Teaching Power Cycles by Comparative First- and Second-Law Analysis of Their Evolution

1997 ◽  
Vol 25 (1) ◽  
pp. 13-31 ◽  
Author(s):  
William R. Dunbar ◽  
Noam Lior
Keyword(s):  
Power Plants ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Energy Systems ◽  
Thermal Engineering ◽  
Second Law ◽  
Intellectual Curiosity ◽  
Educational Approach ◽  
Power Cycles ◽  
Second Law Analysis

The teaching of power cycles in courses of thermodynamics or thermal engineering was traditionally based on first-law analysis. Second-law analysis was typically taught later, and not integrated with it. This approach leaves the student ignorant of the effect of operating parameters and cycle modifications on the accompanying exergy (availability) magnitudes and component irreversibilities, which are necessary for evaluating the potential for further system improvements. It also leaves many of the students with an ambiguous understanding of the exergy concept and its use. Consonant with the gradual changes in this educational approach, which increasingly attempt to integrate first- and second-law analysis, this paper recommends a strategy which integrates exergy analysis into the introduction and teaching of energy systems, demonstrated and made didactically appealing by an examination of the historical evolution of power plants, emphasizing the objectives for improvements, accomplishments, constraints, and consequently the remaining opportunities. Important conclusions from exergy analysis, not obtainable from the conventional energy analysis, were emphasized. It was found that this approach evoked the intellectual curiosity of students and increased their interest in the course.

Exergy Analysis of a Solar Heating System

1995 ◽  
Vol 117 (3) ◽  
pp. 249-251 ◽  
Author(s):  
Geng Liu ◽  
Y. A. Cengel ◽  
R. H. Turner
Keyword(s):  
Exergy Analysis ◽  
Energy Analysis ◽  
Second Law Of Thermodynamics ◽  
Heating System ◽  
Solar Heating ◽  
Second Law ◽  
Exergy Destruction ◽  
Thermal Systems ◽  
Heating Systems ◽  
Second Law Analysis

Exergy destruction associated with the operation of a solar heating system is evaluated numerically via an exergy cascade. As expected, exergy destruction is dominated by heat transfer across temperature differences. An energy analysis is also given for comparison of exergy cascade to energy cascade. Efficiencies based on both the first law and second law of thermodynamics are calculated for a number of components and for the system. The results show that high first-law efficiency does not mean high second-law efficiency. Therefore, the second-law analysis has been proven to be a more powerful tool in identifying the site losses. The procedure used to determine total exergy destruction and second law efficiency can be used in a conceptual design and parametric study to evaluate the performance of other solar heating systems and other thermal systems.

Second Law Analysis of Spray Evaporation

1990 ◽  
Vol 112 (2) ◽  
pp. 130-135 ◽  
Author(s):  
S. K. Som ◽  
A. K. Mitra ◽  
S. P. Sengupta
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Entropy Generation ◽  
Exergy Analysis ◽  
Droplet Evaporation ◽  
Second Law ◽  
Hot Gas ◽  
Second Law Analysis ◽  
Initial Drop ◽  
Parallel Stream

A second law analysis has been developed for an evaporative atomized spray in a uniform parallel stream of hot gas. Using a discrete droplet evaporation model, an equation for entropy balance of a drop has been formulated to determine numerically the entropy generation histories of the evaporative spray. For the exergy analysis of the process, the rate of heat transfer and that of associated irreversibilities for complete evaporation of the spray have been calculated. A second law efficiency (ηII), defined as the ratio of the total exergy transferred to the sum of the total exergy transferred and exergy destroyed, is finally evaluated for various values of pertinent input parameters, namely, the initial Reynolds number (Rei = 2ρgVixi/μg) and the ratio of ambient to initial drop temperature (Θ∞′/Θi′).

Second Law Analysis of an Energy Storage System Consisting of an Electrolysis Plant and the Graz Cycle With Internal H2/O2 Combustion

2019 ◽  
Author(s):  
Simeon Dybe ◽  
Tom Tanneberger ◽  
Panagiotis Stathopoulos
Keyword(s):  
Energy Storage ◽  
Power Plants ◽  
Storage System ◽  
Electric Energy ◽  
Energy Storage System ◽  
Working Fluid ◽  
Energetic Efficiency ◽  
Second Law ◽  
Electric Energy Storage ◽  
Second Law Analysis

Abstract The expansion of renewable energy generation must go hand in hand with measures for reliable energy supply and energy storage. A combination of hydrogen and oxygen as storing media provided from electrolysis at high pressure and zero emission power plants is a very promising option. The Graz cycle is an oxy-fuel combined power cycle that can operate with internal H2/O2 combustion and steam as working fluid. It offers thermal efficiencies up to 68.5% (LHV). This work applies a second law analysis to the Graz cycle and determines its exergetic efficiency. Exergy destruction is broken down to the cycle’s components thus providing insights on the location and magnitude of the cycle’s inefficiencies. A sensitivity analysis identifies the cycle’s exergetic and energetic efficiency as a function of representative parameters, offering an approach for future improvements. The combination of the cycle with an electrolysis plant is subsequently analyzed as an electric energy storage system. The round trip efficiency of the storage and back conversion system is computed by taking into account the additional compression of the reactants. As part of this analysis, the effect of the electrolyzer’s operational pressure is studied by comparing several commercial electrolyzers.

Exergy Analysis of Various Absorption Heat Transformer Systems Using Classical and Modified Gouy–Stodola Equation

2015 ◽  
Vol 23 (01) ◽  
pp. 1550006 ◽  
Author(s):  
T. Goel ◽  
G. Sachdeva
Keyword(s):  
Exergy Analysis ◽  
Waste Heat ◽  
Lithium Bromide ◽  
Second Law ◽  
Operating Parameters ◽  
Classical Approach ◽  
Exergy Destruction ◽  
Second Law Analysis ◽  
Heat Transformer ◽  
Study Performance

In the present study, performance evaluation of three different configurations of absorption heat transformer (AHT) is carried out by supplying the waste heat of same mass and same temperature; and exergy analysis is done using both the classical and modified Gouy–Stodola equation. For this a mathematical model is developed for all the three arrangements in Engineering Equation Solver. Water–lithium bromide is used as a working pair. The results of exergy destruction with classical and modified Gouy–Stodola equation are compared for different systems. Further various operating parameters are varied to predict the performance of the systems on the basis of second law analysis. The result showed that the amount of hot fluid produced in absorber is more for system 3 as compared to other configurations. The irreversibility calculated by the modified approach comes out to be 25.78%, 23.60%, and 23.45% more than the exergy destruction obtained by the classical approach in the three cases, respectively. Thus, there is a need to employ the modified approach of Gouy–Stodola equation for calculating the real irreversibility which helps in predicting the scope of improvement and the performance of the system more accurately.

scholarly journals Thermodynamic Analysis of a Steam Power Plant with Double Reheat and Feed Water Heaters

2014 ◽  
Vol 6 ◽  
pp. 940818 ◽  
Author(s):  
M. M. Rashidi ◽  
A. Aghagoli ◽  
M. Ali
Keyword(s):  
Heat Load ◽  
Exergy Analysis ◽  
Low Pressure ◽  
Second Law ◽  
Feed Water ◽  
Steam Temperature ◽  
Steam Power ◽  
Low Pressure Turbine ◽  
Water Heaters ◽  
Second Law Analysis

A steam cycle with double reheat and turbine extraction is presented. Six heaters are used, three of them at high pressure and the other three at low pressure with deaerator. The first and second law analysis for the cycle and optimization of the thermal and exergy efficiencies are investigated. An exergy analysis is performed to guide the thermodynamic improvement for this cycle. The exergy and irreversibility analyses of each component of the cycle are determined. Effects of turbine inlet pressure, boiler exit steam temperature, and condenser pressure on the first and second laws' efficiencies are investigated. Also the best turbine extraction pressure on the first law efficiency is obtained. The results show that the biggest exergy loss occurs in the boiler followed by the turbine. The results also show that the overall thermal efficiency and the second law efficiency decrease as the condenser pressure increases for any fixed outlet boiler temperature, however, they increase as the boiler temperature increases for any condenser pressure. Furthermore, the best values of extraction pressure from high, intermediate, and low pressure turbine which give the maximum first law efficiencies are obtained based on the required heat load corresponding to each exit boiler temperature.

Thermodynamic analysis of a coal gasification and split Rankine combined cogeneration plant. Part 2: Exergy analysis

2005 ◽  
Vol 219 (3) ◽  
pp. 179-185 ◽  
Author(s):  
S De ◽  
S K Biswal
Keyword(s):  
Thermodynamic Analysis ◽  
Parametric Study ◽  
Coal Gasification ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Plant Part ◽  
Second Law ◽  
Operating Parameters ◽  
Cogeneration Plant ◽  
Component Level

In continuation of the energy analysis in Part 1 of this paper, an exergy analysis of the conceptualized advanced combined cogeneration plant is discussed in this part of the paper. This exergy analysis at the component level identifies the major sources of destruction of work potential. A parametric study has been carried out, for the same design and operating parameters as in Part 1, to explore the second-law performance of components of the plant against variations in these parameters.

scholarly journals Dynamic Extended Exergy Analysis of Photon Enhanced Thermionic Emitter Based Electricity Generation

2021 ◽  
Author(s):  
Canberk Unal ◽  
Emin Acikkalp ◽  
David Borge-Diez
Keyword(s):  
Environmental Impact ◽  
Electricity Generation ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Energy Systems ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Related System ◽  
Social Data ◽  
Energy Flows

Exergy is the very useful tool to evaluate energy systems besides energy analysis based on the first law of the thermodynamics. In contrast to energy, exergy is not conserved and always decreases. There are many types of exergy analysis involving exergoeconomic, exergoenvironmental, advanced exergy-based analyses, extended exergy analysis etc. In this study, an application of the extended exergy analysis is performed. In extended exergy analysis, not only energy related system is considered but also all materials and energy flows’ exergy, non-energetic and immaterial fluxes (capital, labor and environmental impact) are turned into exergy equivalent values and utilized in the analysis, which are calculating for local econometric and social data. These methods can be applied to societies or energy based or non-energy-based system. In this study, dynamic exergy analysis and extended exergy application of electricity generation from photon enhanced thermionic emitter is conducted. According to results, some important values can be listed as; extended exergy destruction, conventional based exergy destruction, extended exergy efficiency, conventional exergy efficiency, extended sustainability ratio, conventional sustainability ratio, extended exergy-based depletion ratio and conventional exergy-based depletion ratio are 542106006 MJ, 542084601 MJ, 0.01094, 0.01094, 1.011, 1.011, 0.978 and 0.989 respectively.

Thermodynamic Analysis and Optimisation of Mixed Fluid Turbine Power Plants

1999 ◽  
Author(s):  
M. Belli ◽  
M. Stumbo ◽  
D. Vinarova
Keyword(s):  
Power Plants ◽  
Power Level ◽  
Water Injection ◽  
Simulation Program ◽  
Second Law ◽  
Power Cycles ◽  
Decision Variables ◽  
Computer Simulation Program ◽  
The Difference ◽  
General Computer

Abstract This paper discusses the thermodynamics of power cycles where steam or water are mixed with air to improve the performance of stationary gas turbine cycles. A general computer simulation program is presented; several components (compressor, combustor, turbine, recovery boiler, saturator, recuperator, inter-cooler, after-cooler) are modelled obtaining a transfer function between in-coming and out-coming fluids. Coupled with this simulation program, an optimisation is carried out using a decomposition strategy based on the second law of thermodynamic and a concept for costing the components of the cycles. A large number of decision variables can by optimised with enhanced convergence to an optimum. As results, a large number of simulations and optimisations are performed for three different plants (STIG, HAT and a cycle with water injection both in the compressor and in the combustor). A wide number of comparisons shows the difference between the cycles and the power level at which each plant gives the lowest exergoeconomic costs.

Second law analysis of wind turbine power plants: Cesme, Izmir example

Energy ◽  
2011 ◽  
Vol 36 (5) ◽  
pp. 2535-2542 ◽  
Author(s):  
Omer Baskut ◽  
Onder Ozgener ◽  
Leyla Ozgener
Keyword(s):  
Wind Turbine ◽  
Power Plants ◽  
Second Law ◽  
Second Law Analysis
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