THE MAXWELL-STEFAN FORMULATION OF IRREVERSIBLE THERMODYNAMICS FOR SIMULTANEOUS HEAT AND MASS TRANSFER

We consider constitutive relations for diffusion and simultaneous heat conduction in an n-coraponent non-ideal fluid mixture. Using the ideal gas treatment of Hirschfelder, Curtiss and Bird as a basis, we develop the generalization of the Maxwell-Stefan diffusion equations. The application of the second law of thermodynamics is shown to impose non-negativity constraints on the defined diffusion coefficients, D _ik The practicalusefulness of the Generalized Maxwell-Stefan formulation is demonstrated by a few examples.     

THE MAXWELL-STEFAN FORMULATION OF IRREVERSIBLE THERMODYNAMICS FOR SIMULTANEOUS HEAT AND MASS TRANSFER

We consider constitutive relations for diffusion and simultaneous heat conduction in an n-coraponent non-ideal fluid mixture. Using the ideal gas treatment of Hirschfelder, Curtiss and Bird as a basis, we develop the generalization of the Maxwell-Stefan diffusion equations. The application of the second law of thermodynamics is shown to impose non-negativity constraints on the defined diffusion coefficients, D_ik The practicalusefulness of the Generalized Maxwell-Stefan formulation is demonstrated by a few examples.     

THERMODYNAMICS OF SOLVENT EXTRACTION

ABSTRACT

The fundamental thermodynamic characteristics of aqueous electrolyte solutions and organic solutions which affect solvent extraction are summarized and the influence of metal complexation and hydration on the distribution ratios is discussed. The thermodynamics of extraction systems, including synergistic systems, is reviewed. The influence of structural aspects of the complexing extractant agents on these thermodynamic parameters is also reviewed.     

THERMODYNAMICS OF THE WATER-FOODSTUFF EQUILIBRIUM

The thermodynamic analysis of the water-foodstuff equilibrium is reviewed, showing how partial molar and integral enthalpies and entropies can be obtained and indicating how to manipulate the experimental data for this purpose. The need for accurate and precise data is stressed and one experimental approach is recommended. Experimental results of desorption of water from Granny Smith apples provide information which is consistent from the thermodynamical standpoint. It is noted that the value of monolayer thickness corresponding to a minimum in integral entropy is substantially different from the value predicted by the BET equation.     

THERMODYNAMICS OF CONCENTRATED ELECTROLYTE SOLUTIONS

A new equation is derived for the activity coefficient of an electrolyte in a liquid solvent (such as water) as a function of electrolyte concentration. This equation contains contributions from long-range electrostatic forces and from short-range attractive forces; it holds from high dilution to the solubility limit. The new equation is based upon extended Debye-Huckel theory for long-range effects and upon the local-composition concept for short-range effects. For a single-electrolyte solution, the new equation contains only one adjustable energy parameter and three other parameters that are ion-specific, not electrolyte-specific. Therefore, extension to multicomponent electrolyte solutions follows without additional assumptions. Ion-specific parameters are reported for H⁺, K⁺, Li^-, Br^- and Cl^- ions. Calculated and experimental activity coefficients are in excellent agreement for aqueous solutions of HBr, HC1, KBr, KCl, LiBr and LiCl.     

THERMODYNAMICS OF THE WATER-FOODSTUFF EQUILIBRIUM

The thermodynamic analysis of the water-foodstuff equilibrium is reviewed, showing how partial molar and integral enthalpies and entropies can be obtained and indicating how to manipulate the experimental data for this purpose. The need for accurate and precise data is stressed and one experimental approach is recommended. Experimental results of desorption of water from Granny Smith apples provide information which is consistent from the thermodynamical standpoint. It is noted that the value of monolayer thickness corresponding to a minimum in integral entropy is substantially different from the value predicted by the BET equation.     

THE IRREVERSIBLE ADSORPTION OF PLUTONIUM HEXAFLUORIDE†

The room temperature adsorption of PuF_6(g) on a solid substrate was compared to the adsorption of UF6(g) on the same surface. Significantly more PuF_6(g) was adsorbed at pressures in the range of 1.2 to 0.2torr, accompanied by the evolution of molecular fluorine. The adsorbed UF₆ was easily desorbed by reducing the pressure. Most of the adsorbed PuF₆ remained on the surface when subjected to the same treatment.     

THERMODYNAMICS OF ALKANOLAMINE+WATER SYSTEM

Design of gas treating processes requires knowledge of the vapor-liquid equilibrium behavior of the (acid gas + aqueous alkanolamine) system. The present study is focused on thermodynamics and associated nonideal behavior of binary MEA + H₂O, DEA + H₂O, and MDEA + H₂O systems, which is required to predict the vapor-liquid equilibrium of acid gases such as CO₂ and H₂S over aqueous alkanolamine solutions. Determination of binary interaction parameters and analytical prediction of infinite dilution activity coefficient, heats of solution at infinite dilution, the excess Gibbs free energy, and excess enthalpy for nonideal alkanolamine-water systems are the objectives of this study.     

SUBORDINATION OF STATIONARY PROCESSES

Abstract. Let X ={ X ( t ), t ε T ∁ R} be a ( L ₂ -) stationary process and suppose that N ={ N ( t ), t ≥ 0} is an infinitely divisible process, independent of X. Then ={ ( t ) = X ( N ( t )), t ≥ 0} is again a stationary process. In this paper, we relate the spectral properties of the original process X and the derived or subordinated process .     

尿素工艺进展

论述了国外尿素生产中几种主要工艺技术的最新进展;介绍了国外公司新技术和新工艺的开发,应用及其意义;并对我国的尿素生产技术和装置改造提出了相应的建议。     

THERMODYNAMICS OF MOISTURE SORPTION IN ALFALFA PELLETS

ABSTRACT

Experimental data on sorption isotherms of alfalfa pellets were used to determine the thermodynamic functions (differential heat of sorption, spreading pressure, net integral enthalpy and entropy) of the pellets. The thermodynamic functions were then utilized in modeling the specific heats of pellets as a function of moisture content. The estimated values of the thermodynamic functions at different moisture contents confirmed the results of an earlier study on the influence of moisture sorption on the physical integrity of the pellets. The changes in the thermodynamic properties and physical integrity were prominent when the moisture of the pellets were between 0.10 and 0.12 (mass fraction basis). Using the differential heat of sorption, it was determined that alfalfa pellets have higher affinity for moisture uptake when compared to wheat and lentils. The specific heat of the solids of alfalfa pellets had a parabolic relationship with moisture whereas the specific heat of water fraction increased linearly with moisture content of the pellets.     

THERMODYNAMICS OF MOISTURE SORPTION IN ALFALFA PELLETS

Experimental data on sorption isotherms of alfalfa pellets were used to determine the thermodynamic functions (differential heat of sorption, spreading pressure, net integral enthalpy and entropy) of the pellets. The thermodynamic functions were then utilized in modeling the specific heats of pellets as a function of moisture content. The estimated values of the thermodynamic functions at different moisture contents confirmed the results of an earlier study on the influence of moisture sorption on the physical integrity of the pellets. The changes in the thermodynamic properties and physical integrity were prominent when the moisture of the pellets were between 0.10 and 0.12 (mass fraction basis). Using the differential heat of sorption, it was determined that alfalfa pellets have higher affinity for moisture uptake when compared to wheat and lentils. The specific heat of the solids of alfalfa pellets had a parabolic relationship with moisture whereas the specific heat of water fraction increased linearly with moisture content of the pellets.     

ON-LINE MONITORING OF PAPERMAKING PROCESSES

As part of our continuing effort to improve monitoring and control in the pulp and paper industry, this work is concerned with fault detection and diagnosis in the papermaking process. It analyzes on-line data gathered from the real industrial process, investigates the cause/effect relationships, identifies latent variables responsible for paper machine operation and paper quality, and constructs multivariate control charts for more effective supervision and control. Based on multivariate statistical analysis, a new diagnosis method using the directional property of the observation residuals is also developed.     

反应精馏工艺流程的合成

反应精馏工艺是近年来倍受重视的研究领域之一,但反应精馏工艺流程的选择目前仍然靠人们的经验和实验探索．本文通过对传统化工工艺流程的理论分析,阐明了传统工艺流程与反应精馏工艺流程的相互关系,从而提出了一种反应精馏工艺流程的构成方法．     

ANALYSIS OF BATCH CRYSTALLIZATION PROCESSES

The analysis of batch crystallization processes normally requires the consideration of the time-dependent, batch conservation equations (e.g., population, mass, and energy balances), together with appropriate nucleation and growth kinetic equations. The solution of these integro-differential equations is relatively difficult, even by numerical techniques. This review outlines the advances that have been made in the experimental techniques and data analyses which can be used to study the crystallization kinetics and the crystal size distribution (CSD) in batch suspension crystallizers. Several simple and useful methods are discussed which include characterization of CSD maximum, cumulative CSD approach, SSBCR crystallizer, thermal response technique, maximum allowable growth rate, and desupersaturation curve technique.     

ANALYSIS OF BATCH CRYSTALLIZATION PROCESSES

The analysis of batch crystallization processes normally requires the consideration of the time-dependent, batch conservation equations (e.g., population, mass, and energy balances), together with appropriate nucleation and growth kinetic equations. The solution of these integro-differential equations is relatively difficult, even by numerical techniques. This review outlines the advances that have been made in the experimental techniques and data analyses which can be used to study the crystallization kinetics and the crystal size distribution (CSD) in batch suspension crystallizers. Several simple and useful methods are discussed which include characterization of CSD maximum, cumulative CSD approach, SSBCR crystallizer, thermal response technique, maximum allowable growth rate, and desupersaturation curve technique.     

溴化锂第二类吸收式热泵热力过程的Yong分析

通过计算机模拟，对溴化锂第二类吸收式热泵热力过程和热泵系统各部件进行了详细计算，提出了循环倍数、工作液浓溶液浓度、蒸发温度、冷却温度对Yong效率的影响程度。指出了Yong损失的分布，计算了Yong损系数和Yong效率。     

温度载荷对复合材料热力学性能的影响

由于复合材料内部纤维与树脂的热膨胀系数差异很大,尤其是树脂性能对温度载荷较为敏感,服役时复合材料环境的高低温变化将使其热力学性能与常温状态产生较大差异。采用Maxwell本构模型,探讨了温度变化对树脂材料本构关系的影响。假设纤维为稳定材料,即其性能不随温度变化,依据复合材料细观力学理论选择六边形代表体积元为分析对象,建立了复合材料在温度载荷下热力学的本构模型。并分别讨论了温度载荷下复合材料内部纤维体分比和纤维排列方式变化对其热力学性能的影响,实现了热-力耦合作用下复合材料的跨尺度分析。     

铌锌酸铅基陶瓷相变的热力学分析

ＰＺＮ基陶瓷在烧结过程中都要经历由焦绿石相朝钙钛矿相的转变。ＰＺＮ基陶瓷中钙钛矿相含量的多少与添加剂的种类及数量密切相关，本工作根据化学热力学理论，讨论了内应力对化学势的影响，建立了一个热力学模型，并用该模型讨论了ＰＺＮ基陶瓷在烧结时的相变过程。