Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configu...Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configurations, hindering use of a recuperator in Helium cycles and conditioning the outlet turbine temperature in CO2 ones. In both cycles, it is possible to take advantage of the exhaust thermal energy by coupling the Brayton to a Rankine cycle, with an organic fluid in the helium case （iso-butane has been investigated） and steam in the CO2 case. The highest efficiency achieved with Helium cycle is 38.5% using Organic Rankine Cycle and 32.6% with Helium alone. The efficiency changes from 46.7% using Rankine cycle to 41% with CO2 alone. The Helium cycle is highly sensitive to turbine efficiency and in a moderate way to compressor efficiency and pressure drops, being nearly insensitive to thermal effectiveness in heat exchangers. On the other hand, CO2 is nearly insensitive to all the parameters.展开更多
A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated ...A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).展开更多
Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In th...Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In this study,we examined the performance of the solar parabolic trough collector(SPTC)integrated combined cogeneration system for the purpose of power generation as well as recovery of waste exhaust heat from the R-SCO_(2) cycle with the help of the organic Rankine cycle(ORC).An exergy and energy analysis was performed for a combined recompression cycle(R-SCO_(2)-ORC)by varying the input variables such as intensity of solar irradiation(Gb),pressure at the inlet of SCO_(2) turbine(P_(5)),mass flow rate of SCO_(2)()&mSCO_(2) inlet temperature of SCO_(2) turbine(T5),inlet temperature of main compressor(T_(9))and effectiveness of the high-and low-temperature recuperator( HTR and LTR).Eight organic working fluids were considered for the ORC:R123,R290,isobutane,R1234yf,R1234ze,toluene,isopentane and cyclohexane.The study revealed that R123-based R-SCO_(2)-ORC demonstrates the highest thermal and exergy efficiency:~73.4 and 40.89%at G_(b)=0.5 kW/m^(2);78.8 and 43.9%at P_(5)=14 MPa;63.86 and 35.57%at T5=650 K;74.84 and 41.69%at&mSCO 7kg s;2=/85.83 and 47.82%at T_(9)=300 K;84.57 and 47.11%at HTR 65;=0.85.06 and 47.38%at LTR 65,=0.respectively.Alternatively,R290 showed the minimum value of exergy and thermal efficiency.As can be seen,the maximum amount of exergy destruction or exergy loss occurs in a solar collector field,~58.25%of the total exergy destruction rate(i.e.6703 kW)and 18.99%of the solar inlet exergy(i.e.20562 kJ).Moreover,R123 has the highest net work output,~4594 kJ at T5=650 K and 6176 kJ at T_(9)=300 K.展开更多
文摘Brayton power cycles for fusion reactors have been investigated, using Helium in classical configurations and CO2 in a recompression layout. Thermal sources from the reactor have strongly constrained the cycle configurations, hindering use of a recuperator in Helium cycles and conditioning the outlet turbine temperature in CO2 ones. In both cycles, it is possible to take advantage of the exhaust thermal energy by coupling the Brayton to a Rankine cycle, with an organic fluid in the helium case （iso-butane has been investigated） and steam in the CO2 case. The highest efficiency achieved with Helium cycle is 38.5% using Organic Rankine Cycle and 32.6% with Helium alone. The efficiency changes from 46.7% using Rankine cycle to 41% with CO2 alone. The Helium cycle is highly sensitive to turbine efficiency and in a moderate way to compressor efficiency and pressure drops, being nearly insensitive to thermal effectiveness in heat exchangers. On the other hand, CO2 is nearly insensitive to all the parameters.
基金supported by the Shandong Provincial Natural Science Foundation of China(No.ZR2019MEE045)the National Natural Science Foundation of China(No.51776203)the Key Project of National Natural Science Foundation of China(No.61733010)。
文摘A novel power and cooling cogeneration system which combines a supercritical CO_(2) recompression cycle(SCRC), an ammonia-water absorption refrigeration cycle(AARC) and a Kalina cycle(KC) is proposed and investigated for the recovery of medium-temperature waste heat. The system is based on energy cascade utilization, and the waste heat can be fully converted through the simultaneous operation of the three sub-cycles. A steady-state mathematical model is built for further performance study of the proposed system. When the exhaust temperature is 505℃, it is shown that under designed conditions the thermal efficiency and exergy efficiency reach 30.74% and 61.55%, respectively. The exergy analysis results show that the main exergy destruction is concentrated in the heat recovery vapor generator(HRVG). Parametric study shows that the compressor inlet pressure, the SCRC pressure ratio, the main compressor and the turbine I inlet temperature, and the AARC generator pressure have significant effects on thermodynamic and economic performance of the combined system. The findings in this study could provide guidance for system design to achieve an efficient utilization of medium-temperature waste heat(e.g., exhaust heat from gas turbine, high-temperature fuel cells and internal combustion engine).
文摘Nowadays,the recompression supercritical carbon dioxide(R-SCO_(2))cycle has emerged as a promising option for power conversion systems because of its boundless potential to tackle energy and environmental issues.In this study,we examined the performance of the solar parabolic trough collector(SPTC)integrated combined cogeneration system for the purpose of power generation as well as recovery of waste exhaust heat from the R-SCO_(2) cycle with the help of the organic Rankine cycle(ORC).An exergy and energy analysis was performed for a combined recompression cycle(R-SCO_(2)-ORC)by varying the input variables such as intensity of solar irradiation(Gb),pressure at the inlet of SCO_(2) turbine(P_(5)),mass flow rate of SCO_(2)()&mSCO_(2) inlet temperature of SCO_(2) turbine(T5),inlet temperature of main compressor(T_(9))and effectiveness of the high-and low-temperature recuperator( HTR and LTR).Eight organic working fluids were considered for the ORC:R123,R290,isobutane,R1234yf,R1234ze,toluene,isopentane and cyclohexane.The study revealed that R123-based R-SCO_(2)-ORC demonstrates the highest thermal and exergy efficiency:~73.4 and 40.89%at G_(b)=0.5 kW/m^(2);78.8 and 43.9%at P_(5)=14 MPa;63.86 and 35.57%at T5=650 K;74.84 and 41.69%at&mSCO 7kg s;2=/85.83 and 47.82%at T_(9)=300 K;84.57 and 47.11%at HTR 65;=0.85.06 and 47.38%at LTR 65,=0.respectively.Alternatively,R290 showed the minimum value of exergy and thermal efficiency.As can be seen,the maximum amount of exergy destruction or exergy loss occurs in a solar collector field,~58.25%of the total exergy destruction rate(i.e.6703 kW)and 18.99%of the solar inlet exergy(i.e.20562 kJ).Moreover,R123 has the highest net work output,~4594 kJ at T5=650 K and 6176 kJ at T_(9)=300 K.
