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1 – 10 of over 2000Ozgur Balli, Alper Dalkıran and Tahir Hikmet Karakoç
This study aims to investigate the aviation, energetic, exergetic, environmental, sustainability and exergoeconomic performances of a micro turbojet engine used in unmanned aerial…
Abstract
Purpose
This study aims to investigate the aviation, energetic, exergetic, environmental, sustainability and exergoeconomic performances of a micro turbojet engine used in unmanned aerial vehicles at four different modes.
Design/methodology/approach
The engine data were collected from engine test cell. The engine performance calculations were performed for four different operation modes.
Findings
According to the results, maximum energy and exergy efficiency were acquired as 19.19% and 18.079% at Mode 4. Total cost rate was calculated as 6.757 $/h at Mode-1, which varied to 10.131 $/h at Mode-4. Exergy cost of engine power was observed as 0.249 $/MJ at Mode-1, which decreased to 0.088 $/MJ at Mode-4 after a careful exergoeconomic analysis.
Originality/value
The novelty of this work is the capability to serve as a guide for similar systems with a detailed approach in the thermodynamic, thermoeconomic and environmental assessments by prioritizing efficiency, fuel consumption and cost formation. This investigation intends to establish a design of the opportunities and benefits that the thermodynamic approach provides to turbojet engine systems.
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Kaiwen Pang, Yaojun Li, Wei Yang and Zhuqing Liu
This study aims to develop and validate a new cavitation model that considers thermodynamic effects for high-temperature water flows.
Abstract
Purpose
This study aims to develop and validate a new cavitation model that considers thermodynamic effects for high-temperature water flows.
Design/methodology/approach
The Rayleigh–Plesset equation and “B-factor” method proposed by Franc are used to construct a new cavitation model called “thermodynamic Zwarte–Gerbere–Belamri” (TZGB) by introducing the thermodynamic effects into the original ZGB model. Furthermore, the viscous term of the Rayleigh–Plesset equation is considered in the TZGB model, and the model coefficients are formulated as a function of temperature. Cavitating flows around the NACA0015 hydrofoil under different water temperatures (25°C, 50°C and 70°C) at the angle of attack of 5° are calculated.
Findings
Results of the investigated temperatures show good agreement with the available experimental data. Given that the thermodynamic and viscosity effects are included in the TZGB model and the model coefficients are treated as a function of temperature, the TZGB model shows better performance in predicting the pressure coefficient distribution and length of cavity than the original ZGB cavitation model and other models do. The TZGB model aims to determine the thermodynamic and viscosity effects and perform better than the other models in predicting the mass transfer rate, particularly in high-temperature water.
Originality/value
The TZGB model shows potential in predicting the cavitating flows at high temperature and the computational cost of this model is similar to that of the original ZGB model.
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The paper attempts to address both resource consumption and recycling effectiveness, using concepts from thermodynamics: entropy production for evaluating the costs (resource…
Abstract
Purpose
The paper attempts to address both resource consumption and recycling effectiveness, using concepts from thermodynamics: entropy production for evaluating the costs (resource consumption) and statistical entropy for evaluating the benefits (separation of materials) of recycling processes.
Design/methodology/approach
Resource consumption, in this context, is to be understood as the overall thermodynamic devaluation of matter and energy flows. The recycling effectiveness, on the other hand, can be measured by the process's ability to reduce the “mixedness” of the material flows, using statistical entropy (entropy of mixing) as an indicator. Statistical entropy has been used by others as an indicator for the performance of waste separation processes, and its application to metal recycling seems straightforward. Entropy production has been applied as a measure for resource consumption in copper production. Here, the two concepts are combined to reach an expression describing the resource efficiency of recycling.
Findings
The theoretical description of the approach is supported by an example calculation for copper recycling. The findings suggest a near perfect effectiveness of the copper separation when processing medium grade copper scrap in a primary copper smelter. The resource consumption, on the other hand, is quite large when compared to the service of the process, giving rise to a rather small thermodynamic efficiency (in terms of the definition of efficiency as applied in this paper).
Research limitations/implications
Both measures used here, recycling efficiency and recycling effectiveness, are very demanding concerning the data basis, making applications time consuming. These drawbacks can be overcome by linking material flow tools (e.g. LCA software) with thermodynamic databases. More examples have to be considered to show the practical relevance of the approach.
Originality/value
The paper addresses effectiveness and efficiency using a common denominator, thermodynamic entropy. This unification helps in ranking different recycling options regarding their performance in terms of technical effectiveness and resource consumption.
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The “thermodynamic model” constitutes a unified theoretical framework for the coupled simulation of carrier and energy flow in semiconductor devices under general ambient…
Abstract
The “thermodynamic model” constitutes a unified theoretical framework for the coupled simulation of carrier and energy flow in semiconductor devices under general ambient conditions such as, e.g., the presence of a quasi‐static magnetic field or the interaction with an electromagnetic radiation field (light). The current relations governing particle and heat transport are derived from the principles of irreversible phenomenological thermodynamics; the driving forces include drift, diffusion, thermal diffusion, and deflection by the Lorentz force. All transport coefficients may be interpreted in terms of well‐known thermodynamic effects and, hence, can be obtained from theoretical calculations as well as directly from experimental data. The thermodynamic model allows the consistent treatment of a wide variety of physical phenomena which are relevant for both the operation of electronic devices (e.g., lattice heating, hot carrier and low temperature effects) and the function of microsensors and actuators (e.g., thermoelectricity, galvanomagnetism and thermomagnetism).
Managing the urban housing plan of a very fast-growing city may be difficult if the scientific input, i.e. thermodynamic architecture and the climate change challenges, is not…
Abstract
Purpose
Managing the urban housing plan of a very fast-growing city may be difficult if the scientific input, i.e. thermodynamic architecture and the climate change challenges, is not factored into its initial framework. Recent building plan in some parts of a growing city located in a developing country was adopted for the purpose of this research. The purpose of this study is to investigate the impact of poor urban planning on humans.
Design/methodology/approach
The reverberation time analysis was carried using the Ecotect software. In total, 15-year surface temperature data were obtained (1999-2013) from the Global Land Data Assimilation System. Thermal distributions were calculated using beta probability and Gaussian distribution. Also, the parametric study of the solar constant was accomplished using possible mathematical outcomes.
Findings
It was discovered that irrespective of the fabrics of building, air properties and materials within a building, the total heat and sound absorptions are high for the life form. Necessary recommendations were made for further study.
Research limitations/implications
Only the outdoor impact was calculated.
Practical implications
There should be more proactive measures by the urban planning authorities.
Social implications
There would be wide spread of diseases and very low thermal comfort.
Originality/value
This paper illustrates on the most ignored parameter in environmental architecture.
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New non-equilibrium systems theory is a very important theoretical and methodological base of survey and understanding of contemporary economic systems and processes. Equilibrium…
Abstract
Purpose
New non-equilibrium systems theory is a very important theoretical and methodological base of survey and understanding of contemporary economic systems and processes. Equilibrium is considered one of the basic conditions of existence and evolution of natural and social systems, according to scientific literature. Generally speaking, it can be presented as true. But the problem is that classical imagination perceives equilibrium as something real and stable – something more stable than basic condition of evolution of systems. Non-equilibrium state was usually understood as something negative, something destructive and something which has to be eliminated. Non-equilibrium state was understood as an anomaly, as an expression of weakening of system security and as a road to extinction. Thermodynamics comes with an idea that equilibrium is a “short” state of the system, equilibrium is very relative and all systems try to meet it, but they will never reach it. Equilibrium is usually connected with classical science and non-equilibrium state is connected with thermodynamics paradigm, with a new methodology of science. Non-equilibrium state is often seen as a basic condition – as an internal source of system evolution and its activities. Non-equilibrium state is a base of new arrangement of systems. Misunderstanding of contemporary non-equilibrium state theory and new expressions or aspects of dynamic processes can bring about negative impacts on the survey and establishment of new global economic system, e.g. new national and local economic systems. Therefore, the non-equilibrium state theory is a methodological base of new perception and survey of contemporary economic systems.
Design/methodology/approach
A study of non-equilibrium thermodynamics.
Findings
Irreversibility and non-equilibrium, occurring in each process and evolutionary phase of economic systems, are connected with accidents and openness. Openness of systems enables (and causes) diversification toward wider system or environment and penetration of external elements and processes to internal structure of the system. A system like this is more sensitive to external and internal changes. Considering this, it is very important to be aware of the fact that entropy has different behavior in “closed” systems – different from behavior in open systems. Open economic systems communicate with external environment, interact with external systems and they exchange the energy. They consume energy of external environment and penetrate it. Elements, nodes and joints in open systems can communicate, connect and integrate with elements, nodes and joints from external systems. The growth of entropy is “smoother” and equilibrium of the system, its sub-systems and elements proceeds despite the non-equilibrium state of elements of the own system. They have to communicate and exchange the energy with external environment. This is because of the non-equilibrium state.
Originality/value
This is an original thermodynamic approach to the importance of non-equilibrium in the development of economic systems.
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Xie Xuejun, Yuanlin Zhang, Rui Wang, Yu Zhang and Mianzhao Ruan
The hollow copper wires of the generator are seriously corroded in cooling water. This paper aims to explore the mechanism of copper corrosion by thermodynamic calculation and…
Abstract
Purpose
The hollow copper wires of the generator are seriously corroded in cooling water. This paper aims to explore the mechanism of copper corrosion by thermodynamic calculation and kinetic experiments and to find out the precise pH range for preventing corrosion of copper in stator internal water and dual internal water cooled generators.
Design/methodology/approach
Thermodynamic and kinetic studies were carried out for the purpose of preventing the corrosion of hollow conducting copper wires in the internal cooling water. Thermodynamic calculation results demonstrate hollow copper wires electrochemically corroded by oxygen rather than acids (H+) and find out a precise anti-corrosion pH range. Kinetic experiments research on the effect of the pH value and oxygen concentration on corrosion and protection methods of copper in desalted water.
Findings
Research results demonstrate that, in the internal cooling water, hollow copper wires are electrochemically corroded by oxygen, rather than acids (H+). The method of preventing copper from corrosion in the desalted water is to control the pH value of the stator cooling water and the dual water inner cooling water between 7.86-8.86 and 7.86-9.26, respectively.
Originality/value
The thermodynamic calculation and potentiometric-pH diagram are used to obtain the accurate pH range of the inner cooling water and inner cooling water in the inner cooling water system. The kinetic experiments provide data support for the effect of temperature, pH value and oxygen concentration.
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Hector Barrios-Piña, Stéphane Viazzo and Claude Rey
The purpose of this paper is to show a thermodynamic analysis to determine the contribution of each term of the total energy balance.
Abstract
Purpose
The purpose of this paper is to show a thermodynamic analysis to determine the contribution of each term of the total energy balance.
Design/methodology/approach
The thermodynamic analysis comprises a number of numerical simulations where some terms, typically ignored by the commonly used approximations, are removed from the total energy equation to quantify the effects in the flow and heat transfer fields. The case study is the differentially heated square cavity flow, in which the effects of work done by the pressure forces contribute significantly to the energy balance. Because local magnitudes are computed here for discussion, the dimensional form of the governing equations is preferred and a numerical model without any restrictive approximation about the role of the pressure is used.
Findings
The results show that the work of gravity forces term is in perfect balance with the work of pressure forces term, and thus, ignoring the contribution of one of them yields an incorrect solution. In addition, it is shown that the assumption of zero divergence of the Boussinesq approximation can be erroneous, even for a natural convection flow case where the temperature difference is very small.
Research limitations/implications
As the flow and heat transfer governing equations are complex, simplifying assumptions are generally used; that is, the Boussinesq and low Mach number approximations. These assumptions are systematically adopted without any validation process and without considering that they modify the physical meaning of one or more of the thermodynamic quantities, particularly the pressure. This fact results in inconsistencies of the different forms of energy.
Originality/value
This is the first time that the terms of the total energy balance are quantified in such a way, in a differentially heated square cavity flow, which is a case study addressed by several authors.
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Laurens Weiss and Wolfgang Mathis
The conventional treatment of thermal noise is based on Nyquist’s theorem. This theorem has only been derived for linear, reciprocal (we define “reciprocal networks” as networks…
Abstract
The conventional treatment of thermal noise is based on Nyquist’s theorem. This theorem has only been derived for linear, reciprocal (we define “reciprocal networks” as networks that are built of reciprocal network elements) networks. In this paper a description of thermal noise in reciprocal non‐linear RLC networks is presented. This description is derived from first principles, i.e. from a direct application of non‐equilibrium thermodynamics (irreversible thermodynamics) to electrical networks. As an example, the class of “complete” non‐linear networks is considered. Using the idea of equivalent n‐ports, the theory’s extension to certain classes of transistor circuits should be possible.
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The electrochemical approach to corrosion problems has been stressed before, but here the author dwells more on the thermodynamic aspects since comparatively small changes in…
Abstract
The electrochemical approach to corrosion problems has been stressed before, but here the author dwells more on the thermodynamic aspects since comparatively small changes in energy, and hence in chemical activity, which are caused by stress may result in very marked changes in the damaging effects of corrosion. Part 1 of the article opens with a thermodynamic approach covering borderline corrosion and the corrosion of crystals, and then deals with the effect of stress on chemical attack. Following this is a comprehensive survey of types of metal deformation (e.g. slip, cleavage and grain boundary movement) and concludes with data regarding the properties of grain boundaries and the effect of temperature and rate of loading. Stress corrosion is the major subject to be covered next month.