Heat Engine Research Articles

Numerical analysis of inclined magnetic force impact on cross liquid flowing with widening shallow and heat generating

ABSTRACT The creation, utilisation, conversion, and exchange of thermal energy are all covered under the thermal engineering subject of heat transfer. Heat transfer plays a major role in engineering and industrial sectors like food packaging, food additive manufacturing, electronic cooling, microturbine, etc. Scientists across the world have tried to explore the impact of heat transfer on fluid past an expandable surface due to its exciting applications in industries like polymer production, paper production, crystal glass manufacturing, etc. This article has unique exploration, and it emphasises interpreting the Cross fluid flow along stretching surface with convective heat transport analysis by using the Lie group methodology. We investigated the implication of inclined upper-convected Maxwell fluid magnetohydrodynamic (MHD) movement through a penetrable strained plate. To solve nonlinear differential equations and clearly determine their absolute invariants, the Lie group approach is introduced. For the numerical solution of non-linear ordinary differential equations with boundary conditions, the fourth-order Runge–Kutta procedure with shelling performance is utilised. Plots showing the impacts of motivated and non-motivated MHD are researched and examined for the alterations of many parameters, and statistical graphs are given to explain the physical values. It is evident that opposing behaviour occurs in connection to temperature captivation and generation parameters together with motivated and non-motivated MHD. Under an amplified, heat-generating parameter and Deborah number, the rate of heat transmission increases. The Lie group investigation of Cross liquid in the presence/absence of inclined and non-inclined has not been investigated yet in the available literature.

Multidisciplinary Design Methodology for Micro-Gas-Turbines—Part II: System Analysis and Optimization

Abstract Owing to their high specific energy capabilities, ultramicrogas turbines (UMGT) are a high-potential technology to provide portable electric power supply for applications with demand of less than 1 kW. UMGT conceptual design is challenged by small-scale effects augmenting interdisciplinary dependencies leading to highly coupled, nonlinear component interactions. This work provides a novel approach to conceptual UMGT design by combining reduced order component and system modeling with constrained multi-objective optimization. Hereby, Part I presents integrated design and performance modeling of compressor, turbine, combustor, and generator. In Part II, the heat engine and generator modules are merged into a system framework by establishing conceptual UMGT rotor geometry and engine design. Following bearing selection and lifetime assessment, experimentally validated reduced order models are developed for heat transfer and rotordynamic analysis. Using the elaborated framework, a constrained multi-objective system optimization of a 300 W engine is performed based on ten design parameters and comparing SiAlON and Inconel 718 as potential rotor materials available for additive manufacturing. Hereby, bearing lifetime, system efficiency, and specific power are maximized while meeting rotordynamic, structural, and thermal requirements. Evaluating the results, interdisciplinary effects are highlighted, and two optimum engine configurations are suggested.

Thermal transport in thermoelectric materials of SnSSe and SnS[formula omitted]: A non-equilibrium Monte-Carlo simulation of Boltzmann transport equation

In the present work, thermal transport and the energy conversation in two thermoelectrically efficient candidates of Janus SnSSe and SnS2 are investigated within the non-equilibrium Monte Carlo simulation of the phonon Boltzmann equation. The phonon analysis has been performed to determine the contributed phonon in heat transport. The results present that the dominant participating phonons are the ones from the longitudinal acoustic (LA) branch while the least belongs to the transverse acoustic (TA) modes. Both materials reached the very high maximum temperature in response to the implied wasted heat. This is attributed to the low presence of the critical TA phonons which are on one hand fast enough to leave the hotspot but on the other hand have frequencies commensurable to ZA phonons’ frequency. Also, the temperature profile achieved during the heating and cooling of the materials is studied. It is obtained that the heat propagation through the SnS2 is, at first, swifter, which results in a temperature gradient through the whole material which is less than that of the SnSSe. As the time passes, the heat transfer that is directly related to the material thermal conductivity, slows down. So, the behavior of the SnS2 and SnSSe, in case of the heat propagation status, becomes similar. Moreover, the behavior of the thermoelectric figure of merit (zT), the efficiency (η), and the generated voltage have been figured out. It is stated that the higher zT and η do not guarantee a larger generated Seebeck voltage. This is true, while the generated Seebeck voltage is related to the temperature difference between the heated and the cold junction. Accordingly, how far the temperature of matter rises in response to the implied wasted heat is directly related to the obtained voltage. Mainly, it is presented that the maximum temperature that a material achieves, alongside the temperature gradient and the material property Seebeck coefficient, are essential in introducing thermoelectrically efficient materials with reasonable thermal to electrical energy conversion, useful for thermal engineering.

Improving performance of quantum heat engines using modified Otto cycle

The efficiency of a quantum heat engine is maximum when the unitary strokes of the quantum Otto cycle are adiabatic. On the other hand, this may not be always possible due to small energy gaps in the system, especially at the critical point (CP) where the gap between the ground state and the first excited state vanishes and the system gets excited. With the aim to regain this lost adiabaticity, we modify one of the unitary strokes of the Otto cycle by allowing the system to first evolve with a time dependent Hamiltonian as in the case of a usual Otto cycle, followed by an additional evolution with a different time independent Hamiltonian so that the system reaches a less excited state. This will help in increasing the magnitude of the heat absorbed from the hot bath so that the work output and efficiency of the engine can be increased. We demonstrate this method using an integrable model and a non-integrable model as the working medium and discuss the generality and limitations of this method. In the case of a two spin system, the optimal value for the time till which the system needs to be freely evolved is calculated analytically in the adiabatic limit. The results show that implementing this modified unitary stroke significantly improves the work output and efficiency of the engine, especially when it crosses the CP.

Simulation-Based Thermal Fatigue Validation Test Development for Exhaust Manifold

Abstract Exhaust manifolds in diesel engines undergo continuous thermal cycle loading of varying thermal cycles with different mean, amplitude, and rate of temperature change created by application duty cycles. This makes analysis and testing of the exhaust manifold to meet the thermal mechanical fatigue life expectation of different applications challenging. In this paper, a simulation-based product development approach, which uses application duty cycles, simulation models of different capabilities, including three-dimensional Finite element simulation model, one-dimensional (1D) physis-based damage model to develop an abusive thermal cycle engine test for validating exhaust manifold, is presented.

ВЛИЯНИЕ ОТКАЗА РАБОТЫ ОБЛИЦОВОЧНЫХ ПАНЕЛЕЙ НА ТЕПЛОТЕХНИЧЕСКИЕ СВОЙСТВА НАВЕСНЫХ ВЕНТИЛИРУЕМЫХ ФАСАДНЫХ КОНСТРУКЦИЙ

Abstract. One of the most common solutions for external enclosing wall structures are hinged ventilated façade structures, which, thanks to the use of air layers, provide increased energy efficiency. However, such systems have a number of drawbacks, including the formation of cold bridges in the places of attachment of facade panels, which can lead to significant problems in the operation of the system. In addition, it is known that individual facade panels can fall and refuse to work, which leads to a violation of the closure of the air layer and negatively affects the thermal properties of the structure. Therefore, it is necessary to take into account both the shortcomings of the facade structure itself and the problems associated with its operation in order to correctly assess the impact of the failure of the facade panels on the thermal properties of the structure as a whole. This problem is one of the most important for systems of hinged ventilated facades, as it can lead to a complete loss of thermal engineering properties of the structure. This study considers a theoretical solution to the problem of calculating the heat transfer resistance of air layers in hinged ventilated facade structures and organizing this solution into a consistent design methodology for further investigation of the effect of the fall of facing panels on thermal engineering properties of hinged ventilated facades. The main question of the study, consisting in assessing the impact of the failure of the cladding panels on the thermal properties of hinged ventilated facade structures, is considered in accordance with the provisions of the developed methodology and its subsequent mathematical analysis. The need for such a study is justified by the need to determinethe most effective ways to eliminate the shortcomings of hinged ventilated facade structures and increase their thermal properties.
 Materials and methods: analysis of scientific and technical literature, mathematical analysis of the dependence of the resistance to heat transfer of air layers on the geometric parameters of the structure.
 Subject of research: air layers in hinged ventilated façade structures.
 Results: mathematical dependences are obtained that allow us to estimate the change in the moisture content of the thermal insulation material of hinged facade systems, the air velocity in the air layer and the air temperature in the air layer because of facing panel’s failure. 
 Conclusions: failure of facing panels of hinged facade systems leads to a change in the humidity of the thermal insulation and the parameters of the air layer, which can lead to exceeding regulatory requirements.

Thermal-hydraulic performance of turbulent flows across a heated round tube installed through several perforated twisted tapes

Purpose The purpose of this study is to advance turbulent thermal convection inside the constant heat-flux round tube inserted by multiple perforated twisted tapes. Design/methodology/approach The novel design of this study is accomplished by inserting several twisted tapes and drilling some circular perforations near the tape edge (C1, C3, C5: solid tapes; C2, C4, C6: perforated tapes). The turbulence flow appearances and thermal convective features are examined for various Reynolds numbers (8,000–14,000) using the renormalization group (RNG) κ−ε turbulent model and Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm. Findings The simulated outcomes reveal that inserting more perforated-twisted tapes into the heated round tube promotes turbulent thermal convection effectively. A swirling flow caused by the twisted tapes to produce the secondary flow jets between two reverse-spin tapes can combine with the main flow passing through the perforations at the outer edge to enhance the vortex flow. The primary factors are the quantity of twisted tapes and with/without perforations, as the perforation ratio remains at 2.5 in this numerical work. Weighing friction along the tube, C6 (four reverse-spin perforated-twisted tapes) brings the uppermost thermal-hydraulic performance of 1.23 under Re = 8,000. Research limitations/implications The constant thermo-hydraulic attributes of liquid water and the steady Newtonian fluid are research limitations for this simulated work. Practical implications The simulated outcomes will avail the inner-pipe design of a heat exchanger inserted by multiple perforated twisted tapes to enhance superior heat transfer. Originality/value These twisted tapes form tiny circular perforations along the tape edge to introduce the fluid flow through these bores and combine with the secondary flow induced between two reverse-spin tapes. This scheme enhances the swirling flow, turbulence intensity and fluid mixing to advance thermal convection since larger perforations cannot produce large jet velocity or the position of perforations is too far from the tape edge to generate a separated flow. Consequently, this work contributes a valuable cooling mechanism toward thermal engineering.

Numerical heat featuring in radiative convective ternary nanofluid under induced magnetic field and heat generating source

The study of nanoliquid characteristics and their heat performance have attracted the interest of engineers. These engineered fluids have high thermal conductivity due to which such liquids are reliable for different engineering applications including heating/cooling of buildings, thermal and mechanical engineering, etc. Therefore, the current research design provides a new ternary nanoliquid model for the heat transport process under induced magnetic field effects, mixed convection, heating source and thermal radiations. The modeling has been done by implementing the ternary fluid characteristics and supportive transformations and then for results simulation; bvp4c is coded successfully. It is scrutinized that a higher inductive magnetic field (0.1–0.4) and nanoparticles amount (0.01–0.07) are better to resist the movement while the wedge parameter ([Formula: see text] promotes it. By promoting the heating source, Eckert and [Formula: see text], the heat transfer process is observed rapidly while the mixed convective number [Formula: see text] controls it. Further, the particular used ternary nanoliquid is examined and found to be good for cooling purposes.

Femtosecond Laser-induced Ultrafast Growth of Volcanic-shaped Graphene Micropillars

Surface micropillars are capable of significantly altering material properties, including anti-reflection, structural color, wettability, and adhesion. Conventional methods for fabricating micropillars are both time-intensive and material-consuming. Recently, a nature-inspired light-induced self-growth method has been proposed to avoid the drawbacks of conventional methods. However, this method suffers from slow growth rates (slower than 3.3 × 102 μm/s) and restricted precursor material (limited to heat-shrinkable shape-memory polymer). Herein, we developed the light-induced method based on femtosecond laser thermal accumulation engineering and realized the self-growth of micropillars on thermal-stable polymers. By inducing localized carbonization rather than heat shrinkage with a high repetition rate laser, given the instantaneous release of large amounts of gases and highly localized stresses during laser carbonization, unique graphene micropillars grow rapidly and spontaneously from the polyimide surface with a growth rate of 4.5 × 103 μm/s. The growth rate of micropillars is increased by an order of magnitude compared to previously reported light-induced methods. Furthermore, the dimensions of these micropillars, including height, diameter, and spacing, can be precisely controlled by modulating the heat accumulation. Last but not least, solar absorbers and light-driven actuators are flexibly fabricated using this method, demonstrating its practical applicability.

Toward zero carbon emissions: High thermal efficiency low speed two-stroke marine engine using pure ammonia fuel

As the future development trend and the crucial link to achieving the carbon peaking and carbon neutrality goals in China, the achievement of “zero carbon” emissions in low-speed two-stroke marine engines is currently in the preliminary stages of exploration. Ammonia fuel is one of the main zero-carbon energy sources of interest for marine engines. The primary challenges associated with ammonia application include its high self-ignition temperature, low laminar flame speed, and lengthy ignition delay time. Although stable combustion can be achieved with the assistance of a small amount of highly active carbon-based fuel, carbon emissions are still inevitable. To obtain “zero carbon” emissions, the high-temperature cylinder gas recirculation strategy (HTCGR) was innovatively proposed to realize the possible application of pure ammonia. However, the heat transfer loss by using pure ammonia fuel is enhanced by 289% compared to the diesel mode. Therefore, the main objective of this article is to investigate ways to decrease heat transfer loss and further improve the thermal efficiency of the two-stroke engine from the perspective of energy distribution, and the effect of the circulating high-temperature gas, swirl ratio, and fuel distribution on heat transfer loss was systematically numerically studied in this manuscript. As a result, the heat transfer losses can be decreased up to 38.80% by lowering the CGR rate and adjusting the fuel distribution, and the ITE can be improved from 48.85% in the diesel model to 51.19% in the ammonia mode. However, to avoid incomplete combustion in the engine, a minimum CGR rate of 13.3% is basically required for the compression ignition of pure ammonia fuel.

Reverse osmosis-based water treatment for green hydrogen production

We analyze the use of excess natural gas (currently flared/vented) to instead treat oilfield-produced water via reverse osmosis (RO) to generate ultrapure electrolysis-grade water (Total Dissolved Solids (TDS): 0.028‐0.5 ppm) for green hydrogen production. We combine an analytical ε-MTU model and CPavg model to predict average permeate concentration, to obtain improved estimates of electrolysis-grade water production from RO systems. The theoretical upper limit of the recovery of a RO system (similar to Carnot efficiency of heat engines) is established. Analysis is conducted for conditions corresponding to Niobrara Shale field (TDS: 29.1 g/L), as well as for brackish water (TDS: 5-15 g/kg) and seawater (TDS: 35–45 g/kg) feeds. Results show that electrolysis-grade water production can be as high as 0.75 m3 per cubic meter of water treated, with 1.38 m3 of natural gas providing the required energy. This translates to hydrogen production of 74.6 kg per cubic meter of produced water treated. Relatively low volumes of gas can treat large water volumes (<4 % of excess gas in Niobrara Shale can treat the entire quantity of produced water). These numbers highlight the benefits of our approach of utilizing two waste streams to create a high-value commodity, critical for decarbonization.

Gain-assisted quantum heat engine based on electromagnetically induced transparency

We propose a scheme to realize a gain-assisted quantum heat engine (QHE) based on electromagnetically induced transparency (EIT), which consists of a three-level Λ-type atomic system interacting with two thermal reservoirs and a coupling field. The gain without inversion is induced to the system via spontaneously generated coherence (SGC) between two lower levels. The SGC has significantly affect on the system’s dynamics, resulting in an enhancement of the emission cross-section and spectral brightness of the QHE.

Numerical investigation of surface wettability effect on two-phase closed thermosyphon

A two-phase closed thermosyphon (TPCT) is promising for heat removal due to its simple structure and high performance in heat transfer. However, investigating the phase change process in TPCT through experiments with current technology is still challenging. To study the various surface wettability effects on TPCT, this is the first systematical volume of fluid (VOF) method-based numerical study. The wettability in terms of contact angles (5°, 40°, 120°, and 175°) is endowed on the surfaces of TPCT. The numerical results of heat transfer coefficients of the TPCT show good agreement compared with the correlations. The simulation results reveal that the hydrophilic evaporator and the hydrophobic condenser benefit heat transfer. Within the input power of 376.14 W, the hydrophilic evaporator can reduce the thermal resistance of the evaporator to 35.3 % and delays the vapor film formation. The hydrophobic condenser decreases the thermal resistance of the condenser at 3.64 % and prevents filmwise condensation. The surface wettability is critical to the temperature distribution along the evaporator, but the main temperature drop is located between the adiabatic section and the condenser. It is also noted that the thermal resistance of the condenser is dominant to the overall thermal resistance. This study provides a detailed physical insight into the surface wettability effect on TPCT and benefits the future design in thermal engineering applications.

Protection of the Purification Station Thermal Engines Against the Effects of Hydrogen Sulfide by the Coupling of a Chemical and Biological Treatment of the Produced Biogas

Protection of the Purification Station Thermal Engines Against the Effects of Hydrogen Sulfide by the Coupling of a Chemical and Biological Treatment of the Produced Biogas

Comprehensive investigation of a novel multi-segment heat exchanger for PCM/MF based ocean thermal engine: Numerical analysis, model reduction and experimental work

Phase change material/metal foam based exchangers are widely used in thermal energy storage and ocean engineering. In this paper, a novel heat exchanger called multi-segment heat exchanger is proposed for installation on an ocean thermal engine. This heat exchanger has several concentric circular shaped thin slices inside, which divide the interior into several small areas. During the melting process, independent vortices were formed in each segment. Three aspects of research were conducted: (i) in the investigation of heat transfer enhancement mechanisms, by numerically solving the N-S equations, the reason for enhanced heat transfer in the multi-segment heat exchanger was explained using the field synergy principle theory, and the influence of dimensions and environmental parameters on the melting process was analyzed. Results show that the optimal ratio of height to radius (H/R) for each segment is 1 and the total melting time is reduced by 31–38 %; (ii) for model reduction, by simplifying the full order physical equations for conduction dominant and convection dominant processes separately, ordinary differential equations describing multi-segment heat exchangers were obtained, which can be used for rapid prediction in the engineering practice. The calculation time of the reduced order model is within 0.1 s; (iii) in experimental work, an experimental set-up was built to test the original and the multi-segment heat exchangers, respectively. The numerical work and reduced order model were validated, and results showed that the proposed heat exchanger reduced the melting time by 34 %.

Neural network architecture to optimize the nanoscale thermal transport of ternary magnetized Carreau nanofluid over 3D wedge

SignificanceIncorporation of nanoparticles in base fluid water is significant for analysis of thermal behavior of nanofluid mixtures, which has various applications in materials science and thermal engineering, and supervised neural scheme predicts the thermal behavior by solving Carreau nanofluid model. MotiveThis article brings the investigation related to prediction of thermal transport of a ternary magnetized hybrid nanofluid [(Al2O3, CuO, TiO2)/H2O] with a three-dimensional Carreau nanofluid model over a wedge. Three nanoparticles dispersed in water (H2O). Inclined magnetic field is considered for judgement of velocity profile and thermal radiation is utilized to scrutinize the temperature distribution of nanofluid. The Carreau mathematical model is chosen to depict the rheological characteristics of non-Newtonian fluids at very high and very low shear rate. MethodologyPhysical assumptions creates the system of Partial differential equations (PDEs) and these are converted into ordinary differential equations (ODEs) by similarity tool. Further ODEs are dealt with bvp4c scheme and further prediction of solution is made by Levenberg-Marquardt neural network (LM-NN) supervised neural scheme. FindingsIncreased volume friction coefficients of nanoparticles increases the transport of heat. High inclined magnetic effect, thermal radiation, pressure gradient and shear strain parameter predict higher thermal transport.

A machine learning based approach for predicting Pool boiling heat transfer coefficient of CNT + GO nanoparticle coated surfaces

The use of machine learning in the field of thermal engineering not only enhance the accuracy of predictions but also allows the investigation of parametric effects and the understanding of intricate mechanisms in boiling heat transfer. In this investigation, pool boiling experiment is performed on CNT + GO coated copper surface to generate the dataset. Twelve number of coated samples are prepared and 180 number of datasets is created from the pool boiling experiment. Five different Machine learning algorithms such as Support Vector Regression, Least Square Support Vector Regression, Gaussian Process Regression, Extreme Learning Machine, and Artificial Neural Network is used for modelling purpose. The grid search optimization technique is utilized to fine tune the hyperparameters. The predictive features for heat transfer coefficient encompassed concentration of nano fluid, substrate dipping time, wall superheat, heat flux. Among these algorithms, Gaussian process regression and extreme learning machine exhibited superior performance in accurately predicting the heat transfer coefficient. The statistical assessment of the GPR, including R2, RMSE, MSE, and MAE, yielded values of 0.9998, 0.0009, 0.00, and 0.0023 respectively. Consequently, integrating the GPR and ELM can distinguish hidden patterns and relationships inside experimental data. It can contribute to the advancements in pool boiling research.

A novel temperature prediction method in complex indoor environments based on parameter estimation

This article proposes a novel temperature prediction technique for complex indoor environments based on parameter estimation. The method utilizes the Boussinesq approximation to establish a thermal model and estimate key parameters including pressure terms, heat transfer coefficients, and thermal diffusivity. An approximate approach is adopted to simulate the thermal dynamics of an indoor space. By comparing simulation results under an initial temperature with actual measurements, accurate parameter values are obtained. The estimated parameters can then be applied to achieve high-accuracy temperature prediction given varying initial conditions in the same environment. Moreover, the method can be formulated into a state-space model, enabling offline optimal temperature control. Through identifying the governing parameters via data-driven modeling, it provides an effective engineering tool for analyzing heat transfer and regulating temperature in intricate indoor settings. Rigorous derivation and sufficient validation demonstrate the reliability of this method. Given its potential in fields like architecture design and thermal engineering, this technique offers valuable impacts and insights for temperature management in enclosed environments.

Investigation of the thermo-convective characteristics of a flow passing through a partially heated channel filled with a porous medium saturated with a hybrid nanofluid

As part of this study, we used three-dimensional numerical simulations to look into mixed thermal convection in a nanofluid that flows in a partially heated cylindrical channel without being able to be compressed. Our study specifically focused on two distinct configurations: the investigation of mixed thermal convection in the laminar regime using a hybrid nanofluid under both porous and nonporous conditions. The study adds to the scientific understanding of heat transfer processes in complex fluid–solid systems and contributes to the ongoing advancement of knowledge in the fields of thermal engineering and nanofluid research. This research involved investigations into varying nanoparticle volume fractions (0%–4%), Reynolds numbers within the range of 200–800, Richardson numbers between 1 and 2, and a fixed Darcy number of Da = 10 − 8 . Our analytical methodology involved a thorough assessment of temperature, velocity, and heat distributions within the hybrid nanofluid. The study we did showed that adding nanoparticles made the base fluid’s effective thermal conductivity much better. This made the transfer rate go up. Specifically, the thermal conductivity of the Al2O3-CuO-water hybrid nanofluid displayed noteworthy improvement. Furthermore, the incorporation of a porous matrix substantially enhanced the overall efficiency of the heat transfer process.

Buoyancy driven bioconvective Casson nanofluid flow over a vertical stretching cylinder in Darcy–Forchheimer permeable medium with Arrhenius activation energy and chemical reaction

A mathematical framework is conceived to analyze the flow of Darcy–Forchheimer Casson nanofluid around a vertically stretchable cylinder, taking into account the convective boundary conditions. The heat and mass transport phenomena are visualized in the existence of activation energy and gyrotactic microorganisms with buoyancy effects. Additionally, an external magnetic field is applied to the flow problem. This particular model finds applications in biomedical engineering, the oil and gas industry, heat exchangers and thermal systems, environmental engineering, and renewable energy. By employing suitable transformations to transform partial differential equations into ordinary ones, the MATLAB function bvp4c package is utilized to numerically solve the equations. The findings presented through graphs illustrate the influence of various parameters on velocity, heat and mass transfer, and the density of gyrotactic microorganisms. The analysis revealed that fluid momentum decreases with increasing porosity numbers, while higher activation energy values enhance concentration. Moreover, an increase in the Peclet number reduces the microorganism’s distribution. Tables compute the motile microorganism’s density, Nusselt number, and Sherwood number. A substantial rise in activation energy prominently increases concentration, accompanied by a decrease in the Sherwood number. The density of microorganisms rises with higher values of the curvature parameter, Prandtl number, and Brownian motion parameter, but decreases with an increasing Hartman number. Noteworthy concordance is noted when juxtaposing the findings of this investigation with those of earlier scholarly research.