混合电解质溶液热力学——从渗透系数计算溶质活度系数的新型公式和计算方法

从热力学基本关系式出发,应用变量替换,导出从混合电解质溶液的渗透系数计算溶质活度系数的通用热力学方程。分别讨论了在以离子强度I和组分离子强度分数y为变量,或以总离子浓度m和组分离子浓度分数y为变量时方程的各种实用形式。以m和y为变量的方程与C. Pan的方程相同,但不需要两电解质具有相同电价形式的限制。从电解质溶液的理论分析导出渗透系数φ的合适的函数式,使φ的曲面拟合能在较大的浓度区间上进行且有较高的精度。将拟合的φ曲面函数式代入本文的方程能非常简单地求出溶质的活度系数,解决了I=0端点的广义积分问题。四个体系的计算结果与Pitzer方程的结果吻合,本文的公式和计算方法还适用于溶质为非挥发性的非电解质体系。     

改进的准正规溶液模型

基于亚正规溶液模型和准正规溶液模型组合得到改进的准正规溶液模型,将正规溶液模型的参数Ω表示为浓度和温度的函数,需要2个温度下组元活度的实验数据拟合出模型的3个参数.应用该模型计算了6个全浓度二元熔渣体系,平均相对误差在5%以下,与实验数据吻合;4个存在饱和浓度的二元熔渣体系,平均偏差较大,与实验数据吻合不好,但与正规溶液模型比较,计算结果较优.     

基于自然电位的充填裂隙溶质运移特征试验研究

为精细描述充填裂隙溶质运移过程及其特征,设计加工了充填裂隙溶质运移试验模型,开展了不同流速条件下溶质运移试验,研究了充填裂隙溶质运移特征,结合不同测点自然电位(SP)实时动态监测数据,详细刻画了充填裂隙内部溶质运移过程。结果表明,在试验流速范围内,水流符合达西定律；随着流速增加,取样口处溶质峰值浓度增加,初始到达和峰值到达时间均减少。不同流速条件下,溶质运移过程中自然电位响应呈现出相似特征,均反映出溶质弥散前锋与溶质弥散峰值浓度区随水流动均呈匀速运移状态。利用峰值自然电位数据计算的水流宏观平均流速与采用溶质峰值浓度计算结果基本一致,但峰值自然电位计算流速值更接近根据流量计算平均流速,且流速越大,二者误差越小；同一流速条件下,随着溶质运移距离增加,自然电位峰值呈对数规律增加。     

对羟基苯甘氨酸硫酸盐溶解度及介稳区的测定

利用激光监视装置 ,测定了对羟基苯甘氨酸硫酸盐在水 -丙酮 -酸度溶液中的溶解度和结晶介稳区 .从分析结果可知 :随着溶剂中水的增加 ,对羟基苯甘氨酸硫酸盐的溶解度略有增加 ;酸度增加 ,其溶解度有较大幅度的增加 .溶液酸度对介稳区宽度影响较大 .最后 ,用简化的溶解度模型关联溶解度数据 ,计算的溶解度和实验值符合良好 .     

论溶液中外场对溶质扩散的协同强化作用

从液体似晶结构的“格子”理论出发,推导了有外场存在情况下溶液溶质扩散转移的动力学方程。通过与 Fick 定律形式比较,得到了有外场作用的溶液溶质扩散系数表达式,由此讨论了强化扩散传质过程中外场与化学势场的协同关系,即溶液溶质扩散传质流的大小不仅与各场强度量梯度的大小及系统的物性有关,还与外场同化学势场的配合有关。进一步分析得到:外场的引入之所以能够强化和控制溶液溶质扩散,其本质是外场的引入可对溶液的粘度产生影响,关于这一论点可由文献 [7] 的实验研究所证实,并与本文的理论研究结果一致。     

模型流体扩散系数与温度关系的分子动力学模拟

采用分子动力学(MD)模拟的方法,计算了模型流体氩及氩/氪溶液的自扩散系数和互扩散系数,及其与温度的关系.计算结果表明:对不同状态下氩的自扩散系数的计算与实验结果符合较好,误差在10%左右;采用Green-Kubo法和Einstein法计算的扩散系数相等;扩散系数与温度的关系均服从D=D0e-E/RT的关系,对Ar/Kr体系自扩散系数和互扩散系数的MD模拟结果进行拟合,得到Ar、Kr自扩散系数及互扩散系数的活化能分别为1 278 J/mol、1 340 J/mol和1 296 J/mol.     

模型流体扩散系数与温度关系的分子动力学模拟

采用分子动力学(MD)模拟的方法,计算了模型流体氩及氩/氪溶液的自扩散系数和互扩散系数,及其与温度的关系.计算结果表明:对不同状态下氩的自扩散系数的计算与实验结果符合较好,误差在10%左右;采用Green-Kubo法和Einstein法计算的扩散系数相等;扩散系数与温度的关系均服从D=D0-e E/RT的关系,对A r/K r体系自扩散系数和互扩散系数的M D模拟结果进行拟合,得到Ar、Kr自扩散系数及互扩散系数的活化能分别为1278J/mol、1340J/mol和1296J/mol.     

常压下环己烷-环己酮二元体系汽液平衡研究

为了计算多元体系的汽液平衡关系,采用改进的Rose汽液平衡釜测定常压(101.3 kPa)下环己烷-环己酮二元体系汽液平衡数据,并对数据进行热力学一致性检验,结果表明实验数据符合热力学一致性.以汽相组成的误差平方和作为目标函数,分别用Wilson方程和NRTL方程关联实验数据,得到分子交互作用能量参数,并对汽液平衡计算值与实验值进行比较,发现二者偏差较小,可以满足工程上分离设计的需要.     

苯甲醇-甲醇与苯甲醇-乙醇二元体系汽液平衡

实验测定了苯甲醇-甲醇、苯甲醇-乙醇体系在常压下的汽液平衡数据,采用Herrington法对数据进行了热力学一致性检验,结果表明所测数据符合热力学一致性.同时依据测定的汽液平衡数据计算出苯甲醇及甲醇、乙醇的无限稀释活度系数,求出Wilson活度系数模型参数,并计算了苯甲醇-甲醇、苯甲醇-乙醇体系于303.15 K的汽液平衡数据.     

25℃时MgCl_2-H_2O-酰胺(DMA、DMF、FA)体系相平衡数据的计算

本文将Pitzer电解质溶液理论应用于MgCl_2-N,N-二甲基乙酰胺(DMA)-H_2O、MgCl_2-N,N-二甲基甲酰胺(DMF)-H_2O以及MgCl_2-甲酰胺(FA)-H_2O三个三元体系,建立了活度系数关系式。通过关联相平衡数据,得到了这三个体系中的粒子相互作用参数值。并在此基础上计算了这三个三元体系的相平衡数据,取得了较好的结果。证实了Pitzer电解质溶液理论可以用于电解质和非电解质的混合体系.     

Theoretical investigations on heat transfer to H_2O/CO_2 mixtures in supercritical region

The supercritical H_2O/CO_2 mixture is the working fluid to drive a turbine in a novel power generation system with coal gasified in supercritical water. This system is promising because of zero pollution emission in contrast to the conventional coal-fired power plant. Heat transfer coefficients of the supercritical H_2O/CO_2 mixtures are important to design heat transfer devices in this system, which is similar to the role of heat transfer to supercritical water in conventional systems. However, heat transfer to supercritical mixtures has received less attention. Here, we show that the supercritical mixtures with H_2O being one of the components, have similar convection heat transfer behavior to supercritical pure fluids for temperatures and pressures above the critical point of H_2O. This phenomenon was demonstrated from two aspects. Firstly, the forced convection heat transfer coefficients of supercritical mixtures were numerically calculated using the simulation model for supercritical pure fluids and using the thermophysical properties(density, heat capacity, thermal conductivity and viscosity) of supercritical mixtures as input.The calculated results agree well with experimental data in the supercritical region. Secondly, the calculated results also agree well with the correlations for supercritical pure fluids. The mechanisms were investigated by molecular dynamics simulations on the diffusion of supercritical mixtures. These results lay the foundation for predicting convection heat transfer coefficients of supercritical mixtures and for designing heat transfer devices with supercritical mixtures as heat transfer fluids.     

废旧轮胎片体-风化料混合物压实特性的试验研究

为了推进废旧轮胎在土木工程中的应用,选择废旧轮胎片体(tire derived aggregates, TDA)与分布广且价格低的风化料混合形成混合料,并用TDA在混合料中以0~60%的掺量,通过大尺寸击实设备开展重型击实试验,研究废旧轮胎片体-风化料混合物的压实特性。试验结果表明,混合料的击实曲线与纯风化料的击实曲线有明显差异,增加废旧轮胎片体的掺量能够有效减小混合料的最大干密度,能减小混合料的最优含水率,废旧轮胎片体-风化料混合物是一种性能优良的轻质填料。根据室内试验结果,TDA掺量为20%时,混合料的最大干密度和最优含水率分别为1.865 g/cm³和6.25%;TDA掺量为40%时,混合料的最大干密度和最优含水率分别为1.600 g/cm³和4.90%,给出了不同掺量混合料击实指标建议值供设计参考。     

快速凝固FGH95合金粉末的非平衡溶质分配

测定了用等离子旋转电极雾化工艺方法生产的FGH95合金粉末颗粒的枝晶偏析,并运用显热容法计算了合金粉末颗粒快速凝固过程中的非平衡溶质分配系数．结果表明：FGH95合金粉末颗粒枝晶间富Mo、Nb、Ti元素而贫Ni、Co、W元素;随着粉末颗粒尺寸的减小,溶质分配系数远离平衡值的程度增大,枝晶偏析也明显减小．     

Effects of correlative factors on the interdendritic melt flow brought by the bulge in continuous casting slabs

The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.     

A mechanical model for three-phase permanent deformation of asphalt mixture under repeated load

On basis of the Burgers model, a new model consisting of modified dashpot and Van Der Poel model was derived from rheological and viscoelastic theory. Subsequently, triaxial repeated load permanent deformation tests of AC16 asphalt mixtures were conducted to validate this new developed model. Parameters of new developed model were obtained by a nonlinear regression analysis of test data, and then permanent strains and flow number of each mixture were calculated. The experimental results prove that the new developed model can well describe three phases permanent deformation of asphalt mixture under repeated load and it can be used for pavement mechanical analysis and rutting prediction.     

倾斜地下水含水层混合3维溶质运移数值模拟

针对不规则地下水含水层中溶质运移简化数值模拟问题,根据不规则地下水含水层特点,提出了柱体单元水头梯度平均面的概念。在水头梯度平均面的基础上,采用有限单元法推导柱体单元水平向溶质通量,而柱体单元垂向溶质运移通量则采用有限差分法进行推导,通过联合利用有限单元法和有限差分法计算柱体单元节点溶质均衡项,根据不规则柱体单元溶质均衡项计算结果,编制Fortran程序,建立倾斜地下水含水层混合3维溶质运移数值模拟模型。运用该模型模拟了不同条件下地下水中溶质运移过程,将模拟结果与解析解进行对比分析,模拟得到的溶质浓度结果正确、合理。该模型适用于倾斜地下水含水层中溶质运移模拟,具有节省计算工作量,单元剖分灵活的优点。同时,当Peclet数较大时,该模型分别在水平向和垂向采用迎风加权格式进行计算,有效地消除了边界附近出现的数值跳动现象,模型也适用于Peclet数较大的情况。     

Thermal stress and fracture temperature prediction for flexible pavement

Analytical solutions of thermal stresses in multilayered elastic system whose materials characteristics are dependent on temperature are derived by a transfer matrix and integral transformation method.The resulting formulation is used to calculate thermal stresses in the low temperature cracking problem of asphalt pavement.Numerical simulations and analyses are performed using different structural combinations and material characteristics of base course.And fracture temperatures are predicted for a given flexible pavement constructed with three types of asphalt mixtures based on the calculated results and experimental data.This approach serves as a better model for real pavement structure as it takes into account the relationships between the material characteristics and temperature in the pavement system.     

纤维增强金属基复合材料中凝固溶质偏析的数值计算方法

根据合金凝固过程中的守恒定律和传输原理,建立了纤维增强金属基复合材料在凝固过程中溶质传递的数学模型,并建立和推导了复合材料中凝固溶质偏析的数值计算方法。     

含水乙醇重整混合气层流燃烧的实验研究

利用纹影高速摄影技术,在定容燃烧弹内模拟研究了不同过量空气系数、不同成分含水乙醇重整混合气的层流燃烧特性参数,并利用CHEMKIN软件模拟计算了重整混合气的绝热火焰温度。结果表明,模拟重整混合气的层流传播速度随过量空气系数的增大而减小,随混合气中氢含量比例的增加而增加;重整混合气燃烧会降低NO、CO的排放。