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An exergy analysis has been carried out for an irreversible Braysson cycle. The analytical formulae of power output and exergy efficiency are derived. The influences of various parameters on the exergy performance are analyzed by numerical calculation, and the results obtained have been compared with those of Brayton cycle under the same conditions. It is shown that the exergy loss in the combustion...
A<space>thermodynamic for the effect of the annualized cost of a component on the production cost in 1000<space>kW gas-turbine cogeneration system was studied by utilizing the generalized exergy balance and cost-balance equations developed previously. Comparison between typical exergy-costing methodologies were also made by solving a predefined cogeneration system, CGAM problem. It was...
This paper outlines a newly emerging body of work that relies on exergy analysis and thermodynamic optimization in the design of energy systems for modern aircraft. Exergy analysis establishes the theoretical performance limit. The minimization of exergy destruction brings the design as closely as permissible to the theoretical limit. The system architecture springs out of this constrained optimization...
The effects of conduction and heat generation due to viscous dissipation in annuli is a topic of interest to researchers, since the applications include aerospace, food processing, electric machines, etc. In the present study, temperature rise and entropy generation in a cylindrical annuli due to conduction and viscous dissipation are considered. In the mathematical formulation, the flow developed...
It is shown that Van Mieghems available potential energy for the atmosphere can be derived, in a local formulation, from an extension of the concept of exergy. The available potential energy can be interpreted as exergy applied to each layer of a thermally stratified atmosphere. This interpretation allows the application of well-known exergy theorems to the atmosphere and, therefore, deepens the thermodynamic...
A procedure to establish the optimal performance parameters for the minimum entropy generation during the collection of solar energy, is presented. The Entropy Generation Number, N s , and the criterion for the optimal thermodynamic operation of a collector under nonisothermally, finite-time conditions, are reviewed. The Mass Flow Number, M, corresponding to the optimum flow of working fluid...
Thermodynamic analysis of the thermomechanical coupling in a tangential Couette flow is presented for the Nahme number Na range of 0.5<Na<2.5. In the analysis, the temperature and velocity gradients, obtained from the series solutions in the Brinkman number Br, have been used for Newtonian fluids whose viscosity and thermal conductivity are expressed as linear functions of temperature. The entropy...
The exergy of an energy form or a substance is a measure of its usefulness or quality or potential to cause change. A<space>thorough understanding of exergy and the insights it can provide into the efficiency, environmental impact and sustainability of energy systems, are required for the engineer or scientist working in the area of energy systems and the environment. Further, as energy policies...
An exergy analysis of a solid polymer fuel cell power system for transportation applications is reported. The analysis was completed by implementing the fundamental governing second law equations derived for the system into a fuel cell performance model developed previously. The model analyzes all components of the system including the fuel cell stack and the air compression, hydrogen supply, and...
Exergy analysis is applied to a turbojet engine over flight altitudes ranging from sea level to 15000 m (~50000 ft), to examine the effects of using different reference-environment models. The results of this analysis using a variable reference environment (equal to the operating environment at all times) are compared to the results obtained using two constant reference environments (sea level and...
A general endoreversible refrigeration cycle model which includes the irreversibility of heat transfer across finite temperature differences and the heat leak loss between the external heat reservoirs is used to analyze the rate of exergy output of a multi-stage combined refrigeration system. The relations between the rates of exergy output and refrigeration and between the rate of exergy output and...
Partial exergy losses appearing in particular parts of thermal systems have been defined. Balance equations determining these losses have been formulated. The problem of calculation of partial exergy losses in cogeneration processes has been discussed. Sequence method of calculation of partial exergy losses has been presented. Examples of calculation of partial exergy losses have been developed.
The collective role of radiation and convection modes of heat transfer in a solar driven heat engine is investigated through a finite time thermodynamics analysis. Heat transfer from hot reservoir is assumed to be radiation and/or convection dominated. The irreversibilities due to these finite rate heat transfers were considered in determining the limits of efficiency and power generation that were...
This paper presents a novel approach to the evaluation of energy conversion processes and systems, based on an extended representation of their exergy flow diagram. This approach is a systematic attempt to integrate into a unified coherent formalism both Cumulative Exergy Consumption and Thermo-economic methods, and constitutes a generalisation of both, in that its framework allows for a direct quantitative...
The thermodynamic optimization of a mechanically driven solar heat pump is presented. A new expression to describe the optimal thermal performance under finite operating conditions considering the internal and external irreversibilities during actual operation is derived. The optimum ratio between the condenser and collector-evaporator conductances (UA) determines the coefficient of performance (COP)...
This paper uses the hydraulic and polytropic efficiency concepts in a domain wider than that of their original definition. A generalized Bernoulli equation taken from previous papers is also considered. The aim is to find a general statement yielding hydraulic efficiency values ranging from one to zero, and a relative dissipative term, suitably chosen, that varies between zero and one. This will be...
A central theme of industrial ecology (IE) is the idea of using the cyclical resource-use patterns observed in mature, biological ecosystems as a model for designing increasingly mature 'industrial ecosystems' whose productivity relies less on resource extraction and waste emission. In this two part series, we will use a thermodynamic interpretation of ecosystem evolution to strengthen this biological-industrial...
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