The theory covers cases when the exergy concept is not fully relevant. An indicator called work content factor is used to quantify the proportion of available work in a given amount of energy. ...General expressions have been obtained for the flux of available work transported by particles, the rate of work deficiency and the work content factor. More specific results have been obtained for the work content factor of the low-speed and ultra-relativistic particle fluxes, respectively, by using several assumptions concerning the number of energy states, the mean occupation number of the energy states, the entropy and the module and direction of the particles speed. The theory includes extraction of work from particle fluxes governed by classical kinetic theory and heat as particular cases and has been applied to fluxes of fermions (electrons) and bosons (Helium-4) in both the low-speed and ultra-relativistic case. It has been shown that the emission of thermal photons is several orders of magnitude lower than the stimulated particle emission by the primary work extractor. As a result, a unique expression of the work content factor of the ultra-relativistic particle fluxes has been obtained for both fermions and bosons while another expression has been derived for low-speed fermions and bosons. Generally, the work content factor decreases by increasing the temperature Tc of the primary work extractor. In some cases, at large values of Tc and small values of the average directional factor of the source of particle, work cannot be extracted from the energy of the particle flux.
•The formalism covers cases when the concept of exergy is not relevant.•New concepts such as the rate of work deficiency and energy quality are used.•The theory takes into account that systems in nature are usually statistically deformed.•The theory may be used for fluxes of bosons, fermions and boltzons.•Particular cases such as fluxes of ultra-relativistic or classical particles are presented.
Stress-induced martensite formation is the predominant mechanism during the deformation of various functional and structural Ti- alloys. To predict the performance of these alloys, stress-induced ...martensite formation was modeled as a function of crystal orientation and stress state. We present an integrated micromechanical modeling approach using finite element (FE) analysis and an elastic spectral solver based on Fast Fourier Transforms (EFFT), which allows direct correlation of the available work from martensite formation under complex stress-states in an in-situ characterized microstructure. The model is applied as a virtual analogue of an experimental 3-point bending test of a metastable β Ti–10V–2Fe–3Al alloy containing 5% α. The FE model incorporates the experimental β microstructure from electron backscattering diffraction (EBSD) with anisotropic elastic behavior. The EFFT solver uses strain fields in two local regions from the FE model to predict local stresses in experimental microstructures containing β and α phases. The stress and orientation data are used to predict the available work from stress-induced α″ martensite formation of the six different α″ variants. It was found that stress and available work concentrated around the tips of lamellar α, making these regions preferred nucleation sites for α″ formation, which is in excellent agreement with the in-situ experimental observations. This suggests that the local stress conditions in the β phase play a more important role in triggering α″ formation than the compositional inhomogeneity in the β phase at α-β interfaces. Using the integrated model, the first variants forming at low levels of deformation could be confidently predicted. However, the transformation behavior at elevated levels of deformation could not be properly captured. This indicates the need of further model improvement, including Dirichlet boundary conditions for the EFFT solver and accounting for the role of plasticity induced by phase transformation.
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•Multi zone combustion model used for second law analysis of dual fuel LTC.•Crank-resolved and cumulative zone-wise entropy generation quantified.•Introduced two new engine-size-independent second ...law-based performance metrics.•Parametric studies completed to characterize second law trends in dual fuel LTC.
While dual fuel low temperature combustion (LTC) has been studied before, a detailed second law analysis of dual fuel LTC is not yet available in the open literature. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. For the present study, a 2.4-l single-cylinder research engine operating at a nominal load of 6bar BMEP and 1700rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the “lost available indicated mean effective pressure” (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52–61 percent) and the burned zone (31–39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645–768kPa and FCIs in the range of 32.8–39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy.
This work is aimed at study of maximum available work and irreversibility (mixing, combustion, unburned, and friction) of a dual-fuel diesel engine (H2 (hydrogen)–diesel) using exergy analysis. The ...maximum available work increased with H2 addition due to reduction in irreversibility of combustion because of less entropy generation. The irreversibility of unburned fuel with the H2 fuel also decreased due to the engine combustion with high temperature whereas there is no effect of H2 on mixing and friction irreversibility. The maximum available work of the diesel engine at rated load increased from 29% with conventional base mode (without H2) to 31.7% with dual-fuel mode (18% H2 energy share) whereas total irreversibility of the engine decreased drastically from 41.2% to 39.3%. The energy efficiency of the engine with H2 increased about 10% with 36% reduction in CO2 emission. The developed methodology could also be applicable to find the effect and scope of different technologies including exhaust gas recirculation and turbo charging on maximum available work and energy efficiency of diesel engines.
•Energy efficiency of diesel engine increases with hydrogen under dual-fuel mode.•Maximum available work of the engine increases significantly with hydrogen.•Combustion and unburned fuel irreversibility decrease with hydrogen.•No significant effect of hydrogen on mixing and friction irreversibility.•Reduction in CO2 emission along with HC, CO and smoke emissions.
•Thermodynamic analysis of actual power generating thermal cycles is performed.•The latter is achieved using NSGA algorithm and thermodynamic modeling.•Three well known decision making methods are ...carried out to indicate optimum values of outputs obtained with optimization process.
The key objective of this research is to find out the best assessment principles for irreversible power generating thermal cycles. These approaches, which can be found through previous works, are the ecological coefficient of performance, exergetic performance coefficient and maximum available work. Irreversible Carnot power cycle is defined as system. External and internal irreversibilities are encompassed in the thermodynamic analysis. In this paper, two scenarios are defined in the optimization progression. The outputs of each scenarios are studied individually. Throughout the first scenario, with the aim of maximize the ecological coefficient of performance (ECOP), the exergetic performance criteria (EPC) and maximum available work (MAW), multi-objective optimization algorithms is engaged. Furthermore, throughout the second scenario, three objective functions comprising the first law efficiency (η), the exergetic performance criteria (EPC) and maximum available work (MAW) are maximized at the same time via multi objective optimization approaches. The multi objective evolutionary approaches (MOEAs) coupled with non-dominated sorting genetic algorithm (NSGA-II) approach is applied in the present paper. Decision making is performed via three well-known approaches comprising LINAMP and TOPSIS and FUZZY. Finally, error analysis of the outputs are accomplished for the aforementioned system.
•Performance analysis of irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas is studied.•Multi-objective optimization approach is carried out for performance optimization.•3 ...decision-making methods are employed to select final answers.
In last decades, nano technology developed. Since, nano scale thermal cycles will be possibly employed in the near future. In this research, a nano scale irreversible Brayton cycle is investigated thermodynamically for optimizing the performance of the aforementioned cycle. Ideal Maxwell–Boltzmann gas is employed as a working fluid in the system. In this paper, two scenarios are employed in the multi-objective optimization process; however, the outcomes of each of the scenarios are evaluated independently. In the first scenario, in order to maximize the dimensionless Maximum available work and energy efficiency of the system, multi-objective optimization algorithms is employed. Furthermore, in the second scenario, two objective functions comprising the dimensionless Maximum available work and the dimensionless Ecological function are maximized concurrently via employing multi objective optimization algorithms. The multi objective evolutionary approaches on the basis of non-dominated sorting genetic algorithm method are employed in this paper. Decision making is done via three methods including linear programming techniques for multidimensional analysis of preference and Technique for order of preference by similarity to ideal solution and Bellman–Zadeh. Finally, error analysis is implemented on the results obtained from each scenario.
Deformation‐induced α′′ martensite formation is essential to the mechanical properties of a variety of metastable β Ti alloys by extending elasticity or contributing to work‐hardening during plastic ...deformation. Nevertheless, to date, a comprehensive analysis of the effect of β texture and applied stress state on the martensitic transformation to α′′ is still lacking. The present study therefore provides a detailed analysis of the work which is made available from the shape strain of the martensitic transformation under a variety of in‐plane stress states and as a function of β crystal orientation. The available work was found to strongly depend on the applied stress state and the parent grain orientation. The shape strain of the martensitic transformation was obtained from applying the phenomenological theory of martensite crystallography. In cases where this theory was not applicable, an approximation of the shape strain by the Bain strain was found to provide a good approximation of the available work. Analysis of three different metastable β Ti alloys showed no strong effect of the alloy composition on the available work. Martensite formation from typical cold‐ and warm‐rolling β texture components under different stress states is discussed. Cases are highlighted to show how the cold‐ and warm‐rolling β textures can be tailored to hinder martensite formation upon subsequent industrial forming operations.
The effect of applied stress state and β crystal orientation on available work from β‐to‐α′′ martensite formation in metastable β Ti alloys is analysed. Predictions based on an available work criterion show a strong effect of stress and crystal orientation, and consequences for forming processes and typical β textures are discussed.
Previously overlooked literature now brought to my attention has resulted in the following nomenclatural conclusions: 1) The species known since 2013 as Gromphas inermis Harold, 1869 must be called ...G. lacordairii (Oken, 1834), whose original combination was Coprobius lacordairii. Gromphas inermis is a new junior subjective synonym of G. lacordairii; 2) Gromphas was made available by Dejean, in 1836, not Brullé, in 1837; the former, therefore, should be credited with the authorship; and 3) the type species of Gromphas is Coprobius lacordairii Oken, 1834 by original monotypy, not Onitis aerugionosusPerty, 1830 by subsequent monotypy. Also discussed is the publication year of G. jardimCupello & Vaz-de-Mello, 2015. This leads me to address the problem of zoological works first published in electronic-only versions with their own pagination and which are later reissued integrated into a journal′s volume and repaginated. It is here argued that these two versions – the detached and the volume-integrated ones – should be deemed separate available works, and that new nomenclatural acts can be made available from detached versions. If this is accepted, the later publication of the volume-integrated versions has no bearing on the availability of the earlier detached versions. I also introduce new data on the type series of Onitis aeruginosus (currently, Gromphas aerugionosa) and G. inermis, new specimens of the rare G. jardim, mislabelled specimens of G. amazonica Bates, 1870, and newly discovered specimens of the vanished G. dichroaBlanchard, 1846. The latter include the new record from Santa Catarina state, Brazil. The disappearance of G. dichroa since 1954, including the possibility that it might be extinct, is discussed. Le genre Gromphas Dejean, 1836 (Coleoptera, Scarabaeinae): nomenclature, distribution et conservation, avec une contribution au débat sur les publications électroniques en zoologie. La littérature précédemment ignorée et maintenant portée à mon attention a abouti aux conclusions nomenclaturales suivantes: 1) l′espèce connue depuis 2013 sous le nom de Gromphas inermis Harold, 1869 doit être appelée G. lacordairii (Oken, 1834), dont la combinaison originale était Coprobius lacordairii. Gromphas inermis est un nouveau synonyme subjectif junior de G. lacordairii; 2) Gromphas a été rendu disponible par Dejean, en 1836, et non par Brullé, en 1837; c′est donc le premier qui doit être crédité de la paternité; 3) l′espèce type de Gromphas est Coprobius lacordairii Oken, 1834 selon la monotypie originale, et non Onitis aerugionosusPerty, 1830 selon la monotypie ultérieure. L′année de publication de G. jardim Cupello & Vaz-de-Mello, 2015, est également discutée. Ceci m′amène à aborder le problème des travaux zoologiques publiés pour la première fois en version électronique avec leur propre pagination et qui sont ensuite réédités, intégrés dans le volume d′une revue et repaginés. L′argument avancé ici est que ces deux versions – la version détachée et la version intégrée au volume – devraient être considérées comme des œuvres disponibles distinctes, et que de nouveaux actes nomenclaturaux peuvent être rendus disponibles à partir des versions détachées. Si l′on accepte ce point de vue, la publication ultérieure des versions intégrées au volume n′a aucune incidence sur la disponibilité des versions détachées antérieures. Je présente également de nouvelles données sur les séries types d′Onitis aeruginosus (présentement Gromphas aerugionosa) et de G. inermis, de nouveaux spécimens du rare G. jardim, des spécimens mal étiquetés de G. amazonica Bates, 1870 et des spécimens nouvellement découverts de G. dichroaBlanchard, 1846, qui a disparu. Ces derniers comprennent le nouveau signalement de l′État de Santa Catarina, Brésil. La disparition de G. dichroa depuis 1954, y compris la possibilité qu′il soit éteint, est discutée.
•Methods used for evaluation of irreversible Carnot power engines are investigated.•All methods compared each other.•Numerical results are presented and discussed.•It is concluded that ECF is the ...most effective method.
In this study, thermodynamic optimization criteria used for assessing thermal engines are investigated and compared. The Purpose of this is to determine the most advantageous criteria. An irreversible Carnot cycle is analyzed by using five different methods and results are compared. According to calculations, the ecological function criterion (ECF) is defined as the most convenient optimization method. Although, its work output is less than the maximum work criteria and maximum available work (MAW), it has advantageous in terms of entropy generation and first law efficiency. In addition, ecological coefficient of performance (ECOP) and exergetic performance criteria (EPC) values provide minimum entropy generation and maximum efficiency at their maximum, however, their work output is very small. ECF obtains its maximum values at x=0.488 (377.175kW) for endoreversible cycle and at x=0.477 (329.812kW) for irreversible cycle. For these reasons, ECF is suggested as the best optimization criteria.
•Response Surface Methodology was developed to analyze the heat exchanger.•The available work loss minimization was introduced as a new criterion.•The interacting effects of geometric parameters were ...considered in the study.•The optimum geometric parameters of the heat exchanger were acquired and verified.
In this paper, a numerical study is performed to investigate the effects of geometrical parameters on the thermodynamic performance of the helically coiled recuperative heat exchanger in a Joule–Thomson (J–T) cryocooler. A novel optimization model is developed based on the available work loss minimization for the recuperative heat exchanger. The experiments are conducted based on four factors: L, Dt, S, Ds, one level: Nd, and the results are analyzed according to the principle of Response Surface Methodology (RSM). The final predicted optimum combination of geometrical parameters for the heat exchanger is: L = 430.5 mm, Dt = 0.45 mm, S = 5.41, Ds = 4.3 mm. The optimization results are in good agreement with our model, and the deviations of predicted values are less than 1.32%. The model and results presented here for the optimization of the heat exchanger can provide helpful guidance and a new way for the optimization of J–T cryocooler.
