Maxwell-Stefan方程在多元相间传质方面的应用

多元物系传质过程与二元物系传质过程有着本质的区别，由于组分间的交互作用，多元物系传质各组分传质效率不相等，其分布范围可在-∞至 ∞之间，某些组分可能产生逆向传质、渗透传质、传质障碍等传质奇异现象，这些现象用传统的二元物系传质规律如Fick定律等无法做出解释，必须用Maxwell-Stefan方程进行描述。先概述了Maxwell—Stefan方程的由来、求解方法，然后具体介绍在多元相间传质中的应用。     

Hamilton—Jacobi—Bellman方程在最优投资中的应用

建立简单的衍生证券投资组合模型，利用HJB方程，讨论了在一定假设条件下衍生证券最优投资问题，得到相关投资策略与无风险投资收益率及风险投资期望收益率之间定量关系。并利用得到的定量关系式，讨论了投资策略与无风险收益率及风险投资期望收益率之间定性关系；同时也说明了人民币降息对国民经济的调控作用。     

对时间的分数阶扩散方程在图像恢复中的应用

提出了一种包含对时间的分数阶导数的非线性扩散方程,它是对Perona-Malik的非线性扩散方程和Cuesta提出的方程的推广,介于非线性抛物方程和非线性双曲方程之间,从而能有效地控制扩散过程,使得在去除图像噪声的同时能够尽可能地保留图像的边缘等细节信息.数值试验结果显示,该方程比Perona-Malik的非线性扩散方程有更好的去噪效果.     

非饱和含湿多孔介质传热传质的渗流模型研究

综述了非饱和含湿多孔介质传热传质模型研究的发展。从多相渗流和扩散迁移机制出发建立以温度、压力和饱和度为基本变量的实用化三参数模型。该模型由一组描述水－汽质量守恒、空气质量守恒和能量守恒的非线性偏微分方程组成。利用该模型对埋管的热过程、砂土物性测量、毛细滞后现象、回湿过程、突发高温作用下多孔介质内部的传热传质过程和冻融过程进行了研究。为了模型的进一步应用,仍需对束缚水饱和度以下毛细压力与饱和度的关系、导热系数的影响因素及其获取方法、非饱和多孔介质传热传质的边界效应和滞后效应的物理机理等方面深入研究。非饱和多孔介质中溶质的运移更是一个饶有意义的研究课题。     

含湿多孔介质传热传质三参数渗流模型研究方法

回顾了含湿多孔介质传热传质模型的发展，系统地介绍了三参数渗流模型概括的基本传递机制和物性数据，特别是松散介质的物性数据的获取方法。以埋管周围砂土内的传热传质动态过程研究为例，给出了不同边界条件的描述，介绍了介质物性数据及初始温度、含湿饱和度等的确定方法。最后，给出了常功率加热条件下，浅埋水平管道周围温度、含湿饱和度以及压力分布变化情况     

离心流化床中多孔介质干燥的传热传质研究

通过对典型的多孔湿物料在离心流化床中干燥过程的理论分析,将含湿多孔介质传热传质过程和物料与气流之间的外部传递过程相耦合,导出了离心流化床的控制方程组,在此基础上,可以对离心流化床中湿物料的干燥过程进行数值模拟。     

基于Maxwell-Stefan双扩散模型的煤层气注气数值模拟

目前煤层气注气数值模拟软件中均以扩展Langmuir模型模拟多组分气体吸附/解吸,以拟稳态单孔扩散模型和Fick定律描述煤层基质中气体扩散,虽然简单,便于应用,但存在较大局限性。以试验数据为依据,评价扩展Langmuir、IAS和2D PR-EOS多组分气体吸附模型可靠性,并建立Maxwell-Stefan双扩散模型模拟气体扩散过程。最后,将双扩散模型与煤储层气水两相多组分渗流模型耦合,利用IMPES方法求解研究煤层气注气过程。研究表明:2D PR-EOS模型预测结果优于扩展Langmuir和IAS模型;注气初期基质中多组分气体吸附和甲烷解吸速率较快,之后逐渐变缓;该模拟方法可以较为准确地模拟煤层气衰竭和注气开发过程,预测煤基质中气体各组分浓度分布,为煤层气注气开发的研究及现场应用提供有效的技术手段。     

CPL蒸发器多孔芯传热传质特性的数值模拟

对不同热流密度下CPL蒸发器多孔芯内相变工质的流动与传热特性进行了数值计算研究．计算所采用的是加入了非饱和传热传质段的三层数学模型．计算结果表明,多孔芯内液相含量的变化十分明显,为将多孔芯的汽液相变区处理为非饱和多孔区提供了充分依据．当热流密度增加时,非饱和区域的厚度开始变薄,且在热流增大到一定程度后,干饱和区域的出现对整个多孔芯的传热传质产生了较大影响．     

A novel theoretical model for mass transfer of hollow fiber hemodialyzers

A novel theoretical model for mass transfer of hollow fiber bundles in hemodialyzers is presented. In the model, a hemodialyzer is considered as a porous zone which is composed of two non-interpenetrating porous flow zones.Firstly, the dialysate side (shell side) is thought as a porous medium zone. Then by solidifying the dialysate flow zone and the occupied zone by hollow fiber membrane, the rest zone of bemodialyzer (i.e. blood side or lumen side) is considered as a porous medium zone too. Finally, the interface of the two flow zones is the fiber membrane through which mass transfer is performed. The dialysate and blood flows are all described by Navier-Stokes equations with Darcy momentum source terms. Kedem-Katchaisky equations as other source terms are added into Navier-Stokes equations to simulate the permeating flux through the membrane. All equations must be coupled together in the process of computing. The model is validated by the experimental data in literature. The simulative results show that the predicted clearances agree well with the experimental data, and the model in this paper is better than other models for the forecast of clearance.     

A novel theoretical model for mass transfer of hollow fiber hemodialyzers

Hemodialyzers have been applied to hemodialysiswidely. In order to get accurate mass transfer coefficient and clearance to determine treatment time, their masstransfer models have been studied deeply. The domesticstudy on hemodialyzers is later, focuses on experiment, and seldom refers to theoretical mechanism[1,2], but theoverseas research is more in-depth. Simple one-dimensional models have been used to simulate mass transfer in hemodialyzers by many re-searchers[3—7]. Their models assumed …     

粗糙多孔保温层的热质耦合传递分形研究

粗糙多孔保温层内部的热质耦合传递过程广泛存在于能源利用、机械隔热等工程中,为了更加真实地体现该热质耦合传递过程,将粗糙的孔隙通道描述为短周期正弦变化的毛细管道,根据达西定律、能量守恒定律和牛顿冷却定律,同时考虑粗糙度和粗糙密集度两个影响因素,提出了粗糙毛细管道的渗流系数和对流换热系数模型,分析了粗糙表面对渗流系数和对流换热系数的影响。结果表明,渗流系数模型的理论预测值与实验数据相吻合;渗流系数与面积分形维数、粗糙密集度呈正相关,与迂曲分形维数、粗糙度呈负相关;对流换热系数与渗流系数、粗糙度和粗糙密集度呈正相关,与面积分形维数、迂曲分形维数呈负相关。     

Field synergy principle of heat and mass transfer

Simultaneous heat and mass transfer widely exists in nature and engineering, and it is of vital importance to enhance heat and mass transfer efficiency. In this paper, field synergy equation of heat and mass transfer is derived from its energy equation. Results show that the total transferred heat （including the conducted heat and the heat transferred by mass diffusion through the heat transfer interface） is determined by the values of fluid velocity and enthalpy gradient as well as the value of synergy angle α of velocity vector and enthalpy gradient field. Decreasing the value of α enhances the heat and mass transfer. This means the higher the synergy of velocity vector and enthalpy gradient field, the higher the total transferred heat. By the synergy principle of heat and mass transfer, some methods may be developed to improve the heat and mass transfer efficiency.     

多孔表面槽道对沸腾传热影响的实验研究

报道了开槽密度和深度对R11工质在烧结多孔表面池沸腾换热影响的实验研究,观察发现,多孔表面开槽,蒸汽从槽道逸出,液体从多孔区吸入到受热面,沸腾换热增强,沸腾可分为液体灌注,槽道起泡和底部蒸干3个区,对特定的多孔层,合理开槽可获得较好的换热效果。