Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, w...Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, work of compression 1, refrigerating coefficient of performance e and power N for drive of compressor were compared. These characteristics were calculated for eight refrigerants at temperature of their condensation 30 ℃ and temperatures of boiling -15℃ and -30 ℃. The calculations show that the use of isothermal compression of refrigerant vapor ensures economy of energy during refrigerating machine operation.展开更多
Air compressors are vital and have numerous industrial applications. Approximately 8% of the annual operating electricity consumption in industrial countries is constituted by due to the use of air compressors. Becaus...Air compressors are vital and have numerous industrial applications. Approximately 8% of the annual operating electricity consumption in industrial countries is constituted by due to the use of air compressors. Because the poor heat transfer to the environment in the rapid compression process, the compression is non-isothermal, the efficiency of compressors is restricted. To improve their efficiency and achieve isothermal compression, this study proposes energy conversion reciprocating piston quasiisothermal compression using a water spray. First, a mathematical model of a reciprocating piston compressor with water sprays was established. Through experimental investigation and simulations, the mathematical model was validated. The energy conversion characteristics of the reciprocating piston compressor were then studied. To reduce compression power and enhance compression efficiency, it was first discovered that the critical parameters were the input pressure of the driving chamber, water spray mass, and compression volume ratio, which were then evaluated thoroughly. The higher the inlet pressure of the driving chamber, the faster the air compression velocity. Additionally, the compression efficiency was elevated as the water spray mass was gradually increased for a given compression volume ratio. When the compression volume ratio was increased from 2 to 3,the compression power increased from 172.7 J/stroke to 294.2 J/stroke and the compression efficiency was enhanced from 37.3%(adiabatic) to 80.6%. This research and its performance analysis can be referred to during the parameter design optimisation of reciprocating piston quasi-isothermal compression systems using water sprays.展开更多
The voltage-biased current-voltage （I-V） characteristics of intrinsic Josephson junctions （IJJs）, which are fabricated with misa- ligned high temperature superconducting Tl2Ba2CaCu2O8 （T1-2212） thin film, are in...The voltage-biased current-voltage （I-V） characteristics of intrinsic Josephson junctions （IJJs）, which are fabricated with misa- ligned high temperature superconducting Tl2Ba2CaCu2O8 （T1-2212） thin film, are investigated experimentally. Three charac- teristic regions in the I-V curve are observed at 47 K. In the low voltage part, the current firstly increases and then decreases slowly with increasing the biased voltage, which is shown as a bump. In the next region, the current slightly increases with in- creasing the biased voltage until a sudden decrease of the current appears. Thereafter, branch structure forms with increasing the voltage on the I-V characteristic. The influence of the self-heating on the I-V characteristics is investigated and the temper- ature dependence of the I-V characteristics is measured to explore these characteristics in detail.展开更多
文摘Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, work of compression 1, refrigerating coefficient of performance e and power N for drive of compressor were compared. These characteristics were calculated for eight refrigerants at temperature of their condensation 30 ℃ and temperatures of boiling -15℃ and -30 ℃. The calculations show that the use of isothermal compression of refrigerant vapor ensures economy of energy during refrigerating machine operation.
基金supported by the National Natural Science Foundation of China(Grant Nos.51375028&51605013)the Pneumatic and Thermodynamic Energy Storage and Supply Beijing Key Laboratory
文摘Air compressors are vital and have numerous industrial applications. Approximately 8% of the annual operating electricity consumption in industrial countries is constituted by due to the use of air compressors. Because the poor heat transfer to the environment in the rapid compression process, the compression is non-isothermal, the efficiency of compressors is restricted. To improve their efficiency and achieve isothermal compression, this study proposes energy conversion reciprocating piston quasiisothermal compression using a water spray. First, a mathematical model of a reciprocating piston compressor with water sprays was established. Through experimental investigation and simulations, the mathematical model was validated. The energy conversion characteristics of the reciprocating piston compressor were then studied. To reduce compression power and enhance compression efficiency, it was first discovered that the critical parameters were the input pressure of the driving chamber, water spray mass, and compression volume ratio, which were then evaluated thoroughly. The higher the inlet pressure of the driving chamber, the faster the air compression velocity. Additionally, the compression efficiency was elevated as the water spray mass was gradually increased for a given compression volume ratio. When the compression volume ratio was increased from 2 to 3,the compression power increased from 172.7 J/stroke to 294.2 J/stroke and the compression efficiency was enhanced from 37.3%(adiabatic) to 80.6%. This research and its performance analysis can be referred to during the parameter design optimisation of reciprocating piston quasi-isothermal compression systems using water sprays.
基金supported by the National Natural Science Foundation of China(Grant Nos.61176119,61171028,51002081 and 61101018)
文摘The voltage-biased current-voltage （I-V） characteristics of intrinsic Josephson junctions （IJJs）, which are fabricated with misa- ligned high temperature superconducting Tl2Ba2CaCu2O8 （T1-2212） thin film, are investigated experimentally. Three charac- teristic regions in the I-V curve are observed at 47 K. In the low voltage part, the current firstly increases and then decreases slowly with increasing the biased voltage, which is shown as a bump. In the next region, the current slightly increases with in- creasing the biased voltage until a sudden decrease of the current appears. Thereafter, branch structure forms with increasing the voltage on the I-V characteristic. The influence of the self-heating on the I-V characteristics is investigated and the temper- ature dependence of the I-V characteristics is measured to explore these characteristics in detail.
