The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image *** this paper,the moving single-frame and lo...
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The spatiotemporal evolution of hairpin vortex structures in a fully developed turbulent boundary layer is investigated qualitatively and quantitatively by using two image *** this paper,the moving single-frame and long-exposure(MSFLE)image method is used to intuitively track the evolution process of a hairpin vortex,while the moving particle image velocimetry(moving-PIV)method is applied for obtaining a moving velocity field for quantitative *** to the structural characteristics of the hairpin vortex,an inclined light sheet with an appropriate inclination of 53°is arranged to capture the complete hairpin vortex structure at Re_(θ)=97–*** addition,the core size and the rotational strength of a hairpin vortex are further defined and quantified by the Liutex vector *** evolution process of a complete hairpin vortex structure observed by MSFLE shows that the shear along the normal direction leads to an increasing strength of the hairpin vortex,accompanied by a lifting vortex head and a distance decrease between two vortex legs during the dissipation *** combining moving-PIV with the Liutex identification,the spatiotemporal evolution of four typical regions of a hairpin vortex projecting into a 53°cross-section is *** results show that the process from the generation to the dissipation of a single hairpin vortex can be well characterized and recorded by the Liutex based on the core size and rotational intensity,and the evolution process is consistent with the MSFLE *** to the statistics of vortex core size and rotation intensity along time,the evolution of the hairpin vortex necks and legs can be described as a process of enhancement followed by *** the vortex head,its evolution maintains longer attributed to its far-from-wall position,which consists of an absolute enhancement process(stage 1)with an increasing rotation strength and a constant core size,and an absolute dissipation(stage 2)with a dec
The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed...
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The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.
The photochemical system,which utilizes only solar energy and H_(2)O/CO_(2) to produce hydrogen/carbon-based fuels,is considered a promising approach to reduce CO_(2) emissions and achieve the goal of carbon *** date,...
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The photochemical system,which utilizes only solar energy and H_(2)O/CO_(2) to produce hydrogen/carbon-based fuels,is considered a promising approach to reduce CO_(2) emissions and achieve the goal of carbon *** date,numerous photochemical systems have been developed to obtain a viable solar-to-fuel production system with sufficient energy ***,more effort is still needed to meet the requirements of industrial *** this review,we systematically discuss a typical photochemical system for solar-to-fuel production,from classical theories and fundamental mechanisms to raw material selection,reaction condition optimization,and unit device/system advancement,from the viewpoint of ordered energy ***-of-the-art photochemical systems,including photocatalytic,photovoltaic-electrochemical,photoelectrochemical,solar thermochemical,and other emerging systems,are *** highlight the existing bottlenecks and discuss the developing trend of this ***,optimization strategies and new opportunities are proposed to enhance photochemical systems with higher energy efficiency.
This paper discusses thermo-conductive plastic finned tube radiators used in water saving type powerstations. First, the development of thermo-conductive plastics is introduced. Second, in order todetermine the ration...
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This paper discusses thermo-conductive plastic finned tube radiators used in water saving type powerstations. First, the development of thermo-conductive plastics is introduced. Second, in order todetermine the rational geometric dimensions of thermo-conductive plastic finned tubes, an objectivefunction which takes the minimum volume of the consumed material for making finned tubes as an ob-ject is introduced. On the basis of the function, the economy comparison between thermaxonductiveplastic finned tubes and metal finned tubes is conducted.
In this study, chlorine anchored pyrrole-based conjugated porous polymers (CPPs) with distinct pore properties were synthesized using the Knoevenagel reaction and the double chain condensation method. The partially cr...
In this study, chlorine anchored pyrrole-based conjugated porous polymers (CPPs) with distinct pore properties were synthesized using the Knoevenagel reaction and the double chain condensation method. The partially crosslinked and partially oxidized structures of the materials exhibit a unique microstructure integrating interconnected nets and molecular hooks. This architecture utilizes pore channels for physical interception of Hg(II), while synergistic chemical immobilization at N, O, and Cl active sites enables multifunctional enhancement of Hg(II) capture efficiency. Among these materials, the maximum adsorption capacity reached 1183 mg·g −1 , demonstrating ultrahigh selectivity. Moreover, the adsorbents maintained > 90 % removal efficiency over 10 adsorption–desorption cycles, confirming excellent reusability. Mechanistic studies revealed that Hg(II) adsorption primarily whin material pores through hydrogen bonding and coordination interactions, and their synergistic interactions. This work highlights the efficiency of the double chain condensation design strategy in advancing conjugated porous polymers for the removal of heavy metals, particularly Hg(II), from wastewater.
Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to *** ...
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Direct Numerical Simulations have been carried out to study the forced convection heat transfer of flow through fixed prolate particles for a variety of aspect ratios ar={5/4,5/3,5/1}with Reynolds number(Re)up to *** variations of the solid volume fraction c={0.1,0.2,0.3}with four Hermans orientation factors S={−0.5,0,0.5,1}are *** has been found that changes in S cause prominent variations in the Nusselt *** general,Nusselt number increases with the decrease of *** all three aspect ratios,the Nusselt number remains a linear function of S at different c and ***,it is concluded that,for heat transfer from prolate muti-particle system,the effects of orientations cannot be ignored.A new correlation for Nusselt number has been developed for arrays of prolate particles using the simulation data as a function of Re,c,S and ar.
China is the largest producer and consumer of calcium carbide in the *** calcium carbide industry is an indispensable industry to support the basic life of *** huge production capacity of calcium carbide is accompanie...
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China is the largest producer and consumer of calcium carbide in the *** calcium carbide industry is an indispensable industry to support the basic life of *** huge production capacity of calcium carbide is accompanied by a large number of solid waste carbide *** to the immature treatment technology of carbide slag,a large number of carbide slag are stacked on-site,resulting in land occupation,air-drying,easy take-off ash,and pollution of the environment and water *** China,calcium carbide is mainly used to produce acetylene and further utilized,80%of which is used to produce polyvinyl chloride(PVC).A large amount of carbide slag is not used,while only a small part is used in the traditional building materials industry,flue gas desulfurization,sewage treatment,etc.,however,the economic benefits are ***,converting the solid waste carbide slag produced by the calcium carbide industry into high value-added CaCO3,CaCl2,CaSO4 whiskers,*** become a potential way to expand the development field of the calcium carbide industry and is environmentally *** paper focuses on summarizing the traditional and emerging high value-added utiliza-tion technologies of carbide slag,and then introduces the application research of carbide slag in carbon emission ***,the defects of these technologies are summarized and further research directions are *** study provides basic guidance for the diversified development of efficient resource utilization of carbide *** abstract Diversified development of calcium carbide industry,resource utilization of solid waste carbide slag and its application of carbon emission reduction have been fully reviewed.
Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or *** optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important **...
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Supercritical water fluidized bed(SCWFB)is a promising reactor to gasify biomass or *** optimization design is closely related to wall-to-bed heat transfer,where particle convective heat transfer plays an important *** paper evaluates the particle convective heat transfer coefficient(h_(pc))at the wall in SCWFB using the single particle *** critical parameters in the single particle model which is difficult to get experimentally are obtained by the computational fluid dynamics-discrete element method(CFD-DEM).The contact statistics related to particle-to-wall heat transfer,such as contact number and contact distance,are also *** results show that particle residence time(τ),as the key parameter to evaluate h_(pc),is found to decrease with rising velocity,while increase with larger thermal boundary layer thickness.τfollows a gamma function initially adopted in the gas-solid fluidized bed,making it possible to evaluate h_(pc) in SCWFB by a simplified single particle *** theoretical predicted h_(pc) tends to increase with rising thermal gradient thickness at a lower velocity(1.5 U_(mf)),while first decreases and then increases at higher velocity(1.75 and 2 U_(mf)).h_(pc) occupies 30%-57%of the overall wall-to-bed heat transfer coefficient for a particle diameter of 0.25 *** results are helpful to predict the overall wall-to-bed heat transfer coefficient in SCWFB combined with a reasonable fluid convective heat transfer model from a theoretical perspective.
The Reynolds stress transport equation model (DSM) is used to predict the strongly swirling turbulent flows in a liquid-liquid hydrocyclone, and the predictions are compared with LDV measurements . Predictions properl...
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The Reynolds stress transport equation model (DSM) is used to predict the strongly swirling turbulent flows in a liquid-liquid hydrocyclone, and the predictions are compared with LDV measurements . Predictions properly give the flow behavior observed in experiments, such as the Rankine-vortex structure and double peaks near the inlet region in tangential velocity profile, the downward flow near the wall and upward flow near the core in axial velocity profiles. In the inlet or upstream region of the hydrocyclone, the reverse flow near the axis is well predicted, but in the region with smaller cone angle and cylindrical section, there are some discrepancies between the model predictions and the LDV measurements. Predictions show that the pressure is small in the near-axis region and increases to the maximum near the wall. Both predictions and measurements indicate that the turbulence in hydrocy-clones is inhomogeneous and anisotropic.
Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, takin...
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Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, taking the issue of optical distortion into account, an analytical model was proposed to estimate and correct the liquid holdup in gas-liquid annular flow through a circular pipe using high-speed camera method. The error in the liquid holdup measurement generated from different refractive indices among transparent circular pipe, liquid film and air core was firstly theoretically analyzed based on the geometric optics. Experimental tests were then carried out to identify the difference as well as to validate the proposed model. Results indicated that the prediction of the liquid holdup has a good performance with the experimental data(i.e., mean relative error is 4.1%) and the measured liquid holdup is larger than the real one. It was found that the measured liquid holdup is larger than the real one. Generally, when the real liquid holdup gets smaller, the discrepancy between the measured liquid holdup by image and the real liquid holdup becomes more significant. Thus, after measuring the liquid holdup from the images, the value of the measured liquid holdup must be corrected by the present model in order to obtain the real liquid holdup.
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