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学者姓名：孙志新
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Abstract ：
Two-stage Rankine cycles draw more and more attention with the increasing trade of LNG (liquefied natural gas) and the recovery of both the cold exergy of LNG and the thermal exergy of low temperature heat source. To figure out the best configuration of two-stage Rankine cycles, three mostly studied configuration, cascade twostage ORC (organic Rankine cycle), parallel two-stage ORC and two-condensation ORC are optimized and compared under different heat source temperatures and different NG distribution pressures. Ten substances are selected as the working fluids. The evaporation, condensation and expander inlet temperatures of both ORCs and the LNG regasification pressure are optimized to obtain the maximum exergy efficiency. The results show that both the increase of heat source temperature and the decrease of NG distribution pressure can improve the exergy efficiencies greatly. The increase of heat source temperature not only increases the optimal key parameters but also affects the ranking of optimal fluids, while the increase of NG distribution pressure only affects the optimal parameters. Different from conventional Rankine cycles, there is also an optimal condensation temperature to match the heat absorption line of LNG and it increases with increase of the NG distribution pressure. The LNG regasification pressure is a key parameter which determines the proportion of power outputs between ORCs and direct expansion cycles. The thermodynamic performances of parallel two-stage ORC and two-condensation ORC are almost the same, which are obviously better than that of cascade two-stage ORC. Both parallel two-stage ORC and two-condensation ORC with ammonia as the working fluid achieve the maximum efficiency of 30.54% under the heat source temperature of 200 degrees C and the NG distribution pressure of 3 MPa. Two-condensation ORC is the optimum configuration with both good thermodynamic and economic performances. The lowest electricity production cost of two-condensation ORC achieved in this paper is 0.033$/kW.h. The environmental side effect caused by working fluid leakage is negligible compared with the saved CO2 emission via the electricity generation.
Keyword ：
Fluid selection Fluid selection Liquefied natural gas Liquefied natural gas Parameter optimization Parameter optimization Power generation Power generation Rankine cycle Rankine cycle
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| GB/T 7714 | Sun, Zhixin , Zhang, Han , Zhang, Tianfeng et al. Optimizations and comparison of three two-stage Rankine cycles under different heat source temperatures and NG distribution pressures [J]. | ENERGY CONVERSION AND MANAGEMENT , 2020 , 209 . |
| MLA | Sun, Zhixin et al. "Optimizations and comparison of three two-stage Rankine cycles under different heat source temperatures and NG distribution pressures" . | ENERGY CONVERSION AND MANAGEMENT 209 (2020) . |
| APA | Sun, Zhixin , Zhang, Han , Zhang, Tianfeng , Lin, Li , Lin, Kui . Optimizations and comparison of three two-stage Rankine cycles under different heat source temperatures and NG distribution pressures . | ENERGY CONVERSION AND MANAGEMENT , 2020 , 209 . |
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Abstract ：
In this paper, the new configuration of transcritical CO2 refrigeration cycle combined with a thermoelectric subcooler and an ejector (TES + EJE) is proposed. The thermoelectric subcooler is installed after the gas cooler in the transcritical CO2 refrigeration cycle with an ejector. Comparisons are carried out with the conventional transcritical CO2 refrigeration cycle (BASE), CO2 cycle with a thermoelectric subcooler (TES) and CO2 cycle with an ejector (EJE). Maximum cooling coefficient of performance (COPc) is obtained for the new TES + EJE cycle with a simultaneous optimization of subcooling temperature and discharge pressure. The improved new cycle exhibits higher COPc and lower discharge pressure compared with the other three cycles. Compared with the BASE cycle, the maximum COPc of the TES + EJE cycle is increased by 39.34% and the corresponding optimum discharge pressure is reduced by 8.01% under given operation conditions of 5 degrees C evaporation temperature and 40 degrees C gas cooler outlet temperature. The effects of the subcooling temperature, discharge pressure, gas cooler outlet temperature and evaporation temperature on the TES + EJE system performance are also discussed by energy and exergy analysis and results present here.
Keyword ：
Carbon dioxide Carbon dioxide Cooling coefficient of performance Cooling coefficient of performance Ejector Ejector Exergy loss rate Exergy loss rate Thermoelectric subcooler Thermoelectric subcooler Transcritical refrigeration cycle Transcritical refrigeration cycle
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| GB/T 7714 | Liu, Xi , Fu, Ruansong , Wang, Zhiqiang et al. Thermodynamic analysis of transcritical CO2 refrigeration cycle integrated with thermoelectric subcooler and ejector [J]. | ENERGY CONVERSION AND MANAGEMENT , 2019 , 188 : 354-365 . |
| MLA | Liu, Xi et al. "Thermodynamic analysis of transcritical CO2 refrigeration cycle integrated with thermoelectric subcooler and ejector" . | ENERGY CONVERSION AND MANAGEMENT 188 (2019) : 354-365 . |
| APA | Liu, Xi , Fu, Ruansong , Wang, Zhiqiang , Lin, Li , Sun, Zhixin , Li, Xuelai . Thermodynamic analysis of transcritical CO2 refrigeration cycle integrated with thermoelectric subcooler and ejector . | ENERGY CONVERSION AND MANAGEMENT , 2019 , 188 , 354-365 . |
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Abstract ：
ORC is a good solution to recover the cold exergy of LNG (liquefied natural gas) and the thermal exergy of low grade heat simultaneously. The optimal working fluids and parameters change greatly with different configurations and heat source temperatures. In this paper, three different ORC configurations: SORC (single-stage ORC), PTORC (parallel two-stage ORC) and CTORC (cascade two-stage ORC), combined with DEC (direct expansion cycle) are analyzed and compared. Up to seven key parameters of sixty four fluid combinations under four heat source temperatures are optimized by the particle swarm optimization. The results show that PTORC is more suitable for lower heat source temperatures and CTORC performs better for higher heat source temperatures. PTORC+DEC with ammonia/ethane as the fluid combination yields the maximum efficiency of 17.36% for the heat source temperature of 50 degrees C. CTORCs without DEC, also with ammonia/ethane as the fluid combination, achieve the maximum efficiencies of 19.49%, 21.69% and 24.37% for the heat source temperatures of 100, 150 and 200 degrees C, respectively. The optimal turbine inlet temperatures are usually their upper bounds and the optimal condensation temperatures are the normal boiling temperatures of the fluids. There are optimum evaporation temperatures for all configurations, which increase with the heat source temperature. (C) 2018 Elsevier Ltd. All rights reserved.
Keyword ：
Liquefied Natural Gas Liquefied Natural Gas Low grade heat Low grade heat Optimization Optimization Organic Rankine Cycle Organic Rankine Cycle Power generation Power generation
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| GB/T 7714 | Sun, Zhixin , Lai, Jianpeng , Wang, Shujia et al. Thermodynamic optimization and comparative study of different ORC configurations utilizing the exergies of LNG and low grade heat of different temperatures [J]. | ENERGY , 2018 , 147 : 688-700 . |
| MLA | Sun, Zhixin et al. "Thermodynamic optimization and comparative study of different ORC configurations utilizing the exergies of LNG and low grade heat of different temperatures" . | ENERGY 147 (2018) : 688-700 . |
| APA | Sun, Zhixin , Lai, Jianpeng , Wang, Shujia , Wang, Tielong . Thermodynamic optimization and comparative study of different ORC configurations utilizing the exergies of LNG and low grade heat of different temperatures . | ENERGY , 2018 , 147 , 688-700 . |
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Abstract ：
NG (Natural gas) distribution pressure varies in a wide range in different applications and has significant effect on system exergy efficiency. RC (Rankine cycle) and DEC (direct expansion cycle) can utilize the cold and pressure exergies of LNG (liquefied natural gas), respectively. In this paper, SRC (single-stage RC), PTRC (parallel two-stage RC) and CTRC (cascade two-stage RC) with and without DEC are optimized by Particle Swarm Optimization and compared to obtain the optimal configurations for different NG distribution pressures. Propane, propylene, ethane and ethylene are adopted as the working fluids. The results show that the addition of DEC could increase the exergy efficiency by lifting the evaporation temperature of LNG. CTRC + DEC with propane/ethylene and CfRC + DEC with propane/ethane as the working fluid achieve the largest exergy efficiencies of 23.89% and 18.25% at NG distribution pressures of 1 MPa and 2 MPa, respectively. PTRC + DEC with propane/ethane is the optimal system with maximum exergy efficiencies of 15.18%, 13.24%, 11.7% and 10.4% at NG distribution pressures of 3, 4, 5 and 6 MPa, respectively. PTRC + DEC with ethane as the working fluid in both cycles is a generally suitable system for all NG distribution pressures with high efficiency and only one type of working fluid. (C) 2017 Elsevier Ltd. All rights reserved.
Keyword ：
Fluid selection Fluid selection Liquefied natural gas Liquefied natural gas Parametric optimization Parametric optimization Power generation Power generation Rankine cycle Rankine cycle
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| GB/T 7714 | Sun, Zhixin , Xu, Fuquan , Wang, Shujia et al. Comparative study of Rankine cycle configurations utilizing LNG cold energy under different NG distribution pressures [J]. | ENERGY , 2017 , 139 : 380-393 . |
| MLA | Sun, Zhixin et al. "Comparative study of Rankine cycle configurations utilizing LNG cold energy under different NG distribution pressures" . | ENERGY 139 (2017) : 380-393 . |
| APA | Sun, Zhixin , Xu, Fuquan , Wang, Shujia , Lai, Jianpeng , Lin, Kui . Comparative study of Rankine cycle configurations utilizing LNG cold energy under different NG distribution pressures . | ENERGY , 2017 , 139 , 380-393 . |
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