POLARIZATION BEHAVIOR OF PACKED-BED ELECTRODES: A COMPARATIVE STUDY OF EXPERIMENTAL AND MODELING RESULTS

The current distribution and overall polarization behavior of electrodeposition at a flow-through (packed bed or fluidized bed) electrode are modeled by means of a one-dimensional model involving a primary reacting species and a simultaneous side reaction. The model equations are solved by orthogonal collocation; the time and storage requirements compare favorably to those of finite-difference methods. Experimental data obtained using a packed-bed electrode are compared with the model predictions and various methods of fitting the data are compared.     

THE INDIRECT ELECTROCHEMICAL DESTRUCTION OF DILUTE CYANIDE SOLUTIONS BY PACKED-BED ELECTRODES

The indirect oxidation of cyanide at low concentrations was investigated experimentally with packed-bed electrodes. Experiments were performed by electrolyzing at various applied current densities, NaCI additions, initial pH values and flow rates. The performances of the cyanide oxidation in flow-by and flow-through electrodes were also examined. Cuprous ion was found to have an effect of accelerating the indirect cyanide destruction. A small amount of CO from the gaseous products of the cyanide electrolysis was also detected by gas chromatography in this work. An apparent rate equation with packed-bed screens best fitted by linear regression was also proposed in this study.     

A UNIFIED COLLOCATION ALGORITHM FOR PACKED-BED CHEMICAL REACTOR SIMULATION

Mathematical models of packed-bed catalytic reactors are aimed to predict the conversions and temperature profiles in both fluid and solid phases within the reactor. Although very general models can be mathematically formulated, usually several simplifying hypothesis are introduced for the fluid phase and/or the solid phase, in order to overcome computational difficulties

We describe in this paper a computational algorithm based on Orthogonal Collocation Method on finite elements, with elimination of the knot unknown functions, coupled with an integration method for stiff ordinary differential equations. This has been used in the development of a computer code, which allows us to find the transient behavior of the reactor by solving the equation relative to the external field, coupled with those describing the transient behavior in the catalyst particles, for a wide class of reactor models. The most general examined model includes axial dispersion in the external fluid phase, interphase mass and heat transfer resistances, intraphase mass resistance and any given kinetic scheme with complex reaction rate expressions.     

NUMERICAL MODELING AND EXPERIMENTAL STUDY OF PARTICLE-LADEN COAXIAL JETS

The structure of turbulent, dilute, particle-laden, coaxial jets, injected into a still environment, was studied both theoretically and experimentally. A new stochastic particle dispersion model (Fluctuation-Spectrum-Random-Trajectory model) was used to predict the particle motion and particle dispersion in turbulence. At the same time, the jet properties were measured by means of a Malvern Laser Diffraction Instrument and a computer-controlled, color-changeable, high speed, stroboscopic photography (CCHSP) system. The predictions of the mean flow properties of the two-phase and of the particle concentration distributions showed good agreement with the experimental data. Finally, a number of predictions of the behaviour of particle-laden, coaxial jets were performed and obtained satisfactory results. The characteristics of the particle-laden, coaxial jets were described.     

气—固多相同轴射流的数值模拟和试验

本文提出了一个新的气-固多相湍流运动的模型(脉动频谱随机颗粒轨道模型),它计及了湍流涡团对颗粒扩散作用,并通过体平均方法求出颗粒的速度场和浓度场。同时建立了气-固多相射流试验台,采用激光衍射仪、高速变色频闪摄影法等对气-固多相同轴射流进行了实验研究。实验和上述模型模拟的结果吻合较好。     

氧化锆电池中金属电极的极化及活化处理

用铂浆和银浆通过涂覆、焙烧工序在ZrO2电解质片上制备铂和银电极,在400－600℃、大气条件下用“三电极”法测取了这些电极的极化曲线,发现Pt,Ag电极有近乎相同的极化规律,Ag电极的极化倾向大于Pt电极。采用电化学方式对上述电极进行活化处理,使电极的极化倾向大为降低,Ag电极的活化效果大于Pt电极,并将电极活化归结为ZrO2电解质表面的部分还原。     

GFRP筋与橡胶混凝土粘结性能试验研究

为了研究GFRP直径、橡胶取代率及立方体抗压强度对GFRP筋橡胶混凝土粘结性能的影响,按照CSA标准设计了15组标准粘结试件。抗拔试验结果表明:拉拔试件的破坏形态大多为拔出破坏;GFRP直径、橡胶取代率及立方体抗压强度对粘结强度均有影响,其中粘结强度随GFRP筋直径的增大而下降,随橡胶取代率的增加而下降,随立方体抗压强度的增加而提高。     

GFRP筋与再生混凝土粘结性能试验研究

为了系统研究GFRP直径、再生混凝土粗骨料取代率、立方体抗压强度及劈裂强度四因素对GFRP筋再生混凝土间粘结性能的影响,按照CSA标准设计制作了12组标准粘结试验并进行抗拔试验。试验结果表明,再生混凝土粗骨料取代天然骨料对粘结破坏形态影响不大,破坏形态以拔出破坏为主;但平均粘结强度随着再生混凝土粗骨料取代率的增大而下降;立方体抗压强度、劈裂强度两者对平均粘结强度的影响较为相似,均显示出随强度下降而下降的趋势;由于剪力滞后的影响,平均粘结强度随GFRP筋直径的增大而下降。     

用锦西焦加CGG针焦生产Ф450mm高功率石墨电极

分析了锦西焦与CGG油系针状焦的特性；以锦西焦为主加CGG油系针状焦为原料，生产Ф450mm高功率石墨电极，并对其生产过程中的工艺进行控制。结果表明：用锦西焦为主加CGG油系针状焦生产Ф450mm高功率石墨电极是完全可行的。     

医用微型玻璃电极的结构与特性

医用微型玻璃电极采用固体可逆接触式结构 ,直径 2mm ,长约 7～ 8mm。电极用于测定人体胃液pH值与电位差 ,可诊断胃病与早期发现胃癌。研究了微型玻璃电极敏感玻璃膜的成分与性质 ,在Li2 OLa2 O3SiO2 系统中加入摩尔分数为 2 %的Ta2 O5可提高敏感玻璃的耐水性与电导率。电极在 pH值为 1～ 9范围内具有良好的Nernst响应性 ,而且重现性和稳定性均比较好。电极的酸误差较小 ,电势随时间的漂移率约为 1.5mV/h。对 2 5只大白鼠胃液的 pH值和电位差进行测定 ,测得大白鼠胃液的pH值范围为 2～ 5。与PB 2 0型SartoriusAG酸度计所测的pH值相比较 ,得知此种电极的平均偏差较小 ,约为± 0 .2。人体正常胃液酸度范围的pH值为 2～ 3 ,由此判断电极用于人体胃液的测定是可能的。     

新颖填充床光催化反应器的辐射能分布模拟

采用以玻璃弹簧为载体的新颖负载型光催化剂 ,设计实验测试该催化剂的辐射能分布状况 ,通过实验测量修正双通量模型的参数 ,并使用修正双通量模型进行计算 ,上述实验值与理论计算值吻合较好 ,说明修正双通量模型可准确模拟多相光催化反应器的辐射能传递行为 .最后 ,采用该模型描述了由此负载型催化剂构成的平板式填充床光催化反应器内的辐射能分布和吸收状况     

电化学反应器中析气电极的电流分布模型及实验研究

根据质量平衡和槽电压平衡原理,提出了析气电极电流分布的数学模型.在理论分析中应用了改进的Bruggman公式和电极遮盖度系数.采用微机控制的电位测量系统和组合电极实测了电流分布规律及其影响因素.结果表明,模型计算值与实验值能良好地符合.     

非恒温非绝热固定床反应器非均相模型及其求解

非恒温非绝热固定床反应器广泛应用于强放热的反应体系,由于传热、传质阻力的存在,使得流体中的温度、浓度和催化剂表面处不同,按拟均相二维模型求得的结果和实际情况存在较大的偏差。为此利用分层次的反应器建模思想,建立了非恒温非绝热固定床反应器的非均相二维模型,并用正交配置法对该模型进行了求解,示例给出了萘氧化成邻苯二甲酸酐的模拟结果。     

GFRP圆柱抗侧向弯曲性能试验研究

通过3根GFRP空心圆柱和3根GFRP-混凝土实心柱构件的侧向受弯试验,得到各试件的荷载-位移和荷载-应变关系曲线以及极限荷载。试验结果表明,随着纤维纵横向铺层比例的提高,空心构件的极限承载力以及抗弯刚度均有所提高,而实心构件仅增大极限承载力,但对抗弯刚度影响不大;长径比越小,空心和实心构件的极限承载力和抗弯刚度均增大,且实心构件相比于空心构件的承载力增长幅度较大。     

DRYING OF BIOLOGICAL PRODUCTS WITH SIGNIFICANT VOLUME VARIATION. EXPERIMENTAL AND MODELING RESULTS FOR POTATO DRYING.

ABSTRACT

This work is devoted to the experimental investigation and theoretical modeling of biological products with high initial moisture content which implies significant volume contraction. Firstly, experimental equipment which was designed to continuously determine variations in the global moisture content and in the temperature of the sample is introduced. Furthermore, the equipment is controlled by a PC which records experimental information in real time. In particular, measurement of the radial and temporal distributions of moisture content and temperature during the drying process of the homogeneous porous media potato are given. The mean moisture content and temperature curves are also given.     

DRYING OF BIOLOGICAL PRODUCTS WITH SIGNIFICANT VOLUME VARIATION. EXPERIMENTAL AND MODELING RESULTS FOR POTATO DRYING.

This work is devoted to the experimental investigation and theoretical modeling of biological products with high initial moisture content which implies significant volume contraction. Firstly, experimental equipment which was designed to continuously determine variations in the global moisture content and in the temperature of the sample is introduced. Furthermore, the equipment is controlled by a PC which records experimental information in real time. In particular, measurement of the radial and temporal distributions of moisture content and temperature during the drying process of the homogeneous porous media potato are given. The mean moisture content and temperature curves are also given.     

电极隧道窑二次焙烧温度曲线的实验研究

为了得到最佳电极隧道窑二次焙烧曲线,对二次焙烧的工艺参数———最高气相温度及初始段升温速率进行了实验研究。结果表明,最佳工艺参数：初始温度为２８０℃,最高焙烧温度为７６０℃,６００℃之前的平均升温速率在０９℃／ｍｉｎ,降温速率不大于７℃／ｈ;并给出了理想的二次焙烧曲线     

HOT AIR AND MICROWAVE DRYING OF ONIONS: A COMPARATIVE STUDY

This comparative study of conventional (hot air) drying and microwave drying of the onion was carried out on a hot air pilot plant drier for conventional drying where all characteristics (temperature, humidity, and velocity) could be adjusted and controlled. A data logger connected to a computer captured all data. And for microwave drying, a drying tunnel Fitted with a forward/backward movement was used. Mass loss and product surface temperature were monitored for both processing. Factors controlled where: frequency of movement, microwave power, air extraction rate. Other elements included shape (slices/pieces) and variety of product

Drying duration and maximum drying rate constituted comparative criterion for the processes. Quality was measured by the reducing sugars and polyfructans content. Analysis of variance for the microwave drying process suggests that the effective factors were microwave power followed by onion variety and shape respectively. For quality criterion by far the most effective was variety, followed by the interaction of shape and the forward-backward movement of the conveyor. For conventional drying the most effective factor was air temperature for drying duration, and variety for maximum drying rate.     

不同外形GFRP变形筋的粘结性能试验比较

GFRP变形筋的外形是影响GFRP筋与混凝土粘结性能的重要因素。本文利用拔出试验研究8种不同外形的GFRP变形筋与混凝土之间的粘结性能,比较了不同外形的GFRP变形筋的粘结强度。试验结果表明,GFRP变形筋的粘结强度较高,最佳肋间距不应超过直径的2.5倍,肋高度应不小于直径的3%。     

HOT AIR AND MICROWAVE DRYING OF ONIONS: A COMPARATIVE STUDY

ABSTRACT

This comparative study of conventional (hot air) drying and microwave drying of the onion was carried out on a hot air pilot plant drier for conventional drying where all characteristics (temperature, humidity, and velocity) could be adjusted and controlled. A data logger connected to a computer captured all data. And for microwave drying, a drying tunnel Fitted with a forward/backward movement was used. Mass loss and product surface temperature were monitored for both processing. Factors controlled where: frequency of movement, microwave power, air extraction rate. Other elements included shape (slices/pieces) and variety of product

Drying duration and maximum drying rate constituted comparative criterion for the processes. Quality was measured by the reducing sugars and polyfructans content. Analysis of variance for the microwave drying process suggests that the effective factors were microwave power followed by onion variety and shape respectively. For quality criterion by far the most effective was variety, followed by the interaction of shape and the forward-backward movement of the conveyor. For conventional drying the most effective factor was air temperature for drying duration, and variety for maximum drying rate.