Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing...Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing arrangement of phase change material(PCM)capsules,inducing radial porosity oscillation.In this study,an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation.Its fluid flow and heat transfer were analyzed.With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed,the corresponding relationships between the arrangement of capsules and porosity oscillation were identified.The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid(HTF)velocity.As a result,radial temperature distributions and liquid fraction distributions of PCMs were further affected.The effects of different dimensionless parameters(e.g.,tube-to-capsule diameter ratio,Reynolds number,and Stefan number)on the radial characteristics of HTF and PCMs were discussed.The results showed that different diameter ratios correspond to different radial porosity distributions.Further,with an increase in diameter ratio,HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease.The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF-while higher Reynolds numbers can lead to a proportional improvement of velocity,an increase in Stefan number can promote heat storage of the packed bed LHS system.展开更多
An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m I...An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m ID and 1.0m in length. The range of the inclination angle is 45°-9° from the horizontal. The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing xlD at various inclination angles. At the same x/D, the mean liquid slug length and Taylor bubble length increase first, and then decrease with decreasing inclination angles, with the maximum at 60°. In the vertical tube, standard deviation of the nitrogen Taylor bubble iength increase with the increasing xlD. For the inclined tube, standard deviation of the nitrogen Taylor bubble length increases first, and then decreases with the increasing x/D. Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.展开更多
An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.01...An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.018 m and 0.014 m in inner diameter and 1.0 m in length.The range of the inclination angles is 0-45° from the vertical.The statistical method is employed to analyze the experimental data.The experiment was focused on the effect of the inclination angle on the initial position distribution of Taylor bubbles.The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles.The experimental results show that the initial position of Taylor bubble increased first,and then decreased with the increasing inclination angle,with the maximum at 30°.The standard deviation of the initial position of Taylor bubble in tubes was different with different inner diameters.The lognormal shape was fitted to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.展开更多
The segregated flow pattern, which occurs in a 26.1 mm diameter, horizontal, stainless steel test section, is investigated. Pressure gradient and in situ phase distribution data were obtained for different combination...The segregated flow pattern, which occurs in a 26.1 mm diameter, horizontal, stainless steel test section, is investigated. Pressure gradient and in situ phase distribution data were obtained for different combinations of phase superficial velocities ranging from 0.05 m.s^-1 to 0,96 m.s^-1. For the current small Eoetvoes number liquid-liquid system （EOD=4.77）, the dominant effect of interfacial tension and wall-wetting properties of the liquids over the gravity is considered. The approach introduces the closure relationship for the case of turbulent flow m a rough pipe, and attempts to modify the two-fluid model to account for the curved interface. In present flow rates range, wave amplitudes were found small, while interfacial mixing was observed. An adjustable definition for hydraulic diame- ters of two fluids and interfacial friction factor is adopted. The predicted pressure gradient and in situ phase distribution data have been compared with present experimental data and those reported in the literature.展开更多
The present work explores how much IGCC can benefit from warm gas clean-up（WGCU）in comparison with conventional cold gas clean-up（CGCU） and what are the respective contributions of dry particulates removal and war...The present work explores how much IGCC can benefit from warm gas clean-up（WGCU）in comparison with conventional cold gas clean-up（CGCU） and what are the respective contributions of dry particulates removal and warm gas desulfurization （WGD） in a plant-wide point of view. Influences of key parameters of WGD on ther- modynamic performance of IGCC plant including desulfurization temperature, oxygen concentration in the re- generation stream, and H2S removal efficiency are discussed. It is obtained that the net efficiency of IGCC with full WGCU experiences an improvement of 1.77 percentage points compared with IGCC with full CGCU. Of which, dry particulates removal without water scrubber contributes about 1 percentage point. The influence of desulfurization temperature on thermodynamic performance of IGCC with WGD is weak especially when it is higher than about 350~C, which indicates that more focus should be put on investment cost, technical feasibility and sorbent stability for the selection of optimal operation temperature. Generally, 2%-3% of oxygen concentra- tion in the regeneration stream might be reasonable in a thermodynamic performance point of view. In addition, the improvement of 0.31 percentage points can be obtained by removal of H2S in the syngas from 27 ppm to 3 ppm.展开更多
基金This work is supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(51521004)the National Natural Science Foundation of China(51906150).
文摘Owing to its high heat storage capacity and fast heat transfer rate,packed bed latent heat storage(LHS)is considered as a promising method to store thermal energy.In a packed bed,the wall effect can impact the packing arrangement of phase change material(PCM)capsules,inducing radial porosity oscillation.In this study,an actual-arrangement-based three-dimensional packed bed LHS model was built to consider the radial porosity oscillation.Its fluid flow and heat transfer were analyzed.With different cylindrical sub-surfaces intercepted along the radial direction in the packed bed,the corresponding relationships between the arrangement of capsules and porosity oscillation were identified.The oscillating distribution of radial porosity led to a non-uniform distribution of heat transfer fluid(HTF)velocity.As a result,radial temperature distributions and liquid fraction distributions of PCMs were further affected.The effects of different dimensionless parameters(e.g.,tube-to-capsule diameter ratio,Reynolds number,and Stefan number)on the radial characteristics of HTF and PCMs were discussed.The results showed that different diameter ratios correspond to different radial porosity distributions.Further,with an increase in diameter ratio,HTF velocity varies significantly in the near wall region while the non-uniformity of HTF velocity in the center region will decrease.The Reynolds and Stefan numbers slightly impact the relative velocity distribution of the HTF-while higher Reynolds numbers can lead to a proportional improvement of velocity,an increase in Stefan number can promote heat storage of the packed bed LHS system.
基金Supported by the National Natural Science Foundation of China （50476015） and National High Technology Research and Development Program of China （2006AA09Z333）.
文摘An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer. The experimental tube is 0.018 m ID and 1.0m in length. The range of the inclination angle is 45°-9° from the horizontal. The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing xlD at various inclination angles. At the same x/D, the mean liquid slug length and Taylor bubble length increase first, and then decrease with decreasing inclination angles, with the maximum at 60°. In the vertical tube, standard deviation of the nitrogen Taylor bubble iength increase with the increasing xlD. For the inclined tube, standard deviation of the nitrogen Taylor bubble length increases first, and then decreases with the increasing x/D. Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.
基金Supported by the National Natural Science Foundation of China （50476015） and National High-Yech Research and Develop ment Program of China （2006AA09Z333）.
文摘An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera.The tubes in the experiment are 0.018 m and 0.014 m in inner diameter and 1.0 m in length.The range of the inclination angles is 0-45° from the vertical.The statistical method is employed to analyze the experimental data.The experiment was focused on the effect of the inclination angle on the initial position distribution of Taylor bubbles.The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles.The experimental results show that the initial position of Taylor bubble increased first,and then decreased with the increasing inclination angle,with the maximum at 30°.The standard deviation of the initial position of Taylor bubble in tubes was different with different inner diameters.The lognormal shape was fitted to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.
基金the National High Technology Research and Development Program of China (2006AA09Z333)
文摘The segregated flow pattern, which occurs in a 26.1 mm diameter, horizontal, stainless steel test section, is investigated. Pressure gradient and in situ phase distribution data were obtained for different combinations of phase superficial velocities ranging from 0.05 m.s^-1 to 0,96 m.s^-1. For the current small Eoetvoes number liquid-liquid system （EOD=4.77）, the dominant effect of interfacial tension and wall-wetting properties of the liquids over the gravity is considered. The approach introduces the closure relationship for the case of turbulent flow m a rough pipe, and attempts to modify the two-fluid model to account for the curved interface. In present flow rates range, wave amplitudes were found small, while interfacial mixing was observed. An adjustable definition for hydraulic diame- ters of two fluids and interfacial friction factor is adopted. The predicted pressure gradient and in situ phase distribution data have been compared with present experimental data and those reported in the literature.
基金support for this work by the International Science & Technology Cooperation Program of China (2010DFB70560) and(2010GH0902)
文摘The present work explores how much IGCC can benefit from warm gas clean-up（WGCU）in comparison with conventional cold gas clean-up（CGCU） and what are the respective contributions of dry particulates removal and warm gas desulfurization （WGD） in a plant-wide point of view. Influences of key parameters of WGD on ther- modynamic performance of IGCC plant including desulfurization temperature, oxygen concentration in the re- generation stream, and H2S removal efficiency are discussed. It is obtained that the net efficiency of IGCC with full WGCU experiences an improvement of 1.77 percentage points compared with IGCC with full CGCU. Of which, dry particulates removal without water scrubber contributes about 1 percentage point. The influence of desulfurization temperature on thermodynamic performance of IGCC with WGD is weak especially when it is higher than about 350~C, which indicates that more focus should be put on investment cost, technical feasibility and sorbent stability for the selection of optimal operation temperature. Generally, 2%-3% of oxygen concentra- tion in the regeneration stream might be reasonable in a thermodynamic performance point of view. In addition, the improvement of 0.31 percentage points can be obtained by removal of H2S in the syngas from 27 ppm to 3 ppm.
