Heat Engine Research Articles

Amended FRW universe: thermodynamics and heat engine

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

Isotonic separation enabled efficient low-grade heat conversion with thermal-responsive ionic liquids

The osmotic heat engine (OHE) stands out as a promising approach for converting low-grade heat into electricity owing to its scalability. However, challenges arise from the substantial latent heat consumption or the restricted concentration difference during the regeneration stage, constraining improvements in energy efficiency and power density. Here, we introduce an isotonic separation process to a thermal-responsive ionic liquid (IL)-based OHE system, where the water-rich phase of the IL after phase transition is further filtrated into pure water and another part of the IL-rich phase with constant osmotic pressure. This isotonic process amplifies the net energy generated in the mixing process. Ultimately, a state-of-the-art Carnot-relative efficiency of 48% is achieved within a temperature difference of 25–40 °C, where the hot side is maintained at 60 °C. Additionally, a forward-osmosis device yields an exemplary peak power density of 10.9 W/m2.

Lanthanum Oxide-Barium Oxide Nanofluid with Enhanced Thermal Engineering Application

Lanthanum Oxide-Barium Oxide Nanofluid with Enhanced Thermal Engineering Application

Numerical investigation of thermal radiation with entropy generation effects in hybrid nanofluid flow over a shrinking/stretching sheet

Abstract The need for efficiency in nanotechnology has spurred extraordinary development. Hybrid nanofluids, which are base fluids injected with nanoparticles, have a great potential for thermal enhancement in thermal systems. Particularly promising for magnetic thermal engineering are magnetic hybrid nanofluids. Understanding dynamic transport in Graphene Oxide (GO)–Fe3O4/H2O and GO/H2O nanofluids over stretching and shrinking surfaces, with severe entropy consequences, is still uncharted territory. To fully grasp this complexity, our study examines the numerical investigation of entropy formation in magnetohydrodynamic (MHD) hybrid nanofluids. The aim of this study is to establish a mathematical framework for understanding entropy production in the context of MHD, unsteady, incompressible flow of hybrid nanofluid flow over surfaces that experience both stretching and shrinking. The investigation encompasses the influence of MHD effects and nonlinear thermal radiation on flow behavior. The governing modeled form is modified into solvable representations in Cartesian configuration and then addressed utilizing the built-in bvp4c approach in MATLAB. For numerous quantities of the relevant parameters, several key features of flow and heat transmission are explored, discussed, and illustrated utilizing tables and graphs. Furthermore, the heat transfer properties in a magnetic field have been improved dramatically. The comprehensive entropy generation rate was condensed by up to 41% as opposed to refined water, according to the findings from the analysis.

Dynamics of heat release in a dual-fuel engine

The increasing attention to the use of dual-fuel engines with compression ignition leads to the need to study the thermal engineering processes occurring in them. A model for calculating the thermal engineering stages in a cylinder of a dual-fuel engine with a refined composition of the working fluid is presented, including the determination of fuel supply characteristics, fuel injection and evaporation functions and allowing theoretically to determine with high accuracy the pressure function, cycle operation, power, efficient and thermal criteria for the operation of a dual-fuel engine. The paper attempts to show the mutual relationship between the individual processes of heat generation, their influence on the design parameters under the operating conditions characteristic of a dual-fuel engine, as well as on the operating conditions of components and parts.

Williamson Nanofluid Over A Cone and Wedge: Numerical Modelling of Hydromagnetic Brownian Motion Using the Extended Darcy Model

The originality of this experiment lies in examining how the Lorentz force and Fr affect the Williamson fluid as it moves over the cone and wedge, two very different geometries. Along with the modifiable parameters of non-isothermal settings, the effects of Soret and Dufour are also taken into account. The non-linear equations of conservation are converted into the ordinary differential equations by utilizing appropriate similarity transformations. Finally, solutions to the system of ODEs are obtained by employing a finite difference scheme known as bvp4c in MATLAB. The relative tolerance of the scheme is set to 10−6 and a grid size of 10−3. The stability and convergence of the scheme have been verified by the grid point stability test. The behaviour of momentum of molecules and their thermal and mass diffusion of the fluid, and also the velocity–gradient, temperature-gradient, and species-gradient are portrayed explicitly and deliberated in detail for the influence of numerous fluid parameters. It is found that the heat-transmission on the surface of the cone is advanced than the wedge, and the rate of transmission of heat is supreme for Newtonian fluid in comparison to Williamson fluid. In contrast to the cone, the wedge has a greater impact of Fr on velocity, temperature, and concentration. Additionally, it is discovered that the enlarged values of the Williamson parameter decrease fluid velocity while increasing temperature and concentration dispersion. By adjusting the surface suction, magnetic field strength, and permeability of the porous material, fluid velocity can also be reduced to a minimum. Fr, M, Nt, and K all increase fluid temperature, while the suction parameter decreases fluid temperature. Non-Newtonian fluid has applications in the field of lubrication in numerous devices such as micro heat exchangers, micro cooling systems, micromixers, and so on. This study has a substantial influence on numerous engineering applications that analyse energy transfer in thermal equipment, designing heat exchanger devices and engines of gas turbines.

Badania wpływu pola magnetycznego na proces tworzenia kamienia w urządzeniach termicznych

Water is used as working fluids in hydro and thermal power engineering, as well as in heat supply and cooling systems. In the process of heating water in water-heating boilers, scale forms due to the precipitation of crystals of mineral additives and mineral salts. Over time, the accumulation of scale with low thermal conductivity leads to a decrease in the internal diameter of the pipes. Consequently, the flow of liquid is hindered, the hydraulic resistance increases and the thermal conductivity of the device decreases. The scale layer is usually removed by acid washing of the internal heat exchange surfaces or mechanical washing. However, both methods involve the use of a substantial amount of chemicals and result in highly polluted wastewater. In addition, it significantly increases operating costs. The article uses statistical methods for processing experimental data, and generally accepted methods for conducting experiments to study the patterns of scale formation using control and measuring instruments and accurate methods for measuring technological parameters. The main purpose of the paper is to study the influence of a constant magnetic field on the formation of mineral salts deposits on the surface of walls of thermal appliances used in chemical, oil refining, and food processing industry. The influence of a constant magnetic field on the formation of scale on the surface of the walls of the heating element in a water heater has been established. According to the results of an experiment aimed at preventing the accumulation of mineral salt deposits on the surface of the heating element in a water heating boiler under the influence of a magnetic field, the amount of mineral salt precipitate deposited on such surface can be reduced up to 5.2 times. Consequently, the prevention of mineral scale formation is achieved, eliminating the need to use expensive chemicals. The stable operation of the devices contributes to enhanced thermal efficiency. Under the influence of a magnetic field, scale formation decreases on average by a factor of 5, as long as the water temperature does not exceed 70°C. However, if the temperature rises above 90°C, the scale formation rate gradually increases.

Optimization analysis of an endoreversible quantum heat engine with efficient power function

Abstract We study the optimal performance of an endoreversible quantum dot heat engine, in which the heat transfer between the system and baths is mediated by qubits, operating under the conditions of a trade-off objective function known as the maximum efficient power function defined by the product of power and efficiency of the engine. First, we numerically study the optimization of the efficient power function for the engine under consideration. Then, we obtain some analytic results by applying a high-temperature limit and compare the performance of the engine at maximum efficient power function to the engine operating in the maximum power regime. We find that the engine operating at maximum efficient power function produces at least 88.89 % of the maximum power output while at the same time reducing the power loss due to entropy production by a considerable amount. We conclude by studying the stochastic simulations of the efficiency of the engine in maximum power and maximum efficient power regime. We find that the engine operating at maximum power is subjected to fewer power fluctuations as compared to the one operating at maximum efficient power function.

An artificial neural network-based numerical estimation of the boiling pressure drop of different refrigerants flowing in smooth and micro-fin tubes

Abstract In thermal engineering implementations, heat exchangers need to have improved thermal capabilities and be smaller to save energy. Surface adjustments on tube heat exchanger walls may improve heat transfer using new manufacturing technologies. Since quantifying enhanced tube features is quite difficult due to the intricacy of fluid flow and heat transfer processes, numerical methods are preferred to create efficient heat exchangers. Recently, machine learning algorithms have been able to analyze flow and heat transfer in improved tubes. Machine learning methods may increase heat exchanger efficiency estimates using data. In this study, the boiling pressure drop of different refrigerants in smooth and micro-fin tubes is predicted using an artificial neural network-based machine learning approach. Two different numerical models are built based on the operating conditions, geometric specifications, and dimensionless numbers employed in the two-phase flows. A dataset including 812 data points representing the flow of R12, R125, R134a, R22, R32, R32/R134a, R407c, and R410a through smooth and micro-fin pipes is used to evaluate feed-forward and backward propagation multi-layer perceptron networks. The findings demonstrate that the neural networks have an average error margin of 10 percent when predicting the pressure drop of the refrigerant flow in both smooth and micro-fin tubes. The calculated R-values for the artificial neural network’s supplementary performance factors are found above 0.99 for all models. According to the results, margins of deviations of 0.3 percent and 0.05 percent are obtained for the tested tubes in Model 1, while deviations of 0.79 percent and 0.32 percent are found for them in Model 2.

Proposal for composite quantum electromagnetically induced transparency heat engine coupled by a nanomechanical mirror

Abstract This paper introduces a quantum heat engine model that utilizes an ultracold atomic gas coupled with a nanomechanical mirror. The mirror’s vibration induces an opto-mechanical sideband in the control field, affecting the behavior of the cold gas and subsequently influencing the output radiation of the engine. The model incorporates mirror vibration while omitting cavity confinement, establishing a bridge between a multi-level atom–laser interacting system that plays with coherences and the mechanical vibration of the nanomechanical mirror, which jointly function as heat engines. Three distinct heat engine configurations are proposed: the first involves a vibration-free three-level Λ-type system, the second introduces nanomechanical vibration to the three-level Λ-type system, and the third constitutes a composite engine that combines the previous setups along with nanomechanical vibration. The spectral brightness of a three-level heat engine is diminished with mirror vibration, whereas for a composite heat engine, there is a slight enhancement in the brightness peak. However, the maximum brightness is attained when there is no vibration. Comparisons between the proposed model and an ideal system are made regarding entropy balance, adhering to the constraints of the second law of thermodynamics. The model observed that when subjected to mirror vibration, the proposed heat engines diverged from the characteristics expected in an ideal heat engine.

EMHD stagnation point flow of dusty hybrid nanofluid over a permeable stretching sheet: Radiative solar applications

The primary objective of this paper is to investigate the impact of dusty hybrid nanofluid electromagnetohydrodynamics (EMHD) on the stagnation point flow in the presence of solar radiation. Base fluids contain ethylene glycol, water, silver, titanium alloy, and suspended dust particles. Nonlinear differential equations with two or more independent variables define fluid flow phenomena. The governing equations can be solved by the MATLAB solver by employing a suitable numerical method, like R–K fourth order via shooting method. The isothermals for various parametric values have been explained. Because it has the potential to greatly advance the disciplines of industrial and thermal engineering, this proposed model is useful. When compared to using a single base fluid, the combination of two additional base fluid qualities provides noteworthy results. Because we were able to acquire a lower freezing point than water and better heat conductivity than pure ethylene glycol when we employed the combination of the two base fluids. Glycol water is used in car coolant and solar heating systems for a variety of purposes. Impact of embedded physical quantities like electric field parameter, ratio of specific heat, porosity parameter, stagnation parameter, radiation parameter, heat source parameter, and fluid particle interaction parameter for both velocity and temperature are illustrated graphically. Dust particles have a notable impact on various sectors, including the food and pharmaceutical industries. Specifically, they are special importance in applications such as wastewater treatment, solids drying, and the presence of plastic-coated metal items. In the present work, we observe that the stagnation parameter enhances the momentum boundary layer (MBL) thickness because the dusty fluid dominates the dusty hybrid nanofluid while incorporating the Ag + Ti alloy/EG + Water. The radiation becomes more efficient at evenly spreading heat, potentially resulting in a more uniform temperature distribution. Silver and titanium alloy particles may affect the thermal conductivity of dusty hybrid nanofluid when compared to the dusty fluid. The porosity parameter enhances the fluid flow and penetration by the porous medium, which lowers friction between the skin and the surface and reduces resistance.

Effects of Arrhenius kinetic on the magnetized nanofluid flow through a porous stretchable cylinder with slip conditions

ABSTRACT This research addresses the implications of slip on the magnetohydrodynamic transport properties of Newtonian nanofluids. The study employs Buongiorno’s theoretical framework and focuses its attention on a cylindrical object that experiences tensile deformation inside a medium characterized by porosity. In contrast to the often observed boundary conditions that presume a constant temperature and concentration, the current research utilizes hydrodynamic and thermal slip conditions. The recognition of many significant elements, including the Arrhenius activation energy, magnetic field, and viscous dissipation, also has important significance. The phenomena of interest pertaining to fluid flow is first defined and afterward converted into a nondimensional form by including relevant commonalities. In order to do a thorough examination of the current situation, the shooting algorithm and the b v p 4 c technique are used. Graphical and tabular representations are used to demonstrate the implications of several emerging features on the velocity, temperature, and dispersion of nanoparticles. The observed data suggests that a rise in chemical reaction parameters leads to a drop in nanoparticle concentration distributions, but the activation energy parameter exhibits an opposite tendency. It is discovered that the boundary layer thickness under slip flow circumstances differs from that seen without slip flow. The Sherwood number rises when the chemical reaction parameter gets higher, whereas the activation energy parameter escalates in the opposite direction. The present research covers a broad variety of applied sciences applications, with a special emphasis on thermal oil recovery, geothermal reservoirs, chemical engineering, and nuclear reactor cooling.

Phonon transport characteristics of α, β, and γ crystalline phases of magnesium hydride from first-principles-based anharmonic lattice dynamics

The superior gravimetric and volumetric hydrogen capacities of magnesium hydride (MgH2) make it a promising candidate material for solid-state hydrogen storage. However, the slow kinetics of hydrogen atoms and the high thermodynamic stability of MgH2 hinder its practical application. To address the challenging issue of adsorption–desorption in MgH2, structural engineering involving nanostructuring has been used to improve the hydrogen-storage characteristics of this material. However, although structural engineering and thermal management significantly influence material properties, no microscopic understanding of the heat conduction property of pristine MgH2 exists. Further advances in the thermal engineering of MgH2-based hydrogen-storage materials require a better understanding of heat conduction in pristine MgH2, particularly knowledge of how the crystalline phases of MgH2 depend on the hydrogen concentration and external pressure. This study uses first-principles-based anharmonic lattice dynamics to quantitatively investigate the intrinsic thermal conductivity of heat-carrying phonons in pristine MgH2 with three different crystalline phases α, β, and γ. The results show that the thermal conductivity of MgH2 depends on the crystalline phase and that the magnitude of the thermal conductivity increases in the order α, γ, and β. In contrast, the volumetric heat capacity and mean squared displacements of the constituent atoms are similar for all three phases. Furthermore, as observed for the pressure dependence of phonon transport, increasing the pressure reduces the thermal conductivity of all phases. However, for the γ and β phases, these reductions are relatively moderate because of the competing effects of group velocity and relaxation time, which have opposite dependencies on pressure. Finally, modal analysis indicates that the spectral features of the phonon transport properties under an applied external pressure are comparable to those at atmospheric pressure. These results should help tailor the heat dissipation of MgH2 while maintaining its hydrogen adsorption–desorption performance through structural engineering.

The quantum Carnot-like heat engine: The level degenerate case

The two-level quantum heat engines have been studied extensively. Before that, the optimization of most heat engines was mainly concentrated in non-degenerate cases. We consider the level degeneracy, then calculate the maximum operation time and the irreversible dissipation coefficient of the two-level system under the scheme of linear tuned levels. In the high-temperature limit, we find that the level degeneracy affects the maximum power of the two-level heat engine. Especially in the case of the same degeneracy of the ground state and the excited state, the influence is the greatest. In addition, we also show that the degeneracy does not affect the efficiency at maximum power and the consistent relation of the two-level Carnot-like heat engine.

Performing SiO2-MWCNT/water hybrid nanofluid with differently shaped nanoparticles to enhance first- and second-law features of flow by considering a two-phase approach

AbstractThe utilization of hybrid nanofluids has gained essential consideration in thermal engineering. Changes in the thermal characteristics of the base fluid are responsible for the improved thermal conductivity brought about by hybrid nanoparticles and their shapes. For this goal, in this paper, the two-phase 60%:40% SiO2-MWCNT/water hybrid nanofluid flow at the Reynolds number range of 3000–10,000 in a square duct is investigated concerning first- and second-law analysis. The turbulent flow regime is modeled using the RNG k–ε turbulence approximation. The hybrid nanofluid is modeled via a mixed model. The parameters used in this study are three different nanoparticle shapes (cylindrical, spherical, and platelet) and nanoparticle volume fractions (0.2%, 0.6%, and 1.0%). The distributions of the Nusselt number, friction factor, entropy generation, exergy destruction, exergy efficiency, temperature, and velocity contours are investigated in detail for the above parameters. It is found that the most significant increases in PEC are seen in hybrid nanofluids with the PC and PP shapes, at 2.27 and 3.24%, respectively. It has been shown that the exergy destruction of hybrid nanofluids with the second nanoparticle forms C and P is 43.90% and 58.74% more than that of a S one when PS-, PC-, and PP-shaped nanoparticles are utilized. The hybrid nanofluid with the PS shape has the highest exergy efficiency, whereas the SP-shaped nanofluid has the lowest.

Many-body enhancement in a spin-chain quantum heat engine

Many-body enhancement in a spin-chain quantum heat engine

Efficiency of a microscopic heat engine subjected to stochastic resetting.

We explore the thermodynamics of stochastic heat engines in the presence of stochastic resetting. The setup comprises an engine whose working substance is a Brownian particle undergoing overdamped Langevin dynamics in a harmonic potential with a time-dependent stiffness, with the dynamics interrupted at random times with a resetting to a fixed location. The effect of resetting to the potential minimum is shown to enhance the efficiency of the engine, while the output work is shown to have a nonmonotonic dependence on the rate of resetting. The resetting events are found to drive the system out of the linear response regime, even for small differences in the bath temperatures. Shifting the reset point from the potential minimum is observed to reduce the engine efficiency. The experimental setup for the realization of such an engine is briefly discussed.

Experimental investigation and artificial neural network-based modelling of thermal barrier engine performance and exhaust emissions for methanol-gasoline blends

In recent years, due to environmental concerns and the depletion of fossil fuels, alternative fuel use and alternative emission reduction methods have gained importance in the automotive industry. In addition, methanol is used as an alternative fuel in gasoline engines with coated piston engines. This study first presents an experimental investigation of engine performance and exhaust emissions for a partially thermal barrier lined piston engine operating on methanol-gasoline blends. In the second phase the obtained data is then used to develop an Artificial Neural Network (ANN) based model to predict engine performance and exhaust emissions for methanol-gasoline blends. The developed ANN model was trained and validated using MATLAB. The results of the experimental study showed that the use of methanol-gasoline blended fuel in the engine provides better engine performance and reduced exhaust emissions compared to gasoline fuel. According to the results obtained, an increase of 3.7 % in effective power and a decrease in NOx and HC emissions by 19 % and 18 %, respectively, compared to the STD case when both coating and alternative fuel are used in the engine. With the established ANN models, engine performance parameters and exhaust emission parameters were predicted with 99 % and 98 % accuracy respectively.

Performance improvement of a fractional quantum Stirling heat engine

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

Investigation of damage mechanisms in thermomechanical fatigue of nickel-based single-crystal alloys

Thermomechanical fatigue (TMF) is essential for ensuring the safety and efficiency of various thermal engineering systems, however, the underlying damage mechanisms remain unclear. In the present work, a damage evolution model is used to quantify damage mechanisms in nickel-based single-crystal superalloy DD6. The isothermal creep-fatigue model combining the fatigue and creep damages is developed to elucidate their interactions and validated by the tension-dwelling experiments. Finally, the experimentally measured TMF damage is quantitatively decomposed into fatigue, creep and extra TMF components. Significant TMF damage in the in-phase TMF is identified, especially in the [001] specimens, potentially attributed to the non-isothermal creep or oxidation, while damage in out-of-phase TMF aligns with the spiking oxidation mechanism.