共查询到20条相似文献,搜索用时 3 毫秒
1.
采用格子Boltzmann方法模拟多孔介质内的流动过程,通过预测渗透率,比较了单松弛模型、多松弛模型和熵格子模型在多孔介质计算中的优劣,为研究多松弛模型中各自由参数的影响,选择了12种组合进行模拟,此外,还将大涡模拟与格子Boltzmann方法相结合模拟了多孔介质内高Reynolds数下的流动及流型的转变。结果表明:单松弛模型和熵格子模型预测的渗透率随黏度逐渐增大,而多松弛模型得到的结果随黏度变化很小,另外,多松弛模型中不同松弛参数的组合对结果有较大的影响,通过比较推荐了模拟多孔介质时的最佳组合,计算结果与经验公式吻合较好。大涡模拟与多松弛模型结合较好地预测了多孔介质内流型的转变,Reynolds数越大,多孔介质内的涡越多,并且变大。 相似文献
2.
多孔介质内的气泡熟化行为广泛存在于CO2封存等领域,为探究多孔介质内气泡的熟化特性,本文采用空气作为模拟气体,通过可视化实验和数值计算,对双孔隙和四孔隙气泡熟化过程进行了研究,阐释了多孔介质非均质性对熟化过程的影响规律。结果表明:在双孔隙气体饱和度较小情况下,虽然也发生正向熟化,但是孔隙结构的存在使熟化速率明显低于自由流体情况;四孔隙研究显示多孔介质非均质性对气泡熟化过程影响显著,由于孔隙的几何限制,气泡在某些情况下会发生逆Ostwald熟化,即生长的气泡在充满当前孔隙空间后会停止生长并反向熟化导致尺寸缩小;在非均质多孔介质中,由于熟化作用,气泡有传质到大孔隙区域趋势,导致大孔隙区域富集大气泡,存在泄漏风险,从而影响封存。 相似文献
3.
4.
Zhenyu Xu 《Drying Technology》2017,35(7):785-801
This article uses a novel, fully coupled method to solve the isothermal slow drying of porous media in laminar flow. The film effect is included and a novel logistic equation is used to relate the pore network variables with the external field variables. The model is used to simulate the drying of several thin porous media with different aspect ratios in a flow. One, two, or all sides of the pore network are opened to the flow. The studies show that the higher exposed area vs. total volume ratio leads to faster drying while the orientation of the porous media is immaterial. 相似文献
5.
将多孔介质简化为一簇变截面毛细管组成的毛细管束,根据多孔介质的颗粒直径、颗粒排列方式、孔喉尺度比以及束缚水饱和度,计算出变截面毛细管的喉道半径和孔隙半径。在考虑多孔介质喉道和孔隙中单个气泡的受力和变形基础上,利用质量守恒定理和动量守恒定理,推导出单个孔隙单元内液相的压力分布和孔隙单元两端的压力差计算公式,最终得到多孔介质的压力分布以及多孔介质中泡沫当量直径计算方法。利用长U型填砂管对多孔介质中稳定泡沫的流动特性进行了实验研究,并对实验结果和计算结果进行了对比。结果表明:稳定泡沫流动时多孔介质中的压力分布呈线性下降,孔喉结构和泡沫干度是影响泡沫封堵能力的主要因素;泡沫的封堵能力随泡沫干度的增加而先增加后降低,在泡沫干度为85%时达到最强封堵能力。 相似文献
6.
Guanghua Ye Xinggui Zhou Jinghong Zhou Weikang Yuan Marc‐Olivier Coppens 《American Institute of Chemical Engineers》2017,63(1):78-86
The effects of the catalyst pore network structure on multiphase reactions in catalyst pellets are investigated by using the experimentally validated pore network model proposed in our recent work (AIChE J, 62 , 451, 2016). The simulations display hysteresis loops of the effectiveness factor. The hysteresis loop area becomes significantly larger, when having small volume‐averaged pore radius, wide pore‐size distribution, and low pore connectivity; however, the loop area is insensitive to pellet size, even though it affects the value of the effectiveness factor. The hysteresis loop area is also strongly affected by the spatial distribution of the pore size, in particular for a bimodal pore‐size distribution. The pore network structure directly influences mass transfer, capillary condensation, and pore blocking, and subsequently passes these influences on to the hysteresis loop of the effectiveness factor. Recognizing these effects is essential when designing porous catalysts for multiphase reaction processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 78–86, 2017 相似文献
7.
A finite-element-based method is presented for evaluating the effective gas diffusion coefficient of porous solids. Using
this method, the 3-D micro-scale geometries of the porous solids are constructed under the ANSYS platform by the parametric
code; the relation between effective gas diffusivity and micro-scale features of random-distributed porous solids is established.
The results show that in random-distributed pore media, there is a percolation threshold ε
p, and this percolation threshold decreases with increasing coordination number of the pore network. The relationship between
the effective diffusivity and porosity is strongly nonlinear when the porosity, ε, is less than a certain value ε
L
; for ε > ε
L
, the relationship becomes quasi-linear. This dividing point ε
L
decreases with increasing coordination number. The larger the coordination number of the pore network, the higher the effective
gas diffusivity. Based on the simulation results and observations, a formula relating the effective diffusion coefficient
with porosity is proposed. 相似文献
8.
9.
Wei‐Wei Yan Zhong‐Di Su Hong‐Jun Zhang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(3):456-461
BACKGROUND: Biofiltration technology has received much attention due to its effectiveness, low cost and environment friendly properties. It is used to remove odors caused chiefly by hydrogen sulfide (H2S) via biological treatments. RESULTS: In this study, numerical simulations using the thermal lattice Boltzmann method are implemented to investigate the effect of non‐isothermal conditions on heterogeneous flow through three biofilter models that are partly filled with porous media. The generalized Navier–Stokes model based on the Brinkman‐Forchheimer–extended Darcy model is used to make several assumptions. CONCLUSIONS: The numerical results indicate that the Rayleigh number has significant influence on the removal efficiencies of biofilters. There also exist critical Rayleigh numbers for biofilters under non‐isothermal conditions. If the Rayleigh number is less than the critical value, the flow heterogeneity will reduce with increasing Rayleigh number; otherwise, the flow heterogeneity will enhance with increasing Rayleigh number. Moreover, it was found that the performances of biofilters can be improved by designing non‐isothermal conditions between the porous media layers, i.e. by adjusting the Rayleigh number to optimize the detention time of waste air. © 2012 Society of Chemical Industry 相似文献
10.
通过建立沿管壁恒热流加热的渗流实验系统,实验研究了悬浮颗粒在饱和多孔介质内以及入口界面处的沉积和运移特性。着重研究了有无加热条件,以及不同加热温差,相同多孔介质和进口悬浮液浓度情况下,实验段入口界面处与内部的颗粒沉积量变化,以及沿程不同位置处的压力变化。并对实验过程中的渗流稳定性及各测点温度和多孔介质段渗透系数进行了分析。结果表明:相对渗透率kt/k0在不同温差下有明显不同;多孔介质与进口流体界面处的沉积量随温差的增大而增加,沉积结构的稳定性降低;多孔介质段颗粒沉积强度随温差的增大而增大,实验结果可为今后的理论分析提供验证依据。 相似文献
11.
We study the mobilization and subsequent flow in a porous medium of a fluid with a yield stress, modeled as a Bingham plastic. We use single-capillary expressions for the mobilization and flow in a pore-throat, and a pore-network model that accounts for distributed yield-stress thresholds. First, we extend the statistical physics method of invasion percolation with memory, which models lattice problems with thresholds, to incorporate dynamic effects due to the viscous friction following the onset of mobilization. Macroscopic relations between the applied pressure gradient and the flow rate for single-phase flow are proposed as a function of the pore-network microstructure and the configuration of the flowing phase. Then, the algorithm is applied to model the displacement of a Bingham plastic by a Newtonian fluid in a porous medium. The results find application to a number of industrial processes including the recovery of oil from oil reservoirs and the flow of foam in porous media. 相似文献
12.
A pore network study of evaporation from the surface of a drying non‐hygroscopic porous medium
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alireza Attari Moghaddam Abdolreza Kharaghani Evangelos Tsotsas Marc Prat 《American Institute of Chemical Engineers》2018,64(4):1435-1447
The phenomena occurring at the surface of a porous medium during drying in the capillary regime are investigated by pore network simulations. The impact of the formation of wet and dry patches at the surface on the drying rate is studied. The simulations indicate an edge effect characterized by a noticeable variation of saturation in a thin layer adjacent to the porous surface. Also, the results indicate a significant nonlocal equilibrium effect at the surface. The simulation results are exploited to test Schlünder's classical model which offers a simple closure relationship between the evaporation rate and the degree of occupancy of the surface by the liquid. In addition to new insights into the surface phenomena, the results open up new prospects for improving the continuum models of the drying process. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1435–1447, 2018 相似文献
13.
地下岩石孔隙中小颗粒的运移和沉积会使得储层渗透性能降低,影响石油开发。为了探究悬浮颗粒在多孔介质中的流动过程,采用格子Boltzmann方法对三维多孔介质内流体和颗粒的运动过程进行了数值模拟,采用有限体积颗粒法构建多孔介质中骨架颗粒和悬浮颗粒。通过Half-Way反弹格式实现流体与颗粒间的相互作用,考虑孔隙结构、入口流速、孔隙率和颗粒直径对颗粒流动特性的影响,探究颗粒的运移和沉积规律。结果表明,入口速度对不同孔隙结构下颗粒的运动作用显著。随着入口速度增大,颗粒与颗粒、孔隙壁面以及流体之间的动量和能量交换作用增强,缩短了颗粒的运移路径,颗粒沉积率逐渐变小,颗粒拟温度增大。孔隙率的下降强化了颗粒间的碰撞,孔隙率由0.581降低至0.400,使得颗粒拟温度提升至9倍。颗粒拟温度随颗粒直径的增加而增加。但随着孔隙率增加,颗粒轴向速度增加,颗粒最高轴向速度可达入口流速的11倍,而颗粒接触力降低。 相似文献
14.
A numerical study of dynamic capillary pressure effect for supercritical carbon dioxide‐water flow in porous domain
下载免费PDF全文
![点击此处可从《American Institute of Chemical Engineers》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Diganta B. Das Bhupinder S. Gill Luqman K. Abidoye Kamal J. Khudaida 《American Institute of Chemical Engineers》2014,60(12):4266-4278
Numerical simulations for core‐scale capillary pressure (Pc)‐saturation (S) relationships have been conducted for a supercritical carbon dioxide‐water system at temperatures between 35°C and 65°C at a domain pressure of 15 MPa as typically expected during geological sequestration of CO2. As the Pc‐S relationships depend on both S and time derivative of saturation ( ) yielding what is known as the “dynamic capillary pressure effect” or simply “dynamic effect,” this work specifically attempts to determine the significance of these effects for supercritical carbon dioxide‐water flow in terms of a coefficient, namely dynamic coefficient (τ). The coefficient establishes the speed at which capillary equilibrium for supercritical CO2 (scCO2)‐water flow is reached. The simulations in this work involved the solution of the extended version of Darcy's law which represents the momentum balance for individual fluid phases in the system, the continuity equation for fluid mass balance, as well as additional correlations for determining the capillary pressure as a function of saturation, and the physical properties of the fluids as a function of temperature. The simulations were carried out for three‐dimensional cylindrical porous domains measuring 10 cm in diameter and 12 cm in height. τ was determined by measuring the slope of a best‐fit straight line plotted between (1) the differences in dynamic and equilibrium capillary pressures against (2) the time derivative of saturation (dS/dt), both at the same saturation value. The results show rising trends for τ as the saturation values reduce, with noticeable impacts of temperature at 50% saturation of aqueous phase. This means that the time to attain capillary equilibrium for the CO2‐water system increases as the saturation decreases. From a practical point of view, it implies that the time to reach capillary equilibrium during geological sequestration of CO2 is an important factor and should be accounted for while simulating the flow processes, for example, to determine the CO2 storage capacity of a geological aquifer. In this task, one would require both the fundamental understanding of the dynamic capillary pressure effects for scCO2‐water flow as well as τ values. These issues are addressed in this article. © 2014 American Institute of Chemical Engineers AIChE J 60: 4266–4278, 2014 相似文献
15.
基于均匀各向同性多孔介质、达西渗流和理想气体假设,考虑Klinkenberg效应建立了针对具有纳米尺度孔径的低渗透率多孔介质中的渗流模型。针对致密球形破碎样品的压力脉冲实验,建立了相应的边界条件,同时利用有限差分方法获得其实验腔的压力变化曲线的数值解。通过对渗流方程进行量纲1化,引入了与孔隙率、渗透率和滑移参数有关的量纲1参数Z、Z*和bK。通过改变参数Z、Z*和bK研究了样品边界处压力的变化规律,给出了一种数据处理方法,对于致密球形破碎多孔介质的压力脉冲实验,通过对实验测量的样品边界处压力曲线的分析,结合偏微分方程正问题的数值解,可以确定样品的孔隙率、渗透率和滑移参数,从而更为简便地分析压力脉冲衰减曲线实验数据,得到致密多孔介质样品渗透率。 相似文献
16.
17.
Alexis Tran‐Viet Alexander F. Routh Andrew W. Woods 《American Institute of Chemical Engineers》2014,60(3):1193-1201
Experiments explore the reduction in permeability of a porous bead pack when a suspension of thermally responsive polymer is injected and the temperature then increased above the thermal activation temperature. The change in permeability is greater with higher polymer concentration, provided that the ionic concentration of the solution is sufficient for floc formation. The time for activation of the blocking effect is within tens of seconds to minutes of when the polymer solution is heated. This is consistent with the timescale for diffusion‐limited aggregation, although the detailed value depends on the geometry and polymer concentration. Dynamical experiments demonstrate that once the porous media is blocked, adding additional polymer has no effect. The mechanism for permeability reduction may be modeled in the context of a pore‐network model, and we build a simple model to illustrate the permeability reduction as a function of the fraction of pores links which are blocked. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1193–1201, 2014 相似文献
18.
19.
Well defined experiments and numerical analyses are conducted to determine the importance of dynamic effect in capillary pressure relationships for two‐phase flow in porous media. Dynamic and quasi‐static capillary pressure‐saturation (Pc‐Sw) and, ?Sw/?t‐t curves are determined. These are then used to determine the dynamic effects, indicated by a dynamic coefficient (τ) in the porous domains which establishes the speed at which flow equilibrium (?Sw/?t = 0) is reached. τ is found to be a nonlinear function of saturation which also depends on the medium permeability. Locally determined τ seems to increase as the distance of the measurement point from the fluid inlet into the domain increases. However, the functional dependence τ‐Sw follows similar trends at different locations within the domain. We argue that saturation weighted average of local τ‐Sw curves can be defined as an effective τ‐Sw curve for the whole domain which follows an exponential trend too. © 2012 The Authors. AIChE Journal, published by Wiley on behalf of the AIChE. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. AIChE J, 58: 3891–3903, 2012 相似文献
20.
Multiscale and multilayer structural modeling and simulation on drying of grain packing porous media
Yuejin Yuan Libin Tan Zhe Zhao Yingying Xu Yu Zhao Yueding Yuan 《Drying Technology》2016,34(14):1664-1676
ABSTRACTAiming at the problem of multilayer physical structure for the skeleton of porous media, a multiscale and multilayer structural model of heat and mass transfer processes for drying of grain packing porous media was established by applying the pore network method and multiscale theory. An experimental study on rice drying was conducted in order to validate this model. The simulation and experimental results indicated that the established model could explain the mechanical properties of rice drying well. The rate of heat transfer was faster than the rate of mass transfer and there was a higher moisture gradient inside the rice grain. The diffusion coefficient of rice embryo played an important role in the drying process, and whose effect on drying was larger than the diffusion coefficient of rice hull and chaff. The moisture was imprisoned effectively inside the rice when the diffusion coefficient of rice embryo was very small. 相似文献