大型反应精馏塔板上传质的二维定数混合池模拟

介绍了大型塔板涉及反应精馏的传质与操作过程,通过对塔板上液体流动分布以及化学反应过程的分析,建立了能够关联液体流速分布和化学反应的塔板液相浓度计算模型。最后将二维定数混合池模型与描述传质的微分方程联立,利用有限元法求解了大型反应精馏塔板上的液相浓度分布。

密封箱式炉气氛碳势偏差对工件碳浓度分布的影响

根据大量随炉渗碳试样的剥层定碳分析数据,结合对炉气氛的跟踪试验结果,对密封箱式炉渗碳气氛的组分和碳势控制进行了分析研究。在用氧探头单因素控制碳势的情况下将碳势的理论计算值与定碳分析结果进行了比较,在实际生产条件下对碳浓度场进行了数值模拟,从而推断渗碳工艺过程中不同阶段碳势波动对渗层碳分布的影响。

Method of calculation of a methane concentration field in gob areas with a known velocity field based on the model of stream tubes

The control equations of gas concentration field in gob areas with a known velocity field are partial differential equations with variable coefficients,whose traditional mathematical calculation methods are very complex.A numerical simulation method can be used to calculate the gas concentration field,but it also needs considerable amounts of computer resources and the relations of gas concentration at different points of the gob area are undefined.Based on the model of stream tubes,the conservation equations of mass and gas components within the stream tube are used to deduce the equations of a gas concentration field in a gob area with a known velocity field.This method of calculation of a gas concentration field is applied in a gob area with a U-type ventilation working face,which suggests that this new method has the virtue of exact calculations is simple to operate and has a clear physical interpretation.

Numerical simulation of dust distribution at a fully mechanized face under the isolation effect of an air curtain

At a fully mechanized working face of a coal mine as prototype,we investigated,by simulation,the flow field and dust distribution during the process of its isolation by a curtain of air,using the CFD software, Fluent.The results show that the air curtain installed on the shearer can effectively prevent the dust （especially the respirable dust）from diffusing into the work area of the operator,reducing the dust concentration on the side of the operator and greatly improving his working environment.The field application of the air curtain shows that the dust-isolation effect of an air curtain is quite noticeable.The isolation efficiency for respiratory dust is over 70%and,as well,it has good dust-isolation effect for nonrespiratory dust.The air curtain is a useful way to resolve the problem of dust-isolation at a fully mechanized working face.It has a practical background elsewhere with more extensive applications.

Numerical Simulation of Concentration Field on Liquid Side around Bubble during Rising and Coalescing Process in Non-Newtonian Fluid

On the basis of Navier-Stockes equation and convection-diffusion equation, combined with surface tension and penetration models, the equations of moment and mass transfer between bubble and the ambient non-Newtonian liquid were established. The formation of a single bubble from a submersed nozzle of 1.0 mm diameter and the mass transfer from an artificially fixed bubble into the ambient liquid were simulated by the volume-of-fluid （VOF） method. Good agreement between simulation results and experimental data confirmed the validity of the numerical method. Furthermore, the concentration distribution around rising bubbles in shear thinning non-Newtonian fluid was simulated. When the process of a single ellipsoidal bubble with the bubble deformation rate below 2.0 rises, the concentration distribution is a single-tail in the bubble＇s wake, but it is fractal when thebubble deformation rate is greater than 2.0. For the overtaking of two in-line rising bubbles, the concentration distribution area between two bubbles broadens gradually and then coalescence occurs. The bifurcation of concentration distribution appears in the rear of the resultant bubble.

Thermal convection driven by a heat-releasing scalar component

In this paper,we investigate the thermal convection flow which is driven by a heat-releasing concentration field.Different from our previous work on the internally heated double diffusive convection(IHDDC),in the current internally heated Rayleigh-Bénard convection(IHRBC),the fluid density depends solely on the temperature field and the concentration field only serves as the internal heat source.Linear stability analyses reveal that the most unstable mode is always the stationary one.The critical Rayleigh number,which measures the strength of the unstable driving force,decreases with the Schmidt number(the ratio between the viscosity and the molecular diffusivity of concentration field),but increases with the Prandtl number(the ratio between the viscosity and the thermal molecular diffusivity).Fully developed flows are then studied by three-dimensional direct numerical simulations.The unifying model developed for IHDDC can also be used to describe the transport properties for the current flow.The characteristic widths are smaller for the plumes descending from the top plate than those ascending from the bottom one.