On the mechanisms of secondary flows in a gas vortex unit

The hydrodynamics of secondary flow phenomena in a disc‐shaped gas vortex unit (GVU) is investigated using experimentally validated numerical simulations. The simulation using ANSYS FLUENT^® v.14a reveals the development of a backflow region along the core of the central gas exhaust, and of a counterflow multivortex region in the bulk of the disc part of the unit. Under the tested conditions, the GVU flow is found to be highly spiraling in nature. Secondary flow phenomena develop as swirl becomes stronger. The backflow region develops first via the swirl‐decay mechanism in the exhaust line. Near‐wall jet formation in the boundary layers near the GVU end‐walls eventually results in flow reversal in the bulk of the unit. When the jets grow stronger the counterflow becomes multivortex. The simulation results are validated with experimental data obtained from Stereoscopic Particle Image Velocimetry and surface oil visualization measurements. © 2018 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 64: 1859–1873, 2018     

Continuous emulsion polymerization of styrene in a single Couette–Taylor vortex flow reactor

The effect of the geometrical and operational parameters on the mixing characteristics of a Couette–Taylor vortex flow reactor (CTVFR) were investigated and were correlated with the same parameters by using the tank‐in‐series model. Continuous emulsion polymerization of styrene was conducted at 50°C in a CTVFR to clarify the effects on kinetic behavior and reactor performance of operational parameters such as rotational speed of inner cylinder (Taylor number), reactor mean residence time, and emulsifier and initiator concentrations in the feed streams. It was found that steady‐state monomer conversion and particle number could be freely varied only by varying the Taylor number. In order to explain the observed kinetic behavior of this polymerization system, a mathematical model was developed by combining the empirical correlation of the mixing characteristics of a CTVFR and a previously proposed kinetic model for the continuous emulsion polymerization of styrene in continuous stirred tank reactors connected in series (CSTRs). On the basis of these experimental results, it was concluded that a CTVFR is suitable for the first reactor (prereactor) of a continuous emulsion polymerization reactor system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1931–1942, 2001     

预酸化度对柠檬酸废水厌氧处理的影响

以柠檬酸废水为研究对象,研究了预酸化度对上旋流厌氧反应器处理性能的影响。研究结果表明,预酸化度对上旋流厌氧反应器系统的COD去除率、出水VFA、污泥增长量、产气量有明显的影响。随着预酸化度的提高,可以提高厌氧系统的COD去除率,降低出水VFA,增加沼气产量,但降低了颗粒污泥增长的速度。在实际工程应用中,控制预酸化度在20%~30%可以保持厌氧系统稳定高效的COD去除效果,同时保证颗粒污泥的快速增长。     

Function and effect of the inner vortex on the performance of cyclone separators

The inner vortex plays a key role in the performance of cyclone separators. To explore the function and effect of the inner vortex in cyclone separators, a series of metal rods and metal blades are inserted in the typical Lapple cyclone separator to reduce the intensity of the inner vortex. First, the changes in general performance of cyclones are measured by experimental methods after insertion of the metal rods and metal blades. The flow field and particle motion are then simulated, respectively, by means of a Reynolds stress model (RSM) and a Lagrangian particle tracking (LPT) model. The results show that when the length of the metal blades is less than the boundary between the inner and outer vortexes, that is, the outer vortex remains unchanged and the inner vortex is destroyed partly, the separation efficiency remains constant and the pressure drop significantly decreases. When the length of the metal blades exceeds the boundary, the inner vortex is completely destroyed, and the outer vortex is significantly damaged, which results in sharp decrease of both the separation efficiency and pressure drop. The results indicate that the inner vortex has a notable effect on the pressure drop and virtually none on the separation efficiency. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4508–4518, 2017     

Experimental study of the relationship between separation performance and lengths of vortex finder of a novel de-foulant hydrocyclone with continuous underflow and reflux function

To solve the blockage and defer the fouling of sewage heat exchanger, a novel de-foulant hydrocyclone with continuous underflow and reflux function was proposed. Experimental results demonstrated that the novel hydrocyclone had a remarkable behavior on separating the sand (75–250 μm) and foulant (<4 mm). The continuous underflow and reflux function could significantly improve the separation efficiency by relieving the particle re-entrainment and eliminating the air core without increasing energy consumption (<17 kPa) and split ratio (<10%) considerably. Besides, the range of optimum vortex finder length was proportional to the particle density.     

平直和柱面小翼涡发生器诱发流动特性PIV实验研究

在Re=700、攻角α=60°时,利用粒子图像测速技术(PIV)研究了矩形通道内平直和柱面小翼诱发的流动结构,获得涡发生器(VG)后1~3倍弦长距离的速度场和涡量场。结果表明,三角小翼的涡结构主要分布在斜边中心和后缘角区;梯形和矩形小翼的涡结构主要分布在前缘翼梢区域和后缘区域;此外,柱面梯形小翼中心区域的涡结构明显,影响范围最大。随着流动的进行,涡结构强度逐渐减弱,三角小翼仅维持一个主涡向下继续运动;梯形和矩形小翼也仅维持一个主涡和一个后缘角涡的结构。随着斜截角的减小,前缘和中心区域诱发高强度涡结构的能力增强,影响范围也广,而后缘角涡的影响范围较小,且与底部壁面的距离较远。     

润滑油在内插同轴交叉翼型涡产生器管内流动与传热特性分析

以润滑油为工质,采用数值方法对圆管内插同轴交叉等腰梯形涡产生器的管内流动与传热进行了数值模拟,分析了不同结构参数如扭率（T_r=3,4,5,6）、间距比（S_s/W=0.8,0.9,1.1,1.2）和基带宽度比（W_b/W=0.30,0.45,0.60,0.75）对圆管内插同轴交叉等腰梯形涡产生器的管内流动与传热特性的影响。结果表明：在相同Re下,平均Nusselt数Nu_m、二次流强度Se、强化传热因子JF均随扭率和间距比的减小而增大,而其与基带宽度比的变化没有明显规律,阻力系数f随着扭率的减小和基带宽度比的增大而增大,间距比对f的影响甚微。在相同结构参数下,JF和Se均随Re的增大而增大。在Re=50~1000范围内,相比于光滑圆管,内插不同结构参数的同轴交叉涡产生器的Nu_m增加了32.8%~208.6%,f增加了3.38~8.92倍,JF最大可达1.434。Nu_m与Se呈幂函数相关,内插同轴交叉翼型涡产生器管内的二次流强度决定了其对流换热强度。     

A review of the statistical turbulence theory required extending the population balance closure models to the entire spectrum of turbulence

The models for fluid particle breakage and coalescence due to turbulence are generally limited to the inertial subrange of isotropic turbulence and infinite Reynolds numbers. A rigorous procedure for extending the fluid particle breakage and coalescence closures to the entire spectrum of isotropic turbulence and for a wider range of Reynolds numbers can be established based on statistical turbulence theory. The modeling procedure consists of a three‐dimensional (3‐D) literature model energy spectrum for the dissipation, inertial, and energy containing subranges of isotropic turbulence, and an exact literature integral relation for determining the second‐order longitudinal structure function from the 3‐D energy spectrum. A review of the requisite statistical turbulence theory and the use of the model energy spectrum is provided, because the necessary details are not easily accessible in the chemical engineering literature and misconceptions are found in the publications of the previous modeling attempts. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1795–1820, 2016     

扁管换热器内纵向涡强度与换热强度对应关系

纵向涡强化传热技术在管翅式换热器中得到了广泛的应用。但是一直以来对纵向涡强化传热的研究主要停留在涡产生器结构参数及布置方式对换热的影响方面,文献对纵向涡强度与换热强度之间定量关系的研究鲜有报道。建立了采用纵向涡强化传热的扁管管翅换热器数值模型,采用二次流强度参数Se分析了翅片及涡产生器结构参数变化时,通道内纵向涡强度与换热强度之间的定量关系;并定量分析了通道中涡产生器引起的纵向涡强度增量与传热强化量之间的定量关系。结果表明:翅片及涡产生器结构参数变化时,Nu、Se与Re之间,以及阻力系数f与Re及Se之间均不存在定量对应关系,但Se与Nu以及ΔSe与ΔNu之间存在对应关系。这表明,在布置有纵向涡产生器的扁管管翅换热器翅侧通道内,纵向涡强度决定了通道内的换热强度。