The Experts below are selected from a list of 1476 Experts worldwide ranked by ideXlab platform
Lingen Chen - One of the best experts on this subject based on the ideXlab platform.
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exergy based ecological optimization for a four temperature level absorption heat pump with heat resistance heat leakage and Internal Irreversibility
International Journal of Heat and Mass Transfer, 2019Co-Authors: Lingen Chen, Xiaoyong Qin, Zhihui XieAbstract:Abstract Based on irreversible four-temperature-level (FTL) cycle models, an ecological criterion function of absorption heat pump (AHP) plants is proposed. This function can attain a compromise in inter restricted relations between exergy output and exergy loss of AHP plants. Relations among ecological function, coefficient of performance (COP), heating load, exergy output and exergy loss, and various loss factors are derived. Simplified relations are derived when various Irreversibility factors can be ignored. The exergy-based ecological characteristics are analyzed through numerical examples. The results can provide some new suggestions about parameter selection for practical AHP plants.
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effect of specific heat variations on irreversible otto cycle performance
International Journal of Heat and Mass Transfer, 2018Co-Authors: Yanlin Ge, Lingen ChenAbstract:Abstract Considering Internal Irreversibility loss, friction loss and heat transfer loss, an irreversible Otto cycle model is built up by using finite-time thermodynamics with air standard assumption. Using the various irreversible losses in the cycle to compute the entropy generation rate, the optimal ecological function performance of the cycle is studied when the specific heats of working fluid are nonlinear relation with its temperature. Some important expressions, including ecological function, entropy generation rate, efficiency and power output, are obtained. The cycle ecological function performances with constant specific heats, specific heats changed with linear and nonlinear relations of its temperature are compared. Moreover, the impacts of Internal Irreversibility loss, friction loss and heat transfer loss on ecological function performance are analyzed. The results show that optimization of the exergy-based ecological function not only represents a compromise between the power output and the rate of entropy generation but also represents a compromise between the power output and the thermal efficiency, the specific heat models have no qualitative effect and only have quantitative effect on the performance characteristics of ecological function versus power output and ecological function versus efficiency, and the ecological function, power output and efficiency decrease with the increase of heat transfer, friction and Internal Irreversibility losses.
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work output and thermal efficiency optimization for an irreversible meletis georgiou cycle with heat transfer loss and Internal Irreversibility
Applied Thermal Engineering, 2017Co-Authors: Lingen Chen, Chang Liu, Huijun FengAbstract:Abstract An irreversible model of Meletis-Georgiou cycle (MGC) is investigated in this paper. Finite time thermodynamic (FTT) theory is introduced, and Internal Irreversibility of the cycle (IIC) and heat transfer loss (HTL) are considered. The expressions of the work output (WO) and thermal efficiency (TE) of the MGC are obtained, and they are maximized with respect to the volume ratios. The effects of the IIC on the WO and TE are analyzed, and the optimal cycle performances are obtained. It shows that the compression ratio (CR) has its optimal value, which makes the WO or TE reach to its maximum. Therefore, the relationship between WO and TE is loop-shaped one, which is coincidence with the performance of real engine. The results enrich the theoretical studies of the rotary engine and provide some guidelines for practical devices.
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ecological performance of four temperature level absorption heat transformer with heat resistance heat leakage and Internal Irreversibility
International Journal of Heat and Mass Transfer, 2017Co-Authors: Xiaoyong Qin, Lingen Chen, Shaojun XiaAbstract:Abstract Based on irreversible four-temperature-level (FTL) cycle model of absorption heat transformer (AHT) plants with heat resistance, heat leakage and Internal Irreversibility, an exergy-based ecological criterion function of is proposed, which can attain a compromise in inter restricted relations between exergy output and exergy loss of AHT plants. When all losses are considered and different losses are ignored, detailed expressions and simplified expressions among ecological function, exergy output, exergy loss, and various loss factors are derived. Using illustrative calculations, the effects of various loss factors on the general characteristics and the optimal ecological characteristics are analyzed. The expressions and conclusions obtained herein are general, which can provide some new guidelines about parameter selection for practical AHT plants.
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exergy based ecological performance of an irreversible otto cycle with temperature linear relation variable specific heat of working fluid
European Physical Journal Plus, 2017Co-Authors: Yanlin Ge, Lingen ChenAbstract:Considering Internal Irreversibility loss (IIL), friction loss (FL) and heat transfer loss (HTL), an irreversible Otto cycle (IOC) model is built up by using air standard (AS) assumption. Based on finite-time thermodynamics (FTT), computing entropy generation rate (EGR) by using the irreversible losses in the cycle, the ecological function (EF) performance of the cycle is optimized when the specific heat (SH) of the working fluid (WF) varies with temperature with linear relation. Some important expressions, including efficiency, power output, EGR and EF, are obtained. Moreover, the effects of variable SH of WF and three losses on cycle performance are investigated. The research conclusion can provide some guidelines for the actual Otto cycle engine performance optimization.
Haoran Xu - One of the best experts on this subject based on the ideXlab platform.
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performance improvement of a direct carbon solid oxide fuel cell through integrating an otto heat engine
Energy Conversion and Management, 2018Co-Authors: Haoran Xu, Bin Chen, Houcheng Zhang, Jinliang Yuan, John T S Irvine, Meng NiAbstract:Abstract A novel system consisting of an external heat source, a direct carbon solid oxide fuel cell (DC-SOFC), a regenerator and an air standard Otto cycle engine is proposed to improve the performance of the DC-SOFC. Considering the electrochemical/chemical reactions, ionic/electronic charge transport, mass/momentum transport and heat transfer, a 2D tubular DC-SOFC model shows that the overall heat released in the cell can be smaller than, equal to or larger than the heat required by the Internal Boudouard reaction. Three different operating modes of the proposed system are identified, and accordingly, analytical expressions for the equivalent power output and efficiency of the proposed system are derived under different operating conditions. The modeling results show that the Otto heat engine can effectively recover the waste heat from the DC-SOFC for additional power production especially at large operating current density. Comprehensive parametric studies are conducted to investigate the effects of the different operating conditions of DC-SOFC on its performance and heat generation. The effects of compression ratio, Internal Irreversibility factor and power dissipation of the Otto heat engine on the system performance improvement are also studied.
Huijun Feng - One of the best experts on this subject based on the ideXlab platform.
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work output and thermal efficiency optimization for an irreversible meletis georgiou cycle with heat transfer loss and Internal Irreversibility
Applied Thermal Engineering, 2017Co-Authors: Lingen Chen, Chang Liu, Huijun FengAbstract:Abstract An irreversible model of Meletis-Georgiou cycle (MGC) is investigated in this paper. Finite time thermodynamic (FTT) theory is introduced, and Internal Irreversibility of the cycle (IIC) and heat transfer loss (HTL) are considered. The expressions of the work output (WO) and thermal efficiency (TE) of the MGC are obtained, and they are maximized with respect to the volume ratios. The effects of the IIC on the WO and TE are analyzed, and the optimal cycle performances are obtained. It shows that the compression ratio (CR) has its optimal value, which makes the WO or TE reach to its maximum. Therefore, the relationship between WO and TE is loop-shaped one, which is coincidence with the performance of real engine. The results enrich the theoretical studies of the rotary engine and provide some guidelines for practical devices.
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heating load cop exergy loss rate exergy output rate and ecological analyses and optimisations for irreversible universal steady flow variable temperature heat reservoir heat pump cycle model
Journal of The Energy Institute, 2011Co-Authors: Huijun Feng, Leida ChenAbstract:AbstractThe performance of an irreversible universal steady flow heat pump cycle model with variable temperature heat reservoirs is analysed and optimised by using finite time thermodynamics. The universal heat pump cycle consists of two heat absorbing branches, two heat releasing branches and two irreversible adiabatic branches, with the losses of heat resistance and Internal Irreversibility. Expressions of heating load, coefficient of performance (COP), exergy output rate, exergy loss rate and ecological function of Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles are derived. There exists an optimal heat conductance distribution and an optimal thermal capacity rate matching between the working fluid and heat reservoir which leads to maximum heating load, maximum exergy output rate and maximum ecological function respectively. Performance comparisons among heating load, COP, exergy output rate, exergy loss rate and ecological function objectives are carried out. The effects of t...
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heating load cop exergy loss rate exergy output rate and ecological optimizations for a class of generalized irreversible universal heat pump cycles
Revista Mexicana De Fisica, 2010Co-Authors: Huijun FengAbstract:The optimal performance of a class of generalized irreversible universal steady flow heat pump cycle model, which consists of two heatabsorbing branches, two heat-releasing branches and two irreversible adiabatic branches with the losses of heat-resistance, heat leakage and Internal Irreversibility is analyzed by using finite time thermodynamics. The analytical formulae about heating load, coefficient of performance (COP), exergy loss rate, exergy output rate and ecological function of the universal heat pump cycle are derived. Moreover, performance comparisons among maximum COP condition, a given exergy output rate condition and maximum ecological function condition are carried out by using numerical examples. It is shown that the ecological function objective is an excellent candidate objective with the ideal of an ecological and long-term goal. The effects of heat leakage and Internal Irreversibility on the cycle performance are discussed. The universal cycle model gives a unified description of seven heat pump cycles, and the results obtained include the performance characteristics of Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles with the losses of heat-resistance, heat leakage and Internal Irreversibility.
Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.
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Local stability of a non-endoreversible Carnot refrigerator working at the maximum ecological function
Applied Mathematical Modelling, 2014Co-Authors: Fengrui SunAbstract:Abstract Local stability of a non-endoreversible Carnot refrigerator at the maximum ecological function is studied with Newton’s heat transfer law between working fluid and heat reservoirs. The steady state of the refrigerator working at the maximum ecological function is steady. It is derived that a general expression of relaxation time described as stability of the system refers to heat capacity C , total heat exchange area F , temperature ratio of heat reservoirs τ , the degree of Internal Irreversibility ϕ , heat transfer coefficients α and β . Distributing information of phase portraits of system is obtained. The results can provide some theoretical guidelines for the designs of practical refrigerator.
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ecological optimization of an irreversible otto cycle
Arabian Journal for Science and Engineering, 2013Co-Authors: Lingen Chen, Fengrui SunAbstract:The optimal ecological performance of an irreversible air-standard Otto cycle with heat transfer, friction and Internal Irreversibility is analyzed by using finite-time thermodynamics. The relations between the ecological function and the power output as well as between the ecological function and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of Internal Irreversibility, heat transfer loss and friction loss on the cycle performance are analyzed. The results indicate that the optimization of the exergy-based ecological function not only represents a compromise between the power output and the rate of entropy generation but also represents a compromise between the power output and the thermal efficiency. This work can provide guidelines for the design of practical Internal combustion engines.
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ecological optimization of an irreversible quantum carnot heat engine with spin 1 2 systems
Physica Scripta, 2010Co-Authors: Xiaowei Liu, Lingen Chen, Fengrui SunAbstract:A model of a quantum heat engine with heat resistance, Internal Irreversibility and heat leakage and many non-interacting spin-1/2 systems is established in this paper. The quantum heat engine cycle is composed of two isothermal processes and two irreversible adiabatic processes and is referred to as a spin quantum Carnot heat engine. Based on the quantum master equation and the semi-group approach, equations of some important performance parameters, such as power output, efficiency, entropy generation rate and ecological function (a criterion representing the optimal compromise between exergy output rate and exergy loss rate), for the irreversible spin quantum Carnot heat engine are derived. The optimal ecological performance of the heat engine in the classical limit is analyzed with numerical examples. The effects of Internal Irreversibility and heat leakage on ecological performance are discussed in detail.
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ecological optimization of an irreversible harmonic oscillators carnot heat engine
Science China-physics Mechanics & Astronomy, 2009Co-Authors: Xiaowei Liu, Lingen Chen, Fengrui SunAbstract:A model of an irreversible quantum Carnot heat engine with heat resistance, Internal Irreversibility and heat leakage and many non-interacting harmonic oscillators is established in this paper. Based on the quantum master equation and semi-group approach, equations of some important performance parameters, such as power output, efficiency, exergy loss rate and ecological function for the irreversible quantum Carnot heat engine are derived. The optimal ecological performance of the heat engine in the classical limit is analyzed with numerical examples. Effects of Internal Irreversibility and heat leakage on the ecological performance are discussed. A performance comparison of the quantum heat engine under maximum ecological function and maximum power conditions is also performed.
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Profit performance optimisation for an irreversible Carnot refrigeration cycle
International Journal of Ambient Energy, 2008Co-Authors: Lingen Chen, Z. Zheng, Fengrui SunAbstract:SYNOPSIS The finite time exergoeconomic performance of a Newtonian law system generalised irreversible Carnot refrigeration cycle with heat resistance, heat leakage and Internal Irreversibility is investigated in this paper. The operation of the generalised irreversible Carnot refrigeration cycle is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimisation of the generalised irreversible Carnot refrigeration cycle is performed by taking profit as the objective. The relationships between profit and temperature ratio of refrigerant, between COP (coefficient of performance) and temperature ratio of refrigerant, as well as the optimal relationship between profit and COP of the cycle are derived. The focus of this paper is to obtain the compromised optimisation between economics (profit) and energy utilisation factor (COP) for the generalised irreversible Carnot refrigeration cycle, by identifying the optimum COP at maximum profit, which is termed as the ...
Bahri şahin - One of the best experts on this subject based on the ideXlab platform.
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Research Article Performance Optimization of an Air-Standard Irreversible Dual-Atkinson Cycle Engine Based on the Ecological Coefficient of Performance Criterion
2016Co-Authors: Guven Gonca, Bahri şahinAbstract:License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper presents an ecological performance analysis and optimization for an air-standard irreversible Dual-Atkinson cycle (DAC) based on the ecological coefficient of performance (ECOP) criterion which includes Internal irreversibilities, heat leak, and finite-rate of heat transfer. A comprehensive numerical analysis has been realized so as to investigate the global and optimal performances of the cycle. The results obtained based on the ECOP criterion are compared with a different ecological function which is named as the ecologic objective-function and with the maximum power output conditions. The results have been attained introducing the compression ratio, cut-off ratio, pressure ratio, Atkinson cycle ratio, source temperature ratio, and Internal Irreversibility parameter. The change of cycle performance with respect to these parameters is investigated and graphically presented. 1
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comprehensive performance analyses and optimization of the irreversible thermodynamic cycle engines tce under maximum power mp and maximum power density mpd conditions
Applied Thermal Engineering, 2015Co-Authors: Guven Gonca, Yasin Ust, Bahri şahin, Adnan ParlakAbstract:Abstract This paper presents comprehensive performance analyses and comparisons for air-standard irreversible thermodynamic cycle engines (TCE) based on the power output, power density, thermal efficiency, maximum dimensionless power output (MP), maximum dimensionless power density (MPD) and maximum thermal efficiency (MEF) criteria. Internal Irreversibility of the cycles occurred during the irreversible-adiabatic processes is considered by using isentropic efficiencies of compression and expansion processes. The performances of the cycles are obtained by using engine design parameters such as isentropic temperature ratio of the compression process, pressure ratio, stroke ratio, cut-off ratio, Miller cycle ratio, exhaust temperature ratio, cycle temperature ratio and cycle pressure ratio. The effects of engine design parameters on the maximum and optimal performances are investigated.
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performance optimization of an air standard irreversible dual atkinson cycle engine based on the ecological coefficient of performance criterion
The Scientific World Journal, 2014Co-Authors: Guven Gonca, Bahri şahinAbstract:This paper presents an ecological performance analysis and optimization for an air-standard irreversible Dual-Atkinson cycle (DAC) based on the ecological coefficient of performance (ECOP) criterion which includes Internal irreversibilities, heat leak, and finite-rate of heat transfer. A comprehensive numerical analysis has been realized so as to investigate the global and optimal performances of the cycle. The results obtained based on the ECOP criterion are compared with a different ecological function which is named as the ecologic objective-function and with the maximum power output conditions. The results have been attained introducing the compression ratio, cut-off ratio, pressure ratio, Atkinson cycle ratio, source temperature ratio, and Internal Irreversibility parameter. The change of cycle performance with respect to these parameters is investigated and graphically presented.
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performance optimisation of reciprocating heat engine cycles with Internal Irreversibility
Journal of The Energy Institute, 2006Co-Authors: Adnan Parlak, Bahri şahinAbstract:In the present study, an optimal performance analysis based on maximum power (MP) and maximum efficiency criterion including Internal Irreversibility for steady state operation has been performed for the air standard Dual cycle. It is shown that the effect of Internal Irreversibility such as friction on MP may be characterised by the cycle Irreversibility parameter representing the ratios of entropy differences for the cycle. The presence of this parameter in the equations for the MP and the corresponding efficiency shows that an engine with Internal Irreversibility delivers less power and has a lower efficiency than a reversible engine. The effect of the design parameters such as pressure ratio, cut off ratio and extreme temperature ratio of the cycles has also been investigated under the MP and maximum efficiency conditions on the basis of having the Internal Irreversibility. Also in the present study, performance analysis has been extended to the Otto and Diesel cycles which may be considered as special cases of the Dual cycle.
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effects of Internal Irreversibility and heat leakage on the finite time thermoeconomic performance of refrigerators and heat pumps
Energy Conversion and Management, 2000Co-Authors: Ali Kodal, Bahri şahin, Tamer YilmazAbstract:By using finite time thermodynamic theory, a performance analysis based on the thermoeconomic criterion has been performed for an irreversible refrigerator and a heat pump. The thermoeconomic objective function is defined as the cooling load for the refrigerator and the heating load for the heat pump per unit total cost. The optimal performances and design parameters which maximize the objective functions are investigated. The design parameters under the optimal conditions have been derived analytically, and then, the effects of Internal Irreversibility, heat leakage and the economical parameter on the global and optimal performances have been discussed.