Simple model for gas holdup and liquid velocity of annular photocatalytic external-loop airlift reactor under both bubble and developing slug flow

Based on the momentum conservation approach, a theoretical model was developed to predict the superficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular external- loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm²/s(2cs-SiO)and 5.0 mm²/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predictions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to predict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.     

Quasi 1D modeling of two-phase flow and deposit formation for urea-selective catalytic reduction systems

A quasi 1D model of two-phase flow for a urea-selective catalytic reduction (SCR) system is developed which can calculate not only the generation of reducing agent but also the formation of deposits in the exhaust pipe. The gas phase flow is solved through Euler method, variables are stored on staggered grids, and the semi-implicit method for pressure-linked equation (SIMPLE) algorithm is applied to decouple the pressure and velocity. The liquid phase is treated in a Lagrangian way, which solves the equations of droplet motion, evaporation, thermolysis, and spray wall interaction. A combination of a direct decomposition model and a kinetic model is implemented to describe the different decomposition behaviors of urea in the droplet phase and wall film, respectively. A new 1D wall film model is proposed, and the equations of wall film motion, evaporation, thermolysis, and species transport are solved. The position, weight, and components of deposits can be simulated following implementation of the semi-detailed kinetic model. The simulation results show that a decrease in the exhaust temperature will increase the wall film region and the weight of deposits. Deposit components are highly dependent on temperature. The urea-water-solution (UWS) injection rate can affect the total mass of wall film and expand the film region, but it has little influence on deposit components. An increase in exhaust mass flow can decrease the total weight of deposits on the pipe wall because of the promotion of the mass and heat transfer process both in the droplets and wall film.     

薄壁铸件反重力充填的守恒标量法研究

1　Introduction　SofarthemainalgorithmsadaptedtothenumericalsimulationformouldfillingareMAC ,SMAC[1] ,SOLA VOF[2 ] ,SIMPLEconservativescalarmethod[3] ,etc .Tosimulatemoldfilling ,MACandSMACmethodswilloccupylargequantityofcomputermemory ,andcostmuchcomputationtime .Atpresent ,thealgorithmsusedtosimulatemouldfillingofcastingsmainlyfocusonSOLA VOFandSIMPLEconservativescalar .Com paringwithSOLA VOF ,SIMPLEconservativescalaralgorithmismuchmoresuperior .Inaspectofmomen tumequat…     

Heat Transfer Method for Solid Flow Rate Measurement in Gas-Solid Two Phase Flow

ＨｅａｔＴｒａｎｓｆｅｒＭｅｔｈｏｄｆｏｒＳｏｌｉｄＦｌｏｗＲａｔｅＭｅａｓｕｒｅｍｅｎｔｉｎＧａｓＳｏｌｉｄＴｗｏＰｈａｓｅＦｌｏｗＹｕａｎＺｈｕｌｉｎ（袁竹林）ＬｕＺｕｏｊｉ（卢作基）（ＴｈｅｒｍｏｅｎｅｒｇｙＥｎｇｉｎｅｅｒｉｎｇＲｅｓｅａｒ...     

小型垂直轴风力机叶片气动特性模拟与分析

针对NACA4412翼型风力发电机扰流流动特点,建立了二维和三维不可压缩湍流模型,并对基于流体连续性方程和N-S方程及k-ε湍流模型的二维流场进行数值模拟计算。采用多参考系计算（MRF）模型,用FLUENT模拟了流场内翼型截面的受力情况和速度分布情况,得到了NACA4412翼型风机的气动特性。     

Visualization of structured packing with laser induced fluorescence technique: Two-dimensional measurement of liquid concentration distribution

A method of using laser induced fluorescence(LIF)technique was applied to two-dimensional measurement of the liquid concentration distribution in the 250Y structured packing sheet. The experimental structured packing sheet was made of perspex so that the laser could pass through it. The visualization of the distribution of the liquid concentration in the structured packing sheet was realized. The calibration of the thickness and liquid concentration was carried out firstly and the regression formula I=kcd was acquired, in which concentration c and the liquid film thickness d were both considered. Then the liquid feed of uniform tracer(rhodamine)concentration entered the perspex structured packing from the top under different spraying densities. The corresponding thickness of liquid film on the packing was calculated. Finally, tracer(rhodamine)with a high concentration was injected only at one fixed point of the structured packing under different spraying densities of the liquid. With the known liquid film thickness, the concentration distribution of the tracer can be calculated inside the structured packing sheet.     

Formation mechanism and size prediction of bubble in opposite-flowing T-shaped microchannel

Bubble formation in an opposite-flowing T-shaped microchannel with 40 μm in depth and 120 μm in width was real-time visualized and investigated experimentally by means of a high speed camera. N2 bubbles were generated in glycerol-water mixtures with different concentrations of surfactant sodium dodecyl sulfate (SDS). And the images were captured by the high speed camera linked to a computer. Results indicated that the bubble formation process can be distinguished into three consecutive stages, i.e., expansion, collapse and pinching off. The bubble size decreases with the increase of liquid flow rate and viscosity of liquid phase as well as the decrease of gas flow rate. The surface tension of the liquid phase has no measurable influence on the bubble size. Moreover, a new approach to predicting the size of bubbles formed in the T-shaped microchannel is proposed. And the predicted values agree well with the experimental data.     

气升式内环流反应器的液相流动混合模型

1Introduction Internalairliftloopreactor(AL)[1],originatedfrom bubblecolumn(BC)[2],isanefficientreactor.Itsspe cialsuperiorties,suchasthesimplicityofitsdesign andbettertransportrates,makeitveryattractivein fermentationengineering,wastewatertreatmentand cellsculture.Asisknown,themixinglevelofthe fluidisdirectlyaffectedbytheflowcharacteristicsof liquid.Thetwo phaseflowinreactorisverycomplex andincompletemixingbecauseofbackmixing,dead zone,bypassandtime lapse.Generally,theresearch isbasedontwoi…     

拟合曲线槽干气密封气膜刚度的计算及测试

推导了两光滑平板间干气密封微尺度流动场的非线性雷诺方程,应用PH线性化方法、迭代法对非线性雷诺方程近似求解,得到气膜压力的近似解析式;利用极坐标下的流线方程,通过Maple程序求解压力方程和流线方程得到流线,此流线就是符合条件的拟合曲线。对拟合曲线槽干气密封气膜刚度进行计算与测试,并与螺旋槽进行比较。研究结果表明：在相同工况下,拟合曲线槽干气密封气膜刚度比螺旋槽大,且气膜刚度比螺旋槽稳定,这在工程实践中具有重要意义和应用价值。     

循环流化床烟气脱硫实验研究(英文)

本文在一变速循环流化床反应器试验台上进行了烟气脱硫实验．当Ｃａ／Ｓ摩尔比为１．１,并用两相流喷嘴向反应器内喷入适量水时,脱硫效率可以达到８０％以上．     

Optimization study of a PEM fuel cell performance using 3D multi-phase computational fluid dynamics model

INTRODUCTION Water management is one of the critical opera-tion issues in proton exchange membrane (PEM) fuelcells. Spatially varying concentrations of water inboth vapour and liquid form are expected throughoutthe cell because of varying rates of production andtransport (Sui and Djilali, 2005). Devising betterwater management is therefore a key issue in PEMFCdesign, and this requires improved understanding ofthe parameters affecting water transport in the mem-brane. Proper thermal m…     

CFD Analysis of Gas Distributor in Packed Column--Prediction of Gas Flow and Effect of Tower Internals Geometry Structure

Computational fluid dynamics (CFD) simulations were carried out on the gas flow patterns of twin-tangential annular deflector gas distributor in the absence of liquid flow in a packed column (6.4 m in diameter), and the gas flow field in the column was presented close to reality on the whole. Furthermore, after ame-lioration of this gas distributor frame, turbulence energy and turbulence energy dissipation rate were both decreased greatly.Simulation results showed that the flow pattern and the distribution of gas flow were strongly affected by the column bottom frame; the proper column bottom frame could decrease the flow pressure drop greatly. Multifold factors, such as the column bottom geometry structure and distributor structure which affects the distribution capacity, must be considered.     

UASB厌氧反应器内流场数值模拟

UASB厌氧反应器的流场十分复杂.本文对UASB反应器内流场进行了数值模拟,模拟结果表明,液相在反应器内进行循环,气相直接逸出反应器.气体在反应器内分布不均匀,在空间上变化较大.     

填料塔技术的现状与发展趋势

填料塔是化工类企业中最常用的气、液传质设备之一 ,而塔填料、塔内件及工艺流程又是填料塔技术发展的关键。从塔填料、塔内件以及工艺流程 ,特别是塔填料三方面对填料塔技术的现状与发展趋势作了介绍 ,说明了塔填料及塔内件在填料塔技术中的重要性     

Theoretical analysis of effect of solid phase on cavitation performance of deep-sea mining pump

In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq. (19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.     

Flow Field of Circulating Fluidized Bed Reactor with Venturi Inlet Configuration

Different two-equation k-ε models were used to simulate the gas flow field generated by a new type of circulating fluidized bed reactor with venturi gas distributor. The numerical results were compared with the experimental data. It has been shown that the simulation results from the standard k-ε model have the best match with the experimental data. Based on this model, the gas flow field in the venturi diffuser and riser was analyzed by the concept of velocity nonuniformity and dead zone percentage. Both the nonuniformity of gas velocity and the dead zone percentage reach the maximum at the venturi outlet due to the effect of the vortex. At the same time, it provides a good platform for the further optimization of the inlet configuration of circulating fluidized bed reactor.     

Imaging technologies in oilfield applications

INTRODUCTION Imaging technologies have been widely used in oilfield applications, from micro-scale (mm) X-ray tomography of rock core samples to macro-scale (km) seismic imaging for oil-gas reservoir exploration. In this paper, we describe some recent imaging technologies developed by Schlumberger for oilfield downhole multiphase flow production logging (PL) (multiphase pipe flow rate measurement) and reser- voir-scale cross-well electromagnetic (EM) survey applications. Some field exam…     

Efficiency of Plate Separators for Dispersed Liquid-Liquid Systems

Plate packages are effective and promising appa-ratus for the separation of droplets from non-homoge-neous mixed systems of liquid-liquid dispersion inchemical unit operation for their features of compactconfiguration, low equipment cost and high efficien-cy[1]. The theories of plate separators were proposedand a lot of experimental researches were carried outin 1960s. Walteret alproved that in contrast to tradi-tional gravity settlers, plate packages are successfullyused to improve the separa…     

过冷流动沸腾热传递的分形模型

提出过冷流动沸腾热传递的分形模型,根据加热表面活化点的分形分布得到了过冷流动沸腾热流密度的表达式。从该模型中发现过冷流动沸腾热流密度是壁面过热度、流体的过冷度、流体的主流速度与流体的接触角、流体物理特性的函数关系,并且没有增加新的经验常数。模型预测的结果与实验数据进行了比较,两者是极好的吻合。     

Simulation of two-phase flows of a droplet impacting on a liquid film with an improved lattice Boltzmann model

Based on the lattice Boltzmann method (LBM), an improved pseudo-potential model, combined with a method of adding force term, is used to simulate the two-phase flows caused by a liquid droplet impacting on a liquid film. In this model, the different phases are treated as one fluid, and the interfaces between the vapor and liquid phases can be obtained by density value of the fluid. This variant of the LBM allows one to obtain the densities of vapor and liquid with high accuracy. The model is validated by an example of phase separation. The early stage of the impact of droplet on liquid film is simulated, and the results are qualitatively consistent with physical phenomena.