Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configurat...Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configuration （a hollow half elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT＋2WHu） recommended in previous work has been used in this work. The operating temperatures were 24℃ and 81℃, identified as cold and hot respectively. The effects of superficial gas velocity, agitator speed and the corresponding power input on the local void fraction in two-phase systems are .investigated and discussed. Results show thatth-e increasing of agitator speed or gas flow rate leads to an increase in local-void fraction at the majority of measurement points in both cold and hot systems. However, the unifo,rmity of gas dispersion does not always in crease as the raising of agitator speed and power input. In either cold or hot sparged conditions, the two- and three-phase systems.have similar vertical profiles for void fraction, with maxima in similar locations; however, the void fractions are significantly lower in hot sparging than with cold. In cold operation the presence of particles leads to a lower void fraction at most points, although the local void fractions increase a little with the addition of solid particles at high temperature, in good agreement with the global gas holdup results, and the possible reasons are discussed in this paper. This work can give a better understanding of the differences between cold-gassed and hot-sparged three phase＇stirred tanks.展开更多
Based on trajectory equations of gas bubble,an eddy-bubble interaction(EBI)model was developed. This model considered the effect of non-drag forces and took the eddy-bubble interaction time as the refreshing time scal...Based on trajectory equations of gas bubble,an eddy-bubble interaction(EBI)model was developed. This model considered the effect of non-drag forces and took the eddy-bubble interaction time as the refreshing time scale of turbulent fluctuations.The relationship between the crossing-eddy time and the eddy lifetime was discussed,and the predicted distributions of radial,axial velocities of bubbles and gas holdup were also given. Compared with eddy lifetime(EL)model,the EBI model gives somewhat smaller axial velocity in the upper circulation region and larger velocity in the lower circulation region,causing that fewer bubbles reach the lower circulation region and gas holdup becomes higher in the upper circulation region.The predicted gas holdup by the EBI model approaches closer to the experimental data in the discharge stream region.展开更多
To analyze the bottom slope's effect on the sloshing liquid in floating liquefied natural gas(FLNG)membrane tanks,a simulation model is built and applied to describe the liquid behavior in a sloshing container.The...To analyze the bottom slope's effect on the sloshing liquid in floating liquefied natural gas(FLNG)membrane tanks,a simulation model is built and applied to describe the liquid behavior in a sloshing container.The free surface motion is simulated by the volume-of-fluid method and the standard k-εturbulence model.Experimental data and numerical results from references are used to validate the accuracy of the proposed simulation model.To study the influence of the sloped bottom on the liquid sloshing,different slope sizes and filling ratios are numerically simulated at the lowest natural frequency.The results reveal that the natural frequency can be determined by the average peak values of hydrodynamic parameters.The natural frequency and pressure loading on the tank walls decrease with the increase in the slope size.The peak pressure on the wall decreases by 5.45 kPa with the increase in the slope ratio from 5%to 20%.However,the relationship between the peak pressure and slope ratio is more significant with lower filling rates.Liquid behavior is more stable and independent with the change of the slope structure at a high filling rate(60%).The results of numerical simulation and modeling are expected to provide reference data for the design and operation of the FLNG system.展开更多
Objective To observe the effects of cupping on blood flow under different skins of back in healthy human. Methods With meridian-cupping dredging apparatus to set cupping pressure at -0.04 MPa, cupping was applied at D...Objective To observe the effects of cupping on blood flow under different skins of back in healthy human. Methods With meridian-cupping dredging apparatus to set cupping pressure at -0.04 MPa, cupping was applied at Dhzhui （大椎 GV 14） and bilateral Dazhu （大杼 BL 11） for 10 min in healthy subject. Blood flow monitoring video system of laser speckle was used to record blood flow of GV 14, Shenzhu （身柱 GV 12）, bilateral Feishu （肺俞 BL 13） and Xinshu （心俞 BL 15） before cupping therapy, immediate time of cupping removal and 5 min, 10 rain, 15 min, 20 min, 25 rain and 30 rain after cupping removal. Results Compared before cupping therapy, the blood flow of GV 14, GV 12 and bilateral BL 13 was obviously increased at immediate time of cupping removal （all P〈0.05）. Compared with immediate time of cupping removal, the blood flow of GV 14 at each time point after 20 rain of cupping removal, GV 12 at 10 min and 15 min after cupping removal, bilateral BL 13 at each time point after cupping removal was all obviously decreased （all P〈0.05）. The difference of blood flow of Shendao （神道 GV 11） and bilateral BL 15 before and after cupping therapy was not significantly different （all P〉0.05）. Conclusion The cupping therapy could adjust skin blood flow, which is more obvious near the cupping area.展开更多
A coal slurry mixing tank is a key piece of equipment in the preparation of coal slurry for direct coal liquefaction.It is a gas-liquid-solid three-phase mixing device.Based on the performance of the existing coal slu...A coal slurry mixing tank is a key piece of equipment in the preparation of coal slurry for direct coal liquefaction.It is a gas-liquid-solid three-phase mixing device.Based on the performance of the existing coal slurry mixing equipment,a type of test equipment for horizontal continuous coal slurry preparation was developed,but to this point has limited research results.The test equipment consists of a mixing cylinder,mixer,stirring impeller and other components.Slurry mixing experiments were undertaken using the prototype,testing the performance of the device.A mathematical model was proposed specifically for the operation of a coal slurry mixing tank that is horizontally operated with high slurry concentration and rotary flow.The flow field in the horizontal coal mixing tank was simulated with the computational fluid dynamic (CFD) method.The experimental results match well with the CFD simulation results.Results show that the test device of a coal slurry mixing tank can be used to model the mixing of pulverized coal and the solvent oil.A strong correlation was obtained.展开更多
基金Supported by the National Natural Science Foundation of China （20576009, 20821004） and the National Basic Research Program of China （2007CB714300）. ACKNOWLEDGEMENTS The authors sincerely acknowledge the helpful discussion with Prof John M. Smith [Fluids and Systems Research Centre, School of Engineering （J2）, University of Surrey, Guildford, GU2 7XH, UK].
文摘Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configuration （a hollow half elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT＋2WHu） recommended in previous work has been used in this work. The operating temperatures were 24℃ and 81℃, identified as cold and hot respectively. The effects of superficial gas velocity, agitator speed and the corresponding power input on the local void fraction in two-phase systems are .investigated and discussed. Results show thatth-e increasing of agitator speed or gas flow rate leads to an increase in local-void fraction at the majority of measurement points in both cold and hot systems. However, the unifo,rmity of gas dispersion does not always in crease as the raising of agitator speed and power input. In either cold or hot sparged conditions, the two- and three-phase systems.have similar vertical profiles for void fraction, with maxima in similar locations; however, the void fractions are significantly lower in hot sparging than with cold. In cold operation the presence of particles leads to a lower void fraction at most points, although the local void fractions increase a little with the addition of solid particles at high temperature, in good agreement with the global gas holdup results, and the possible reasons are discussed in this paper. This work can give a better understanding of the differences between cold-gassed and hot-sparged three phase＇stirred tanks.
基金Supported by the National Natural Science Foundation of China（20776121） the Scientific Fund of Hunan Provincial Education Department（07C765 07C744）
文摘Based on trajectory equations of gas bubble,an eddy-bubble interaction(EBI)model was developed. This model considered the effect of non-drag forces and took the eddy-bubble interaction time as the refreshing time scale of turbulent fluctuations.The relationship between the crossing-eddy time and the eddy lifetime was discussed,and the predicted distributions of radial,axial velocities of bubbles and gas holdup were also given. Compared with eddy lifetime(EL)model,the EBI model gives somewhat smaller axial velocity in the upper circulation region and larger velocity in the lower circulation region,causing that fewer bubbles reach the lower circulation region and gas holdup becomes higher in the upper circulation region.The predicted gas holdup by the EBI model approaches closer to the experimental data in the discharge stream region.
基金The National Natural Science Foundation of China(No.51905093)the Natural Science Foundation of Jiangsu Province for Young Scholars(No.BK20180392)。
文摘To analyze the bottom slope's effect on the sloshing liquid in floating liquefied natural gas(FLNG)membrane tanks,a simulation model is built and applied to describe the liquid behavior in a sloshing container.The free surface motion is simulated by the volume-of-fluid method and the standard k-εturbulence model.Experimental data and numerical results from references are used to validate the accuracy of the proposed simulation model.To study the influence of the sloped bottom on the liquid sloshing,different slope sizes and filling ratios are numerically simulated at the lowest natural frequency.The results reveal that the natural frequency can be determined by the average peak values of hydrodynamic parameters.The natural frequency and pressure loading on the tank walls decrease with the increase in the slope size.The peak pressure on the wall decreases by 5.45 kPa with the increase in the slope ratio from 5%to 20%.However,the relationship between the peak pressure and slope ratio is more significant with lower filling rates.Liquid behavior is more stable and independent with the change of the slope structure at a high filling rate(60%).The results of numerical simulation and modeling are expected to provide reference data for the design and operation of the FLNG system.
基金Supported by Natural Science Foundaion of China in 2012(No.81273673)
文摘Objective To observe the effects of cupping on blood flow under different skins of back in healthy human. Methods With meridian-cupping dredging apparatus to set cupping pressure at -0.04 MPa, cupping was applied at Dhzhui （大椎 GV 14） and bilateral Dazhu （大杼 BL 11） for 10 min in healthy subject. Blood flow monitoring video system of laser speckle was used to record blood flow of GV 14, Shenzhu （身柱 GV 12）, bilateral Feishu （肺俞 BL 13） and Xinshu （心俞 BL 15） before cupping therapy, immediate time of cupping removal and 5 min, 10 rain, 15 min, 20 min, 25 rain and 30 rain after cupping removal. Results Compared before cupping therapy, the blood flow of GV 14, GV 12 and bilateral BL 13 was obviously increased at immediate time of cupping removal （all P〈0.05）. Compared with immediate time of cupping removal, the blood flow of GV 14 at each time point after 20 rain of cupping removal, GV 12 at 10 min and 15 min after cupping removal, bilateral BL 13 at each time point after cupping removal was all obviously decreased （all P〈0.05）. The difference of blood flow of Shendao （神道 GV 11） and bilateral BL 15 before and after cupping therapy was not significantly different （all P〉0.05）. Conclusion The cupping therapy could adjust skin blood flow, which is more obvious near the cupping area.
基金Project (No. 2008C21021) supported by the Science and Technology Research Program of Zhejiang Province, China
文摘A coal slurry mixing tank is a key piece of equipment in the preparation of coal slurry for direct coal liquefaction.It is a gas-liquid-solid three-phase mixing device.Based on the performance of the existing coal slurry mixing equipment,a type of test equipment for horizontal continuous coal slurry preparation was developed,but to this point has limited research results.The test equipment consists of a mixing cylinder,mixer,stirring impeller and other components.Slurry mixing experiments were undertaken using the prototype,testing the performance of the device.A mathematical model was proposed specifically for the operation of a coal slurry mixing tank that is horizontally operated with high slurry concentration and rotary flow.The flow field in the horizontal coal mixing tank was simulated with the computational fluid dynamic (CFD) method.The experimental results match well with the CFD simulation results.Results show that the test device of a coal slurry mixing tank can be used to model the mixing of pulverized coal and the solvent oil.A strong correlation was obtained.
