Quantification of Losses and Irreversibilities in a Marine Engine for Gas and Diesel Fuelled Operation Using an Exergy Analysis Approach

2020 ◽  
Author(s):  
Beichuan Hong ◽  
Senthil Krishnan Mahendar ◽  
Jari Hyvönen ◽  
Andreas Cronhjort ◽  
Anders Christiansen Erlandsson
Keyword(s):  
Gas Exchange ◽  
Exergy Analysis ◽  
Transport Sector ◽  
Exergy Destruction ◽  
Two Stage ◽  
Marine Engine ◽  
Turbocharging System ◽  
Engine System ◽  
The Impact ◽  
Exergy Losses

Abstract Large bore marine engines are a major source of fossil fuel consumption in the transport sector. The development of more efficient and cleaner marine engine systems are always required. Exergy analysis is a second-law based approach to indicate the maximum amount of work obtainable from a given system. In this study, an exergy analysis is used to identify losses and improvement potential of a large bore Wärtsilä 31DF four-stroke marine engine system with two-stage turbocharging. An exergy-based framework is implemented on a calibrated 1D engine model to view the evolution of exergy flow over each engine sub-system while operating on different load points fuelled with natural gas and diesel separately. The overall distributions of engine energy and exergy are initially compared at a systematic level regarding the impact of fuel mode and operating load. Furthermore, the engine irreversibilities are characterized as three types: combustion, heat dissipation, and gas exchange losses. The first type, combustion irreversibility, is the largest source of engine exergy losses amounting to at least 25% of fuel exergy. A crank resolved analysis showed that premixed gas combustion produces lower exergy losses compared to diesel diffusion combustion. The second type, thermal exergy transferred and destroyed by heat losses, are summarized for the entire engine system. From the exergy view, the charge coolers present an opportunity to recover about 9% of the brake power at full load. The last type, gas exchange losses, are categorized by accounting the flow losses caused by the valve throttling, fluid friction in pipes and the irreversibility of the two-stage turbocharging system. Most of exergy destruction in gas paths occurs at turbocharging system, where the high pressure turbocharger contributes to around 40% of the total flow exergy destruction.

Comparative Energy and Exergy Analysis of Proposed Gas Turbine Cycle With Simple Gas Turbine Cycle at Same Operational Cost

2019 ◽  
Author(s):  
M. N. Khan ◽  
Ibrahim M. Alarifi ◽  
I. Tlili
Keyword(s):  
Gas Turbine ◽  
Fuel Consumption ◽  
Exergy Analysis ◽  
Pressure Ratio ◽  
Specific Fuel Consumption ◽  
Exergy Destruction ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Gas Turbine Cycle ◽  
The Impact

Abstract Environmentally friendly and effective power systems have been receiving increased investigation due to the aim of addressing global warming, energy expansion, and economic growth. Gas turbine cycles are perceived as a useful technology that has advanced power capacity. In this research, a gas turbine cycle has been proposed and developed from a simple and regenerative gas turbine cycle to enhance performance and reduce Specific fuel consumption. The impact of specific factors regarding the proposed gas turbine cycle on thermal efficiency, net output, specific fuel consumption, and exergy destruction, have been inspected. The assessments of the pertinent parameters were performed based on conventional thermodynamic energy and exergy analysis. The results obtained indicate that the peak temperature of the Proposed Gas Turbine Cycle increased considerably without affecting fuel consumption. The results show that at Pressure Ratio (rp = 6) the performance of the Proposed Gas Turbine Cycle is much better than Single Gas Turbine Cycle but the total exergy destruction of Proposed Gas Turbine Cycle higher than the SGTC.

EXERGY ANALYSIS OF GEOTHERMAL POWER PLANT KAMOJANG 68, 3 MW IN CAPACITY

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Amiral Aziz
Keyword(s):  
Energy Efficiency ◽  
Power Plant ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Preliminary Design ◽  
Exergy Destruction ◽  
Geothermal Power Plant ◽  
Production Wells ◽  
Geothermal Power ◽  
Exergy Losses

The importance of exergy analysis in preliminary design of geothermal power has been proven. An exergy analysis was carried out and the locations and quantities of exergy losses, wastes and destructions in the different processes of the plan were pinpointed. The obtained results show that the total exergy available from production wells KMJ 68 was calculated to be 6967.55 kW. The total exergy received from wells which is connected during the analysis and enter into the separator was found to be 6337.91 kW in which 5808.8 kW is contained in the steam phase. The overall exergy efficiency for the power plant is 43.06% and the overall energy efficiency is 13.05 %, in both cases with respect to the exergy from the connected wells. The parts of the system with largest exergy destruction are the condenser, the turbine, and the disposed waste brinekeywords: exergy, irreversibility, geothermal power plant, KMJ 68

scholarly journals Thermodynamic Limitations and Exergy Analysis of Brackish Water Reverse Osmosis Desalination Process

Membranes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 11
Author(s):  
Alanood A. Alsarayreh ◽  
Mudhar A. Al-Obaidi ◽  
Alejandro Ruiz-García ◽  
Raj Patel ◽  
Iqbal M. Mujtaba
Keyword(s):  
Reverse Osmosis ◽  
Brackish Water ◽  
Exergy Analysis ◽  
Exergy Destruction ◽  
First Pass ◽  
Simulation Results ◽  
Membrane Technologies ◽  
Physical And Chemical ◽  
Exergy Losses ◽  
Reverse Osmosis Desalination

The reverse osmosis (RO) process is one of the most popular membrane technologies for the generation of freshwater from seawater and brackish water resources. An industrial scale RO desalination consumes a considerable amount of energy due to the exergy destruction in several units of the process. To mitigate these limitations, several colleagues focused on delivering feasible options to resolve these issues. Most importantly, the intention was to specify the most units responsible for dissipating energy. However, in the literature, no research has been done on the analysis of exergy losses and thermodynamic limitations of the RO system of the Arab Potash Company (APC). Specifically, the RO system of the APC is designed as a medium-sized, multistage, multi pass spiral wound brackish water RO desalination plant with a capacity of 1200 m3/day. Therefore, this paper intends to fill this gap and critically investigate the distribution of exergy destruction by incorporating both physical and chemical exergies of several units and compartments of the RO system. To carry out this study, a sub-model of exergy analysis was collected from the open literature and embedded into the original RO model developed by the authors of this study. The simulation results explored the most sections that cause the highest energy destruction. Specifically, it is confirmed that the major exergy destruction happens in the product stream with 95.8% of the total exergy input. However, the lowest exergy destruction happens in the mixing location of permeate of the first pass of RO desalination system with 62.28% of the total exergy input.

scholarly journals Analysis and Optimization of Exergy Flows inside a Transcritical CO2 Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1686 ◽  
Author(s):  
Sahar Taslimi Taleghani ◽  
Mikhail Sorin ◽  
Sébastien Poncet
Keyword(s):  
Critical Point ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Performance Criteria ◽  
Exergy Destruction ◽  
Two Phase ◽  
1D Model ◽  
Ejector System ◽  
Exergy Performance ◽  
The Impact

In this study, the exergy analysis of a CO2 (R744) two-phase ejector was performed using a 1D model for both single and double choking conditions. The impact of the back pressure on the exergy destruction and exergy efficiencies was presented to evaluate the exergy performance under different working conditions. The results of two exergy performance criteria (transiting exergy efficiency and Grassmann exergy efficiency) were compared for three modes of an ejector functioning: Double choking, single choking and at the critical point. The behavior of three thermodynamic metrics: Exergy produced, exergy consumed and exergy destruction were evaluated. An important result concerning the ejector’s design was the presence of a maximum value of transiting exergy efficiency around the critical point. The impact of the gas cooler and evaporator pressure variations on the different types of exergy, the irreversibilities and the ejector global performance were investigated for a transcritical CO2 ejector system. It was also shown that the transiting exergy flow had an important effect on the exergy analysis of the system and the Grassmann exergy efficiency was not an appropriate criterion to evaluate a transcritical CO2 ejector performance.

Detailed Energy and Exergy Analysis for a Solar Lithium Bromide Absorption Chiller and a Conventional Electric Chiller (R134a)

2011 ◽  
Author(s):  
Yang Hu ◽  
Laura A. Schaefer ◽  
Volker Hartkopf
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Cooling System ◽  
Residential Buildings ◽  
Lithium Bromide ◽  
Building Energy ◽  
Hot Water ◽  
Exergy Destruction ◽  
Absorption Chiller ◽  
Two Stage

The Building Energy Data Book (2009) [1] shows that commercial and residential buildings in the U.S. consume 39.9% of the primary energy and contribute 39% of the total CO2 emissions. In the operation of buildings, 41.8% of building energy consumption is provided for building cooling, heating, domestic hot water, and ventilation for commercial buildings, while in residential buildings, this percentage increases to 58%. In energy system analysis, the energy approach is the traditional method of assessing the way energy is used in an operation. However, an energy balance provides no information on the degradation of energy or resources during a process. The concept of exergy combines the first law and second law of thermodynamics. The exergy analysis clearly quantifies the energy quality match between the supply and demand sides, and also addresses the exergy destruction (entropy generation) in each component. In this paper, a solar thermal driven absorption cooling system was analyzed for providing cooling to a building, the Intelligent Workplace South Zone at Carnegie Mellon University. The system includes a 52 m2 parabolic trough solar collector, and a 16 kW (4 tons) two-stage lithium bromide absorption chiller. The energy model and newly developed two-stage lithium bromide absorption chiller are programmed and integrated in Engineering Equation Solver (EES). The temperature, enthalpy, entropy, mass flow rate, and mass fraction of lithium bromide in the solar absorption system were presented in steady state operation. The exergy destruction in each component is calculated. The exergy destructions for the solar collector, generator, absorber, and heat exchangers were significantly higher than those in evaporator, condenser and expansion valves, the overall energy and exegetic efficiency were also calculated.

Exergetic Analysis and Assessment of Industrial Furnaces

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Hakan Caliskan ◽  
Arif Hepbasli
Keyword(s):  
Maximum Rate ◽  
Exergy Analysis ◽  
Heating Furnace ◽  
The Other ◽  
Flue Gases ◽  
Exergy Destruction ◽  
Furnace Temperature ◽  
Radiant Tube ◽  
Exergetic Analysis ◽  
Exergy Losses

This study presents exergy analysis of a natural gas-fired radiant tube-heating furnace. In the analysis, actual data over a test period of 3 h were used. Exergy efficiencies, destructions, losses, and entropy generation of the furnace were determined. For an average furnace temperature of 666.6°C, average exergy efficiency value was calculated to be 9.6%. The exergy destruction rate was obtained to be 5.34 kW while exergy rates of the flue gases, exergy losses, and exergy steel were 12.53 kW, 44.28 kW, and 6.6 kW, respectively. On the other hand, the exergy rate of the product (steel) was found to be between 4.61 kW and 9.88 kW over the 15 min test periods, and it reached a maximum rate at the end of the second hour.

scholarly journals Performance Optimizations of the Transcritical CO2 Two-Stage Compression Refrigeration System and Influences of the Auxiliary Gas Cooler

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5578
Author(s):  
Yuyao Sun ◽  
Jinfeng Wang ◽  
Jing Xie
Keyword(s):  
Exergy Analysis ◽  
Energy Analysis ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
System Operation ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Discharge Temperature ◽  
Performance Optimizations

To optimize the performance of the transcritical CO2 two-stage compression refrigeration system, the energy analysis and the exergy analysis are conducted. It is found that higher COP, lower compression power, and less exergy destruction can be achieved when the auxiliary gas cooler is applied. Moreover, the discharge temperature of the compound compressor (HPS) can be reduced by decreasing the temperature at the outlet of the auxiliary gas cooler (Tagc,out). When the Tagc,out is reduced from 30 to 12 ℃, the discharge temperature of the compound compressor (HPS) can be decreased by 13.83 ℃. Furthermore, the COP and the exergy efficiency can be raised by enhancing the intermediate pressure. Based on these results, the optimizations of system design and system operation are put forward. The application of the auxiliary gas cooler can improve the performance of the transcritical CO2 two-stage compression refrigeration system. Operators can decrease the discharge temperature of the compound compressor (HPS) by reducing the Tagc,out, and increase the COP and the exergy efficiency by enhancing the intermediate pressure.

Simulation Study of the Impact of Two-Stage Turbocharged System on Diesel Engine

2012 ◽  
Vol 170-173 ◽  
pp. 3555-3559 ◽  
Author(s):  
Da Lu Dong ◽  
Chang Pu Zhao ◽  
Xiao Zhan Li ◽  
Yun Yao Zhu ◽  
Jun Zhang
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
Two Stage ◽  
Emission Regulations ◽  
Development Direction ◽  
Turbocharging System ◽  
Important Means ◽  
Software Code ◽  
The Impact ◽  
Original Experimental Data

With the increasing strictness of emission regulations, development direction of future diesel engines is toward the high thermal efficiency and low emissions. Supercharging technology is an important means for improving output power of diesel engines. This paper deals with the study of the two-stage turbocharging system of the non-road diesel engine. Based on GT-Power software code, a digital model of 6112 diesel engine was established. The supercharged model was calibrated by using the original experimental data. Then, four types of digital models with different two-stage turbocharging systems were constructed. The best two-stage turbocharging system was determined through investigating the impacts of different options on the performance of diesel engines. It was indicated through the study that two-stage turbocharging system can substantially increase the air flowing into the cylinder which increases the potential of power density. At the same time HC and NOx emissions can reduce. Through this study, a theoretical basis and an important reference for adopting the two-stage turbocharging system of the 6112 diesel engine were provided.

scholarly journals Robust Inferences from a Before-and-After Study with Multiple Unaffected Control Groups

2013 ◽  
Vol 1 (2) ◽  
pp. 209-234 ◽  
Author(s):  
Pengyuan Wang ◽  
Mikhail Traskin ◽  
Dylan S. Small
Keyword(s):  
Sensitivity Analysis ◽  
Control Groups ◽  
Two Stage ◽  
Time Effects ◽  
Unaffected Control ◽  
Group Time ◽  
Before And After ◽  
Group Variation ◽  
The Impact ◽  
Before And After Study

AbstractThe before-and-after study with multiple unaffected control groups is widely applied to study treatment effects. The current methods usually assume that the control groups’ differences between the before and after periods, i.e. the group time effects, follow a normal distribution. However, there is usually no strong a priori evidence for the normality assumption, and there are not enough control groups to check the assumption. We propose to use a flexible skew-t distribution family to model group time effects, and consider a range of plausible skew-t distributions. Based on the skew-t distribution assumption, we propose a robust-t method to guarantee nominal significance level under a wide range of skew-t distributions, and hence make the inference robust to misspecification of the distribution of group time effects. We also propose a two-stage approach, which has lower power compared to the robust-t method, but provides an opportunity to conduct sensitivity analysis. Hence, the overall method of analysis is to use the robust-t method to test for the overall hypothesized range of shapes of group variation; if the test fails to reject, use the two-stage method to conduct a sensitivity analysis to see if there is a subset of group variation parameters for which we can be confident that there is a treatment effect. We apply the proposed methods to two datasets. One dataset is from the Current Population Survey (CPS) to study the impact of the Mariel Boatlift on Miami unemployment rates between 1979 and 1982.The other dataset contains the student enrollment and grade repeating data in West Germany in the 1960s with which we study the impact of the short school year in 1966–1967 on grade repeating rates.

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