A pilot-scale apparatus for continuous supercritical and near-critical water reaction was set up. A high-pressure slurry supplying system was developed to feed the solid material-water slurries. The apparatus features...A pilot-scale apparatus for continuous supercritical and near-critical water reaction was set up. A high-pressure slurry supplying system was developed to feed the solid material-water slurries. The apparatus features temperature up to 600℃, pressure up to 40MPa, residence time from 24s to 15min, maximum amount of slurry supply of 2.4 L·h-1, maximum solid content of slurry up to 10%(by mass) for cellulose from Merck, and resistance to corrosion. Long-time runs of decomposition of cellulose were carried out and steady runs were confirmed. Kinetics of cellulose decomposition was studied. The apparent activation energy evaluated was 147kJ·mol-1. In addition, a new three-step pathway for cellulose hydrolysis was proposed. The derived kinetic equation is in good agreement with the experimental data.展开更多
This study experimentally investigated the critical heat flux(CHF) of departure from nucleate boiling(DNB) of water flowing under near-critical pressures in a 2 m-long vertical upward rifled tube with the size of Φ35...This study experimentally investigated the critical heat flux(CHF) of departure from nucleate boiling(DNB) of water flowing under near-critical pressures in a 2 m-long vertical upward rifled tube with the size of Φ35 × 5.67 mm. Operating conditions included pressures of 18–21 MPa, mass fluxes of 475–1000 kg·m^(-2)·s^(-1), inlet subcooling temperatures of 3–5°C, and wall heat fluxes of 40–960 kW·m^(-2). Tube wall temperature distribution and heat transfer performance in different test conditions were obtained. The effects of the operating parameters on CHF were analyzed. Four heat transfer coefficient correlations were evaluated against our experimental data for further investigation of the two-phase heat transfer characteristics. A heat transfer correlation based on Martinelli number utilized in two-phase region and two empirical correlations used to predict the CHF in rifled tube at near-critical pressures were proposed. Meanwhile, experimental CHF data in rifled tube were compared with six widely used correlations and a CHF look-up table. The CHF enhancement effect in rifled tube is obvious as compared with the CHF data in smooth tube. Results show that DNB occurs at low vapor quality and subcooled region in the rifled tube at near-critical pressures. The increase in pressure leads to the early occurrence of DNB and the decrease in CHF, whereas the increase in mass flux delays the occurrence of DNB and results in the increase in CHF. DNB presents a tendency to move toward the inlet of the rifled tube. At individual operating conditions, DNB and dryout coexist at different sections of the rifled tube.展开更多
The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In...The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.展开更多
The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particula...The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.展开更多
A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The d...A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The decomposition rate of epoxy resin raised rapidly as the reaction time and reaction temperature increased. The decomposition reaction products were characterized by infra-red spectra and gas chromatography-mass spectrometry. The phenol, isopropylphenol, 4, 4＇-（1-methylethylidene） bis-phenol were found as the main compounds in liquid products, which were common monomers from epoxy resin. When reaction was carried out at the temperature of 260℃ -300 ℃, the decomposition mechanism of epoxy resin was envisaged as the ether and ester bonds cracking.展开更多
A Glaser coupling reaction of terminal alkynes in the presence of cupric chloride without organic solvents and bases under near-critical water has been developed.
Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication techniqu...Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.展开更多
During last 45 years, two groups of the experimental data on critical heat flux were obtained in bare tubes, covering the pressures from atmosphere to near-critical point. One group of the data were obtained in the in...During last 45 years, two groups of the experimental data on critical heat flux were obtained in bare tubes, covering the pressures from atmosphere to near-critical point. One group of the data were obtained in the inner diameter of 2.32, 5.16, 8.05, 10.0 and 16.0 mm, respectively, with the ranges of pressure of 0.1-1.92 MPa, velocity of 1.47-23.3 m/s, local subcooling of 3.7-108.7 ℃ and heat flux of up to 38.3 MW/m2. Another group of the data were obtained in the inner diameter of 4.62, 7.98 and 10.89 mm, respectively, with the ranges of pressure of 1.7-20.6 MPa, mass flux of 454-4,055 kg/（m2.s） and inlet subcooling of 53-361 ℃. The results showed complicated effects of the pressure, mass flux, subcooling and diameter on the critical heat flux. They were formulated by two empirical correlations. A mechanistic model on the limit of heat transfer capability from the bubbly layer to the subcooled core was also proposed for all the results.展开更多
The hydration of phenylacetylene in near-critical water,assisted with additives（NaHSO4,ZnCl2,FeCl3）,has been successfully conducted with temperature and residence time ranges of 220-300℃and 60-180 min,respectively....The hydration of phenylacetylene in near-critical water,assisted with additives（NaHSO4,ZnCl2,FeCl3）,has been successfully conducted with temperature and residence time ranges of 220-300℃and 60-180 min,respectively.The results showed the catalytic ability is FeCl3ZnCl2NaHSO4.The maximum yield of product acetophenone was 96.68%at 260℃,120 min.Based on the results found,a possible mechanism of hydration of phenylacetylene in near-critical water was proposed.展开更多
An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are i...An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are investigated numerically. It is found that the positron yield is mainly affected by the number of electrons of energies up to several hundreds of MeV. Using near-critical density targets for electron acceleration, the number of high energy electrons can be increased dramatically. Through start-to-end simulations, it is shown that up to 6.78×10106.78×1010 positrons can be generated with state-of-the-art Joule-class femtosecond laser systems.展开更多
In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations t...In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations that relativistic toroidal solitons,composed of intense light self-consistently trapped in toroidal plasma cavities,can be produced by azimuthallypolarized relativistic laser pulses in a near-critical underdense plasma.展开更多
基金Partly supported by Research for Future Program"Integrated field 5,causes and effects of environmental loading and its reduction",the Japan Society for the Promotion of Science(JSPS).
文摘A pilot-scale apparatus for continuous supercritical and near-critical water reaction was set up. A high-pressure slurry supplying system was developed to feed the solid material-water slurries. The apparatus features temperature up to 600℃, pressure up to 40MPa, residence time from 24s to 15min, maximum amount of slurry supply of 2.4 L·h-1, maximum solid content of slurry up to 10%(by mass) for cellulose from Merck, and resistance to corrosion. Long-time runs of decomposition of cellulose were carried out and steady runs were confirmed. Kinetics of cellulose decomposition was studied. The apparent activation energy evaluated was 147kJ·mol-1. In addition, a new three-step pathway for cellulose hydrolysis was proposed. The derived kinetic equation is in good agreement with the experimental data.
基金financially supported by the National Key Research & Development Program of China (Grant No. 2016YFB0600201)
文摘This study experimentally investigated the critical heat flux(CHF) of departure from nucleate boiling(DNB) of water flowing under near-critical pressures in a 2 m-long vertical upward rifled tube with the size of Φ35 × 5.67 mm. Operating conditions included pressures of 18–21 MPa, mass fluxes of 475–1000 kg·m^(-2)·s^(-1), inlet subcooling temperatures of 3–5°C, and wall heat fluxes of 40–960 kW·m^(-2). Tube wall temperature distribution and heat transfer performance in different test conditions were obtained. The effects of the operating parameters on CHF were analyzed. Four heat transfer coefficient correlations were evaluated against our experimental data for further investigation of the two-phase heat transfer characteristics. A heat transfer correlation based on Martinelli number utilized in two-phase region and two empirical correlations used to predict the CHF in rifled tube at near-critical pressures were proposed. Meanwhile, experimental CHF data in rifled tube were compared with six widely used correlations and a CHF look-up table. The CHF enhancement effect in rifled tube is obvious as compared with the CHF data in smooth tube. Results show that DNB occurs at low vapor quality and subcooled region in the rifled tube at near-critical pressures. The increase in pressure leads to the early occurrence of DNB and the decrease in CHF, whereas the increase in mass flux delays the occurrence of DNB and results in the increase in CHF. DNB presents a tendency to move toward the inlet of the rifled tube. At individual operating conditions, DNB and dryout coexist at different sections of the rifled tube.
基金supported by the National Natural Science Foundation of China(Grant No.51506001)Beijing Municipal Education Commission(KM201710005029)National Key R&D Program of China(Grant No.2016YFE0124900)
文摘The organic Rankine cycle(ORC)is a popular technique used in the utilization of low-grade thermal energy.Among wet,dry,and isentropic organic working fluids,the latter two types are more appropriate for ORC systems.In this paper,the definition of turning point on saturated vapor curve of dry fluid and isentropic fluid was given according to the shape of the saturated curve of working fluids in a T-s diagram.On this basis,the model of near-critical region triangle was established.Using this model,the thermodynamic performance of 57 kinds of dry and isentropic organic working fluids in ORC was evaluated.The performance includes the relation between turning point temperature and cycle thermal efficiency,the relation between near-critical region triangle area and cycle thermal efficiency,the relation between near-critical region triangle area and exergy at turning point temperature,the relation between near-critical region triangle area and reciprocal value of slope of saturated vapor curve.Moreover,working fluid selection was also conducted in terms of heat source type.It was found through theoretical analysis results that the popular R123 is an acceptable choice especially for the utilization of closed type heat source.Considering it will be phased out in near future,then cis-butene,butane,trans-butene,and isobutene are worth studying as its successor.Dodecane is worthy of attention and further research and it can be a good choice for utilization of open type heat source.
基金supported by the National Natural Science Foundation of China(No.52076172)。
文摘The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.
基金Funded by the National Natural Science Foundation of China(No.50973023)the Program for New Century Excellent Talents in University(No.NCET-09-0060)
文摘A kind of chemical method that used water as the liquid reaction medium to decompose epoxy resin was studied. The thermosetting epoxy resin was decomposed successfully under the condition of near-critical water. The decomposition rate of epoxy resin raised rapidly as the reaction time and reaction temperature increased. The decomposition reaction products were characterized by infra-red spectra and gas chromatography-mass spectrometry. The phenol, isopropylphenol, 4, 4＇-（1-methylethylidene） bis-phenol were found as the main compounds in liquid products, which were common monomers from epoxy resin. When reaction was carried out at the temperature of 260℃ -300 ℃, the decomposition mechanism of epoxy resin was envisaged as the ether and ester bonds cracking.
基金Project supported by the National Natural Science Foundation of China (Nos. 2037202420172018)+1 种基金 the Excellent Scientist Foundation of Anhui Province (No. 2001040) the Natural Science Foundation of the Education Department of Anhui Province (No. 2002kj25
文摘A Glaser coupling reaction of terminal alkynes in the presence of cupric chloride without organic solvents and bases under near-critical water has been developed.
基金National Grand Instrument Project(No.2019YFF01014402)NSFC innovation group project(No.11921006)National Natural Science Foundation of China(Nos.11775010,11535001,and 61631001).
文摘Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.
文摘During last 45 years, two groups of the experimental data on critical heat flux were obtained in bare tubes, covering the pressures from atmosphere to near-critical point. One group of the data were obtained in the inner diameter of 2.32, 5.16, 8.05, 10.0 and 16.0 mm, respectively, with the ranges of pressure of 0.1-1.92 MPa, velocity of 1.47-23.3 m/s, local subcooling of 3.7-108.7 ℃ and heat flux of up to 38.3 MW/m2. Another group of the data were obtained in the inner diameter of 4.62, 7.98 and 10.89 mm, respectively, with the ranges of pressure of 1.7-20.6 MPa, mass flux of 454-4,055 kg/（m2.s） and inlet subcooling of 53-361 ℃. The results showed complicated effects of the pressure, mass flux, subcooling and diameter on the critical heat flux. They were formulated by two empirical correlations. A mechanistic model on the limit of heat transfer capability from the bubbly layer to the subcooled core was also proposed for all the results.
基金supported by the National Natural Science Foundation of China(Nos.21073064,21003049)
文摘The hydration of phenylacetylene in near-critical water,assisted with additives（NaHSO4,ZnCl2,FeCl3）,has been successfully conducted with temperature and residence time ranges of 220-300℃and 60-180 min,respectively.The results showed the catalytic ability is FeCl3ZnCl2NaHSO4.The maximum yield of product acetophenone was 96.68%at 260℃,120 min.Based on the results found,a possible mechanism of hydration of phenylacetylene in near-critical water was proposed.
基金Supported by the National Basic Research Program of China under Grant No 2013CBA01502the National Natural Science Foundation of China under Grant Nos 11575011 and 11535001+1 种基金the National Grand Instrument Project under Grant No2012YQ030142the UK EPSRC under Grant Nos EP/G054950/1,EP/G056803/1,EP/G055165/1 and EP/M022463/1
文摘An improved indirect scheme for laser positron generation is proposed. The positron yields in high-ZZ metal targets irradiated by laser produced electrons from near-critical density plasmas and underdense plasma are investigated numerically. It is found that the positron yield is mainly affected by the number of electrons of energies up to several hundreds of MeV. Using near-critical density targets for electron acceleration, the number of high energy electrons can be increased dramatically. Through start-to-end simulations, it is shown that up to 6.78×10106.78×1010 positrons can be generated with state-of-the-art Joule-class femtosecond laser systems.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA17040502)。
文摘In the laser–plasma interaction,relativistic soliton formation is an interesting nonlinear phenomenon and important light mode convection in plasmas.Here,it is shown by threedimensional particle-in-cell simulations that relativistic toroidal solitons,composed of intense light self-consistently trapped in toroidal plasma cavities,can be produced by azimuthallypolarized relativistic laser pulses in a near-critical underdense plasma.
