point, the net power output of the system is 10.30 kW e in electricity-only mode and 7.68 kW e in CHP mode. In CHP mode, the heating output is 88.97 kW th. In the two cooling modes, electricity and cooling are produced simultaneously by the ORC and EVCC, respectively. The cooling output ranges between approximately 4.48 and 7.82 kW c. [ABSTRACT FROM AUTHOR]

Due to the scarcity of fossil fuels and the potential for energy shortages, the use of energy-efficient devices is of utmost importance. There is an increasing trend in the utilization of heat pumps in air conditioning systems (heating/cooling) for both residential and commercial buildings. This article focuses on the analysis of the technical and economic aspects of gas engine heat pumps (GEHP) in various climates throughout Iran. The evaluation of this article revolves around two perspectives: that of the consumers and the government. The implementation of GEHP has been carefully considered from the consumers' perspective to ensure it does not have any negative effects on them. Additionally, from the government's point of view, the available resources are considered, and the supply of electricity and gas, along with their cost and energy consumption, are thoroughly investigated by the Ministries of Energy and Petroleum. The findings indicate that, from the consumers' perspective, the economic efficiency of GEHP can be up to 11 times higher than that of electric heat pumps (EHP). Moreover, from the government's viewpoint, GEHP leads to a reduction of over 92 % in electricity consumption, 5 % in gas consumption, and 92 % in annual expenses for the Ministry of Energy. Furthermore, the implementation of GEHP increases the income of the Ministry of Petroleum by 9.8 times. • Gas engine heat pumps (GEHPs) proposed to address electricity grid imbalance in Iran. • Consumer and government benefits of GEHPs across diverse Iranian regions analyzed. • Results show GEHPs reduce electricity consumption & costs for the Ministry of Energy. • GEHPs decrease gas consumption & boost revenue for the Ministry of Petroleum. [ABSTRACT FROM AUTHOR]

One of the main problems in current numerical and simulation methodologies, for optimizing the demand-generation of electricity by concentrating solar power plants, is the lack of thermodynamic parameters which involves the non-equilibrium energy conversion. In this work, the fundamentals of heat transport and energy conversion features are exposed, within the context of the Finite-Time Thermodynamics. From a radiative–conductive heat engine model, three real-world solar concentrating power plants are analyzed, by characterizing some of their less dissipative operation modes via a generalized thermodynamic function called k —efficient power, since it leads us to establish general trade-offs between the operation modes and internal/external design features of indirect solar power systems. Two ways to establish the optimization are defined as follows: The energy reconfiguration process lies in improving the thermal storage system for Eurelios, Gemasolar and Ivanpah plants, while the internal design restructuring propose modifying the heliostats (A H)/receptor area (A R); for example, the receptor area should be reduced namely, Eurelios: A R ∗ < 16 m 2 , Gemasolar: A R ∗ < 251 m 2 and Ivanpah: A R ∗ < 4 , 018 m 2. These optimal processes could be fed back into future works using exergoeconomic and exergoenvironmental analysis. • Three real-world solar concentrating power plants are studied on optimal performance. • An energy reconfiguration process improves the thermal storage systems. • Energy restructuring conditions let us modifying the heliostats/receptor areas. [ABSTRACT FROM AUTHOR]

Heaters are crucial components in Stirling engines, where the working medium adsorbed heat from an external heat source. Enhancing heat transfer within the heater is essential for boosting the operational efficiency of the Stirling engine. In this study, a tube equipped with three-pronged slant rods was employed to improve the heat transfer within the heater under conditions of oscillatory flow. Three pairs of dynamic longitudinal vortices were generated and exhibited regular movement patterns with distinct phase angles. In comparison to the smooth tube configuration, the enhanced tube outlet exhibited a notable increase in the average working-medium temperature by 62 K and 46 K during the entry and return stages, respectively. The degree of heat transfer enhancement was found to be contingent upon the pitch, height, and inclination angle of the slant rod. Optimal heat transfer enhancement was achieved with slant rods featuring a pitch of 26 mm, a height of 3.5 mm, and an inclination angle of 45°. The performance evaluation criterion ranged from 1.29 to 1.81 of enhanced tube compared to smooth tube. These findings underscore the effective enhancement of heat transfer facilitated by the three-pronged slant rods within the Stirling engine's heater. • Three-pronged slant rods were effective for Stirling engine heating tube. • Dynamic vortex structures enhanced heat transfer under oscillatory flow. • Slant rods geometric size greatly affected comprehensive performance. • The cycle average PEC value was in the range of 1.29–1.81. [ABSTRACT FROM AUTHOR]

Efficient engine technologies to convert low-grade heat to electricity are urgently desired. In this work, a conceptual structure of engine for a novel cycle or one-way oscillating flow cycle (OOFC), which consists of two isochoric and two adiabatic processes, is described for low-grade heat utilization. Characteristics of OOFC allows for the working fluid temperature glide to be matched to the decrease in temperature of low-grade heat. Then, thermodynamic model is developed for evaluating the performance. Theoretical simulation results show that maximum specific output works are in the range of 12.2 kJ kg−1 – 79.7 kJ kg−1. Compared to Stirling cycle system, maximum specific output work in OOFC system could be improved by 16.2 %–24.8 %. Compared to ideal Carnot cycle engine system, maximum specific output works in OOFC system is nearly the same and 1.8 %–2.6 % lower. As Carnot cycle engine is ideal while thermodynamic cycle loss and heat transfer loss in cold heat exchangers are considered in OOFC engine, the ratios of maximum specific output work demonstrate that OOFC system could be very promising for low-grade heat utilization as a result of well-matched temperature profile in hot heat exchanger. • Structure of OOFC engine with temperature glide heat addition is described. • Large temperature glide heat rejection is achieved in OOFC engine. • Maximum specific output work of OOFC system is 116 %–125 % of Stirling cycle system. • Maximum specific output work in OOFC system are equivalent to ideal Carnot cycle system. • OOFC engine has well-matched temperature profile for low-grade heat utilization. [ABSTRACT FROM AUTHOR]

Portable electric power generator with a power level of several hundred Watts plays an important role in outdoor activities, emergency relief and tactical power supply. As an external-combustion heat engine with outstanding heat source adaptability, free-piston Stirling generator (FPSG) owns attractive advantages of quietness, high thermal efficiency, and high reliability. This paper proposes a novel ultra-high frequency (UHF) FPSG-based portable power supply system driven by a diesel porous media evaporative combustor (PMEC). An experimental setup was designed and built based on the quasi-one-dimension thermoacoustic impedance matching of the FPSG and three-dimension thermal coupling of steady combustion and alternating flow between FPSG and combustor. The fundamental operating characteristics of the system were investigated in terms of combustion powers and electric loads. Preliminary experimental results show that a maximum output electric power of 350 We at a heating temperature of 875 K and a maximum fuel-to-electric efficiency of 11.98 % were obtained. Computational fluid dynamics (CFD) simulations were employed to delve into the intricate combustion and heat transfer processes, unveiling the formation of carbon deposits and confirming the efficacy of cyclone holes in reducing carbon deposition. This pioneering exploration of 130 Hz UHF and evaporative-combustion coupled heat transfer successfully showcases the feasibility of constructing a high-specific-power FPSG-based portable power system. • An innovative portable power generation system was proposed utilizing a free-piston Stirling generator. • Free-piston Stirling generator with an ultra-high operating frequency exceeding 130 Hz was built to demonstrate a high power density of 70 W/kg. • The integrated design of the high-temperature heat exchanger in the free-piston Stirling electric generator ensures reliability under elevated temperatures and pressures. • The novel design featuring inclined swirl air jet orifices and a gradually shrinking spout effectively eliminates severe carbon deposits, enhancing combustion and heat transfer efficiency. [ABSTRACT FROM AUTHOR]