Heat Engine Research Articles

Experimental studies of thermal behavior, engine performance and emission characteristics of biodiesel / diesel / 1 pentanol blend in diesel engine

The present study investigates the significance of the utilization of biodiesel derived from waste cooking oil in diesel engines and its impact on engine output and environmental pollution after blending with diesel and 1-pentanol. The higher values of the ignition index and comprehensive performance index of 4.34 ×10−4mass/min°C2 and 13.71×10−6 mass2/min2 °C3, respectively, for D70B20P10 (70 % diesel, 20 % biodiesel & 10 % 1-pentanol by volume) indicate superior combustion performance. At full load, carbon monoxide and unburned hydrocarbon emissions from 1-pentanol blended fuels decrease significantly, ranging from 40 % to 52 % and 30.76–46.15 % compared to diesel. The D70B20P10 also showed an improved thermal efficiency of 28.68 % among all tested fuels at full load but slightly lower than diesel (29.56 %). Diesel demonstrated superior in-cylinder pressure (ICP) of 77 bar and heat release rate (HRR) of 41.1 J/ºCA owing to its excellent combustion characteristics. Introducing 5–10 % 1-pentanol in blend improved combustion, elevating ICP and HRR, attributed to enhanced fuel atomization and oxygen content. The sustainable process index value obtained for a global index per person is 0.002×10−4cap Litre-1, which lies between 0 and 1, indicates sustainability and compatibility of biodiesel production demonstration by universal biofuels (Andhra Pradesh).

Modeling of scattering coefficient for biological tissues exposed to near-infrared laser irradiation

Photothermal therapy using a near-infrared laser is a promising noninvasive treatment protocol for metastatic lymph nodes in breast, head, and neck cancers. From a thermal engineering perspective, the key to this therapy is accurately predicting the temperature distribution in the tissue due to laser irradiation. In this study, we focused on quantitatively modeling the scattering coefficient (σs), which changes with heating and significantly impacts the temperature distribution. First, we experimentally determined the change in σs due to heating using biological tissue and attempted to represent σs as a function of thermal damage factor which is based on the Arrhenius equation. Next, this function was incorporated into the radiative transfer equation to perform simulations. The results demonstrated significant agreement with the experimental data compared to those with constant σs. The root mean square error for the simulations with dynamic σs was approximately 2.0 (°C), which was half that of the simulations with constant σs. Although laser scattering in vivo is a complex phenomenon, the method proposed in this study is expected to offer an approach for predicting temperatures and determining appropriate laser power and irradiation time to prevent overheating or underheating in photothermal therapy.

Directing entanglement spreading by means of a quantum East/West heterojunction structure

We extend the translationally invariant quantum East model to an inhomogeneous chain with East/West heterojunction structure. In analogy to the quantum diffusion of particles, we observe a plateaus-shaped entanglement entropy spreading in the heterojunction during time evolution that can be regarded as continuous cycles in a quantum heat engine. In order to figure out the possibility of manipulating the entanglement entropy as a quantum resource, the entropy growth is shown to be determined by the initial occupation and the site-dependent chemical potential, and the former is equivalent to an effective temperature. Through fine adjustment of these parameters, we discover the entanglement flow is simply superposed with those from two sources of the chain. An intriguing relation between our model and the traditional heat engines is subsequently established. Published by the American Physical Society 2024

Measuring thermal contact resistance across solid and liquid interface mediums by thermal imaging technique: Applications on bearing steel

This study introduces a versatile method for measuring thermal contact resistance in bearing steel with solid–solid and liquid–solid interfaces using lock-in thermography (LIT) technique. The method relies on analyzing the lock-in thermal response across the layers of the bearing structure induced by periodic surface-laser heating. Thermal contact resistance is determined from the discontinuous behavior analysis of the thermal response at the solid–solid or liquid–solid contact interface, based on the resolved heat equation for the multilayered structure. The usability of the method is demonstrated through measurements conducted on a conventional bearing steel configuration, using air and lubricating oil as the interface mediums. Furthermore, the versatility of the method allows for investigating the impact of mechanical load on thermal contact resistance. This proposed approach represents an advanced tool for analyzing thermal contact resistance with applications beyond bearing steel to various multilayered materials. It has the potential to assist in enhancing thermal analysis, improving reliability, extending the lifetime, and reducing maintenance costs of different thermal engineering applications including bearings.

Heat engine efficiency for four-dimensional charged AdS black holes in Rastall gravity

In this paper, we analyze the [Formula: see text] criticality and the heat engine efficiency of two black holes, one is the four-dimensional charged AdS black hole in Rastall gravity and the other is the four-dimensional charged AdS black hole surrounded by quintessence in Rastall gravity. For the four-dimensional charged AdS black hole in Rastall gravity, the ratio [Formula: see text] is related to the Rastall parameter [Formula: see text]. When [Formula: see text] the ratio becomes [Formula: see text], which is same as the van der Waals liquid-gas system. Additionally, as the Rastall parameter [Formula: see text] increases, the heat engine efficiency [Formula: see text] of the black hole will increase. Moreover, the efficiency [Formula: see text] decreases rapidly at first and then increases with the entropy [Formula: see text]. But the efficiency ratio [Formula: see text] decreases with the Rastall parameter [Formula: see text]. For the four-dimensional charged AdS black hole surrounded by quintessence in Rastall gravity, as the charge q increases, the critical specific volume [Formula: see text] and the efficiency ratio [Formula: see text] also increase, however, the critical temperature [Formula: see text] and the critical pressure [Formula: see text] gradually decrease. Moreover, the heat engine efficiency [Formula: see text] and the efficiency ratio [Formula: see text] of the black hole are similar to the four-dimensional charged AdS black hole in Rastall gravity.

Математическое моделирование термодинамических процессов в вентиляционных шахтах метрополитена

Objective: To develop recommendations for performing thermal engineering calculations during the ventilation shafts renovation with the creation of internal thermal insulation made of foam glass concrete. Methods: Mathematical modeling by the Metrogiprotrans method of the shaft lining in an elastic medium for specified movements from expanding ice; mathematical modeling by the finite elements method of a system including a ground massive, shaft lining and a load from convection (cold air flow). Results: The criteria for the risk of the ventilation shafts lining destruction during freezing of water-saturated soil behind the lining have been established. It has been established that the destruction of cast-iron lining from the ice expansion depends on the amount of soil resistance and the size of voids behind the lining, but not on the depth of the location of the section under consideration. An influence assessment of the soil thermodynamic characteristics during the ventilation shafts operation in conditions of alternating temperatures has been performed. It was found that as a result of a very wide change in the thermal characteristics of the medium, the temperature behind the lining during thermodynamic calculations changes insignificantly — within 1 °C, and the thermal characteristics of the foam glass concrete layer play a decisive role in heat distribution. Practical importance: The results of the study can be used during the inspection of subway ventilation shafts, as well as an algorithm for conducting thermodynamic calculations for projecting shafts renovation with an insulation made of foam glass concrete.

Thermodynamic analysis of a heat engine: experiments with the Stirling cycle

This paper presents a practical thermodynamic analysis of a desktop Stirling engine to demonstrate some of the fundamental principles involving the conversion of heat to work as part of an introductory undergraduate course. Experimental measurements of temperature, pressure and volume using an Arduino microcontroller allows for the construction of P-ν and T-s process diagrams from thermodynamic relationships. By comparing the quantitative data from actual and ideal cycles, the Stirling engine represents an effective teaching tool for reinforcing core content with students.

Clean energy technologies and energy systems for industry and power generation: Current state, recent progress and way forward

This vision article accompanies a Special Issue of Applied Thermal Engineering dedicated to the Sustainable Development of Energy, Water and Environment Systems (SDEWES) conference series held during 2022, including the 5th SEE SDEWES Conference Vlore, 3rd LA SDEWES Conference Sao Paulo, and 17th SDEWES Conference Paphos. The article discusses a selection of papers presented at these conferences and selected for publication in Applied Thermal Engineering, all connected by a focus on clean energy technologies and systems for the advancement of sustainable thermal energy systems. This research area covers a wide range of technologies but is primarily focused on the power generation sector, energy storage and utilization, efficiency improvements, sustainable technical solutions, and the facilitation of the robust integration of renewable energy resources into wider energy systems. Additional work on previously established research topics is also present, but new directions have crystallized, especially research into thermal management for power devices and microelectronics. Based on the recent contributions to the research field presented in the included papers, this vision article discusses the development and application of cutting-edge technological solutions and identifies the challenges that require focused attention. Current shortcomings of developing and established technologies will be developed by the underlying fundamental research, reduction of prohibitively high costs, expansion of operating conditions, and the inclusion of advanced control approaches, sophisticated combinations of renewable energy sources, and modeling tools for system investigations. Scientists, researchers, and engineers can benefit from the summary of the topics at the forefront of the research field and find guidelines and ways forward for future research activities.

Bioconvective reversible (an esterification process) Casson nanofluid flow over a radiative spinning disc with microorganism

This study describes the Casson (a non-Newtonian fluid) nanofluid bioconvection flow across a spinning disc in the presence of gyrotactic microorganisms, many slips and thermal radiation. Also, the flow is considered as a reversible flow. The esterification process is taken into account. Using the proper variables, a system of extremely nonlinear PDEs is converted into a system of ODEs. To arrive to the solution of such equations, a numerical approach is used. Using the bvp4c approach, nonlinear flow equations can be numerically solved. Investigated are the effects of different numbers on the thermal field, volumetric concentration of nanoparticles and microbiological field. The key characteristics of the parameters in relation to the profiles of the velocity, temperature, concentration and microorganisms are graphically assessed with appropriate physical effects. A graphical explanation is provided for the wall shear stress, local Nusselt number, local Sherwood number and local motile density number. Rate of motile density number shows a prominent difference between reversible and irreversible flows for Brownian motion and Peclet number. The results of the theoretical simulations have dynamic applications in the fields of biotechnology and thermal engineering.

Temperature mapping methods for thermoelastic analyses of the ARIEL spacecraft payload module

The ARIEL mission is a European space project that aims to detect exoplanets with a spacecraft orbiting around the L2 point of the Sun-Earth system. The main payload consists of a Cassegrain telescope composed of mirrors that reflect and concentrate the incoming light from the deep space observations to finally guide it to the detectors. As in many other space missions, a dedicated complex assessment is established during the design phase to evaluate the impact on the optical performance caused by thermoelastic effects, which involves the coordinated work of the thermal, structural, and optical engineers. Despite that well-known and standardized processes and tools are established separately in each involved area, there is a lack of standardization about the way of exchanging the data between them, where additional calculations are required in some cases. This work focuses on the temperature mapping, which is the intermediate step between thermal and structural analyses, where temperatures are transferred to the structural model. The main difficulty of this process is related to the differences in modelling methods and approaches between both models, being necessary the development of an adequate algorithm to find the most accurate transfer of temperatures. This paper shows two different options for temperature mapping, detailing the proposed flowcharts. One of these methods requires the performance of an additional thermal conductive analysis, where a new improved procedure has been implemented in this work to solve some computational issues that made its application for large models difficult or even unfeasible. Both temperature mapping methods have been applied to the payload module of the ARIEL spacecraft, comparing the output results in terms of temperatures, stresses, forces, and displacements to evaluate their differences.

On the design of manifolds for parallel channel systems

In the design of high-performance heat and mass transfer devices such as liquid-cooled heat sinks, catalytic reactors, and catalytic convertors, parallel mini/microchannels are favored owing to their special potentials. Offering low pressure drop, providing high transfer surface area to volume ratio, and being easy to manufacture and optimize have been drawing thermal and chemical engineers attention to parallel channels for past decades. When working with parallel channels, the challenge of flow maldistribution is commonly faced which decreases their efficiency significantly. System total pressure drop and flow uniformity are two parameters that determine the system performance. In the present study, a variety of practical ideas, aiming to enhance parallel channels performance, are studied numerically. Inventive manifold designs with high hydraulic performance are created through the course of this study. The results of these designs are compared with basic conventional designs which show substantial enhancement. Analyzing less successful designs lead us to deep understanding of fluid dynamics in parallel channel heat and mass transfer devices.

Influence of activation energy and variable thermal conductivity on magneto-convective nonlinear thermo-radiative Casson nanofluid containing motile microorganisms over a sinusoidal surface

The activation energy of convective-radiative nanoliquids with sinusoidal walls has garnered significant academic interest in recent years. This focus arises due to the pivotal applications of nanoparticles in thermal engineering, industrial processes, and medical sciences. This article investigates the magnetohydrodynamic heat transfer characteristics of Casson nanofluids containing microorganisms influenced by an oscillatory surface. The study incorporates temperature-dependent viscosity and utilizes Buongiorno’s mathematical model to account for nonlinear thermal radiation, Brownian motion, and thermophoretic effects from using nanomaterials in Casson fluids. These effects enhance thermal conductivity, improving the heat transportation phenomenon while considering gyrotactic microorganism density distributions. The boundary layer flow problem is formulated using partial differential equations and associated boundary conditions, subsequently numerically simulated using the bvp4c function. The investigation explores the thermal behavior of nanoparticles in the presence of bioconvection phenomena, Lorentz force, chemical reactions, and activation energy. As a result, this model addresses variable thermal conductivity and bioconvection aspects in Casson nanofluids over a sinusoidal surface. Numerically computed results for the Nusselt number, motile density, and Sherwood number provide insights into several essential features. The findings reveal that an increase in the Casson fluid parameter correlates with a decreased velocity profile. The assumptions of variable thermal conductivity and temperature-dependent viscosity prove more effective in raising the temperature of nanoparticles. The nanoparticle concentration profile rises noticeably for smaller Schmidt number Sc values when the activation energy parameter is higher than larger Sc values. Additionally, the presence of microorganisms in Casson nanofluids leads to increased temperatures due to an elevation in the bioconvection Rayleigh number. Moreover, heightened oscillating frequency parameters decrease nanoparticle concentration and microorganism density. Including activation energy and oscillating frequency parameters further enhances the understanding of nanoparticle concentration and microorganism density dynamics, offering valuable contributions to theoretical research and practical applications across multiple interdisciplinary fields.

Design Models of Equipment Vapor Compression Refrigeration Cycle To Support Practicum Heat Engine And Fluid Engineering

Design Models of Equipment Vapor Compression Refrigeration Cycle To Support Practicum Heat Engine And Fluid Engineering

Thermal optimization of two-terminal SOT-MRAM

While magnetoresistive random-access memory (MRAM) stands out as a leading candidate for embedded nonvolatile memory and last-level cache applications, its endurance is compromised by substantial self-heating due to the high programming current density. The effect of self-heating on the endurance of the magnetic tunnel junction (MTJ) has primarily been studied in spin-transfer torque (STT)-MRAM. Here, we analyze the transient temperature response of two-terminal spin–orbit torque (SOT)-MRAM with a 1 ns switching current pulse using electro-thermal simulations. We estimate a peak temperature range of 350–450 °C in 40 nm diameter MTJs, underscoring the critical need for thermal management to improve endurance. We suggest several thermal engineering strategies to reduce the peak temperature by up to 120 °C in such devices, which could improve their endurance by at least a factor of 1000× at 0.75 V operating voltage. These results suggest that two-terminal SOT-MRAM could significantly outperform conventional STT-MRAM in terms of endurance, substantially benefiting from thermal engineering. These insights are pivotal for thermal optimization strategies in the development of MRAM technologies.

Non-unique detailed constructions of Curzon-Ahlborn cycle on thermodynamic plane

The Curzon-Ahlborn (CA) cycle is a paradigmatic model of endoreversible heat engines, which yields the so-called CA efficiency as the efficiency at maximum power. Due to the arbitrariness of the relationship between the steady temperature and the time taken for the isothermal process of the CA cycle, the constructions of the CA cycle on the thermodynamic plane are not unique. Here, we give some of the detailed constructions of the CA cycle on the thermodynamic plane, using an ideal gas as a working substance. It is shown that these constructions are equal to each other in the maximum power regime in the sense that they achieve the best trade-off between the work and the inverse cycle-time, known as the Pareto front in multi-objective optimization problems.

Thermal engineering increases current density in AlGaN/GaN superlattice devices

Aluminum gallium nitride/gallium nitride multi-channel superlattice devices are receiving increasing attention as a new paradigm for driving the power density of gallium nitride based transistors toward their theoretical limit. However, the superior electrical performance of superlattice-based transistors is currently limited by excessive Joule-heating. This Letter evaluates what impact the number of superlattice channels and the buffer layer composition has on the reduction of the thermal resistance, i.e., Joule heating, of AlGaN/GaN superlattice devices. A record low thermal resistance (12.51 ± 0.34 K mm W−1) was measured via scanning thermal microscopy for non-castellated superlattice AlGaN/GaN devices with a 100 μm channel width. Overall, the use of a thin gallium nitride buffer layer, in place of a thick aluminum gallium nitride layer, reduced the buffer thermal resistance enabling the accommodation of more superlattice channels (10 vs 6), therefore augmenting the maximum power density of these devices. The superlattice device proposed here not only provides an enhanced thermal dissipation solution for high power density radio frequency electronics, but it also has the benefit of fewer fabrication steps in comparison with previously reported castellated multichannel devices.

Thermo-magnetic convection of MHD Casson fluid in a wavy triangular porous cavity with embedded a cold inverted triangle obstacle

The design of enclosures is crucial in thermal engineering applications and technologies, encompassing areas such as electronics, heat transfer devices, power reactors, heating systems, solar panels, and nuclear power plants. Thermal efficiency in microchannels is optimized and improved by using triangular enclosures with varying aspect ratios. Specifically, the purpose of these triangular enclosures with cool cylinders is to reduce energy loss in nanoscale thermal sinks and thermal exchange devices. The current study aims to explore the thermal radiation effects on magnetohydrodynamic MHD Casson fluid flow within a wavy triangular cavity that includes an embedded cold inverted triangle. The inner inverted triangle is kept at a lower temperature, while the wavy bottom wall of the outer triangular cavity acts as an isothermal heat source at a higher temperature. The numerical solution for this mathematical model is obtained using the open-source finite element software COMSOL. In this study, the wavy triangular enclosure is analyzed for key parameters such as Casson parameter β , Hartmann number Ha , Rayleigh number Ra , numbers of undulation N , radiation Rd and inclination γ . The study presents the local distribution of streamlines, velocity profiles, isothermals, and entropy production, along with the Nu avg . The results reveal the rate of heat transport and total entropy production raise with the increasing number of undulations N and the Casson parameter β , while they decrease with increasing Hartmann number Ha . The number Nu avg rises with the increasing radiation parameter Rd and Rayleigh number Ra . The maximum stream function is observed at an inclination angle of 60 ° .

Теоретические исследования процесса топливоподачи газового двигателя

This article is devoted to theoretical studies of the fuel supply process of a gas engine. It examines the main aspects of the functioning of the fuel supply system, the influence of fuel supply parameters on the efficiency of the engine, as well as problems and solutions. The authors analyze various theoretical models, describe the basic principles of fuel injection systems and discuss current trends in the development of this field. The article is intended for specialists in the field of automotive, mechanics and thermal engineering, as well as for anyone interested in modern technologies in the field of motor transport. Theoretical studies of the gas engine fuel supply process are of great importance in the modern automotive industry. The efficiency of a gas engine depends directly on the correct selection of fuel supply parameters, which makes this topic relevant for research and development. The article analyzes in detail various aspects of the fuel supply process, such as fuel dosing, spraying, system pressure, as well as interaction with other engine systems So, the presented article is a valuable contribution to the field of gas engine fuel supply research and can be useful both for specialists involved in the development of gas engines and for a wide range of readers interested in modern technologies and innovations in the field of automotive technology. Keywords: GAS ENGINE, FUEL SUPPLY, FUEL INJECTION SYSTEM, AGROENGINEERING, INNOVATIONS IN THE FUEL SUPPLY SYSTEM, AGROTECHNICS, FUEL SUPPLY PARAMETERS

Catalytic Advantage in Otto-like Two-Stroke Quantum Engines.

We demonstrate how to incorporate a catalyst to enhance the performance of a heat engine. Specifically, we analyze efficiency in one of the simplest engine models, which operates in only two strokes and comprises of a pair of two-level systems, potentially assisted by a d-dimensional catalyst. When no catalysis is present, the efficiency of the machine is given by the Otto efficiency. Introducing the catalyst allows for constructing a protocol which overcomes this bound, while new efficiency can be expressed in a simple form as a generalization of Otto's formula: 1-(1/d)(ω_{c}/ω_{h}). The catalyst also provides a bigger operational range of parameters in which the machine works as an engine. Although an increase in engine efficiency is mostly accompanied by a decrease in work production (approaching zero as the system approaches Carnot efficiency), it can lead to a more favorable trade-off between work and efficiency. The provided example introduces new possibilities for enhancing performance of thermal machines through finite-dimensional ancillary systems.

SIMULATION OF LIQUID FUEL SPRAY FORMATION AND DISTRIBUTION IN A REACTING TURBULENT FLOW

The paper presentsthe computational experiments of the liquid fuels spray and its droplets distribution in a turbulent reacting flow. Primary and secondary atomization of two types of liquid fuel droplets (isooctane and dodecane) in the presence of combustion was described by the equations of continuity, momentum, internal energy, concentration of components of reacting substances and a two-parameter model for calculating turbulent flow. The study results of the spray, dispersion and combustion of droplets of hydrocarbon liquid fuels in a model combustion chamber when changing the injector injection angle were obtained. The injection angle values varied from 2 to 10 degrees. Based on the computational experiment temperature profiles and concentration characteristics of combustion products and gas in the combustion chamber at various times were obtained. Numerical calculations of the droplets’ Sauter mean diameter distributions have the same dispersion pattern for dodecane. This suggests that the accuracy and adequacy of developed complex model of the formation and distribution of spray in a reacting flow has been confirmed by its strong correlation and good agreement of the modeling results with experimental data from other researchers. This kind of modeling methods and the obtained computational experiments results from them are widely used not only in traditional thermal power engineering, but also in the study of technological processes in the new generation engines chambers, combustion of alternative types of fuels and optimization of their combustion.