Exergetic Efficiencies and the Exergy Content of Terrestrial Solar Radiation

2004 ◽  
Vol 126 (1) ◽  
pp. 673-676 ◽  
Author(s):  
Sean E. Wright ◽  
Marc A. Rosen
Keyword(s):  
Solar Radiation ◽  
Exergy Analysis ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Radiative Fluxes ◽  
Solar Engineering ◽  
Practical Performance ◽  
Maximum Work ◽  
Energy Conversion Devices ◽  
Better Than

In the field of solar engineering the practical performance of solar energy conversion devices is generally evaluated strictly on an energy (first law) basis. However, the second law of thermodynamics determines the maximum work potential or exergy content of radiative fluxes independent of any conceptual device. The work in this paper quantifies the effect of directional and spectral distribution of terrestrial solar radiation (SR) on its exergy content. This is particularly important as the thermodynamic character of terrestrial SR is very different from that of blackbody radiation (BR). Exergetic (second law) efficiencies compare the work output of a device to the exergy content of the radiative source flux rather than its energy flux. As a result, exergetic efficiencies reveal that the performance of devices in practice is always better than what is indicated by the corresponding energy efficiency. The results presented in this paper introduce the benefits of using exergy analysis for solar cell design, performance evaluation and optimization.

scholarly journals Exergy Analysis of Integrated Gas-Steam Cycle

1994 ◽  
Author(s):  
Onkar Singh ◽  
R. Yadav
Keyword(s):  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Second Law Of Thermodynamics ◽  
Heat Recovery Boiler ◽  
Second Law ◽  
Operating Parameters ◽  
Insight Into ◽  
Steam Cycle

The thermodynamic analysis of integrated gas/steam cycle has been carried out on the basis of second law of thermodynamics. The exergy analysis provides a viable understanding of the influence of various parameters on the distribution of losses in the constituent components of the cycle. The paper also provides the insight into the influence of changing operating parameters on the performance of the waste heat recovery boiler, which in turn questions the viability of the integrated gas/steam cycle.

Discussion of Energy Consumption Analysis Method on Energy System

2011 ◽  
Vol 130-134 ◽  
pp. 1578-1581
Author(s):  
Cai Juan Zhang ◽  
Li Gang Wang ◽  
Ling Nan Wu ◽  
Tong Liu ◽  
Qiang Lu ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Economic Analysis ◽  
Energy Saving ◽  
Exergy Analysis ◽  
Energy Analysis ◽  
Rapid Development ◽  
Second Law Of Thermodynamics ◽  
Energy Utilization ◽  
Second Law ◽  
Analysis Method

With the social rapid development, the earth's limited primary energy such as coal, oil, natural gas etc will be exhausted; energy problem has caused worldwide widespread attention. Therefore, under the development of renewable energy, without exception, each country is actively trying to explore the new theory and using energy-saving and technology to improve energy utilization ratio and reduce the energy consumption and the harm on environment. Scientific analysis of energy saving is an important link of digging energy saving potential, effective energy analysis method plays a pivotal role in implementing saving energy. This paper summarized several energy analysis methods on the basis of the first and second law of thermodynamics, introduced the most widely used enthalpy analysis method, entropy analysis, exergy analysis and exergy economic analysis which are based on the second law of thermodynamics, introduced emphatically the specific consumption analysis theory development with exergy analysis and exergy economic analysis.

Exergy Analysis of Data Centres-Effect of the Rack Location and Airflow Direction on the Thermal Performance

2016 ◽  
Vol 846 ◽  
pp. 36-41
Author(s):  
Babak Fakhim ◽  
Masud Behnia ◽  
Steven W. Armfield
Keyword(s):  
Temperature Distribution ◽  
Numerical Analysis ◽  
Thermal Performance ◽  
Exergy Analysis ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Temperature Profiles ◽  
Data Centre ◽  
The Impact ◽  
Data Centres

In this paper, a numerical analysis of flow and temperature distribution of a small raised-floor data centre is conducted in order to evaluate the thermal performance of the data centre. The flow patterns and temperature profiles established leads to a detailed exergy analysis of the data centre, which results in better understanding of irreversibilities in room airspace. The impact of the rack location in the data centre room and the airflow direction through perforated tiles on the thermal performance of the data centre is investigated using first-law and second-law of thermodynamics.

Exergy Analysis of Transcritical Regenerative Organic Rankine Cycle Using Isobutane

2013 ◽  
Vol 442 ◽  
pp. 183-186
Author(s):  
Kyoung Hoon Kim
Keyword(s):  
Exergy Analysis ◽  
Organic Rankine Cycle ◽  
Internal Heat ◽  
Second Law Of Thermodynamics ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Second Law ◽  
Source Temperature ◽  
Internal Heat Exchanger ◽  
Maximum Value

Exergy analysis is performed for transcritical Organic Rankine Cycle (ORC) with internal heat exchanger based on the second law of thermodynamics. Effects of source temperature as well as turbine inlet pressure (TIP) are investigated on the exergy destructions (or anergies) of the system as well as exergy efficiency. Results show that irreversibility of the system decreases with increasing TIP or decreasing source temperature. Exergy efficiency decreases with increasing source temperature; however has a maximum value with respect to TIP.

scholarly journals ‘The optimization of a jet turbojet engine by PSO and searching algorithms’

2019 ◽  
Author(s):  
Sorush Niknamian
Keyword(s):  
Sea Level ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Second Law Of Thermodynamics ◽  
Computer Code ◽  
Exergy Efficiency ◽  
Second Law ◽  
Combustion Chambers ◽  
Software Environment ◽  
Turbojet Engine

The turbojet engine operates on the ideal Brayton cycle (gas turbine) and consists of six main parts: diffusers, compressors, combustion chambers, turbines, afterburners and nozzles. Using computer code writing in MATLAB software environment, exergy analysis on all selected turbojet engine components, exergy analysis on J85-GE-21 turbojet engine for selective height of 10008000 meters above sea level at speeds of 200 m/s and temperatures of 10, 20 and 40 ° C have been provided and then, according to the system functions, the system is optimized based on the PSO method. For the purpose of optimization, variables of Mach number, efficiency of the compressor, turbine, nozzle and compressor pressure ratio are considered in the range of 0.6 to 1.4, 0.8 to 0.95, 0.8 to 0.95 and 7 to 10, respectively. The highest exergy efficiency of different parts of the engine at sea level with an inlet air velocity of 200 m/s corresponds to a diffuser with 73.1%. Then, the nozzle and combustion chamber are respectively 68.6% and 51.5%. The lowest exergy efficiency is related to compressor with 4%. After that, the afterburner is ranked second with 11.6%. Also, the values of entropy produced and the efficiency of the second law before optimization were 1176.99 and 479 w/k respectively and the same values after optimization were 1129 and 51.4 w/k respectively which is identified. After the optimization process, the amount of entropy produced is reduced and the efficiency of the second law of thermodynamics has increased.

scholarly journals Exergetic performance of VCR system with TiO2-nano additive in the compressor oil

2020 ◽  
pp. 58-58
Author(s):  
Fatih Selimefendigil ◽  
HakanF. Oztop
Keyword(s):  
Exergy Analysis ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Step Method ◽  
Particle Volume ◽  
Vapor Compression Refrigeration

Exergy analysis of a vapor-compression refrigeration system with TiO2 nanoadditives in the compressor oil was performed. Two-step method was used for the preparation of nano-oil for various solid particle volume fractions between 0% and 1%. Irreversibilities were determined by using second law of thermodynamics. Reduction in total irreversibility is achieved with nanoparticle inclusion and it was significant for higher particle volume fraction.

scholarly journals ANALISIS EKSERGI PENGERINGAN IRISAN TEMULAWAK

2016 ◽  
Vol 36 (01) ◽  
pp. 96
Author(s):  
Lamhot Parulian Manalu ◽  
Armansyah Halomoan Tambunan
Keyword(s):  
Exergy Analysis ◽  
Second Law Of Thermodynamics ◽  
Exergy Efficiency ◽  
Energy Utilization ◽  
Second Law ◽  
Process Conditions ◽  
Drying Process ◽  
Conservation Of Energy ◽  
Thin Layer Drying ◽  
Curcuma Xanthorrhiza

Java turmeric (Curcuma xanthorrhiza Roxb.) is a medicinal plant used as raw material for making herbal medicine, its rhizome cut into slices and dried so called simplicia. Curcuma has a harvest moisture content is high enough to need a great energy for drying. Generally, the theory used to analyze the energy efficiency is the first law of thermodynamics that describes the principle of conservation of energy. However, this theory has limitations in measuring the loss of energy quality. To determine whether the energy used in the drying process has been used optimally in terms of quality, the second law of thermodynamics -known as exergy analysis- is used. The purpose of this study is to determine the efficiency of the thin layer drying of curcuma slices with exergy analysis. The results show that the process conditions affect the energy utilization ratio and exergy efficiency of drying. Exergy analysis method based on the second law of thermodynamics has been used to determine the amount of exergy destroyed so that the efficiency of the drying process can be determined more accurately. Exergy efficiency varies between 96.5%-100% for temperatures of 50 °C to 70 °C at 40% RH and 82.3% - 100% for 20% to 40% RH at 50 °C.Keywords: Drying, energy, exergy efficiency, curcuma slices ABSTRAKTemulawak (Curcuma xanthorrhiza Roxb.) merupakan tanaman obat yang simplisianya digunakan sebagai bahan baku pembuatan jamu atau obat tradisional. Pengeringan merupakan proses utama dalam memproduksi simplisia. Untuk menganalisis efisiensi energi suatu proses pengeringan umumnya digunakan hukum termodinamika pertama yang menjelaskan tentang prinsip kekekalan energi. Akan tetapi teori ini mempunyai keterbatasan dalam mengukur penurunan kualitas energi. Untuk mengetahui apakah energi yang digunakan pada proses pengeringan sudah digunakan secara optimal dari sisi kualitas, digunakan hukum termodinamika kedua atau yang dikenal dengan analisis eksergi. Tujuan penelitian ini adalah menentukan efisiensi proses pengeringan lapisan tipis irisan temulawak dengan metode analisis energi dan eksergi. Dalam studi ini, metode analisis energi dan eksergi berdasarkan hukum termodinamika pertama dan kedua telah digunakan untuk menghitung rasio penggunaan energi dan besaran eksergi yang musnah (exergy loss). sehingga efisiensi proses pengeringan irisan temulawak dapat ditentukan secara akurat. Hasil penelitian menunjukkan bahwa kondisi proses pengeringan mempengaruhi rasio penggunaan energi dan efisiensi eksergi pengeringan. Semakin tinggi suhu dan RH pengeringan maka rasio penggunaan energi semakin rendah dan efisiensi eksergi semakin tinggi. Efisiensi eksergi pengeringan temulawak bervariasi antara 96,5%-100% untuk selang suhu 50 oC hingga 70 oC pada RH 40% serta 82,3% - 100% untuk selang RH 20% hingga 40% pada suhu 50 oC. Kata kunci: Pengeringan, energi, efisiensi eksergi, temulawak

Statistical Exergy-Based Analysis of a Steam Power Plant for Concept Verification and Plant Optimization

2015 ◽  
Author(s):  
Sari S. Mira ◽  
John H. Doty
Keyword(s):  
Power Plant ◽  
Exergy Analysis ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Plant Design ◽  
Steam Power ◽  
Steam Power Plant ◽  
Input Parameters ◽  
Plant Optimization ◽  
Derived Design

In this statistical exergy study of a conventional power plant, the concept of statistical exergy analysis as an alternative to common engineering approaches is examined. The statistical aspect is drawn from conducting Analysis of Variance (ANOVA) factorial design on the components of a proposed system. The exergy aspect comes in the extension of the typical energy analysis on engineering systems to include the limitations on the system imposed by the second law of thermodynamics. To test this approach, a steam power plant discussed in an example exercise in Cengel and Boles’ 5th Edition Thermodynamics textbook was used as the subject of analysis. Effects of three input parameters on 13 responses were closely examined. While using only 8 data points, the analysis still showed highly reliable and predictable results with square of residuals (R2) values of almost 100%. Predicted R2 values ranged between 88% and 99% with one outlier of 14.36%, depending on the input parameters. Derived from the results, a new plant design concept was proposed and analyzed. This design eliminated all theoretically unnecessary drivers of exergy destruction in the plant. It also utilized the force of gravity to achieve the desired power output. The design showed an increase of 3.85% to 18% in kilowatts of work output and 5% to 7% in first and second law efficiencies. In this case, the derived design was shown to be impractical due to difficult maintenance as well as the difficulty in reaching the required pressures without a pump. However, this method of statistical exergy analysis is still valuable, as practicality of application will vary from one proposed system to another.

scholarly journals STATEMENT OF THE SECOND LAW OF THERMODYNAMICS ON THE BASIS OF THE POSTULATE OF NONEQUILIBRIUM

2019 ◽  
Vol 16 (32) ◽  
pp. 698-712
Author(s):  
Vladimir V. RYNDIN
Keyword(s):  
Equilibrium State ◽  
Quantitative Measure ◽  
Second Law Of Thermodynamics ◽  
Irreversible Processes ◽  
Second Law ◽  
Unequal Distribution ◽  
Maximum Work ◽  
Reversible Processes ◽  
Objective Property ◽  
Physical Laws

Most physical laws are quantitative expressions of the philosophical laws of the conservation of matter and its properties of motion. The first law of thermodynamics (FLT) is an analytical expression of the law of conservation of motion when its shape changes. As for the second law of thermodynamics (SLT), it has not yet been clarified which property of matter does not change during the course of reversible processes and changes during the course of irreversible processes in an isolated system (IS). Hence, a large number of the SLT statements and an abundance of material to clarify these formulations. The author of the SLT is based on the “postulate of nonequilibrium”, according to which there is an objective property of matter - “nonequilibrium”, which characterizes the unequal distribution of matter and movement in space. All processes (reversible and irreversible) can proceed only in nonequilibrium systems. This leads to the only formulation of the second law of thermodynamics: when the reversible (ideal) processes occur in an isolated system, the nonequilibrium is preserved, and with the occurrence of irreversible (real) processes – decreases. When the system reaches an equilibrium state, the nonequilibrium disappears, and all processes cease. As a quantitative measure of the nonequilibrium of the system, we consider the maximum work that can be done when a nonequilibrium system transitions to an equilibrium state. The following quantities are used to calculate this work: “potential difference”, “entropy difference”, change in exergy. All these values decrease in the course of real (irreversible) processes in the isolated system and do not change in the course of reversible processes. As a result, a generalized expression of the SLT through the quantitative characteristics of the nonequilibrium of the system in the form of an inequality, which includes R. Claudius’s inequality for changing the entropy of an isolated system, is obtained.

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