Experimental study of NiO electrical conductivity changes under low oxygen pressures

The electrical conductivity of NiO was measured at 740°C in an oxygen pressure range of 10^–2 –1.3 Torr. By means of continuous recording, longtime experiments were performed. The results show that for any admittance of oxygen, the electrical conductivity initially increased and then decreased to its initial value. For pressures higher than 0.1 Torr the decrease of the signal was reduced and the time required to attain the initial value sometimes reached several days. These results suggest that the electrical conductivity changes may be considered as a transitory phenomenon connected to attaining gassolid equilibrium.     

基于电容层析成像和模糊模式识别的油气两相流流型辨识新方法的研究

基于电容层析成像和模糊模式识别技术别提出了一种油气两相流流型辨识的新方法。建立了12电极电容层析成像流型自动识别系统，该系统利用Tikhonov正则化原理并结合SIRT(Simultaneous Reconstruction Techniques)算法进行图像重建。Tikhonov正则化原理用于克服图像重建过程中的不适定问题，SIRT算法用于提高最终重建图像的质量。根据流型的随机和模糊特性，提出了一种根据管截面重建图像进行流型辨识的模糊流型判别方法。研究结果表明，提出的流型辨识新方法是有效的。对于层状流、核心流、环状流、均相流等流型，流型辨识的准确率高于95％，辨识一个流型所用的时间小于0.3秒。对于塞状流，流型辨识的准确率高于90％。     

微通道中两相流压降与传质的研究

以氮气和水为实验体系,采用均质混合模型,研究微混合器的微通道中两相流通过微通道的压降,并测定了两相流的传质系数.结果表明,微通道当量直径为95.2 μm,气体速率为1.089～4.355 m/s,液体速率为0.006 41～0.170 90 m/s的条件下,均质混合模型计算压降值与实测值吻合良好.气速为1.633～3.484 m/s,液速为0.025 6 m/s时,随着气速增加,传质系数呈递增的趋势.气速为1.633～3.484 m/s,液速为0.019 2 m/s时,随着气速增加,传质系数先增加后降低然后再增加.传质系数对液速变化更为敏感.     

A computational investigation of non-isothermal gas-solid flow in a U-bend

The non-isothermal gas-solid flow through a U-bend of a pneumatic conveying dryer system is calculated using the commercial CFD program Fluent 6.1. Steady-state, incompressible and non-isothermal gas-solid flows are employed to simulate the cases. Variables studied include: particle diameter, particle density, solid loading ratio, feed gas temperature, heat flux through the wall, gas velocity and bend radius ratio on heat transfer phenomena between gas and solid particles. Validation is done by comparing calculation results with the available experimental data provided by Baughn et al. [J.W. Baughn, H. Iacovides, D.C. Jackson, B.E. Launder, Local heat transfer measurements in turbulent flow around a 180° pipe bend, Journal of Heat Transfer 109 (1) (1987) 43-48] and Depew and Farbar [C.A. Depew, L. Farbar, Heat transfer to pneumatically conveyed glass particles of fixed size, Journal of Heat Transfer 85 (1963) 164-172].In general, data validations of both cases show good agreement. The gas temperature decreases and the solid temperature increases along the axial direction of the pipe due to transfer of heat from the gas phase to the solid phase. The gas temperature decreases significantly at the outer bend wall due to an accumulation of particles, which causes much more energy to be transferred from the gas to solid phases. At the inner bend wall, the gas temperature decreases slightly but the solid temperature increases significantly due to a low concentration of particles. A U-bend significantly increases the local and area average Nu numbers, but not the mass average Nu number. The slip velocity and particle distribution are the major factors influencing the value of the mass average Nu number.     

Boundary layer model for char combustion and gasification

A non-steady boundary layer model is developed for numerical simulation of combustion and gasification of a single shrinking char particle. The model considers mass and energy conservation coupled with heterogeneous char reactions producing CO and homogeneous oxidation of CO to CO₂ in the boundary layer surrounding the char particle. Mass conservation includes accumulation, molecular diffusion, Stefan flow and generation by chemical reaction. Energy conservation includes radiation transfer at the particle surface and heat accumulation within the particle. Simulation results predict experimentally measured conversion and temperature profiles of a burning Spherocarb particle in a laminar flow reactor. Effects of bulk oxygen concentration and particle size on the combustion process are addressed. Predicted particle temperature is significantly affected by boundary layer combustion of CO to CO₂. With increasing particle size, char gasification to char combustion ratio increases, resulting in decreasing particle temperature and increasing peak boundary layer temperature.     

［Bmim］BF4-H2O-Na2CO3离子液体双水相体系液液相平衡数据的测定与关联

用浊点法测定了四氟硼酸1-丁基-3-甲基咪唑—水—碳酸钠体系在常压30℃下的溶解度曲线及密度曲线，并用经验方程进行了关联。用浊点—密度法测定了该体系的液液相平衡数据，绘制了相应的相图。结果表明：双水相体系一相以离子液体和水为主，碳酸钠的含量很少，另一相以碳酸钠和水为主，离子液体的含量很少。该体系既可作为萃取分离体系，也可作为从水溶液中分离回收离子液体的初步体系。用Othmer-Tobias+Bancroft经验方程对相平衡数据进行关联，最大相对误差为94.99%， 最大平均相对误差为15.69%，关联结果不理想。提出用Othmer-Tobias经验方程+溶解度方程对其进行关联，最大相对误差为4.52%，最大平均相对误差为2.77%，关联精度较高，该方法可适用于有一组分含量较低的体系的液液相平衡的关联计算。     

CONDENSING HEAT TRANSFER IN AN ADVANCED TWO-PHASE CLOSED THERMOSYPHON

1 INTRODUCTIONClosed thermosyphon has been developed to enhance heat transfer and recover wasteheat in various process industries [1,2].Stimulated by this success,a new type oftwo-phase closed thermosyphon was designed by inserting respectively two inner tubesinto the thermosyphon,one in the boiling section and the other in the condensing sec-tion.The two-phase flow boiling heat transfer coefficient was calculated successfully onthe basis of Chen's dual-mechanism [3].A boiling heat transfer model for thetwo-phase closed thermosyphon with an inner tube in the boiling section was pro-     

旋风分离器两相流研究综述

综述了旋风分离器内部流场、颗粒运动和数值计算模型的理论研究发展历程。     

A Numerical Sirnulation of Gas-Particle Two-Phase Flow in a Suspension Bed Using DifFusion Flux Model

A mathematical modei of two-dimensional turbulent gas-particle twophase flow based on the modified diffusion flux modei (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux modei, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by k-ε-kp two-fluid modei, which shows a reasonable agreement. It is confirmed that the modified diffusion flux modei is suitable for simulating the multi-dimensional gas-particle two-phase flow.     

高矣物的特性对双水相相图和头孢氨苄及7-ADCA分配行为的影响

A series of ethylene oxide(EO)-propylene oxide (PO) random co-polymers (EOPO) were used to form aqueous two-phase systems (ATPS) with ammonium sulfate.Effects of EOPO′s properties on the phase separation behaviors and on the partition of cephalexin and 7-aminodesacetoxicephalosporanic acid(7-ADCA) in ATPS were investigated.Both the molar mass and molar ratio of EO to PO of EOPO could greatly influence partition behaviors of cephalexin and 7-ADCA as well as the binodal curve of ATPS. With the increase of molar mass of co-polymer or the decrease of molar ratio of EO to PO,the critical point of ATPS decreased,the binodal curve became more asymmetry,and both cephalexin and 7-ADCA followed the same tendency to partition into the polymer-poor bottom phase.The experimental results shows that it is feasible to partition cephalexin and 7-ADCA in either the polymer-rich top phase or the polymer-poor bottom phase by choosing a specific phase-forming EOPO.