On reduced modeling of mass transport in wavy falling films

In many industrial units such as packing columns, falling film reactors, etc., the liquid phase is designed as a falling film. It is well known that the mass and heat transfer in laminar wavy film flows is significantly enhanced compared to flat films. The kinetic phenomena underlying the increase in mass and heat transfer are, however, still not fully understood. For an efficient design of falling film units, computational models that account for these enhanced transport mechanisms are of key importance. In this article, we present a reduced modeling approach based on a long‐wave approximation to the fluid dynamics of the film. Furthermore, we introduce a new two‐dimensional (2D) high‐resolution laser‐induced luminescence measurement technique. Both in the numerical simulation results and in the high‐resolution 2D‐concentration measurements obtained in the experiments we observe similar patterns of high concentrations locally, especially in the areas close to the wave hump. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2265–2276, 2018     

Lattice Boltzmann simulation of asymptotic longitudinal mass dispersion in reconstructed random porous media

To research macroscopic mass transport characteristics of porous media, a lattice Boltzmann method (LBM) approach was utilized to calculate asymptotic longitudinal mass dispersion. In this study, a D2Q9 model with multi‐relaxation‐time (MRT) collision operator, which is appropriate for incompressible flow with a high Péclet number without refining the lattice, was chosen. With respect to the microstructure of porous media, random placement (RP) method was applied to obtain randomly positioned particles. Based on the exhausted numerical results presented in the study, a new correlation of longitudinal mass dispersion was established. By comparing with available experimental data in the literature, reasonable agreements are observed in a wide porosity range from 0.3 to 0.7, indicating the validity of the proposed correlation. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2770–2780, 2018     

Heat/mass transfer from a neutrally buoyant sphere by mixed natural and forced convection in a simple shear flow

Building on the work of Yang et al. in 2011, the finite difference method and the Boussinesq approximation were applied to solve the time‐dependent Navier‐Stokes, convection diffusion and continuity equations in spherical coordinates. An idealized condition, the mass transfer from a neutrally buoyant sphere in a horizontal simple shear flow with natural convection was numerically simulated for the first time in this work. In the hybrid transfer case, the outwardly spiraling streamlines enhanced the transfer process, but the counter‐gravity spiraling streamlines near the sphere hindered the natural convection and the spatial dilution action weakened the natural convection transfer process. These competing effects led to nonmonotonic behavior of the Nusselt number with Reynolds number. Results from these previously undocumented cases were summarized into correlations for predicting Nusselt numbers at finite Reynolds numbers for various Grashof and Prandtl numbers. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2816–2827, 2018     

环形分布器内变质量流动的CFD模拟研究

环形分布器是实现导热介质在列管式固定床反应器壳程均匀流动的关键部件,文中采用计算流体力学方法(CFD)对环形分布器内的变质量流动进行了模拟研究。首先计算了环形通道内的速度和静压力分布,在此基础上研究了穿孔阻力系数随开孔几何结构以及入口流体流速的变化规律。模拟结果表明:环形通道内存在较明显的速度梯度和压力梯度;随着流体不断分流,在流道内的流动速度不断减小,静压力逐渐增大。因此,需要沿流动方向将开孔直径逐渐减小,以增大穿孔阻力,从而实现流体的均布。对穿孔阻力系数变化规律的研究结果表明:穿孔阻力系数ξ与出口和主流道的流速比ui/u、厚径比δ/di和入口雷诺数Re0有关。在模拟范围内,ξ先随ui/u的增大而减小,到达一个临界值后,ξ不再随ui/u的增大而变化;δ/di对ξ影响不太明显;当Re0属于湍流范围时,ξ随Re0的变化不太明显,但是总体随Re0的增大而减小。     

撞击流微反应器气液传质研究

在T型对撞反应器的基础上,对其结构进行改进,设计了旋流锥型对撞、T型旋撞和旋流锥型旋撞(二次旋转)3种撞击流反应器。用化学吸收法测量了这几种不同结构的微反应器在气液二相逆流接触条件下平均相界比表面积α及液相吸收传质系数kL;进而分析了反应器进口结构、尺寸和流体流量等条件对传质性能的影响。结果表明:旋撞比直撞的传质系数大,二次旋撞的比一次旋撞的传质系数要大;撞击区进口尺寸越小,气液流体的流量越大,反应器的传质系数越大;液相传质系数较常规气液接触设备的至少高1—2个数量级,其传质强化的原因主要源于微反应器内相界比表面积大幅度地增加。     

聚丙烯催化剂性能评价

通过熔体流动速率和等规指数测试、扫描电子显微镜观察评价了国内外几种聚丙烯(PP)催化剂,考察了催化剂的活性、流动性、氢调敏感性等.结果表明:1#催化剂具有较高的活性,可达38.92 kg/g,且氢调敏感性和抗杂质能力较强,但用其生产的PP粉料中存在粒子开裂和大量粉末;2#和3#催化剂活性较低,但工艺可操作性好.PP粉料的粒子大小均匀、致密、粉末少;5#催化剂活性最高,但PP灰分高、细粉较多;6#催化剂聚合活性较高,但PP灰分最高、细粉含量大.     

植物性食品中氯丹残留量快速测定方法

建立用气相色谱仪法快速测定植物性食品中氯丹残留量。试样经丙酮提取,正己烷萃取,使用HP-5色谱柱分离,ECD测定。结果表明,顺式氯丹、反式氯丹与氧氯丹能够很好分离,在0．2-100pg,L线性关系良好（r≥O．999）。在2．0-10．0．g／kg的添加水平范围内的平均回收率为82．8％-94．6％,相对标准偏差为2．0％-6．5％。顺式氯丹、反式氯丹与氧氯丹该方法检出限均为0．5gg／kg。     

紫铜基体上组合电刷镀厚镍层的工艺

研究了快速镍、低应力镍刷镀时间对紫铜表面镍镀层的厚度、显微硬度及结合强度的影响。单层快速镍及单层低应力镍较适宜的刷镀时间为15～20min。采用15min快速镍与15min低应力镍交替组合刷镀镍,所得镍镀层的厚度、显微硬度及耐淬火次数分别达50μm、400HV及46次,镀层组织清晰而均匀,镀层与镀层之间、镀层与基体之间结合良好,符合理想厚镍镀层的性能要求。     

网板填料复合旋转床的流体力学与传质性能

开发了一种新型的气液接触设备——网板填料复合旋转床。常压下以空气-水物系和乙醇-水物系在网板填料复合旋转床中进行流体力学与传质性能实验,考察了气液流量和转子转速对网板填料复合旋转床压降和传质性能的影响。实验结果表明,气体流量和转子转速的增大均使干、湿床气相压降增大;液体流量的增加对湿床压降的影响不明显。回流量和转速的增加均使等板高度减少至一定值后几乎不变。网板填料复合旋转床具有通量大、效率高、压降小的特点。     

胶层厚度对双搭接胶连接接头承载力的影响分析

基于Hart-Smith对双搭接胶连接接头承载力计算公式的推导,分析了胶层最大剪应变(剪应力)和接头所承受荷载的对应计算关系;结合理论推导和试验详细分析了胶层厚度对此类接头承载力的影响,提出可以用"剥离临界值"判断剥离应力是否会导致接头破坏;以胶层最大剪应变(剪应力)与接头所承受荷载的对应计算关系为基础,结合"剥离临界值"完善了双搭接胶连接接头的承载力计算公式。