Design and characterisation of a close-concentric annular reactor for kinetic studies at high temperatures

A novel annular reactor for kinetic studies at high temperature and flow conditions has been designed to keep eccentricity tolerances below 10%. In a previous work, we have shown that it is very important to keep such low eccentricity values in order to collect reliable kinetic data from this type of reactors. As proposed in this study, a modified reactor with the use of a spacer could guarantee an annular duct with low levels of eccentricity. Manufacturing tolerances or deformation effects giving rise to eccentricity can be significantly minimised when using this apparatus. The reactor has been both experimentally and theoretically characterised. Carbon monoxide oxidation was used as a model reaction under mass-transfer limited conditions revealing an eccentricity of ∼5%. With such small eccentricity levels, a concentric annular form can be assumed in the reactor analysis. Simple 1D or 2D models can therefore be inexpensively used in the evaluation of the kinetic data. Also, prior to the design of the annular reactor, a numerical investigation was carried out to clarify the effects of eccentricity, physical properties of the carrier gas and the annular aspect ratio on mass-transfer limitations. Contrary to expectations, a considerable increase in the fuel mass-diffusivity by carrier gas substitution did not change the mass-transfer rates for cases when eccentricity and aspect ratios were high.     

由1,4-萘醌催化合成1,4-二烷氧基萘-2,3-二甲腈

研究了以 1 ,4-萘醌为原料 ,通过溴代、氰化和 O-烷基化三步合成 1 ,4-二烷氧基萘 -2 ,3 -二甲腈。在溴代反应中以溴化试剂代替液溴 ;在氰化和 O-烷基化反应中以溴化十二烷基三甲基铵 (DTMAB)和聚乙二醇(PEG)作为相转移催化剂 ,并采用正交设计法考察了相转移催化剂、固体碱、反应温度等因素对反应的影响 ,其中氰化产物收率达 88.7%。     

Modeling Condensation and Evaporation on Fruit Surface

Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model.     

Analysis and Optimization Laminar Viscous Flow Through a Channel

Optimizing of laminar viscous flow through a pipe by two dimensionless values is investigated analytically. Dimensionless entropy generation and pumping power to heat transfer rate ratio are used as basis for constant viscous and the temperature dependence on the viscosity. For this matter we calculate entropy generation and pumping power for a fully developed in a pipe subjected to constant wall temperature for either constant viscosity and the variable viscosity. The variation entropy generation increase along the pipe length for viscous fluid is drawn, either the variation summation dimensionless entropy generation and the pumping power to heat transfer rate ratio are varying the fluid inlet temperature for fixed pipe length and are varying pipe length for fixed fluid inlet temperature are drawn. For low heat transfer conditions the entropy generation due to viscosity friction becomes dominant and the dependence of viscosity with the temperature becomes essentially important to be considered.     

一种蒸发式冷凝器的新型设计方法

蒸发式冷凝器设计方法的粗糙和繁琐限制其广泛应用,特别是限制其应用于民用和小型商用建筑中。针对上述问题,作者通过实验研究了蒸发式冷凝器的影响因素（进风湿球温度、最小截面风速和喷淋水量）对蒸发式冷凝器热质交换的影响。同时提出了一种新型设计方法,此方法简单,精度较高。适合工程设计、选型和生产应用。     

大伙房水库渗流监测自动化系统建设经验

介绍了大伙房输水工程重要的配套工程——大伙房水库渗流监测自动化系统的设计方法与实施过程，阐明了测位选布与工程衔接、方便系统维护与运行等问题，实现了与原观测系统的设计选点、施工建设、应用开发及数据处理过程等的配合，在保证系统原观测成果连续、设备运行稳定、与其他系统协调友好、施工过程不冲突和不重复的基础上，很好地实现了由传统监测向自动化监测的过渡。     

Charge transfer resistance of spray deposited and compressed counter electrodes for dye-sensitized nanoparticle solar cells on plastic substrates

Electrochemical impedance spectroscopy was used to determine the effective charge transfer resistances of porous dye-sensitized solar cell counter electrodes prepared by low-temperature spray deposition and compression of conductive carbon and platinized Sb-doped SnO₂ powders on indium tin oxide-coated plastic substrates. The charge transfer resistances were 0.5–2 and 8–13 Ω cm², respectively, when using 3-methoxypropionitrile as the electrolyte solvent. The manufacturing method used lends itself to produce mechanically stable and even-quality electrodes in an easy and fast manner.     

Discrete Modeling and Suggested Measurement of Heat Transfer in Gas-Solids Flows

This article presents a two-dimensional transient model for gas-solids flow and heat transfer through pipes using the coupled Computational Fluid Dynamics and Discrete Element Method approach. Numerical simulations have been conducted to examine the modification of fluid thermal structure due to the presence of particles in a pneumatic transport pipeline. Modeled results have demonstrated the key role of transversal motion of rebounding particles in the pipe cross section in altering fluid temperature. Further implementation of this modeling technique in air-drying processes is discussed and possible experimental methods for the measurement of in situ particle and fluid motion and temperature profile are cited.     

A numerical model for induction heating processes coupling electromagnetism and thermomechanics

This paper presents a mathematical and numerical model developed for coupling the various physical phenomena (electromagnetic, thermal and mechanical) taking place in axisymmetrical induction heating processes. All three electromagnetic, thermal and mechanical models are time dependent and take full account of the electromagnetic and thermal non‐linear effect especially with magnetic materials. The electromagnetic problem is discretized and solved in the workpiece, air and inductors. The heat transfer equation and the mechanical equilibrium equations are solved in the workpiece only, both using a finite element method. The mechanical model can take into account thermoelastic–plastic behaviour for the part. The model has been successfully applied to several cases of induction heating. Comparisons between numerical and experimental results show an excellent agreement. Copyright © 2003 John Wiley & Sons, Ltd.     

大庆油田助剂厂3500kt／a常减压减压塔的管道设计

简述了大庆油田助剂厂3500kt/a常减压减压塔的管道布置设计特点,体现出塔类设备的管道设计原则,并结合管道设计的经济性、安全性展开论述。