共查询到20条相似文献，搜索用时 265 毫秒
1.
Short path distillation (SPD) is a kind of high vacuum distillation method, which is suitable for the separation of high boiling, heat sensitivity and viscidity products. In this paper ,through measuring the phase-averaged velocity distributions with a conditional sampling method of the particle imaging velocimetry ( PIV), the liquid flow field that affects the heat and mass transfer of evaporating thin-film in an SPD evaporator is investigated. Measured results show that the flow velocities decrease rapidly apart from the wiper at different wiper velocities, the maximum velocity appears before wipers, and the quicker the wiping, the larger the flow velocity. Meanwhile, the evaluation of numerical calculations is carried out. The measured velocity distributions indicate clearly the effect of the wiper both on the flow field along its moving direction and on the vortices behind the wiper. Simulation data show that the performance of liquid flow field on the heating surface not only agrees with the experimental results well, but also can give further more information, such as the distribution of turbulent kinetic energy. In this study ,turbulent kinetic energy mainly distributes before wipers and laminar flow appears far away from the wipers. 相似文献
2.
对下喷自吸环流反应器内气－液两相流和气－液－团三相流体系的液相局部流动特性进行了实验研究．用改进皮托管对液相瞬时速度进行了测量，并借助湍流统计理论对渡相平均速度、液相湍动速度和湍动微尺度等液相局部流动参数进行了统计分析和处理，着重讨论了喷射液体流量和固体粒子加入量分别对喷射有效区和导流筒内管流区液相局部流动参数的影响． 相似文献
3.
徐涛 《广东轻工职业技术学院学报》2006,5(1):6-8
采用FLUENT6．0软件对整个螺旋隔板花瓣管单管换热器的一段的流场、温度场进行数值模拟，结果显示壳程内的主体流动趋势仍是螺旋状，但在翅片附近速度场的大小和方向变化较大，证明翅片的存在激发了流体的边界层分离和湍动，从而强化了传热。 相似文献
4.
Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter-flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u0 is 12.6 cm/s, the equivalent diameter de is 0.6 cm, the mass concentration of particle is 0.2%,the average particle diameter is about 10 nm and the density is 2 g/cm3. The velocity profiles of both frontal and tail-vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, both tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably, and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no particles. The influences of flow field change in the presence of particles on gas-liquid mass transfer are analyzed and discussed. 相似文献
5.
The trajectory model of dispersed phase drops and distribution model of drop diameters were derived.By numerical simulation,the analytical results indicate that a large number of dispersed phase drops accumulate on the upper plate in different directions and form a hydrodynamic area with the stream-wise location in the range of 0—0.4m,where the flow of trickling film obtains kinetic drive from flowing field.The flowing field of trickling film exhibits an unstable state if the stream-wise location is less than 0.02m,and a stable state otherwise.Moreover,different velocity vectors of drops in the x-y plane result in different interactions between the trickling film and drops.For the non-uniform distribution of drop diameters,there is a stronger interaction between the trickling film and drop if the stream-wise location is less than 0.02m,because the amplitudes of velocity vectors are higher than those in the range of 0.02—1.0m.The result reveals a complexity and diversity of stratified two-phase flowing field.On the other hand,both the basic flowing field and distributions of drop diameters have a great influence on the distributions of comparable kinetic energy of drops.The complicated motions of larger drops are helpful to coalescence because they will consume much more kinetic energy on the trickling film than those of smaller drops.The change of comparable kinetic energy of smaller drops is continuous and steady.The smaller drops are easily entrained by the liquid-liquid flowing field. 相似文献
6.
本文用DLR（近壁低雷诺数）型k-ε紊流模型·BFC（边界拟合曲线坐标变换）法对锥形扩散器内的紊流进行了数值仿真与分析。通过对数值仿真结果和实验结果的比较,分析不同模型常数组、模型函数组和时间步长对时均速度和紊流动能的影响。 相似文献
7.
Scaling properties of Navier-Stokes turbulence 总被引：1，自引：0，他引：1
Zhao-cun Liu 《浙江大学学报(A卷英文版)》2009,10(3):392-397
8.
The effects induced by streamwise conduction on the thermal characteristics of forced convection for single-phase liquid flow
in rectangular microchannel heat sinks under imposed constant wall temperature have been studied. By employing the fin approach
in the first law of analysis, models with and without streamwise conduction term in the energy equation were developed for
hydrodynamically and thermally fully-developed flow under local thermal non-equilibrium for the solid and fluid phases. These
two models were solved to obtain closed form analytical solutions for the fluid and solid temperature distributions and the
analysis emphasized details of the variations induced by the streamwise conduction on the fluid temperature distributions.
The effects of the Peclet number, aspect ratio, and thermal conductivity ratio on the thermal characteristics of forced convection
in microchannel heat sinks were analyzed and discussed. This study reveals the conditions under which the effect of streamwise
conduction is significant and should not be neglected in the forced convective heat transfer analysis of microchannel heat
sinks. 相似文献
9.
Fu-you Tian Lian-feng Huang Li-wu Fan Hong-liang Qian Jia-xi Gu Zi-tao Yu Ya-cai Hu Jian Ge Ke-fa Cen 《浙江大学学报(A卷英文版)》2016,17(2):89-100
The pressure drop over a packed bed with sintered ore particles was studied experimentally. The sintered ore particles were characterized to determine their equivalent particle diameter, bed voidage, and sphericity. The pressure drop experiments were performed on unsorted and sieved particles with various size distributions for a superficial velocity up to 2.4 m/s, covering flow regimes from laminar to turbulent. It was shown that the Ergun equation underestimates the pressure drop for such highly irregular-shaped particles by about 40%. The measured modified friction factor was well correlated to a scaled Ergun equation, which was verified to be valid for the modified particle Reynolds number up to 12 000 toward design and optimization of vertically arranged sinter coolers for waste heat recovery. 相似文献
10.
对自由圆管在其中心部位经受刚性平头弹体横向冲击时的动力学行为进行了实验研究和计算机仿真.研究了不同管径、管长以及不同材质的自由圆管在3种不同直径和质量的平头弹体的横向冲击下的变形历程、最终的变形模态以及能量的分配方式,得到了自由圆管被穿透时子弹的临界速度和临界动能.并把实验和模拟的结果与自由梁模型的情况作了比较和分析. 相似文献
11.
Numerical study of heat transfer characteristics of downward supercritical kerosene flow inside circular tubes 总被引：3，自引：0，他引：3
The heat transfer characteristics of China RP-3 aviation kerosene flowing in a vertical downward tube with an inner diameter of 4 mm under supercritical pressures are numerically studied. A ten-species surrogate model is used to calculate the thermophysical properties of kerosene and the re-normalization group (RNG) k-ε turbulent model with the enhanced wall treatment is adopted to consider the turbulent effect. The effects of mass flow rate, wall heat flux, inlet temperature, and pressure on heat transfer are investigated. The numerical results show that three types of heat transfer deterioration exist for the aviation kerosene flow. The first type of deterioration occurred at the tube inlet region and is caused by the development of the thermal boundary layer, while the other two types are observed when the inner wall temperature or the bulk fuel temperature approaches the pseudo-critical temperature. The heat transfer coefficient increases with the increasing mass flow rate and the decreasing wall heat flux, while the inlet bulk fluid temperature only influences the starting point of the heat transfer coefficient curve plotted against the bulk fluid temperature. The increase of inlet pressure can effectively eliminate the deterioration due to the small variations of properties near the pseudo-critical point at relatively high pressure. The numerical heat transfer coefficients fit well with the empirical correlations, especially at higher pressures (about 5 MPa). 相似文献
12.
根据塑料发泡中复杂流场流体动能气泡成核理论,对圆锥形收敛流道中的流体动能进行了理论解析。通过圆锥形收敛流道的流场分析,经过大量推导,得出了该种流道中流体剪切能、流体延伸能及流体总动能的理论解析。可以进一步用来定量分析圆锥形收敛流道中塑料熔体的气泡成核。 相似文献
13.
Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow. 相似文献
14.
为使大风量、高风速空调箱内的空气流能够迅速地实现均流,开发出了一种草帽型均流板。该均流板能够使空气在仅为0．4～0．6m的距离内将空气由40m／s降低到2．5m／s,并使空气在蒸发器迎风面上均匀分布,以提高蒸发器的换热效果,减小蒸发器结霜的可能性．提高机组的能效比。 相似文献
15.
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. 相似文献
16.
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。 相似文献
17.
建立了含内热源的液池内自然对流与冷却盘管内强制对流耦合传热的三维物理、数学模型,进行了相应的数值模拟计算。分别对不同内热源强度,不同冷却流体流量下液池内流体温度场以及液池与盘管内溶液换热系数进行了分析,得出换热系数随内热源强度和冷却流体流量的变化曲线,并与实验值进行了比较。结果表明盘管冷却传热模型能够较好的反映液池内的换热。 相似文献
18.
Based on the cylindrical cavity expansion theory, a plastic-damage-elastic model is proposed for the penetration problem of geo-material. In the model, the unified strength criterion (Yu, 1991) is adopted as the failure criterion. The distributions of the radial stress and velocity are analyzed. According to the Newton's second law, a series results of the final penetration depth and the impedance load are obtained to different parameter b, when a rigid projectile normally impacts and penetrates a semi-infinite geo-material target with an impact velocity of 300-1200 m/s. By comparing with the test data available, it appears that the method can be used in analyzing the final depth and the impedance load of a rigid projectile penetrating into a semi-infinite target with different impact velocities. 相似文献
19.
With the development of ski-jump energy dissipation for high and large discharge among the hydraulic projects, the effects of characteristics of water flow on energy dissipation are increasingly important. In the present study, the effects of aeration and the initial water thickness on axial velocity attenuation of jet flow were analyzed, using variance analysis and numerical calculated methods. From the analysis of test data, both of the air concentration and initial water thickness are sensitive factors for the axial velocity attenuation of jet flow along the axial way, and there is no significant interaction effect between the aeration and initial water thickness. Aeration has a more significant effect on the axial velocity attenuation of jet flow. Decreasing the initial water thickness of jet flow can reduce the length of jet core, and make the initial position of axial velocity attenuation closer to the nozzle exit. The numerical calculation results show that aeration can contribute to the enhancement of entrainment ability of jet flow, which may improve the interaction between jet flow and surroundings. For ski-jump energy dissipation among the hydraulic projects, combining aeration with decreasing initial water thickness of jet flow is an effective way to enhance the rate of axial velocity attenuation. 相似文献
20.
This paper reports research on the effects of variations in injection velocity and permeability on the heat transfer and flow
through a highly porous medium between two horizontal parallel plates situated at constant distance with constant suction
by the upper plate. Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.
The governing equations are solved by adopting complex variable notations to obtain the expressions for the velocity and temperature
field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs. 相似文献