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Lingen Chen - One of the best experts on this subject based on the ideXlab platform.

  • Finite time exergoeconomic performance of an irreversible intercooled regenerative Brayton cogeneration plant
    Journal of the Energy Institute, 2011
    Co-Authors: Bo Yang, Lingen Chen, Fengrui Sun
    Abstract:

    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.

  • Exergetic Efficiency optimization for real regenerated air refrigerators
    Applied Thermal Engineering, 2011
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    Abstract On the basis of the Exergetic analysis, the performance analysis and optimization is carried out for irreversible regenerated air refrigerators by taking Exergetic Efficiency as the optimization objective using thermodynamic optimization in this paper. Exergetic Efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The analytical formulas of the cooling load, coefficient of performance (COP) and Exergetic Efficiency for the refrigerators are derived. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectivenesses of the hot- and cold- side heat exchangers and regenerator, the efficiencies of the compressor and expander, the pressure recovery coefficient, and the total heat exchanger inventory on the Exergetic Efficiency of the refrigerators are investigated by detailed numerical examples. The results show that the Exergetic Efficiency optimization is an important and effective criterion for the evaluation of irreversible regenerated air refrigerators.

  • Exergetic Efficiency optimization for an irreversible heat pump working on reversed brayton cycle
    Pramana, 2010
    Co-Authors: Yuehong Bi, Lingen Chen
    Abstract:

    This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking Exergetic Efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic Efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and Exergetic Efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the Exergetic Efficiency of the heat pumps are analysed by numerical calculations. The results show that the Exergetic Efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.

  • Exergetic Efficiency optimization for an irreversible quantum brayton refrigerator with spin systems
    Applied Mathematical Modelling, 2010
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    Abstract The purpose of this paper is to study the optimal performance for an irreversible quantum Brayton refrigerator with spin systems, which consists of two isomagnetic field branches connected by two irreversible adiabatic branches. The time evolution of the total magnetic moment M is determined by solving the generalized quantum master equation of an open system in the Heisenberg picture. The time of two irreversible adiabatic processes is considered based on finite-rate evolution in this paper. The optimization region (or criteria) for an irreversible quantum Brayton refrigerator with spin systems is obtained. The relationship between the Exergetic Efficiency e E and dimensionless cooling load R for the irreversible quantum Brayton refrigerator with heat leakage and other irreversibility losses are derived.

  • Ecological, Exergetic Efficiency and heating load optimizations for irreversible variable-temperature heat reservoir simple air heat pump cycles
    Indian Journal of Pure & Applied Physics, 2009
    Co-Authors: Yuehong Bi, Lingen Chen
    Abstract:

    Thermodynamic optimization of an irreversible air heat pump with variable-temperature heat reservoirs and hot- and cold-side counter-flow heat exchangers has been studied. The expressions of the heating load, the Exergetic Efficiency and the ecological function of the heat pump cycle are derived. Performance comparisons among Exergetic Efficiency optimization, ecological optimization and traditional heating load optimization objectives are done. The effect of the pressure ratio of the compressor, the allocation of heat exchanger inventory and the heat capacity rate matching between the working fluid and the heat reservoirs on the optimal performance of the cycle has been investigated by detailed numerical examples. When the performance optimization of the cycle is carried out by selecting the pressure ratio, three optimization objectives give simultaneously attention to the coefficient of performance (COP). The pressure ratio should be the one that is little bigger than the optimum pressure ratio corresponding to maximum COP, however, the results of three optimization objectives are consistent by optimizing the allocation of heat exchanger inventory and optimizing the heat capacity rate matching between the working fluid and the heat reservoirs. The optimum allocations of heat conductance are close to each other, and they are all less than 0.5. The results may provide guidelines for the design and optimization of practical air heat pump plants.

Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.

  • Finite time exergoeconomic performance of an irreversible intercooled regenerative Brayton cogeneration plant
    Journal of the Energy Institute, 2011
    Co-Authors: Bo Yang, Lingen Chen, Fengrui Sun
    Abstract:

    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.

  • Exergetic Efficiency optimization for real regenerated air refrigerators
    Applied Thermal Engineering, 2011
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    Abstract On the basis of the Exergetic analysis, the performance analysis and optimization is carried out for irreversible regenerated air refrigerators by taking Exergetic Efficiency as the optimization objective using thermodynamic optimization in this paper. Exergetic Efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The analytical formulas of the cooling load, coefficient of performance (COP) and Exergetic Efficiency for the refrigerators are derived. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectivenesses of the hot- and cold- side heat exchangers and regenerator, the efficiencies of the compressor and expander, the pressure recovery coefficient, and the total heat exchanger inventory on the Exergetic Efficiency of the refrigerators are investigated by detailed numerical examples. The results show that the Exergetic Efficiency optimization is an important and effective criterion for the evaluation of irreversible regenerated air refrigerators.

  • Exergetic Efficiency optimization for an irreversible quantum brayton refrigerator with spin systems
    Applied Mathematical Modelling, 2010
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    Abstract The purpose of this paper is to study the optimal performance for an irreversible quantum Brayton refrigerator with spin systems, which consists of two isomagnetic field branches connected by two irreversible adiabatic branches. The time evolution of the total magnetic moment M is determined by solving the generalized quantum master equation of an open system in the Heisenberg picture. The time of two irreversible adiabatic processes is considered based on finite-rate evolution in this paper. The optimization region (or criteria) for an irreversible quantum Brayton refrigerator with spin systems is obtained. The relationship between the Exergetic Efficiency e E and dimensionless cooling load R for the irreversible quantum Brayton refrigerator with heat leakage and other irreversibility losses are derived.

  • comparative performance analysis for endoreversible simple air heat pump cycles considering ecological Exergetic Efficiency and heating load objectives
    International Journal of Exergy, 2009
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    The performance analysis and optimisation of endoreversible simple air heat pump with constant-temperature heat reservoirs is carried out by using finite-time thermodynamics. The expressions of the heating load, the Exergetic Efficiency and the ecological function of the cycle are derived. The influences of the pressure ratio of the compressor and the allocation of heat exchanger inventory on the optimal performance of the cycle are investigated by detailed numerical examples. Performance comparisons among Exergetic Efficiency objective, ecological objective and traditional heating load objective are performed. The results may provide guidelines for the design and optimisation of practical air heat pump plants.

  • Comparative performance analysis for endoreversible simple air refrigeration cycles considering ecological, Exergetic Efficiency and cooling load objectives
    International Journal of Ambient Energy, 2006
    Co-Authors: Lingen Chen, Fengrui Sun
    Abstract:

    SYNOPSIS On the basis of Exergetic analysis, the performance analysis and optimisation of endoreversible simple air refrigeration cycles with constant-temperature heat reservoirs is carried out by using the finite-time thermodynamic method in this paper. The expressions for cooling load, ecological function and Exergetic Efficiency of the refrigeration cycle are derived. The influences of pressure ratio of the compressor and allocation of heat exchanger inventory on the optimal performance of the cycle are investigated by detailed numerical examples. Performance comparisons between ecological optimisation objective, Exergetic Efficiency optimisation objective and traditional cooling load optimisation objective are performed. The results may provide guidelines for the design and optimisation of practical refrigeration plants.

Omer Comakli - One of the best experts on this subject based on the ideXlab platform.

Rabah Gomri - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of the potential of application of single effect and multiple effect absorption cooling systems
    Energy Conversion and Management, 2010
    Co-Authors: Rabah Gomri
    Abstract:

    Abstract Owing to the serious environmental problems and the price of the traditional energy resources the use of industrial waste heat or the renewable energy, especially the solar energy, as the driving force for vapour absorption cooling systems is continuously increasing. A particular attention was given to single effect cycle. The main objective of higher effect cycle is to increase system performance when high temperature heat source is available. The purpose of the present study was to investigate the potential for the application of single effect double effect and triple effect absorption cooling cycles for production chilled water. For the three systems identical cold output of 300 kW is used. Simulation results were used to study the influence of the various operating parameters on the performance coefficient, Exergetic Efficiency and the ratio of mass flow rate of refrigerant generated to the heat supplied of the three systems. It is concluded that the COP of double effect system is approximately twice the COP of single effect system and that the COP of triple effect system is slightly less than thrice the COP of single effect system. The Exergetic Efficiency of double effect system and triple effect system increase slightly compared to the Exergetic Efficiency of single effect system. It is found that for each condenser and evaporator temperature, there is an optimum generator temperature. At this point the COP and Exergetic Efficiency of the systems become maximum. Triple effect system generates more vapour refrigerant per unit heat supplied as compared with single effect and double effect systems.

  • second law comparison of single effect and double effect vapour absorption refrigeration systems
    Energy Conversion and Management, 2009
    Co-Authors: Rabah Gomri
    Abstract:

    Abstract In this paper a comparative study between single effect and double effect absorption refrigeration systems with identical cold output is carried out. Simulation results were used to study the influence of the various operating parameters on the performance coefficient, the thermal loads of the components, Exergetic Efficiency (rational Efficiency) and the total change in exergy of the two systems. It is concluded that the COP of double effect system is approximately twice the COP of single effect system but the Exergetic Efficiency of double effect system increase slightly compared to the Exergetic Efficiency of single effect system. It is found that for each condenser and evaporator temperature, there is an optimum generator temperature where the total change in exergy of the single effect and double effect absorption refrigeration systems is minimum. At this point the COP and Exergetic Efficiency of the systems become maximum. In this study and when the evaporation temperature is varied from 4 °C to 10 °C, condenser and absorber temperatures are varied from 33 °C to 39 °C and generator (HPG) temperature is varied from 60 °C to 190 °C the maximum COP values of the single effect refrigeration systems are in the range of 0.73–0.79 and for double effect refrigeration systems are in the range of 1.22–1.42. The maximum Exergetic Efficiency values of the single effect refrigeration systems are in the range of 12.5–23.2% and for double effect refrigeration systems are in the range of 14.3–25.1%.

Kamil Kaygusuz - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation of the Exergetic Efficiency of solar assisted and energy storage heat pump systems
    Energy Conversion and Management, 1992
    Co-Authors: Teoman Ayhan, Omer Comakli, Kamil Kaygusuz
    Abstract:

    In order to investigate the effects of new developments of thermal energy storage techniques on the Exergetic Efficiency of a solar assisted heat pump system with a thermal storage tank, an experimental set up was constructed. This experimental apparatus consists of 18 solar collectors, a latent heat thermal energy storage tank (containing phase change storage material), a heat exchanger, a heat pump with double evaporators and a circulating pump. Experimental results are obtained for typical days during each month of June, July and August for Trabzon (41°N) in this period of the research programme. The Exergetic efficiencies are calculated using the experimental data and comparisons are performed among the different systems.