A two-stage upflow anaerobic sludge blanket (UASB) and sequencing batch reactor (SBR) system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to impro...A two-stage upflow anaerobic sludge blanket (UASB) and sequencing batch reactor (SBR) system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen (TN) removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB (UASB1) to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/(m^3.day), respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^+-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^+-N removal efficiency at relatively low temperature (14.9-10.9℃). More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^+-N once the complete nitrification and denitrification were achieved.展开更多
A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials...A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials in the machine. The particles of the magnetic operating materials, with diameter of 0.5-2 mm and total mass of 950 g, were mounted in the cooling bed. A magnetic field was assembled using NdFeB rare earth permanent magnets. It had the magnetic field space of Φ 34×200 and the magnetic induction of 1.5 T. The water at pH=10 is used as a heat transfer fluid. When the ambient temperature is 296 K, a temperature span of 18 K was achieved after operation of 45 min at a frequency of 0.178 Hz. The temperature span and the output power increase significantly with the increasing velocity of heat transfer.展开更多
Common insulation gas cannot normally work in refrigeration temperature range(153-243 K), especially in extremely cold regions. To solve this problem, this essay uses cubic equation combined with two-parameter model i...Common insulation gas cannot normally work in refrigeration temperature range(153-243 K), especially in extremely cold regions. To solve this problem, this essay uses cubic equation combined with two-parameter model in theorem of corresponding states to estimate dew-point of hybrid gas. The influence of temperature on mixing ratio is studied by using van der Waals equation. The result shows that the mixing ratio is stable during temperature-fall period. Insulation property of CF_4 and CF_4/N_2 in refrigeration temperature range is studied through self-designed low-temperature test system. The result shows when the density of hybrid gas is invariable, temperature changing has less influence on breakdown voltage, and when the mixing ratio is 20%, CF_4/N_2 is the greatest potential hybrid gas.展开更多
Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of s...Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.展开更多
Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water whe...Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained.展开更多
Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines...Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.展开更多
Magnetic properties and magnetic entropy changes of La(Fe_(1-x)Mn_x)_(11.5)Si_(1.5)H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe an...Magnetic properties and magnetic entropy changes of La(Fe_(1-x)Mn_x)_(11.5)Si_(1.5)H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe and hydrogen absorption in 1-atm(1 atm = 1.01325×10~5Pa) hydrogen gas. Under a field change from 0 T to 2 T, the maximum magnetic entropy change for La(Fe_(0.99)Mn_(0.01))_(11.5)Si_(1.5)H_(1.61)is-11.5 J/kg. The suitable Curie temperature and large value of ?S_m make it an attractive potential candidate for the room temperature magnetic refrigeration application.展开更多
The amount of low-temperature heat generated in industrial processes is high,but recycling is limited due to low grade and low recycling efficiency,which is one of the reasons for low energy efficiency.It implies that...The amount of low-temperature heat generated in industrial processes is high,but recycling is limited due to low grade and low recycling efficiency,which is one of the reasons for low energy efficiency.It implies that there is a great potential for low-temperature heat recovery and utilization.This article provided a detailed review of recent advances in the development of low-temperature thermal upgrades,power generation,refrigeration,and thermal energy storage.The detailed description will be given from the aspects of system structure improvement,work medium improvement,and thermodynamic and economic performance evaluation.It also pointed out the development bottlenecks and future development trends of various technologies.The low-temperature heat combined utilization technology can recover waste heat in an all-round and effective manner,and has great development prospects.展开更多
This review summarizes the requirement of low temperature conditions in existing experimental approaches to quantum computation and quantum simulation.
In this paper,an ejector enhanced two-stage auto-cascade refrigeration cycle(EARC)using ternary mixture R600a/R32/R1150 is proposed for application of-80℃freezing.In EARC cycle,an ejector was employed to recover the ...In this paper,an ejector enhanced two-stage auto-cascade refrigeration cycle(EARC)using ternary mixture R600a/R32/R1150 is proposed for application of-80℃freezing.In EARC cycle,an ejector was employed to recover the expansion work in the throttling processes and lifted the suction pressure of the compressor.The performances of the ejector enhanced two-stage auto-cascade refrigeration cycle and conventional auto-cascade refrigeration cycle(CARC)were compared using thermodynamic analysis methods.The influences of the important operation parameters including mass fraction ratio of the mixture,fluid quality at the second separator inlet,condensation temperature,evaporation temperature,and expansion ratio of expansion valve on the performances of EARC cycle were discussed in detail.The results indicate that ternary mixture R600a/R32/R1150 has the optimal mass fraction ratio of 0.45/0.2/0.35 with respect to the maximum COP.The EARC cycle yields higher performance than the CARC cycle in terms of COP,exergy efficiency and volumetric refrigeration capacity.And 4.9%-36.5%improvement in COP and 6.9%-34.3%higher exergy efficiency could be obtained in EARC cycle comparing with CARC cycle.The finding of this study suggests that the EARC cycle has a promising application potential for low temperature freezing.展开更多
We synthesized a potassium gadolinium phosphate K3Gd(PO_(4))_(2)with monoclinic structure(P2_(1/m))by the high-temperature solid-state reaction method.Its lattice constants obtained by Rietveld refinements of XRD curv...We synthesized a potassium gadolinium phosphate K3Gd(PO_(4))_(2)with monoclinic structure(P2_(1/m))by the high-temperature solid-state reaction method.Its lattice constants obtained by Rietveld refinements of XRD curve are a=0.7411 nm,b=0.5624 nm,and c=0.9433 nm.Magnetic and magnetocaloric properties of K_(3)Gd(PO_(4))_(2)were investigated in detail.The magnetic phase transition temperature of K3Gd(PO_(4))2 was determined by ultra-low temperature testing to be 0.58 K.K_(3)Gd(PO_(4))2 exhibits large magnetic entropy changes(-ΔSM).The maximum-ΔSM are 20.2 and 29.4 J/(kg·K)in the magnetic field variation(ΔH)of 1 and 2 T,respectively,which are larger than that of the commercial Gd_(3)Ga_(5)O_(12)(GGG).The maximum adiabatic temperature change(ΔT_(ad))reaches 5.91 K under a magnetic field change(ΔH)of 1 T.K_(3)Gd(PO_(4))_(2)is a potential magnetic refrigeration material for obtaining sub-Kelvin temperatures.展开更多
基金supported by the National Natural Science Foundation of China (No.50978003)the Beijing Natural Science Foundation (No.8091001)+1 种基金the Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality (No.PHR20090502)the State Key Laboratory of Urban Water Resource and Environment (No.QAK200802)
文摘A two-stage upflow anaerobic sludge blanket (UASB) and sequencing batch reactor (SBR) system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen (TN) removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB (UASB1) to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/(m^3.day), respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^+-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^+-N removal efficiency at relatively low temperature (14.9-10.9℃). More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^+-N once the complete nitrification and denitrification were achieved.
基金This project was supported financially by the "863"project Ministry of Science and Technology(2002AA324010).
文摘A reciprocating magnetic refrigerator was developed based on the active magnetic regeneration technology. Rare earth metal Gd and intermetallic compound LaFe11.2Co0.7Si1.1 were used as the magnetic operating materials in the machine. The particles of the magnetic operating materials, with diameter of 0.5-2 mm and total mass of 950 g, were mounted in the cooling bed. A magnetic field was assembled using NdFeB rare earth permanent magnets. It had the magnetic field space of Φ 34×200 and the magnetic induction of 1.5 T. The water at pH=10 is used as a heat transfer fluid. When the ambient temperature is 296 K, a temperature span of 18 K was achieved after operation of 45 min at a frequency of 0.178 Hz. The temperature span and the output power increase significantly with the increasing velocity of heat transfer.
基金Project(51277063)supported by the National Natural Science Foundation of China
文摘Common insulation gas cannot normally work in refrigeration temperature range(153-243 K), especially in extremely cold regions. To solve this problem, this essay uses cubic equation combined with two-parameter model in theorem of corresponding states to estimate dew-point of hybrid gas. The influence of temperature on mixing ratio is studied by using van der Waals equation. The result shows that the mixing ratio is stable during temperature-fall period. Insulation property of CF_4 and CF_4/N_2 in refrigeration temperature range is studied through self-designed low-temperature test system. The result shows when the density of hybrid gas is invariable, temperature changing has less influence on breakdown voltage, and when the mixing ratio is 20%, CF_4/N_2 is the greatest potential hybrid gas.
基金Supported by the National Natural Science Foundation of China(No.51175448,51405424)
文摘Different from the traditional hydraulic oil cooling method,a new type of constant temperature oil tank cooling system based on semiconductor refrigeration technology is designed. This paper studies the principle of semiconductor refrigeration and establishes a heat transfer model. Semiconductor cooler on piping refrigeration is simulated,and influence of the parameters on the outlet temperature,such as pipe pressure difference of inlet and outlet,pipe length,pipe radius,are gotten,and then hydraulic tank semiconductor refrigeration system is proposed. The semiconductor refrigeration system can control temperature at 37 ± 1°C.
基金Supported by Major State Basic Research Development Program of China ("973" Program, No. 2009CB219907)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0936)
文摘Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained.
文摘Several media report highlight on that the pharmaceutical companies require ultra-low temperatures -80<span style="white-space:nowrap;">°</span>C to transport and store its COVID-19 vaccines. This research presents the thermodynamic analysis on cascade refrigeration system (CRS) with several refrigerant pairs which are R32/R170, R123/R170, R134a/R170, R404A/R170, R407c/R170, R410/R170, and the hydrocarbon (HC) refrigerant pair Propane/Ethane, namely R290/R170. Besides, the results of R22/R170 pair, which is not recommended to be used due to phase out of R22 as per Montréal Protocol, are included as base case to compare the novel hydrocarbon pairs in CRS and the old trend of refrigerant pairs. Thermodynamic properties of all these pairs were investigated and compared under different intermediate temperature used in CRS heat exchanger, which thermally connected both the Low and High temperature cycles (LTC) and (HTC). By applying the first law of thermodynamics, the coefficients of performance (COPs) and the specific power consumptions (SPC) in kW/TR are presented and compared. In addition, by applying the second law of thermodynamics the exergetic efficiencies were estimated. The results reveal the promising opportunity of using the HC pair (R290/R170). The minimum SPC in kW/TR is recorded for the pair R123/R170. One the other hand, the highest exegetic efficiency values are observed to be 40%, 38%, and 35% for the pairs R123/R170, R290/R170, and R134/R170, respectively. This research concludes that the HC pair (R290/R170) is highly recommended for CRS applications either to transport the COVID-19 or store it in cold storage rooms in hospitals and clinics. All precautionary measures should be carefully applied in design and operation of HC pair (R290/R170) due to its flammability hazard.
基金Projct supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(Grant No.20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(Grant No.14JCQNJC4000)
文摘Magnetic properties and magnetic entropy changes of La(Fe_(1-x)Mn_x)_(11.5)Si_(1.5)H_y compounds are investigated. Their Curie temperatures are adjusted to room temperature by partial Mn substitution for Fe and hydrogen absorption in 1-atm(1 atm = 1.01325×10~5Pa) hydrogen gas. Under a field change from 0 T to 2 T, the maximum magnetic entropy change for La(Fe_(0.99)Mn_(0.01))_(11.5)Si_(1.5)H_(1.61)is-11.5 J/kg. The suitable Curie temperature and large value of ?S_m make it an attractive potential candidate for the room temperature magnetic refrigeration application.
基金Supported by the National Natural Science Foundation of China(21476119,21406124)Major Science and Technology Innovation Project of Shandong Province(2018CXGC1102).
文摘The amount of low-temperature heat generated in industrial processes is high,but recycling is limited due to low grade and low recycling efficiency,which is one of the reasons for low energy efficiency.It implies that there is a great potential for low-temperature heat recovery and utilization.This article provided a detailed review of recent advances in the development of low-temperature thermal upgrades,power generation,refrigeration,and thermal energy storage.The detailed description will be given from the aspects of system structure improvement,work medium improvement,and thermodynamic and economic performance evaluation.It also pointed out the development bottlenecks and future development trends of various technologies.The low-temperature heat combined utilization technology can recover waste heat in an all-round and effective manner,and has great development prospects.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0303301)the National Natural Science Foundation of China(Grant Nos.11674009 and 11921005)+1 种基金the Beijing Natural Science Foundation,China(Grant No.JQ18002)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)。
文摘This review summarizes the requirement of low temperature conditions in existing experimental approaches to quantum computation and quantum simulation.
基金financially supported by National Natural Science Foundation of China(NSFC)under the grant No.51806160China Postdoctoral Science Foundation(CPSF)under the grant No.2018M640982.
文摘In this paper,an ejector enhanced two-stage auto-cascade refrigeration cycle(EARC)using ternary mixture R600a/R32/R1150 is proposed for application of-80℃freezing.In EARC cycle,an ejector was employed to recover the expansion work in the throttling processes and lifted the suction pressure of the compressor.The performances of the ejector enhanced two-stage auto-cascade refrigeration cycle and conventional auto-cascade refrigeration cycle(CARC)were compared using thermodynamic analysis methods.The influences of the important operation parameters including mass fraction ratio of the mixture,fluid quality at the second separator inlet,condensation temperature,evaporation temperature,and expansion ratio of expansion valve on the performances of EARC cycle were discussed in detail.The results indicate that ternary mixture R600a/R32/R1150 has the optimal mass fraction ratio of 0.45/0.2/0.35 with respect to the maximum COP.The EARC cycle yields higher performance than the CARC cycle in terms of COP,exergy efficiency and volumetric refrigeration capacity.And 4.9%-36.5%improvement in COP and 6.9%-34.3%higher exergy efficiency could be obtained in EARC cycle comparing with CARC cycle.The finding of this study suggests that the EARC cycle has a promising application potential for low temperature freezing.
基金Project supported by the National Key Research and Development Program of China(2022YFB3505102)the National Science Foundation for Excellent Young Scholars(52222107)+1 种基金the National Science Foundation for Distinguished Young Scholars(51925605)the National Natural Science Foundation of China(52171195)。
文摘We synthesized a potassium gadolinium phosphate K3Gd(PO_(4))_(2)with monoclinic structure(P2_(1/m))by the high-temperature solid-state reaction method.Its lattice constants obtained by Rietveld refinements of XRD curve are a=0.7411 nm,b=0.5624 nm,and c=0.9433 nm.Magnetic and magnetocaloric properties of K_(3)Gd(PO_(4))_(2)were investigated in detail.The magnetic phase transition temperature of K3Gd(PO_(4))2 was determined by ultra-low temperature testing to be 0.58 K.K_(3)Gd(PO_(4))2 exhibits large magnetic entropy changes(-ΔSM).The maximum-ΔSM are 20.2 and 29.4 J/(kg·K)in the magnetic field variation(ΔH)of 1 and 2 T,respectively,which are larger than that of the commercial Gd_(3)Ga_(5)O_(12)(GGG).The maximum adiabatic temperature change(ΔT_(ad))reaches 5.91 K under a magnetic field change(ΔH)of 1 T.K_(3)Gd(PO_(4))_(2)is a potential magnetic refrigeration material for obtaining sub-Kelvin temperatures.