Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literatur...Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.展开更多
Aiming at improving the performance of Organic Rankine Cycle(ORC)system with low-grade steam as heat source,this work studied and optimized the main operating parameters of the ORC system.The effects of evapo-ration t...Aiming at improving the performance of Organic Rankine Cycle(ORC)system with low-grade steam as heat source,this work studied and optimized the main operating parameters of the ORC system.The effects of evapo-ration temperature,superheat degree,condensation temperature and regenerator pinch temperature difference on the system performance were obtained.The optimization for the operating parameters is based on the indicators of specific net power output,waste heat pollution,cycle exergy efficiency,and total UA value(the product of overall heat transfer coefficient and heat transfer area of heat exchanger).The results show that the increase of the evaporation temperature and the superheat degree,and the decrease of the condensation temperature and regenerator pinch temperature difference can improve general system performance but lead to weaker economic performance.The optimal evaporation temperature,superheat degree,condensation temperature and regenerator pinch temperature difference are determined as 139℃,4°C,36°C and 8°C,respectively,reaching net power output of 114.73 kW,exergy efficiency of 37.10%.Besides,it is indicated that the regenerative ORC system can reach 13.6%additional net power output compared to the ORC system without the regenerator.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704143,51672102,51632002,and 11604023)the National Key Research and Development Program of China(Grant Nos.2018YFA0305900 and 2016YFB0201204)the Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT-15R23)
文摘Based on ab initio calculations,it is found that the donor center of substitutional sulfur(S)in diamond with C2v symmetry is more stable than that with C3vsymmetry,which is different from previous reports in literature.The energy difference of C2vand C3vstructures is qualitatively affected by the supercell size,and the 216-atom supercell could be proposed as the minimum to obtain stable configuration of substitutional S in diamond.Using supercells of up to 512 atoms,the donor level of substitutional S with C2vsymmetry is deep.
基金supported by the Science and Technology Project of CNOOC Energy Technology&Services Limited(No.HFKJ-AQ201809).
文摘Aiming at improving the performance of Organic Rankine Cycle(ORC)system with low-grade steam as heat source,this work studied and optimized the main operating parameters of the ORC system.The effects of evapo-ration temperature,superheat degree,condensation temperature and regenerator pinch temperature difference on the system performance were obtained.The optimization for the operating parameters is based on the indicators of specific net power output,waste heat pollution,cycle exergy efficiency,and total UA value(the product of overall heat transfer coefficient and heat transfer area of heat exchanger).The results show that the increase of the evaporation temperature and the superheat degree,and the decrease of the condensation temperature and regenerator pinch temperature difference can improve general system performance but lead to weaker economic performance.The optimal evaporation temperature,superheat degree,condensation temperature and regenerator pinch temperature difference are determined as 139℃,4°C,36°C and 8°C,respectively,reaching net power output of 114.73 kW,exergy efficiency of 37.10%.Besides,it is indicated that the regenerative ORC system can reach 13.6%additional net power output compared to the ORC system without the regenerator.
