It has long been recognized that the flow pattern,especially the velocity distribution of the fluid,is of great importance in determining the performance of the equipment using structured packing as its internals.By u...It has long been recognized that the flow pattern,especially the velocity distribution of the fluid,is of great importance in determining the performance of the equipment using structured packing as its internals.By using three-dimensional laser Doppler velocimetry(LDV),the liquid velocity distribution of the glycerol aqueous solution was measured in a typical unit of structured packing(Mellapak 350Y).Time averaged three-dimensional velocity distributions of the unit were measured at different flow rates.The experimental data showed that the liquid velocity profile of the single phase flow was complex because of the special geometry of the unit of structured packing.In the central region of the unit,the liquid was mixed strongly and re-distributed.It was the main cause generating the vortexes and secondary flow.展开更多
To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali...To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.展开更多
We investigate the characteristics of intensity tuning in a single mode microchip Nd：YAG laser with an external cavity. The undulation of laser intensity in a period of A/2 change of the internal cavity length is obs...We investigate the characteristics of intensity tuning in a single mode microchip Nd：YAG laser with an external cavity. The undulation of laser intensity in a period of A/2 change of the internal cavity length is observed. Two different optical feedback cases are performed. One is an external cavity reflector perfectly aligned and the other is an external cavity reflector tilted. However, the fluctuation frequency of laser intensity in a period of A/2 change of the internal cavity length in these two cases is found to be determined by the ratio of external cavity length to internal cavity length. Meanwhile, for the tilted external cavity, the fluctuation frequency is also related to multiple feedbacks in the tilted external cavity.展开更多
文摘It has long been recognized that the flow pattern,especially the velocity distribution of the fluid,is of great importance in determining the performance of the equipment using structured packing as its internals.By using three-dimensional laser Doppler velocimetry(LDV),the liquid velocity distribution of the glycerol aqueous solution was measured in a typical unit of structured packing(Mellapak 350Y).Time averaged three-dimensional velocity distributions of the unit were measured at different flow rates.The experimental data showed that the liquid velocity profile of the single phase flow was complex because of the special geometry of the unit of structured packing.In the central region of the unit,the liquid was mixed strongly and re-distributed.It was the main cause generating the vortexes and secondary flow.
基金Supported by the National Natural Science Foundation of China （No.20476072）.
文摘To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.
基金Supported by the National Natural Science Foundation of China under Grant No 60438010.
文摘We investigate the characteristics of intensity tuning in a single mode microchip Nd：YAG laser with an external cavity. The undulation of laser intensity in a period of A/2 change of the internal cavity length is observed. Two different optical feedback cases are performed. One is an external cavity reflector perfectly aligned and the other is an external cavity reflector tilted. However, the fluctuation frequency of laser intensity in a period of A/2 change of the internal cavity length in these two cases is found to be determined by the ratio of external cavity length to internal cavity length. Meanwhile, for the tilted external cavity, the fluctuation frequency is also related to multiple feedbacks in the tilted external cavity.
