化工高等教育改革的认识与思考

1996年初 ,教育部启动了“高等教育面向 2 1世纪教学内容和课程体系改革计划”。“化工类专业人才培养方案及教学内容体系改革的研究与实践”是这次改革计划中 2 2 1项教学改革项目之一。该项目的牵头单位是天津大学 ,主持单位是华东理工大学、浙江大学和北京化工大学 ,参加单位包括大连理工大学、四川大学和华南理工大学。从 1 996年 1月召开的第1次研讨会开始 ,至 2 0 0 0年 4月召开的第 1 0次研讨会结题总结为止 ,项目组在总负责人余国琮院士领导下 ,以天津大学为牵头单位的 7所学校 ,先后有 2 0 0多名骨干教师和 80 0多名学生 ,历经 4年…     

乙醇－水－4A分子筛体系三相平衡研究

对乙醇－水－４Ａ分子筛体系的气液固三相平衡关系进行了研究．结果表明，吸附剂的加入不改变气相与主体液相间的平衡关系．给出了计算气液固（吸附剂）三相平衡关系的计算方法     

浓度驱动的Rayleigh-Bénard-Marangoni对流光学研究

利用激光作光源 ,通过光学纹影仪系统 ,系统观测了不同质量传递过程中浓度驱动的Rayleigh B啨ｎａｒｄ Marangoni对流结构 .在应用不同吸收剂的基础上 ,考查了密度梯度和表面张力梯度在RBM对流中的作用 .结果表明 ,实验过程中溶剂蒸发所导致的表面冷却和溶质吸收、解吸的热效应是影响RBM对流产生的重要因素 .在实验结果的基础上 ,定性地分析了RBM效应的观测结果 ,为进一步的理论分析提供了依据     

化工学科的发展态势与高等人才的培养

化工学科的发展态势与高等人才的培养天津大学余国琮化工学科一般是指用化学在应或化学／物理分离方法改变原料的化学组成、状态或微观结构而成为产品的一门技术科学。化工学科所涉及的领域很广，不仅覆盖了整个化学工业，而且也渗透到许多工业及技术部门，如能源、环境、...     

Schlieren Visualization of Marangoni Effect in Gas-Liquid Systems

This paper is focused on the Marangoni effect in the gas-liquid mass transfer systems. A series of experiments were conducted to observe Marangoni effect by a laser Schlieren system. Experimental investigations of the occurrence of Marangoni convection were presented. The typical polygonal patterns and even the reaching of chaotic interfacial flow were observed. The visual evidences were discussed and the characteristic time and scale of Marangoni convection were obtained approximately as 0.5 s and 1 mm according to the Schlieren images. From the perspective of hydrodynamic instability, the mechanism of the Marangoni convection was investigated. Though many external factors have influence on the interfacial instability, the local surface-tension gradient is the primary reason for the Marangoni convection. The small-scale interfacial flow increases the surface renewal rate. Consequently, due to the occurrence of the Marangoni effect, the mass transfer rate can be significantly enhanced.     

An Approach to the Estimation of the Packing Efficiency by Considering Gas and Liquid Axial Mixings

Axialmixing ,or“longitudinaldispersion”and“backmixing”interminology,isanimportantnon idealflowphenomenoncommonlyoccurringinchemicalengi neeringprocess,suchasdistillation ,absorption,extrac tion,etc.Thisphenomenonrepresentsadeviationfrompistonflowandusuallyformsaparabolicaxialconcentra tionprofilealongtheflowdirection.Theunfavorableef fectofaxialmixingisthatitdecreasesthemasstransferdrivingforcesandfinallyleadstopoorerseparationeffi ciency.Instructuredpackedtower,althoughtheaxialmixingcanbe…     

Effect of Marangoni Convection on Mass Transfer in Liquid Phase

Marangoni effectis of interestto the chemical en-gineers from both scientific and practical points ofview[1—6]. The Marangoni convection contributes tothe renewal of the interfacial surface and is capable ofincreasing the mass transfer rate, resulting in intensi-fication of separation processes such as distillation,extraction, absorption, and desorption. The theoretical studies of Marangoni instability inthe past were focused on determining the critical tran-sition point. The critical condit…     

An Approach to the Estimation of the Packing Efficiency by Considering Gas and Uquid Axial Mixings

To evaluate the influence of gas and liquid axial mixings on the separation efficiency of packed column, an approximate mathematical solution of HETP (equivalent height to a theoretical plate) under continuous operation has been proposed based on the mixing pool model. The mass transfer and hydrodynamic data of structured packing, Mellapak 350Y, obtained in a high pressure tower have been used to test the validity of the proposed model. Compared with the SRP model and the Gualito model, it is found that for high pressure distillation process the present mathematical prediction shows a mean relative error of about 10% to the experimental data,the accuracy of which is the same as that by the Gualito model but better than that by the SRP model.     

Effect of Ultrafine Particles on Flow Field and Transport Properties near the Interface Around a Moving Bubble

Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter-flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u0 is 12.6cm/s, the equivalent diameter de is 0.6cm, the mass concentration of particle is 0.2%,the average particle diameter is about 10nm and the density is 2g/cm^3. The velocity profiles of beth frontal and tail-vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, beth tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably,and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no partitles. The influences of flow field change in the presence of particles on gas-liquid mass transfer are analyzed and discussed.