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.

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 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.

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.

Derivation of Entropy and Exergy Transport Equations, and Application to Second Law Analysis of Sugarcane Bagasse Gasification in Bubbling Fluidized Beds

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Gabriel L. Verissimo ◽  
Manuel E. Cruz ◽  
Albino J. K. Leiroz
Keyword(s):  
Sugarcane Bagasse ◽  
Fluidized Beds ◽  
Chemical Species ◽  
Second Law Of Thermodynamics ◽  
Transport Equations ◽  
Second Law ◽  
Exergy Destruction ◽  
Gasification Process ◽  
Second Law Analysis ◽  
Biomass Particles

Abstract In the present work, the transport equations for mass, momentum, energy, and chemical species as given by the Euler–Euler formulation for multiphase flows are used together with the second law of thermodynamics to derive the entropy and exergy transport equations, suitable to the study of gas-particle reactive flows, such as those observed during pyrolysis, gasification, and combustion of biomass particles. The terms of the derived equations are discussed, and the exergy destruction contributions are identified. Subsequently, a kinetic model is implemented in a computational fluid dynamics (CFD) open source code for the sugarcane bagasse gasification. Then, the derived exergy destruction terms are implemented numerically through user-defined Fortran routines. Next, the second law analysis of the gasification process of sugarcane bagasse in bubbling fluidized beds is carried out. Detailed results are obtained for the local destructions of exergy along the reactor. This information is important to help improve environmental and sustainable practices and should be of interest to both designers and operators of fluidized bed equipment.

Exergy Analysis of Hot-Water Heating System Conditioning Methods

2013 ◽  
Vol 689 ◽  
pp. 435-438
Author(s):  
Jian Meng Yang ◽  
Nan Cheng ◽  
Wei Wang
Keyword(s):  
Energy Loss ◽  
Total Energy ◽  
Heat Dissipation ◽  
Exergy Analysis ◽  
Second Law Of Thermodynamics ◽  
Heating System ◽  
Hot Water ◽  
Second Law ◽  
Pipe Network ◽  
Quality Regulation

The reasonable heating regulation directly affect the heating of the economy, and thus its exergy analysis is imperative. In order to optimize the heating system, three regulation methods used in heating system are analyzed in this paper. They are quality regulation, flow mass regulation and stage-flow-mass-changing quality regulation. Each method has a different effect on energy saving and energy loss. Based on the second law of thermodynamics, this paper analyzes the total energy loss of these three methods by dividing the heating system into subsystems including boiler , indoor heat dissipation equipment and outdoor pipe network and the circulating pump. It is demonstrated theoretically that flow mass regulation is the best way for saving energy and quality regulation is the worst.

scholarly journals Application of Second-Law Analysis for the Environmental Control Unit at High Ambient Temperature

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3274
Author(s):  
Ammar M. Bahman ◽  
Eckhard A. Groll
Keyword(s):  
Ambient Temperature ◽  
Environmental Control ◽  
Control Unit ◽  
Second Law Of Thermodynamics ◽  
High Ambient Temperature ◽  
Second Law ◽  
Potential Contribution ◽  
Exergy Destruction ◽  
Ambient Conditions ◽  
Second Law Analysis

This paper assesses the application of the second-law of thermodynamics in a military Environmental Control Unit (ECU) to evaluate the exergy destruction (or irreversibility) in each component when operating at high ambient temperature. Experimental testings were conducted on three ECUs, 1.5 (5.3 kW), 3 (10.6 kW), and 5 (17.6 kW) tons of refrigeration (RT), to assess the potential contribution of each component to enhance the overall energy efficiency of the system, and to determine the feasibility of the thermodynamic model presented herein. The analysis provided for extreme high ambient conditions up to 51.7 °C (125 °F). The results yielded that the highest irreversibility was associated with compressors (32.4% to 42.5%). This is followed by the heat exchanges (19.6% to 32.9%) in the case of 1.5-RT and 3-RT units, whereas for the 5-RT unit, the highest irreversibility was associated with the evaporator followed by the one of the compressors. In the 3-RT ECU, the condenser’s second-law efficiency enhanced due to an additional fan, yet the working refrigerant increased the irreversibility in the expansion device. The second-law analysis recognized the components with the highest exergy destruction and identified the direction to enhance the exergetic efficiency of any ECU operating at high-temperature climate.

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′).

Analysis of Throttle Opening Variation Impact on a Diesel Engine Performance Using Second Law of Thermodynamics

2009 ◽  
Author(s):  
B. B. Sahoo ◽  
U. K. Saha ◽  
N. Sahoo ◽  
P. Prusty
Keyword(s):  
Diesel Engine ◽  
Direct Injection ◽  
Fuel Efficiency ◽  
Engine Performance ◽  
Second Law Of Thermodynamics ◽  
Operating Conditions ◽  
Second Law ◽  
Engine Fuel ◽  
Availability Analysis ◽  
Second Law Analysis

The fuel efficiency of a modern diesel engine has decreased due to the recent revisions to emission standards. For an engine fuel economy, the engine speed is to be optimum for an exact throttle opening (TO) position. This work presents an analysis of throttle opening variation impact on a multi-cylinder, direct injection diesel engine with the aid of Second Law of thermodynamics. For this purpose, the engine is run for different throttle openings with several load and speed variations. At a steady engine loading condition, variation in the throttle openings has resulted in different engine speeds. The Second Law analysis, also called ‘Exergy’ analysis, is performed for these different engine speeds at their throttle positions. The Second Law analysis includes brake work, coolant heat transfer, exhaust losses, exergy efficiency, and airfuel ratio. The availability analysis is performed for 70%, 80%, and 90% loads of engine maximum power condition with 50%, 75%, and 100% TO variations. The data are recorded using a computerized engine test unit. Results indicate that the optimum engine operating conditions for 70%, 80% and 90% engine loads are 2000 rpm at 50% TO, 2300 rpm at 75% TO and 3250 rpm at 100% TO respectively.

scholarly journals Advanced Exergy Analysis in the Dynamic Framework for Assessing Building Thermal Systems

Entropy ◽  
2019 ◽  
Vol 22 (1) ◽  
pp. 32 ◽  
Author(s):  
Ana Picallo-Perez ◽  
José M Sala ◽  
George Tsatsaronis ◽  
Saeed Sayadi
Keyword(s):  
Exergy Analysis ◽  
Energy System ◽  
Building Energy ◽  
Hot Water ◽  
Exergy Destruction ◽  
Dynamic Calculation ◽  
Thermal Systems ◽  
Dynamic Framework ◽  
Building Energy System ◽  
First Time

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by distinguishing the inefficiencies that can be prevented by improving the quality (avoidable ED) and the ones constrained because of technical limitations (unavoidable ED). ED is related to the inherent inefficiencies of the considered element (endogenous ED) and those coming from the interconnections (exogenous ED). That information cannot be obtained by any other approach. A dynamic calculation within the experimental facility has been performed after a component characterization driven by a new grey-box modelling technique, through TRNSYS and MATLAB. Novel solutions and terms of ED are assessed for the rational implementation of the DAEA in building energy installations. The influence of each component and their interconnections are valuated in terms of exergy destruction for further diagnosis and optimization purposes.

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