塑料TGJ型填料的流体力学及传质性能研究

在内径φ６００ＭＭ塔中，以空气－氨－水为物系，对塑料ＴＧＪ型填料的流体力学及传质性能进行了研究。获得了该填料的几何特性、泛点填料因子、压降填料因子及传质系数等有关参数。结果表明，塑料ＴＧＪ型填料具有通量大、压降低、气液分布均匀、不易堵塞及传质性能良好等优点。     

金属IMPAC-1填料流体力学与传质性能的研究

在内径为500mm有机玻璃塔中,以空气、水为物系,对金属IMPAC-1型填料的流体力学及传质性能进行了实验研究,获得了该填料的几何特性、流体力学及传质性能数据。与INTALOX DG50相比,传质性能提高近20％以上。为方便工业应用,对数据进行了关联。     

阶梯环填料层流体力学和传质性能研究

本文研究了16 mm聚丙烯阶梯环填料层的压强降和液流的分布特性,研究了液相传质性能。获得了压强降填料因子、泛点填料因子,以及液相真实传质单元高度的关联式。结果表明,阶梯环填料对液体分布的保持性能好,分散常数C值比同尺寸的拉西环大23.4％;传质单元高度比同尺寸的拉西环低20～45％。     

新型金属格栅填料的流体力学及传质性能研究

分析新型金属格栅填料结构特点,设计出锯齿型和平直型舌片的格栅单元。测定了两种格栅单元在不同排列间距下,相邻层间无旋转时的流体力学和传质性能。得出排列间距36mm锯齿型格栅综合性能最优的结论。测定其相邻层间45°旋转排列时流体力学和传质性能,结果表明综合性能优越。     

金属IMPAC—1填料流体力学与传质性能的研究

在内径为５００ｍｍ有机玻璃塔中，以空气，水为物系，对金属ＩＭＰＡＣ－１型填料的流体力学及传质性能进行了实验研究，获得了该填料的几何特性，流体力学及传质性能数据，与ＩＮＴＡＬＯＸＤＧ５０相比，传质性能提高近２０％以上，为方便工业应用，对数据进行了关联。     

塑料花环填料的流体力学及传质性能研究

本实验用空气-水-氨体系,在内径为φ600 mm的塔中,对塑料花环填料进行了流体力学及传质特性的测试。结果表明花环填料通量大、压降低、在高液体负荷下具有极好的传质性能,而且耐腐蚀、不易堵塞。实验测定的塔填料因子和传质系数有设计参考意义。     

塑料花心球填料流体力学及传质性能研究

在φ600填料塔中。用空气-氨-水系统分别对φ30、φ40花心球形填料进行流体力学及传质特性实验研究。结果表明此种填料由于各向同性,对液体有良好的分散作用,其性能与同尺寸环矩鞍相当。     

泡沫陶瓷环形填料的流体力学和传质性能

填料是化工气液传质设备中的核心组成部分,其作用主要是为气液或液液两相提供充分的接触面,强化两相间的传质或传热过程．填料的结构和性能对填料塔的技术经济指标具有决定性的影响．陶瓷填料具有耐腐蚀、价格低廉、润湿性与热稳定性好等特点．但其加工性能差,只能做成简单形状,与其他材质的填料相比,比表面积和空隙率都比较小,流动阻力大,传质性能较差,使其应用受到了一定的限制．     

塑料扁环填料流体力学及传质性能的研究

在内径φ30 0 mm塔中 ,以空气 -氨 -水为物系 ,对塑料扁环填料的流体力学及传质性进行了研究。获得了该填料的几何特性、泛点填料因子ΦF、压降填料因子ΦP及气相传质单元高度 HOG与气相传质系数 KGa,该研究结果对设计有参考价值。     

规整填料塔中离子液体吸收CO2的传质与流体力学性能

在规整填料塔中采用离子液体吸收二氧化碳气体,利用计算流体力学(CFD)软件建立可靠的数学模型,系统考察了离子液体结构及规整填料几何参数对吸收过程的传质特性和流体力学性能的影响规律。结果表明,床层压降随气体流速增大而增大,液相传质系数随液体流速的增大而增大。相同阴离子时,随着阳离子碳链长度的增长,吸收过程压降增大,同时液相传质系数减小。相同阳离子时,不同阴离子的离子液体压降大的同时传质系数也大。但离子液体的结构对压降影响不明显。离子液体筛选主要考虑传质系数和溶解度因素,但二者与离子液体结构表现出相反的规律。两种折线结构的规整填料传质性能优于传统的X型和Y型结构。     

组合环单体填料的流体力学和传质性能

本文介绍了新近研制的组合环单体填料对于汽液接触过程的流体力学与传质性能。实验表明,这种填料具有比矩鞍环填料阻力小、传质效率高的优点,可以代替鲍尔环、矩鞍环等常用填料,以取得良好经济效益。     

模拟分析绒毛运动对传质和吸收过程的强化

消化器官内壁有着多级多尺度结构且运动方式复杂,理解其在消化吸收过程中的作用对人类健康具有重要意义。着眼于人体小肠绒毛,从化学工程师的独特视角出发,建立多物理场耦合模型描述小肠绒毛运动驱动下的营养物质传递与吸收。成功应用动网格方法实现绒毛往返周期运动。同时建立分析方法,量化传质与吸收效果。模拟结果显示绒毛沿着小肠管路轴向的往返运动,可以形成两个特征涡流,有效强化绒毛间流体和外部流体的交换,减小径向传质阻力。绒毛顶部在吸收中起到了关键作用。绒毛运动周期越小,最大传质增强因子越高,吸收量越大。绒毛越高,最大传质增强因子越高,再加上吸收面积越大,总吸收量会显著提升。对于900mm高的绒毛,在运动周期为6 s情况下,传质效果比绒毛不运动时的传质效果提升超过500%。     

一种氨水垂直降膜吸收传质模型

在Harriott理论的基础上,提出一种新的垂直降膜吸收传质模型,将降膜过程中漩涡的作用点由一个几何点扩展到一个区域,将整个降膜流动过程划分为非湍流区和全湍流区.非湍流区内,波峰和波谷域采取了不同的Levich厚度处理方法.在全湍流区,对波动速度进行了修正.理论数据与氨水光管降膜吸收实验数据相比较,偏差在非湍流区不超过10%,在全湍流区不超过15%.扩散系数、Levich厚度及波动周期对传质系数的影响被表示为两个量纲1量之间的关系.     

氨法烟气脱硫SO2吸收传质系数研究

喷淋塔氨法脱硫技术被广泛应用于净化烟气的SO₂,传质系数是喷淋吸收塔重要的设计和运行参数,但目前文献中有关氨法脱硫传质系数的报道很少,还有待进一步研究。在喷淋塔中对氨法脱硫SO₂吸收传质过程进行了实验研究,结合对液滴和塔壁液膜运动的计算,得到不同实验条件下SO₂的吸收传质速率,并建立了氨法脱硫SO₂吸收传质系数表达式。该传质系数包含浆液pH、烟气流速u_g和液气比L/G等主要参数,能够反映不同pH、u_g和L/G条件下SO₂在单位气液接触面积上的传质速率。对比验证结果表明,该传质系数计算得到的SO₂吸收传质速率与实验值之间的相对误差小于±12%,二者能够较好地吻合。建立的传质系数表达式能够为喷淋塔氨法脱硫的优化设计和运行提供理论参考。     

水平管降膜吸收局部传热传质特性的数值模拟

为分析滴状和柱状流型下纯水蒸气水平管外降膜吸收过程的局部传热传质特性,建立非稳态数值模型考虑吸收过程中降膜区和管间区内液相的实际流动特征及气液两相的传质,同时对多管排区域采用实际边界条件,且考虑气液两相的传热过程。溶液的液膜Reynolds数范围为11~38。结果表明,与文献实验对比,相同流量下溶液出口浓度和温度的平均相对误差在2%以内;滴状和柱状流型下,降膜区溶液的平均浓度和温度均迅速下降,管间区先上升后下降,降膜区溶液的局部吸收速率分别约为管间区的10倍和7倍;柱状流型下降膜区的吸收速率明显小于滴状流型,管间区相差很小;吸收达到稳定后,滴状流型下溶液的平均浓度和温度变化均大于柱状流型,四排管降膜区溶液的浓度变化量依次增大,温度变化量依次减小。     

Analysis of mass transfer in a corotating disks catalytic reactor

The flow and mass transfer in a discontinuous reactor configuration consisting of a pair of corotating enclosed disks with a chemical reaction taking place at the disk surfaces have been analyzed. The calculated mass‐transfer efficiencies do not follow the expected dependence because the overall mass‐transfer process is not boundary‐layer controlled, especially at high Schmidt numbers. It has been found in all of the cases investigated that despite the fact that the reactant concentration is continuously dropping with time its spatial distribution, relative to the volume‐averaged value, becomes stationary after a short initial transient. This result implies that the mass‐transfer efficiency in the discontinuous reactor also becomes stationary and the resulting time‐independent value, , obtained either directly from calculation or from the fit of the collected results, provides a fairly good estimate of the reactor operation time needed to achieve the target reactant conversion. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1015–1031, 2015     

Influence of unsteady mass transfer on dynamics of rising and sinking droplet in water: Experimental and CFD study

Experimental and numerical investigations were conducted to study the effect of unsteady mass transfer on the dynamics of an organic droplet released in quiescent water. The situation is important and relevant to deep sea oil spill scenario. The droplet contains two components, one is heavier (immiscible) than water and other is lighter (miscible). When released, with an initial mixture density (890–975 kg/m³) lower than that of surrounding water, droplet rises in the column. The mass transfer of lighter solute component into water causes the droplet density to increase and droplet sinks when the density exceeds that of water. A mass‐transfer correlation accounting for the loss of the solute, based on Reynolds, Grashoff, and Schmidt numbers was developed. A two‐dimensional axisymmetric Computational Fluid Dynamics (CFD) model accounting for species transport was developed to emulate the experimental observations. The study also helped in identifying dominant mass‐transfer mechanisms during different stages of droplet motion. © 2014 American Institute of Chemical Engineers AIChE J, 61: 342–354, 2015     

Simulations of chemical absorption in pilot-scale and industrial-scale packed columns by computational mass transfer

A complex computational mass transfer model (CMT) is proposed for modeling the chemical absorption process with heat effect in packed columns. The feature of the proposed model is able to predict the concentration and temperature as well as the velocity distributions at once along the column without assuming the turbulent Schmidt number, or using the experimentally measured turbulent mass transfer diffusivity. The present model consists of the differential mass transfer equation with its auxiliary closing equations and the accompanied formulations of computational fluid dynamics (CFD) and computational heat transfer (CHT). In the mathematical expression for the accompanied CFD and CHT, the conventional methods of k-ε and are used for closing the momentum and heat transfer equations. While for the mass transfer equation, the recently developed concentration variance and its dissipation rate ε_c equations (Liu, 2003) are adopted for its closure. To test the validity of the present model, simulations were made for a pilot-scale randomly packed chemical absorption column of 0.1 m ID and 7 m high, packed with 1/2^″ ceramic Berl saddles for CO₂ removal from gas mixture by aqueous monoethanolamine (MEA) solutions (Tontiwachwuthikul et al., 1992 ) and an industrial-scale randomly packed chemical absorption column of 1.9 m ID and 26.6 m high, packed with 2^″ stainless steel Pall rings for CO₂ removal from natural gas by aqueous MEA solutions (Pintola et al., 1993). The simulated results were compared with the published experimental data and satisfactory agreement was found between them in both concentration and temperature distributions. Furthermore, the result of computation also reveals that the turbulent mass transfer diffusivity D_tvaries along axial and radial directions. Thus the common viewpoint of assuming constant D_t throughout the whole column is questionable, even for the small size packed column. Finally, the analogy between mass transfer and heat transfer in chemical absorption is demonstrated by the similarity of their diffusivity profiles.     

气升式内环流反应器流场及传质特性数值模拟

采用双流体模型和气液二相流体动力学理论建立了气升式环流反应器流体流动的数学模型,在此模型的基础上利用溶质渗透理论和各向同性湍流理论建立了局部液相体积传质系数数学模型。采用计算流体软件F luent对气升式环流反应器内气液二相流动状况进行模拟,模拟结果较好地解释了气升式环流反应器内的流动行为及传质特性。模拟计算值与文献实验值的吻合说明了模型的可行性。     

Multiscale modelling of mass transfer in gas jets and bubble plumes

The injection of high‐speed gas streams into liquids is common in many industrial applications, such as sparging in multiphase reactors and contacting in mass transfer devices. Modelling the fluid dynamics and associated heat and mass transfer processes in such a system is complex because it involves many governing scales and drastic changes in physical properties. In this study, one formulation of a multiscale computational fluid dynamics model is proposed to simulate the fluid dynamics and mass transfer in such systems. The model uses volume‐of‐fluid interface capturing in regions where high mesh resolution can be attained and the drift‐flux or mixture model approximation in regions where mesh resolution is too low to directly resolve interface dynamics. The model was developed to provide a tunable, automatic transition between the two modelling approaches for both fluid dynamics and mass transfer predictions. The approach was validated through a comparison with results from two published studies. In the first case, the implementation of the drift‐flux model was validated through the simulation of a dispersed gas bubble plume injected into a cylindrical tank. In the second case, the fluid dynamics and mass transfer predictions were compared to results from an experimental study involving the horizontal injection of air into a rectangular tank filled with water for the application of aeration. The results show that the modelling approach can provide a good prediction of the experimental data using only limited fitting of empirical parameters, making it applicable to a broad range of other applications.