平行流列管式固定床反应器分布板的开孔规律

采用动量方程建立了平行流列管式固定床反应器管外流动模型，计算出管外压力分布和速度分布，并用角度为６０°的片状平行流试验模型加以验证，试验结果和模型计算结果取得了良好的一致性。在此基础上，研究了实现管外流动和传热均布的分布板环隙和小圆孔的调节方法。     

错流列管式反应器管间流动与传热的CFD模拟

为保证管间换热介质的均匀流动,利用计算流体力学(CFD)软件Fluent对丙烯氧化制备丙烯醛列管式固定床反应器的管间流动和传热进行了研究。通过比较CFD模拟结果与Bell-Delaware法计算结果,确认了CFD模拟的可靠性。考虑盘环型错流列管式反应器为中心轴对称的结构,采用中心角为15°的片状模型,模拟考察了不同管板环隙对管外冷却介质温度分布和流动压降的影响,结果表明,在反应器的第三块折流板缺口区域附近以及离开折流板一定高度的带状区域存在相对高温区,其位置和形状随管板环隙有明显的变化;管板环隙大小会直接影响管间的总压降和温度分布状况;综合考虑径向温差和总压降,得到了对于不同直径反应器的最优环隙尺寸。模拟结果为设计管间均匀流动的列管式固定床反应器提供了依据。     

并流列管反应器载热体流动模拟研究

针对并流列管反应器,分析管外载热体流动特性,为反应器优化提供参考。建立反应器管外流体空间数值模型,模拟湍流稳态流动特性,分析流体速度分布、速度矢量及压强分布。研究结果表明,管外流体流速分布基本均匀,采用三块分布板的设置利于管外流体的均匀分布;流体经过分布板管板间隙的速度基本一致,速度值远大于管外速度,合理设置管板间隙孔尺寸,利于流体均匀分布;流体进入反应器,压力自下而上逐渐减小,相同高度上流体压力基本一致,为反应器设计及优化提供参考。     

列管式固定床反应器流动与传热研究

本文给出了列管式固定床反应器的环形流道内的压力系数、穿孔阻力系数，平行流和错流形式的反应器管间压力分布以及温度试验结果。综合这些研究结果，可以为大型列管式固定床反应器的设计提供可靠的理论依据。     

径向流反应器流场分布的数值模拟分析

径向流反应器是一种高效节能反应器。为了深入研究四种不同流动类型的径向流反应器的流场分布特征,在验证模拟可行性的基础上,引入多孔介质模型,运用FLUENT软件对不同类型的径向流反应器内的流场进行数值模拟。在边界条件设置一定时,模拟分析四种类型径向流反应器内分流流道与集流流道间的压降沿轴向的变化程度,结果说明:离心流动的流体分布均匀度优于向心流动,П型离心的径向流反应器内部流场分布最均匀,其次是Z型离心流动、П型向心流动、Z型向心流动。     

CFD在自吸式加氢反应器流场研究中的应用

目前自吸式反应器广泛应用于二硝基甲苯加氢等多相流反应过程,但由于其内部流动十分复杂,单纯依靠实验很难得到全面准确的研究结果。为了解决这一问题,以自吸式加氢反应器为研究对象,运用计算流体力学(CFD)Fluent建立三维反应器模型,采用欧拉两相流方法,对空心叶轮自吸式反应器与双圆盘叶轮自吸式反应器内的气液两相流动特性进行了研究,将反应器内的流动可视化。在此基础上将空心叶轮反应器内的吸气特性与实验数据进行对比,验证建立的CFD模型,并对比两种反应器内的局部气含率分布与液相速度矢量图分布。结果表明:空心叶轮自吸式反应器吸气特性的模拟结果与实验结果吻合较好;对于单层桨叶自吸式加氢反应器,相同桨径的空心叶轮比双圆盘叶轮的吸气性能与气液分散性能更好。     

鼓泡床反应器流动特性的CFD研究进展

从计算模型和影响因素2个方面系统综述了鼓泡床反应器内气液两相流CFD的研究进展。介绍了与模型建立相关的多相流模型、湍流模型、相间作用力和气泡尺寸模型的选择和适用情况。总结了表观气速、液相性质、反应器尺寸、分布器和内构件等对反应器流动特性的影响。最后指出了目前存在的不足,并对其发展进行了展望。     

并流列管反应器冷却介质的流动与均布

建立了并流列管反应器管外冷却介质流动的计算模型,对不同直径反应器分流室、集流室中流体压力分布、分布板上小孔分布以及环隙孔孔径进行了研究。结果表明:随着反应器直径增大,分流室、集流室中流体压降增大,分布板上环隙孔孔径减小。过小的环隙孔间隙成为反应器加工和装配的瓶颈。增大反应器分流室和集流室高度,对反应器中心进行不布管,可降低反应器分流室和集流室中流体压降,增大分布板上环隙孔间隙。对直径较大的反应器,可同时采用在反应器中心进行不布管以及增大反应器分流室和集流室高度的方法来降低分流室和集流室中流体压降,使分布板上环形孔间隙不致过小。     

苯乙烯本体热聚合反应器——两种流动模型及操作条件的数学模拟试验

应用电子计算机对两种理想流动模型的苯乙烯本体热聚合反应器进行了初步数学模拟试验。结果表阴,理想平推流反应器优于理想混合流反应器;采用理想混合流反应器时,以2—4级串联,各级反应器体积相等为宜;两种反应器均可取各级反应器操作温度相同和首釜一次进料的操作方式。     

流动模型方法及其在化工中的应用

(续上一讲 )( 3)等温管式反应器反应转化率分布计算例 4:求例 2、例 3中等温管式反应器反应转化率分布解 :利用轴向扩散模型对例 2、例 3中等温管式反应器进行计算机数值求解 [见 ( 4 )等温管式反应器轴向扩散模型数值求解ＢＡＳＩＣ计算程序 ],可以很方便地得到其反应转化率分布。结果如图 2所示。图 2中 ,为了便于比较 ,还给出了不考虑流体返混的理想平推流模型的计算结果。反应器无因次长度Ｚ　　　　反应器无因次长度Ｚ-Ｏ -平推流模型　　　　　　 -Ｏ -平推流模型- -轴向扩散模型　　　　 - -轴向扩散模型图 2　等温管式反应器反…     

Analysis of mass transfer in parallel-flow dialyzer with internal recycle for improved performance

The internal reflux effect on dialysis through the retentate phase of a parallel-flow rectangular module is investigated. Theoretical analysis of mass transfer in the membrane devices with or without recycling is analogous to heat transfer in heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if parallel-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.     

Thermal instability of laminar natural convection flow on inclined isothermal plates

An analysis is made to deteimine the conditions marking the onset of longitudinal vortices in the laminar natural convection flow over a heated isothermal inclined plate. A linear stability theory based on Boussinesq approximation and without the conventional parallel-flow assumption for basic velocity and temperature profiles is employed in the derivation of perturbation equations. An iterative procedure employing a fourth order Runge-Kutta method is applied in the solution of the perturbation equations. A comparison between the neutral stability resuts obtained with and without the commonly used parallel-flow approximation in the stability theory of small disturbances shows that the parallel-flow assumption is an invalid one for the present problem. Solutions are obtained for Pr = 0.72, 1, 2, 10, 100, and ∞ and the critical Rayleigh number marking the onset of longitudinal vortices is found to be a rather weak function of Prandtl number. A comparison of the present neutral stability results for the inclination angles α = 20° ～ 60° with experimental data reported in the literature reveals that the theory predicts critical values which are generally two orders of magnitude lower than the experimental data.     

Heat exchanger system boundary regulation

The boundary feedback regulator design for heat exchangers with delayed feedback is developed. Counter-flow/parallel-flow heat exchanger systems described by a pair of coupled transport hyperbolic partial differential equations (PDEs) with delayed boundary feedback loop modeled by the boundary time lag are considered. The coupled transport hyperbolic PDEs and boundary delay by application of boundary transformation are transformed in the corresponding linear infinite-dimensional system utilized in the regulator design. The regulator design initially addresses a full state feedback controller realization augmented by the observer design to achieve simultaneously output exponential stabilization as well as tracking and disturbance rejection of polynomial and/or harmonic type of reference signals. The simulations studies demonstrate the proposed design for counter-flow and parallel-flow heat exchangers, two common configurations present in industrial practice.     

Hydraulic design of multitubular reactors with a heat carrier flowing in parallel to the tubes

A mathematical model of the liquid heat carrier flow in the intertubular space of parallel-flow multitubular reactors is presented. The model was verified experimentally by measurements carried out in a model multitubular apparatus of rectangular cross-section.If the design of the distributing plates in industrial reactors is based on this model, uniform heat transfer conditions may be achieved throughout the intertubular space. The uniformity of the coolant flow distribution can be quantified by a velocity uniformity index (VUI) introduced in this paper.     

Temperature transients in fixed bed heat regenerators

A numerical solution of the nonlinear distributed parameter dynamics of both parallel-flow and counter-flow fixed bed heat regenerators is presented. The effects of various operating conditions on the fluid and solids temperature transients and on the thermal efficiency of the system are investigated. The character of the response at various levels is found to depend to a large extent on the direction of the initial axial temperature gradient along the solids.     

顺流与逆流板式换热器的性能分析

以顺流与逆流两种形型的板式换热器为研究对象,通过计算热通量,换热效率,换热温差,对这两种换热器的性能进行比较分析。     

基于C++的多效蒸发设计计算程序的开发研究

从传统的试差法入手,结合C 程序语言运行速度快、符合当代软件工程设计要求等的特点,开发出运行效率高、操作方便的多效顺流蒸发过程计算程序,通过实际编程计算,程序操作简单,结果可靠。     

亚硝酸酯合成工艺及反应器选型

简述了酯化反应原理及酯化反应动力学研究进展,提出了酯化反应器应设计为填料塔或板式塔较合适;详细介绍了并流酯化反应工艺与反应精馏工艺流程,比较了两种工艺流程的优缺点及能耗:并流流程的操作弹性大,设备制造简单,但需要设计水洗及干燥设备,蒸汽消耗量大,工艺流程较长;反应精馏工艺流程短,投资减少,但反应精馏塔的设计和制造比较复杂,工艺操作条件严格。     

Effect of recycle-barrier location on membrane extraction in a parallel-flow rectangular module with internal reflux

The influence of recycle-barrier location on membrane extraction through a parallel-flow rectangular module with internal reflux has been investigated. The recycle barrier is placed in the raffinate phase to divide the flow channel into an operating subchannel and a reflux subchannel and thus, there are concurrent flow in one subchannel and countercurrent flow in another subchannel. It was found that the larger part of mass-transfer area for countercurrent-flow channel, as well as the smaller part of mass-transfer area for concurrent-flow channel, is beneficial to total mass-transfer rate. It was also noted that with the recycle-barrier location moving gradually from the centerline of the raffinate phase to create larger mass-transfer area for countercurrent-flow channel, and to decrease mass-transfer area for concurrent-flow channel, the same performance can be achieved with reducing the reflux ratio.     

Analysis of dialysis coupled with ultrafiltration through cocurrently parallel-flow rectangular membrane modules

The mass transfer for the systems of dialysis with ultrafiltration in cocurrently parallel-flow rectangular membrane modules was investigated, based on mass balances with the assumption of uniform ultrafiltration flux. Considerable improvement in separation efficiency is achievable if the effect of ultrafiltration is applied, especially for the system with low mass transfer coefficient. The enhancement in separation efficiency is significantly increased with increasing ultrafiltration flux, as well as with increasing the volumetric flow rates. Furthermore, increasing the volumetric flow rate in retentate phase is more beneficial to mass transfer than increasing in dialysate phase.