Micro-fluidized bed reactor is a new research method for the reduction of iron ore fines. The reactor is op- erated as a differential reactor to ensure a constant gas concentration and temperature within the reactor v...Micro-fluidized bed reactor is a new research method for the reduction of iron ore fines. The reactor is op- erated as a differential reactor to ensure a constant gas concentration and temperature within the reactor volume. In order to understand the dynamic process of the reduction reaction in micro-fluidized bed, a series of kinetic experi- ments were designed. In the micro fluidized bed, the use of shrinking core model describes the dynamic behavior of reduction of iron ore. And the apparent activation energy is calculated in the range of 700--850 ~C while the initial atmosphere is 100% content of CO.展开更多
A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successf...A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.展开更多
The characteristics such as signal noise ratio（SNR） and sensitivity of the fluorescence detection system for micro-fluidic chip influence the performance of the whole system extremely. The confocal laser induced flu...The characteristics such as signal noise ratio（SNR） and sensitivity of the fluorescence detection system for micro-fluidic chip influence the performance of the whole system extremely. The confocal laser induced fluorescence detection system is presented. Based on the debugging of optical and circuit modules, the results of detecting the samples are given and analyzed theoretically, and the improved project is put forward.展开更多
The inclined micro-fluidized bed(MFB)can enhance heat and mass transfer rates compared to the vertically aligned counterparts,but the increased significance of surface forces and wall effects may cause poor fluidizati...The inclined micro-fluidized bed(MFB)can enhance heat and mass transfer rates compared to the vertically aligned counterparts,but the increased significance of surface forces and wall effects may cause poor fluidization performance.In this paper,the effects of column inclination and different particle-to-bed ratios(d_(P)/d_(B))on the solid hydrodynamics are investigated in an inclined micro-fluidized bed.The results validated the suitability of using the Ergun equation to predict minimum fluidization velocities due to small deviations between 1.01 and 1.81 times the theoretical values,for a particle-to-bed ratio ranging from 0.025 to 0.165 at inclinations between 0°and 10°.Investigation into the effects on bed expansion behavior showed that the bed contracted with an increase in bed inclination.An unexpected observation during the bed expansion was the appearance of a secondary high voidage region and the appearance of strong circulation patterns with an increase in bed inclination.A detailed analysis of this phenomenon suggested the presence of a critical angle at 6°and 10°for the 85μm particles,4×4 mm bed cross-section and 165μm particles,1×1 mm bed cross-section,respectively.However,the liquid-solid back-mixing was observed due to the modified particle trajectories resulted in the disappearance of the high voidage region.This paper gives new insights into the micro-fluidization behavior in inclined beds thus contributing to the development of micro-fluidized beds and their future applications.展开更多
Thermal fluctuations have been found to significantly influence the dissipation range of turbulence,an effect beyond the scope of the classical Navier-Stokes equations.In this study,we investigate their impact on turb...Thermal fluctuations have been found to significantly influence the dissipation range of turbulence,an effect beyond the scope of the classical Navier-Stokes equations.In this study,we investigate their impact on turbulent channel flow by numerically solving the fluctuating hydrodynamic equations.Simulation results confirm theoretical predictions that the energy spectrum,dominated by thermal fluctuations,follows a k2 power law.When thermal fluctuations reach sufficient intensity,they disrupt the dominant turbulent structures responsible for most of the kinetic energy,leading to a reduction in large-scale spectral energy.Additionally,thermal fluctuations increase wall skin friction by modifying mean velocity profiles.The injected energy amplifies Reynolds normal stresses while maintaining the magnitude of Reynolds shear stress.Furthermore,thermal fluctuations enhance the symmetry and homogeneity of velocity fluctuations while reducing their intermittency.Despite these effects,the balance between kinetic energy production and dissipation,including both turbulent and thermal contributions,remains preserved.展开更多
The fiuidization behavior of Geldart A particles in a gas-solid micro-fluidized bed was investigated by Eulerian-Eulerian numerical simulation. The commonly used Gidaspow drag model was tested first. The simulation sh...The fiuidization behavior of Geldart A particles in a gas-solid micro-fluidized bed was investigated by Eulerian-Eulerian numerical simulation. The commonly used Gidaspow drag model was tested first. The simulation showed that the predicted minimum bubbling velocities were significantly lower than the experimental data even when an extremely fine grid size （of approximately one particle diameter） was used. The modified Gibilaro drag model was therefore tested next. The predicted minimum bubbling velocity and bed voidage were in reasonable agreement with the experimental data available in literature. The experimentally observed regime transition phenomena from bubbling to slugging were also reproduced successfully in the simulations. Parametric studies indicated that the solid-wall boundary conditions had a significant impact on the predicted gas and solid flow behavior.展开更多
The bed-expansion characteristics of liquid-solid micro-fluidized beds were experimentally studied. Bed columns with inner diameters of 0.8, 1.45, and 2.3 mm were fabricated based on capillaries. Five parti- cle sizes...The bed-expansion characteristics of liquid-solid micro-fluidized beds were experimentally studied. Bed columns with inner diameters of 0.8, 1.45, and 2.3 mm were fabricated based on capillaries. Five parti- cle sizes in a range of 22-58 t^m were investigated. Bed-expansion curves were plotted using visually recorded bed-expansion heights. The bed expansion and initial fluidization behavior were compared with predictions for conventional-scale beds, Evident differences are reflected in lower expansion ratios and higher minimum fluidization velocities for micro-fluidized beds. These were attributed to the increase in the internal surface area of the particle beds and specific surface area of wall contact. The wall effect for micro-fluidized beds at higher particle/bed diameter ratios caused higher local voidage and an increase in expansion ratio. Correlations for the exponent and proportional coefficient in the Richardson-Zaki equation for micro-fluidized beds were proposed. The minimum fluidization velocities were correlated using a modification of the Ergun equation.展开更多
In the research of bio-molecular chips and sensors, extra electric biases are most often employed to control and manipulate the DNA and protein molecules moving through micro/nano-fluidic channels. In order to accurat...In the research of bio-molecular chips and sensors, extra electric biases are most often employed to control and manipulate the DNA and protein molecules moving through micro/nano-fluidic channels. In order to accurately and flexibly control the bio-molecules as they move within the channels, a clear understanding of how the current changes within the buffer solution caused by an applied bias is fundamental. In this report, the current changed value of different buffer solutions, e.g., KC1, TE, and TBE was systematically studied with real-time monitoring and quantitative analysis in the situation of the buffers moving through a fluidic channel with a 5 μm inner diameter, driven by biases of 50 or 100 mV. The results revealed that the relation- ship between the current changed value and the pause interval of the applied electric field is highly consistent with the Hill Equation, which is helpful for accurately detecting and manipulating single biomolecules in microfluidic sensors and biochips.展开更多
基金Sponsored by National Natural Science Foundation of China (50834007)
文摘Micro-fluidized bed reactor is a new research method for the reduction of iron ore fines. The reactor is op- erated as a differential reactor to ensure a constant gas concentration and temperature within the reactor volume. In order to understand the dynamic process of the reduction reaction in micro-fluidized bed, a series of kinetic experi- ments were designed. In the micro fluidized bed, the use of shrinking core model describes the dynamic behavior of reduction of iron ore. And the apparent activation energy is calculated in the range of 700--850 ~C while the initial atmosphere is 100% content of CO.
基金This work was financially supported by the National Natural Science Foundation of China. （No.20271033, 20335020, 90408014）.
文摘A single molecule detection technique was developed by the combination of a single channel poly （dimethylsiloxane）/glass micro-fluidic chip and fluorescence correlation spectroscopy （FCS）. This method was successfully used to determine the proportion of two model components in the mixture containing fluorescein and the rhodamine-green succinimidyl ester.
基金Key Science and Technology Project Tackled of Guangdong Province(B2050070)
文摘The characteristics such as signal noise ratio（SNR） and sensitivity of the fluorescence detection system for micro-fluidic chip influence the performance of the whole system extremely. The confocal laser induced fluorescence detection system is presented. Based on the debugging of optical and circuit modules, the results of detecting the samples are given and analyzed theoretically, and the improved project is put forward.
基金supported by Newcastle University(Gant No.LOC/150025720/400382711).
文摘The inclined micro-fluidized bed(MFB)can enhance heat and mass transfer rates compared to the vertically aligned counterparts,but the increased significance of surface forces and wall effects may cause poor fluidization performance.In this paper,the effects of column inclination and different particle-to-bed ratios(d_(P)/d_(B))on the solid hydrodynamics are investigated in an inclined micro-fluidized bed.The results validated the suitability of using the Ergun equation to predict minimum fluidization velocities due to small deviations between 1.01 and 1.81 times the theoretical values,for a particle-to-bed ratio ranging from 0.025 to 0.165 at inclinations between 0°and 10°.Investigation into the effects on bed expansion behavior showed that the bed contracted with an increase in bed inclination.An unexpected observation during the bed expansion was the appearance of a secondary high voidage region and the appearance of strong circulation patterns with an increase in bed inclination.A detailed analysis of this phenomenon suggested the presence of a critical angle at 6°and 10°for the 85μm particles,4×4 mm bed cross-section and 165μm particles,1×1 mm bed cross-section,respectively.However,the liquid-solid back-mixing was observed due to the modified particle trajectories resulted in the disappearance of the high voidage region.This paper gives new insights into the micro-fluidization behavior in inclined beds thus contributing to the development of micro-fluidized beds and their future applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.12202437,12172352,and 12388101)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0500300)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.WK2090000086)the Key Laboratory of Cross Domain Flight Interdisciplinary technology(Grant No.2023ZY0101).
文摘Thermal fluctuations have been found to significantly influence the dissipation range of turbulence,an effect beyond the scope of the classical Navier-Stokes equations.In this study,we investigate their impact on turbulent channel flow by numerically solving the fluctuating hydrodynamic equations.Simulation results confirm theoretical predictions that the energy spectrum,dominated by thermal fluctuations,follows a k2 power law.When thermal fluctuations reach sufficient intensity,they disrupt the dominant turbulent structures responsible for most of the kinetic energy,leading to a reduction in large-scale spectral energy.Additionally,thermal fluctuations increase wall skin friction by modifying mean velocity profiles.The injected energy amplifies Reynolds normal stresses while maintaining the magnitude of Reynolds shear stress.Furthermore,thermal fluctuations enhance the symmetry and homogeneity of velocity fluctuations while reducing their intermittency.Despite these effects,the balance between kinetic energy production and dissipation,including both turbulent and thermal contributions,remains preserved.
基金financial support from the Ministry of Science and Technology of China with Grant No.2011YQ12003909the ongoing support through the startup fund awarded to Xiaoxing Liu from the "Hundred Talents Program" of the Institute of Process Engineering,Chinese Academy of Sciences
文摘The fiuidization behavior of Geldart A particles in a gas-solid micro-fluidized bed was investigated by Eulerian-Eulerian numerical simulation. The commonly used Gidaspow drag model was tested first. The simulation showed that the predicted minimum bubbling velocities were significantly lower than the experimental data even when an extremely fine grid size （of approximately one particle diameter） was used. The modified Gibilaro drag model was therefore tested next. The predicted minimum bubbling velocity and bed voidage were in reasonable agreement with the experimental data available in literature. The experimentally observed regime transition phenomena from bubbling to slugging were also reproduced successfully in the simulations. Parametric studies indicated that the solid-wall boundary conditions had a significant impact on the predicted gas and solid flow behavior.
基金The authors are grateful to the National Natural Science Foundation of China （Contract Nos. 21376168 and 91434204） for financial support.
文摘The bed-expansion characteristics of liquid-solid micro-fluidized beds were experimentally studied. Bed columns with inner diameters of 0.8, 1.45, and 2.3 mm were fabricated based on capillaries. Five parti- cle sizes in a range of 22-58 t^m were investigated. Bed-expansion curves were plotted using visually recorded bed-expansion heights. The bed expansion and initial fluidization behavior were compared with predictions for conventional-scale beds, Evident differences are reflected in lower expansion ratios and higher minimum fluidization velocities for micro-fluidized beds. These were attributed to the increase in the internal surface area of the particle beds and specific surface area of wall contact. The wall effect for micro-fluidized beds at higher particle/bed diameter ratios caused higher local voidage and an increase in expansion ratio. Correlations for the exponent and proportional coefficient in the Richardson-Zaki equation for micro-fluidized beds were proposed. The minimum fluidization velocities were correlated using a modification of the Ergun equation.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)the Interna-tional Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)the National Natural Science Foundation of China(Grant No.61378083)
文摘In the research of bio-molecular chips and sensors, extra electric biases are most often employed to control and manipulate the DNA and protein molecules moving through micro/nano-fluidic channels. In order to accurately and flexibly control the bio-molecules as they move within the channels, a clear understanding of how the current changes within the buffer solution caused by an applied bias is fundamental. In this report, the current changed value of different buffer solutions, e.g., KC1, TE, and TBE was systematically studied with real-time monitoring and quantitative analysis in the situation of the buffers moving through a fluidic channel with a 5 μm inner diameter, driven by biases of 50 or 100 mV. The results revealed that the relation- ship between the current changed value and the pause interval of the applied electric field is highly consistent with the Hill Equation, which is helpful for accurately detecting and manipulating single biomolecules in microfluidic sensors and biochips.
