APPLICATION OF THE CONSTANT MOLAR FLOW METHOD IN THE STUDY OF MASS TRANSFER OF GASES AND VAPORS IN BIDISPERSE STRUCTURED SOLIDS

In this paper, we provide exact analytical solutions for a new method of constant molar flow of pure gas into a reservoir containing solid adsorbents having a bidispersed structure, such as zeolite, activated carbon and alumina. Depending on the diffusion mechanism, two models are proposed under the isothermal conditions and linear isotherm. One is applicable to zeolite, and the other for alumina and activated carbon. The solutions of these two models are in the form of an infinite series, and its eigenvalues are determined from a transcendental equation. This transcendental equation is such that the eigenvalues are lumped into infinite but countable groups, and in each group there are infinite but countable eigenvalues. The dominant eigenvalues are generally the first ten to thirty eigenvalues (depending on the value of time at which the series is evaluated) in each group. The pressure response of the reservoir is a function of time as the result of the introduction of adsorbate into the reservoir, and as time is sufficiently large it asymptotes to a straight line, of which the slope is a function of the equilibrium parameters only and the intercept is found to be an explicit function of the equilibrium parameters as well as the diffusivities in the macropore and micropore.     

Dynamics of fluid circulation in coupled free and heterogeneous porous domains

Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed.     

An integrated radiotracer approach for the laboratory evaluation of scale inhibitors performance in geological environments

The applicability of a newly developed radiotracer technique as a reliable laboratory procedure for the evaluation of scale inhibitors performance to prevent mineral precipitation is demonstrated. The performance of two new environmentally friendly inhibitors to prevent calcite and barite scale was evaluated experimentally in connection with a standard phosphonate-type scale inhibitor using the radioactive tracer technology. The radiotracers ⁴⁷Ca and ¹³¹Ba were employed in order to monitor at real-time calcite and barite scale formation, respectively. The results show that the developed radiotracer technique can be established as a novel method for the determination of the minimum inhibitor concentration (MIC) under dynamic, reservoir conditions. In addition, the radioactive tritiated water (HTO) was used as a reference water tracer to identify the inhibitors’ properties, such as adsorption/desorption characteristics, in sandpack-flooding tests. Further issues regarding the implementation of the radiotracer technology for the laboratory evaluation of scale inhibitors performance are also discussed.     

气化炉锥底砖、激冷环与下降筒的损毁与解决对策

针对国产化大氮肥水煤浆气化炉中锥底砖、激冷环和下降筒使用过程中出现的问题,分析了损毁原因,分别从技术改进、工艺操作和设备管理等方面提出了相应的解决对策,可以不同程度地延长锥底砖、激冷环、下降筒的寿命。     

Explicit numerical simulation of suspension flow with deposition in porous media: influence of local flow field variation on deposition processes predicted by trajectory methods

A new explicit numerical simulation (ENS) method based on lattice-gas automata (LGA) is introduced here for the flow of solid/fluid suspensions with deposition in porous media. The ENS method explicitly resolves the dynamics of the individual solid particles and the suspending fluid in the domain defined by the pore walls and solid particle surfaces. After describing the new method, it is applied to the study of solid/fluid suspension flow with deposition in a constriction and in a model random porous solid. This study clearly demonstrates that the deposits strongly influence the local flow fields, which in turn affect the deposition process indicating that this interplay should be modelled if accurate results are desired from trajectory methods.     

溶胶-凝胶法制备多孔陶瓷的研究进展

本文综合论述了溶胶-凝胶法制备多孔陶瓷的工艺研究进展以及影响溶胶-凝胶法制备多孔陶瓷的主要因素，并讨论了今后溶胶-凝胶法制备多孔陶瓷的主要研究问题及其发展前景。     

Phenol adsorption on porous and non-porous carbons

Phenol physisorption on a series of porous and non-porous amorphous carbons was studied at 298 K. Grand Canonical Monte Carlo computer simulations were performed to simulate phenol adsorption from the gas phase. Phenol is adsorbed in a solid-like state within the pores and there is no well-developed multilayer regime. The ‘t’ plot method was adapted to phenol adsorption and the results obtained are in agreement with the model solids employed. The simulated adsorption isotherms were compared with experimental results obtained for adsorption from aqueous solutions of phenol. BET surface areas were calculated. Other characteristics of the adsorption system analyzed were: adsorption energy distribution functions, density profiles, distribution of molecules according to gas-solid energy, and local isotherms.     

THERMAL CONVECTIVE INSTABILITY IN TRANSLUCENT POROUS MEDIA WITH RADIATIVE HEAT TRANSFER

The onset of thermal convection in a translucent porous layer is considered. Attention is focused on the effect of radiative heat transfer on the critical Rayleigh-Darcy number and the convection cell shape. If we consider the contribution of radiative heat transfer, the basic temperature profile is non-linear and the thermal convective instability is influenced by the ratio of conduction to radiation heat flux, the temperatures at the boundary surfaces, and radiative parameters such as wall emissivity, scattering albedo and extinction coefficient as well as the usual Rayleigh-Darcy number. Effects of these parameters on the onset of convective instability are investigated with the help of linear stability theory employing the Darcy's law and the radiative transport equation simplified by the P₁ approximation. The increased effective thermal conductivity due lo the radiation inhibits the onset of convection and causes increased critical Rayleigh-Darcy number and decreased convection cell size. The results of the present work may be exploited to find out the optimal diameter of aerogel pellets and the air pressure in the double pane window filled with the translucent silica aerogel granules to suppress natural convection.     

累托石合成孔梯度多孔陶瓷的研究

以累托石为主要原料，煤粉为成孔剂，采用压制成形，在1220℃温度下烧成，制得具有一定孔梯度的多孔陶瓷，研究表明，不同的骨粒粒径及不同的成孔剂粒径的相互混合可制得具有成连续变化孔梯度分布的多孔陶瓷，且随着成孔剂含量的提高，显气孔率增加，强度和体积密度均降低。     

多孔介质模型在核电蒸汽发生器设计中的应用

对基于多孔介质模型开发的核电蒸汽发生器三维热工水力分析程序ATHOS进行介绍．并应用ATHOS对核电蒸汽发生器二次侧的复杂传热传质现象进行数值模拟。获得蒸汽发生器二次侧的流动换热状态,以及二次侧三维两相流场分布,分析结果可作为传热管流致振动、磨损分析及结构设计的输入数据。研究工作表明,多孔介质模型在核电蒸汽发生器设计中具有重要的应用价值。