Finite-time Exergoeconomic Performance Research Articles

Exergoeconomic performance analysis and optimisation of an irreversible-closed intercooled regenerated gas turbine cycle

ABSTRACT Based on finite time thermodynamic (FTT) model for a closed irreversible intercooled regenerated (ICR) gas turbine cycle, the analytical expressions of profit rate, power and efficiency are deduced. The dimensionless profit rate can reach its extreme value while the intercooling pressure ratio gradually increases, and the value has an additional maximum, i.e. the double-maximum, while the total pressure ratio gradually increases. The finite time exergoeconomic performance is maximised by optimising four heat conductance allocations with a given total heat exchanger conductance as well as the intercooling pressure ratio. Further optimising the total pressure ratio can make the double-maximum. Some characteristic parameters’ effects on the cycle exergoeconomic performance are analysed.

Finite-time exergoeconomic performance of a real intercooled regenerated gas turbine cogeneration plant. Part 2: heat conductance distribution and pressure ratio optimization

Finite-time thermodynamics is applied to establish a real intercooled regenerated gas turbine cogeneration plant model in Part 1 of this article and the profit rate performance of the plant is researched using finite-time exergoeconomic analysis. In this part, the optimization of finite-time exergoeconomic performance of the plant is performed by optimizing the intercooling pressure ratio and the heat conductance distributions among the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator together, and it is found that the optimal heat conductance distribution of the regenerator is zero. When the heat conductance distribution of the regenerator is fixed, the results show that there exists an optimal intercooling pressure ratio and a group of optimal heat conductance distributions among the other four heat exchangers, which leads to a maximum dimensionless profit rate for the fixed total pressure ratio. When the total pressure ratio is variable, a double-maximum dimensionless profit rate is obtained. The characteristics of the double-maximum dimensionless profit rate, the corresponding exergetic efficiency, heat conductance distributions and total pressure ratio versus some main design parameters are analyzed in detail. Finally, it is found that the dimensionless profit rate has a thrice-maximum value with respect to the thermal capacitance rate matching between the working fluid and the heat reservoir.

The finite-time exergoeconomic performance of a real, intercooled, regenerated gas-turbine cogeneration plant. Part 1: model description and parametric analyses

Taking into account the heat resistance losses between the heat reservoirs and the working fluid, irreversible compression and expansion losses in the compressors and the turbine, pressure drop losses in the piping and finite thermal capacity rate properties of the heat reservoirs, a real, intercooled, regenerated gas-turbine cogeneration plant model is established using finite-time thermodynamics. The finite-time exergoeconomic performance of the plant is studied by taking the dimensionless profit rate as the optimization objective. Analytical formulae about the dimensionless profit rate and exergy efficiency are derived. By numerical examples, the two cases with fixed and variable total pressure ratios are discussed, and meanwhile the effects of the cycle parameters on the performance of the plant are analyzed. The relationship of the dimensionless profit rate versus exergy efficiency is investigated, and the characteristic curve is found to be loop shaped. Finally, it is found that there exists an optimal consumer temperature that leads to a double-maximum dimensionless profit rate.

Finite-time exergoeconomic optimal performance for an irreversible gas turbine closed-cycle cogeneration plant

Finite-time exergoeconomic performance of an irreversible constant temperature heat reservoir gas turbine closed-cycle cogeneration plant with heat resistance losses in heat exchangers and compression and expansion losses in compressors and turbines is investigated. Heat conductance allocations among hot-, cold- and consumer-side heat exchangers and pressure ratio of the compressor are optimized by taking the maximum profit rate as an objective. There exist a sole group of optimal heat conductance allocations among the three heat exchangers, an optimal pressure ratio of the compressor and an optimal consumer-side temperature, which leads to the maximum dimensionless profit rate.

A unified description of finite time exergoeconomic performance for seven typical irreversible heat-engine cycles

Finite time exergoeconomic performance optimization of a universal irreversible heat-engine cycle model, which consists of two constant thermal-capacity heating branches, two constant thermal-capacity cooling branches and two adiabatic branches, is investigated by taking the profit rate criterion as the optimization objective. The analytical formulae for power, efficiency and profit rate function of the universal irreversible heat-engine cycle model with the losses of heat transfer, heat leakage and internal irreversibility are derived. The focus of this article is to search the compromised optimization between economics (profit rate) and the energy utilization factor (efficiency) for irreversible cycles. Moreover, analysis and optimization of the model are carried out in order to investigate the effects of these losses and cycle process on the performance of the universal irreversible heat-engine cycle model using numerical examples. The results obtained herein include the performance characteristics of seven typical irreversible heat engines, including Carnot, Diesel, Otto, Atkinson, Brayton, Dual and Miller cycles.

Exergoeconomic performance optimization for a combined cooling, heating and power generation plant with an endoreversible closed Brayton cycle

Finite time exergoeconomic performance of a combined cooling, heating and power generation (CCHP) plant composed of one endoreversible closed Brayton cycle and one endoreversible four-heat-reservoir absorption refrigeration cycle is investigated by using finite time thermodynamics. Heat conductance distribution among hot-, cold-, thermal consumer-, generator-, absorber-, condenser- and evaporator-side heat exchangers and compressor pressure ratio are optimized by taking the maximum profit rate as objective. Numerical examples show that there exists a sole group of optimal heat conductance distribution among hot-, cold-, thermal consumer-, generator-, absorber-, condenser- and evaporator-side heat exchangers and an optimal compressor pressure ratio which lead to the maximum profit rate. The effects of design parameters on the optimal performance of the CCHP plant are discussed.

Finite-time exergoeconomic performance analysis and optimisation for generalised irreversible combined heat pump cycles

Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalised irreversible combined heat pump cycle model with irreversibility of finite-rate heat transfer, heat leakage and internal irreversibility is studied in this article. The operation of the generalised irreversible combined heat pump cycle is viewed as a production process with exergy as its output. The performance optimisation of the cycle is performed by taking profit as the objective. The optimal profit rate, optimal coefficient of performance (COP), as well as the relation between the optimal profit rate and COP of the cycle are derived. The focus of this article is to obtain the compromise optimisation between economics (profit rate) and the energy utilisation factor (COP) for the cycle, by searching the optimum COP at maximum profit rate, which is termed as the finite-time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price ratio, on the profit rate performance of the cycle are analysed by detailed numerical examples.

Exergoeconomic optimal performance of an irreversible closed Brayton cycle combined cooling, heating and power plant

A combined cooling, heating and power (CCHP) plant model composed of an irreversible closed Brayton cycle and an endoreversible four-heat-reservoir absorption refrigeration cycle is established by using finite time thermodynamics. The irreversibilities considered in the CCHP plant include heat-resistance losses in the hot-, cold-, thermal consumer-, generator-, absorber-, condenser- and evaporator-side heat exchangers as well as non-isentropic losses in the compression and expansion processes. Equations of exergy efficiency and profit rate of the CCHP plant are derived. Based on the finite time exergoeconomic analysis method, profit rate optimization is carried out by searching the optimal compressor pressure ratio and the optimal heat conductance distributions of the seven heat exchangers for a fixed total heat exchanger inventory and with the help of Powell arithmetic. The effects of some design parameters, including compressor and gas turbine efficiencies, ratio of heat demanded by the thermal consumer to power output, heat reservoir temperature ratios and price ratios on the optimal heat conductance distributions, optimal compressor pressure ratio, maximum profit rate and finite time exergoeconomic performance bound of the CCHP plant are discussed by numerical examples. The results obtained may provide some theoretical guidelines for the designs and operations of the practical CCHP plants.

Exergoeconomic performance of an endoreversible Carnot refrigerator with complex heat transfer law

The finite-time exergoeconomic performance of an endoreversible Carnot refrigeration with a complex heat transfer law, including generalised convective and radiative heat transfer laws, , is investigated in this article. The focus of this article is to obtain the compromised optimisation between economics (profit) and the energy utilisation factor (coefficient of performance, COP) for the endoreversible Carnot refrigerator, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. The obtained results include those obtained in many literatures and can provide some theoretical guidance for the design of practical refrigerators.

Exergoeconomic performance of an endoreversible Carnot heat pump with complex heat transfer law

The finite-time exergoeconomic performance of an endoreversible Carnot heat pump with a complex heat transfer law, including generalized convective heat transfer law and generalized radiative heat transfer law q∝ (Δ T n ) m , is investigated in this paper. The focus of this paper is to obtain the compromised optimization between economics (profit) and the energy utilization factor (coefficient of performance, COP) for the endoreversible Carnot heat pump, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. The obtained results include those obtained in much of the literature and can provide some theoretical guidance for the design of practical heat pumps.

Finite-time exergoeconomic performance optimization for a universal steady flow irreversible heat pump model

The finite-time exergoeconomic performance of a universal steady flow irreversible heat pump cycle model, which consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches with the losses of heat transfer, heat leakage and internal irreversibility, is analysed and optimized by using the theory of finite-time thermodynamics. The analytical formulae for the heating load, coefficient of performance (COP) and profit rate function of the irreversible heat pump cycle model are derived. The optimal heating load, COP and profit rate characteristics are obtained by searching the optimal heat conductance distributions of the hot- and cold-side heat exchangers for a fixed total heat exchanger inventory. Moreover, analysis and optimization of the cycle performance are carried out in order to investigate the effects of heat leakage, internal irreversibility and price ratio on the performance of the cycle by using numerical examples. It is shown that the heat leakage changes the profit rate characteristics qualitatively, and internal irreversibility decreases the profit rate of the cycle quantitatively. The performance characteristics of the steady flow irreversible Diesel, Atkinson, Otto, Brayton, Dual, Miller and Carnot heat pump cycles are included in the universal results obtained herein.

Finite time exergoeconomic performance of an irreversible intercooled regenerative Brayton cogeneration plant

A thermodynamic model of an irreversible intercooled regenerative Brayton heat and power cogeneration plant coupled to constant temperature heat reservoirs is established in this paper using finite time thermodynamics. The intercooler and the irreversible compression and expansion losses in the low and high pressure compressors and the turbine are taken into account. The finite time exergoeconomic performance of the cogeneration plant is investigated. The analytical formulae about dimensionless profit rate and exergetic efficiency are derived. The numerical examples show that there exist two different optimal values of intercooling pressure ratio, which correspond to an optimal value of dimensionless profit rate and an optimal value of exergetic efficiency respectively for the fixed total pressure ratio. There also exist optimal total pressure ratios corresponding to maximum profit rate and maximum exergetic efficiency respectively for the variable total pressure ratio. It is also found that there exist optimal consumer side temperatures, which lead to a double maximum profit rate and a double maximum exergetic efficiency respectively.

Finite time exergoeconomic performance for six endoreversible heat engine cycles: Unified description

The operation of a universal steady flow endoreversible heat engine cycle model consisting of two constant thermal-capacity heating branches, a constant thermal-capacity cooling branch and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the universal endoreversible heat engine cycle is investigated by taking profit optimization criterion as the objective. The analytical formulae for power, efficiency and profit rate function of the universal endoreversible heat engine cycle with heat resistance loss are derived. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (efficiency) for endoreversible cycles. Moreover, analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the universal endoreversible heat engine cycle using numerical examples. The results obtained herein include the performance characteristics of six endoreversible heat engines, including Carnot, Diesel, Otto, Atkinson, Brayton and Dual cycles.

Finite-time exergoeconomic performance optimization for a universal steady-flow endoreversible heat pump model

The finite-time exergoeconomic performance of a universal steady flow irreversible heat pump cycle model, which consists of two heat-absorbing branches, two heat-releasing branches and two adiabati...

Exergoeconomic performance optimization for a steady-flow endoreversible refrigerator cycle model including five typical cycles

The operation of a universal steady-flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches is viewed as a production process with exergy as its output. The finite-time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate as the optimization objective. The relations between the profit rate and the temperature ratio of the working fluid, between the coefficient of performance (COP) and the temperature ratio of the working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (COP) for endoreversible cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical examples. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Profit rate performance optimization for a generalized irreversible combined refrigeration cycle

Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalized irreversible combined refrigeration cycle model with finite-rate heat transfer, heat leakage and internal irreversibility is presented in this paper. The operation of the generalized irreversible combined refrigeration cycle is viewed as a production process with exergy as its output. The performance optimization of the cycle is performed by taking profit as the objective. The optimal profit rate, optimal COP (coefficient of performance), as well as the relation between the optimal profit rate and COP of the cycle are derived. The focus of this paper is to obtain the compromise optimization between economics (profit rate) and the energy utilization factor (COP) for the cycle, by searching the optimum COP at maximum profit rate, which is termed as the finite time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price ratio, on the profit rate performance of the cycle are analysed by detailed numerical examples.

Profit performance optimisation for an irreversible Carnot refrigeration cycle

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 finite time exergoeconomic performance limit. Moreover, the effects of cycle parameters on the performance of the cycle are analysed by using a numerical example.

Maximum profit performance for a class of universal endoreversible steady flow heat engine cycles

SYNOPSIS The operation of a universal steady flow endoreversible heat engine cycle mode consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimisation of the engine is investigated by taking profit optimisation criterion as the objective. The relationships between profit rate and temperature ratio of the working fluid, between thermal efficiency and temperature ratio of the working fluid, as well as the optimal relationship between profit rate and efficiency of the cycle are derived. The focus of this paper is to investigate the compromised optimisation between economics (profit) and the utilisation factor (efficiency) for endoreversible cycles. Moreover, analysis and optimisation of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles, using numerical examples. The results obtained herein include the performance characteristics of Diesel, Otto, Atkinson, and Brayton cycles.

Maximum-profit performance for generalized irreversible Carnot-engines

The operation of a Newton's law system generalized irreversible Carnot-engine with heat resistance, heat leakage and internal dissipation is viewed as a production process with exergy as its output. The finite-time exergoeconomic performance optimization of the engine is investigated by taking the profit maximation criterion as the objective. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (efficiency) for finite-time irreversible cycles. The analytical formulae concerning optimal profit versus efficiency, the maximum profit and the corresponding efficiency are derived.

Effect of heat transfer law on the finite-time exergoeconomic performance of a Carnot refrigerator

The operation of a Carnot refrigerator is viewed as a production process with exergy as its output. The economic optimization of the endoreversible refrigerator is carried out in this paper. The Coefficient of Performance (COP) of the refrigerator is a secondary consideration of the practical engineering effort of maximizing cooling rate and exergy whose goodness is constrained by economical considerations. Therefore, the profit of the refrigerator is taken as the optimization objective. Using the method of finite-time exergoeconomic analysis, which emphasizes the compromise optimization between economics (profit) and the appropriate energy utilization factor (Coefficient of Performance, COP) for finite-time (endoreversible) thermodynamic cycles, this paper derives the relation between optimal profit and COP of an endoreversible Carnot refrigerator based on a relatively general heat transfer law q ∝ �(T n ). The COP at the maximum profit is also obtained. The results obtained involve those for three common heat transfer laws: Newton's law (n = 1), the linear phenomenological law in irreversible thermodynamics (n =− 1), and the radiative heat transfer law (n = 4).  2001 Editions scientifiques et medicales Elsevier SAS