The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the ...The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the microbubble generator directly influences flotation column performance by affecting bubble size and distribution as well as gas holdup in the column. However, the complicated flow inside the generator results in high R&D costs and difficulty in testing. Thus, the CFD software, FLUENT, was used to simulate the gas-liquid two-phase flow inside a self-absorbing microbubble generator. The effect of area ratio, a key structural parameter, was studied in detail. Critical flow-field parameters including velocity, turbulent kinetic energy, minimum static pressure and gas holdup were obtained. The simulation results demonstrate that the optimum area ratio is 3.展开更多
Understanding the near boundary acoustic oscillation of microbubbles is critical for the effective design of ultrasonic biomedical devices and surface cleaning technologies.Accordingly,this study investigates the thre...Understanding the near boundary acoustic oscillation of microbubbles is critical for the effective design of ultrasonic biomedical devices and surface cleaning technologies.Accordingly,this study investigates the three-dimensional microbubble oscillation between two curved rigid plates experiencing a planar acoustic field using boundary integral method(BIM).The numerical model is validated via comparison with the nonlinear oscillation of the bubble governed by the modified Rayleigh-Plesset equation and with the axisymmetric model for an acoustic microbubble in infinite fluid domain.Then,the influence of the wave direction and horizontal standoff distance(h)on the bubble dynamics(including jet velocity,jet direction,centroid movement,total energy,and Kelvin impulse)were evaluated.It was concluded that the jet velocity,the maximum radius and the total energy of the bubble are not significantly influenced by the wave direction,while the jet direction and the high-pressure region depend strongly on it.More importantly,it was found that the jet velocity and the high-pressure region around the jet in acoustic bubble are drastically larger than their counterparts in the gas bubble.展开更多
The microbubble behavior on platinum microheaters immersed in parallel microchannels during flow boiling was experimentally investigated,with the heater driven by pulse-heating.With increasing heat flux of rear face h...The microbubble behavior on platinum microheaters immersed in parallel microchannels during flow boiling was experimentally investigated,with the heater driven by pulse-heating.With increasing heat flux of rear face heater,three representative types of microbubbles,corresponding to three instable tendencies were identified.The relations between boiling instability and bubbles behavior were analyzed.The conclusions indicated that transitions among these bubbles and various departure modes strongly depended on the instability of flow boiling in microchannels.Meanwhile,heating power of the rear face heater was also one of the main factors that affected bubbles incipience and diameters.The results of present study can provide powerful basis for the future design of new micro-fluid functional devices.展开更多
基金Financial supports for this work provided by the National High Technology Research and Development Program of China (No.2008BAB31B02) is gratefully acknowledged
文摘The Cyclonic-Static Microbubble Flotation Column (FCSMC) is currently a widely used, novel type of flotation device. The self-absorbing microbubble generator is the core component of this device. The structure of the microbubble generator directly influences flotation column performance by affecting bubble size and distribution as well as gas holdup in the column. However, the complicated flow inside the generator results in high R&D costs and difficulty in testing. Thus, the CFD software, FLUENT, was used to simulate the gas-liquid two-phase flow inside a self-absorbing microbubble generator. The effect of area ratio, a key structural parameter, was studied in detail. Critical flow-field parameters including velocity, turbulent kinetic energy, minimum static pressure and gas holdup were obtained. The simulation results demonstrate that the optimum area ratio is 3.
文摘Understanding the near boundary acoustic oscillation of microbubbles is critical for the effective design of ultrasonic biomedical devices and surface cleaning technologies.Accordingly,this study investigates the three-dimensional microbubble oscillation between two curved rigid plates experiencing a planar acoustic field using boundary integral method(BIM).The numerical model is validated via comparison with the nonlinear oscillation of the bubble governed by the modified Rayleigh-Plesset equation and with the axisymmetric model for an acoustic microbubble in infinite fluid domain.Then,the influence of the wave direction and horizontal standoff distance(h)on the bubble dynamics(including jet velocity,jet direction,centroid movement,total energy,and Kelvin impulse)were evaluated.It was concluded that the jet velocity,the maximum radius and the total energy of the bubble are not significantly influenced by the wave direction,while the jet direction and the high-pressure region depend strongly on it.More importantly,it was found that the jet velocity and the high-pressure region around the jet in acoustic bubble are drastically larger than their counterparts in the gas bubble.
文摘The microbubble behavior on platinum microheaters immersed in parallel microchannels during flow boiling was experimentally investigated,with the heater driven by pulse-heating.With increasing heat flux of rear face heater,three representative types of microbubbles,corresponding to three instable tendencies were identified.The relations between boiling instability and bubbles behavior were analyzed.The conclusions indicated that transitions among these bubbles and various departure modes strongly depended on the instability of flow boiling in microchannels.Meanwhile,heating power of the rear face heater was also one of the main factors that affected bubbles incipience and diameters.The results of present study can provide powerful basis for the future design of new micro-fluid functional devices.
