Based on the Chinese National Standards involving heat pump water heater and space heating system, performances of the R744/R290 subcritical heat pump system have been discussed and compared with those of the R22 syst...Based on the Chinese National Standards involving heat pump water heater and space heating system, performances of the R744/R290 subcritical heat pump system have been discussed and compared with those of the R22 system, which is widely used in heat pump systems in China nowadays. It can be indicated that R744/R290 mixture can work efficiently as a refrigerant for heat pumps with a large heat-sink temperature rise. When mass fraction of R290 is increased, discharge pressure is reduced. Under the nominal working condition, there is an optimum mixture mass fraction of 20/80 for R744/R290 under conventional condensation pressure. Both the heating COPhs （coefficient of performance） and volumetric heating capacity are increased by about 12.62% and 34.24% respectively compared with those of R22 based system. But for the heat sink with a small temperature rise, R744/R290 system has poorer performances than R22 system. When heat transfer pinch point in evaporator and condensation processes is considered, the degree of superheat has a negative influence upon system performances under the given conditions.展开更多
Profit from their low anisotropy and high upper critical field,iron-based superconductors(IBSs)have great potential for high magnetic fields applications.Significant progress has been made for the current density impr...Profit from their low anisotropy and high upper critical field,iron-based superconductors(IBSs)have great potential for high magnetic fields applications.Significant progress has been made for the current density improvement of(Sr,Ba)0.6K0.4Fe2As2(122-type)IBS wires over the past fourteen years.In this article,an overview of the preparation procedures and key issues affecting the critical current performance of 122-type IBS wires is given,to provide a fundamental understanding of what controls the transport critical current density of 122-type IBS wires.Additionally,the recent developments for 122-type IBS wires are presented and future prospect and challenges in the development of 122-type IBS wires for practical applications are discussed.展开更多
文摘Based on the Chinese National Standards involving heat pump water heater and space heating system, performances of the R744/R290 subcritical heat pump system have been discussed and compared with those of the R22 system, which is widely used in heat pump systems in China nowadays. It can be indicated that R744/R290 mixture can work efficiently as a refrigerant for heat pumps with a large heat-sink temperature rise. When mass fraction of R290 is increased, discharge pressure is reduced. Under the nominal working condition, there is an optimum mixture mass fraction of 20/80 for R744/R290 under conventional condensation pressure. Both the heating COPhs （coefficient of performance） and volumetric heating capacity are increased by about 12.62% and 34.24% respectively compared with those of R22 based system. But for the heat sink with a small temperature rise, R744/R290 system has poorer performances than R22 system. When heat transfer pinch point in evaporator and condensation processes is considered, the degree of superheat has a negative influence upon system performances under the given conditions.
基金supported by the National Key R&D Program of China(2018YFA0704200 and 2017YFE0129500)the National Natural Science Foundation of China(51861135311,U1832213 and 51721005)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB25000000)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(QYZDJ-SSW-JSC026)the International Partnership Program of Chinese Academy of Sciences(182111KYSB20160014)。
文摘Profit from their low anisotropy and high upper critical field,iron-based superconductors(IBSs)have great potential for high magnetic fields applications.Significant progress has been made for the current density improvement of(Sr,Ba)0.6K0.4Fe2As2(122-type)IBS wires over the past fourteen years.In this article,an overview of the preparation procedures and key issues affecting the critical current performance of 122-type IBS wires is given,to provide a fundamental understanding of what controls the transport critical current density of 122-type IBS wires.Additionally,the recent developments for 122-type IBS wires are presented and future prospect and challenges in the development of 122-type IBS wires for practical applications are discussed.
