Using Exergy to Correlate Energy Research Investments and Efficiencies: Concept and Case Studies

Rosen, Marc A.

doi:10.3390/e15010262

Cited by 14 publications

(4 citation statements)

References 65 publications

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“…In turn, the destruction of exergy occurs when there is a decrease in energy quality (Sciubba and Moran 1995). Therefore, exergy is an effective indicator of the potential of a substance to affect the environment (Rosen 2013). So, exergy is the portion of energy that is useful to society.…”

Section: Exergy Analysismentioning

confidence: 99%

Methods in S.I. Engine Modelling: Auto-calibration of Combustion and Heat Transfer Models, and Exergy Analysis

Ayad

Belchior

Sodré

2021

Energy, Environment, and Sustainability

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This chapter reports on a workflow aimed at obtaining deeper insights into spark ignition engines using thermodynamic modelling. This workflow is divided into two steps: (i) Auto-calibration of combustion and heat transfer models using AVL Boost ® and AVL Design Explorer; and (ii) in-cylinder exergy analysis using Wolfram Mathematica ® . Model calibration is usually based on experimental pressure curve and combustion data. However, there is a gap in methods that generate accurate simulation results, while calibrating the combustion and heat transfer models without prior experimental results. Thus, the authors proposed an approach in their earlier work to address this gap. In this chapter, this proposed approach has been complemented with exergy analysis to form a complete workflow for engine research using simulation. This workflow was applied to a 4-cylinder gasoline engine template model as a case study. First, the combustion and heat transfer models are parametrized and used as design variables of an optimization problem. The objective functions in this problem are the combustion phasing, here defined as the crank angle in which the peak cylinder pressure occurs CA pp , and the mechanical load, here defined as the indicated mean effective pressure IMEP. The appropriate temperature constraints were included to guarantee that the engine model was representative of the physical problem. The optimization problem is then solved for a target IMEP and CA pp and the results are analyzed. Afterwards, we begin the exergy analysis of the engine to obtain deeper insights. The resulting curves for the thermodynamic state properties and species' molar fraction are exported from the simulation software to a program in Wolfram Mathematica that does the exergy analysis of the engine, providing deeper insights into the useful work available in the engine, losses due to heat transfer, losses in the exhaust gases, and combustion irreversibilities. This analysis can be very useful in determining the best fuel mixture, operating conditions, and areas for improvement.

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Section: Exergy Analysismentioning

confidence: 99%

Methods in S.I. Engine Modelling: Auto-calibration of Combustion and Heat Transfer Models, and Exergy Analysis

Ayad

Belchior

Sodré

2021

Energy, Environment, and Sustainability

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“…Unlike energy, exergy is conserved only during ideal processes and destroyed due to irreversibilities in real processes [6]. Exergy analysis is based on the first and second laws of thermodynamics, and can be used to identify the main sources of irreversibility (exergy loss) and to minimize the generation of entropy in a given process where the transfer of energy and material take place [3,7]. Exergy analysis is widely used for estimation of how near a process is to "thermodynamic ideality", and has become an effective tool for engineers to reveal the potentials to improve energy efficiency by reducing the inefficiencies in energy systems [8,9].…”

Section: Introductionmentioning

confidence: 99%

Exergy Analysis of a Ground-Coupled Heat Pump Heating System with Different Terminals

Chen

Hao

2015

Entropy

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Abstract:In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP) heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy loss and exergy efficiency of each subsystem are calculated using the expressions derived based on exergy balance equations. The average values of the measured parameters are used for the exergy analysis. The analysis results show that the two largest exergy losses occur in the heat pump and terminals, with losses of 55.3% and 22.06%, respectively, and the lowest exergy efficiency occurs in the ground heat exchange system. Therefore, GCHP system designers should pay close attention to the selection of heat pumps and terminals, especially in the design of ground heat exchange systems. Compared with the scenario system in which fan coil units (FCUs) are substituted for the radiant floors, the adoption of radiant floors can result in a decrease of 12% in heating load, an increase of 3.24% in exergy efficiency of terminals and an increase of 1.18% in total exergy efficiency of the system. The results may point out the direction and ways of optimizing GCHP systems.

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“…Marc A. Rosen introduced and exemplified a methodology describing the relationship between the use of exergy and energy research findings to use the resources more efficiently [1]. Exergy is defined as the maximum theoretical work that can be obtained from a system as it comes to equilibrium with a reference environment.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study on Energy and Exergy Analyses of a CI Engine Performed with Different Multiple Injection Strategies at Part Load: Effect of Injection Pressure

Özkan

2015

Entropy

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Abstract:In this study, a four stroke four cylinder direct injection CI engine was run using three different injection pressures. In all measurements, the fuel quantity per cycle, the pre injection and main injection timing, the boost pressure and the engine speed were kept constant. The motor tests were performed under 130, 140 and 150 MPa rail pressure. During the theoretical part of the study, combustion, emission, energy and exergy analysis were made using the test results. An increase in the injection pressure increases combustion efficiency. The results show that combustion efficiency is not enough by itself, because the increase in the power need of the injection pump, decreases the thermal efficiency. The increase in the combustion temperature, increases the cooling loss and decreases the exergetic efficiency. In addition, the NOx emissions increased by 12% and soot emissions decreased 44% via increasing injection pressure by 17%. The thermal and exergetic efficiencies are found inversely proportional with injection pressure. Exergy destruction is found independent of the injection pressure and its value is obtained as ~6%.

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Using Exergy to Correlate Energy Research Investments and Efficiencies: Concept and Case Studies

Cited by 14 publications

References 65 publications

Methods in S.I. Engine Modelling: Auto-calibration of Combustion and Heat Transfer Models, and Exergy Analysis

Methods in S.I. Engine Modelling: Auto-calibration of Combustion and Heat Transfer Models, and Exergy Analysis

Exergy Analysis of a Ground-Coupled Heat Pump Heating System with Different Terminals

A Comparative Study on Energy and Exergy Analyses of a CI Engine Performed with Different Multiple Injection Strategies at Part Load: Effect of Injection Pressure

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