共查询到20条相似文献,搜索用时 171 毫秒
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引 言在固液两相搅拌反应器中 ,固体颗粒的运动行为直接影响到固液两相流的流体力学及传质特性 ,因此 ,近年来对固液两相体系中颗粒的运动行为研究愈来愈受到重视 .对于流体机械混合操作 ,许多情况下流动均处于湍流区域 ,涉及到多相态时 ,问题变得更为复杂 .颗粒和湍流的相互作用 ,很久以来一直是人们研究的基本问题之一[1~ 3] ,对有固体颗粒存在下液相流体速度及湍流脉动变化规律 ,也是研究人员和工程技术人员关注的重点 .现有文献中用激光测量搅拌槽内固液两相流动的数据很少 ,仅Nouri[3] 测量了六直叶涡轮搅拌槽内固液两相速度分… 相似文献
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毛细管精馏是一种分离共沸物系的新型分离技术,它利用毛细管的固-液相互作用来改变液体混合物的汽液平衡。毛细管通道内的气液两相流型在低气速时以泰勒流为主,今使用计算流体力学方法,对毛细管内泰勒流的多种影响因素,如:壁面作用、气液速率以及流体物性等进行了研究。首先考察壁面作用的影响,发现壁面粗糙度能改变气液柱形状和流场,粗糙度增大使通道内气液两相流型由泰勒流向泡状流转变,流动状态由层流向涡流转变。模拟不同接触角下的气液流动,发现壁面吸附作用在一定程度上影响气液柱长度和气液界面间的形状。通过模拟不同气液速率下的气液流动,观察气液柱长度与气液速率之间的关系。对模拟气液柱长度进行量纲分析,得到了泰勒流的气液柱长度的关联式,将该式与文献测定值进行比较,发现在一定范围内吻合较好。 相似文献
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对黄磷生产磷炉气除尘、冷凝收磷原理进行研究探讨,并介绍温度、喷淋水量及停留时间与冷凝的关系。提出生产操作控制要点,指出冷凝过程中1~#冷凝塔是收磷系统的控制重点,必须有充足的热量,避免骤冷;气液两相良好的接触是提高磷收率的保证;使喷淋水pH控制在4~6,并维持水质良好。 相似文献
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采用计算流体力学软件Fluent、简化的三维Eulerian两相流和Realizable k-e湍流模型,并结合SIMPLE算法对直径40 m的氧化铝赤泥沉降槽内的固液分离过程进行数值模拟,以得到槽内流场形态和赤泥浓度的分布规律. 通过对比计算结果和现场测试数据,并结合自定义分析评价指标,分析了有无溢流围堰和中心下料桶的不同进料方式下沉降槽的固液分离和赤泥沉降的流动规律. 结果表明,去掉沉降槽的溢流围堰后浆液的固相浓度降低84.3%;采用自吸式射流进料管,60~64 g/L固相浓度范围内的浆液在中心桶内所占体积由3.70%提高到14.36%,可有效促进中心桶内赤泥浓度分布的均匀性,提高平底沉降槽内赤泥的沉降分离效率. 相似文献
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Long Fan Nong Xu Xiyong Ke Hanchang Shi 《Journal of the Chinese Institute of Chemical Engineers》2007,38(5-6):425-433
Secondary sedimentation tanks, which are used widely in wastewater treatment, require optimization to improve wastewater treatment efficiency. The flow dynamics is an important parameter for the design of reactors. However, very little literature deals with the flow in secondary sedimentation tanks. Therefore, the flow dynamics in a secondary sedimentation tank is studied in this paper. The solid–liquid two-phase turbulent flow in the tank is modeled with the three-dimensional two-fluid model. Using computational fluid dynamics (CFD), the velocity profile and distribution of solid concentration are given. The use of different baffles in the same tank is also simulated. With the inclusion of the baffle, the distribution of the solid concentration differs greatly. The significant effects of the baffle height and baffle location on the distribution of solid concentrations are also discussed. These results provide useful information for the design of secondary sedimentation tanks. 相似文献
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Olli-Pekka Tossavainen Marko Vauhkonen Kyung Youn Kim 《Chemical engineering science》2006,61(23):7717-7729
Sedimentation monitoring is widely used to control and optimize industrial processes. In this paper we propose a novel computational method for sedimentation monitoring using electrical impedance tomography (EIT). EIT measurements consist of electric current and voltage measurements that are made on the surface of the sedimentation tank and therefore they do not interfere with the sedimentation process. The proposed computational method is based on shape estimation and state estimation formulation of the EIT problem. The sedimentation is parameterized by the locations of the phase interfaces and conductivities of the phase layers. Three different evolution models for the state parameters are considered and the state estimates are computed using the extended Kalman filter algorithm. The performance of the method and the models are evaluated using simulated data from a six electrode EIT measurement configuration. From the results a promising performance of the method can be seen. 相似文献
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运用计算流体动力学方法对中心龙卷流型搅拌槽内部流场进行数值模拟,研究了对数螺旋导流板角度、极角角度、初始半径、导流板高度对搅拌槽内流场的影响,以优化设计用于生产纳米氧化镁的搅拌槽导流板结构. 结果表明,对数螺旋导流板几何尺寸对宏观流场影响显著,当搅拌槽内径300 mm、桨叶为六直叶圆盘搅拌桨、对数螺旋导流板角度45o、极角角度60°、初始半径20 mm、导流板高度30 mm时,搅拌槽内整体流场形成2个循环流动,龙卷流效果明显,混合性能较好,并在纳米氧化镁制备实验研究中得到验证. 相似文献
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LNG接收终端的主要功能是接收、储存和再汽化LNG,并通过天然气管网向电厂和城市用户供气。通过建立接收终端各设备的动态模型,增加了必要的控制系统,对流程进行了动态仿真,针对接收终端季节调峰、卸船和储罐超压3种工况进行了案例分析,得到了以下结论:接收终端调峰期间,外输泵、罐内泵功耗变化规律与外输天然气流量变化规律一致;卸船工况主要对压缩机功耗、再冷凝器入口BOG及LNG流量有影响,整个卸船过程一般需要13 h左右;储罐超压过程中,由于压缩机负荷的调节,对压缩机功耗、再冷凝器压力、再冷凝器入口BOG及LNG流量有较大影响,整个超压事故持续时间为15.2 h;对接收终端工艺的设计和运行提出了建议。 相似文献
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With the electrical network model and object-oriented programming technique, a pressure swing adsorption (PSA) system may be decomposed to four objects: adsorbent column, tank, pressure source, and pipeline. Various flowsheets and operating patterns of PSA may be constructed with different combinations of objects and their topology. The objects are represented by class inheritance and encapsulation. The classes encapsulate the methods of setting up and solving the state equations according to the topological constraints and elemental constraints of resistor, capacitor, inductor and voltage and current sources. A PSA flowsheet may be represented with a heterogeneous list that creates the instances of the classes. The state equations are solved numerically on the basis of the polymorphic mechanism via virtual member functions in C++. A four-bed PSA process, consisting of four adsorbent columns, eight tanks, two constant pressure sources, four variable pressure sources and 30 pipelines, are simulated with the electrical network model. The simulated results agree well with the experimental data, and only 7-20 outer cyclic iterations are required to reach the cyclic steady state. The effect of the dead volume and fluid resistances in pipelines on operating results is examined. Optimal searching for the valve coefficients and operating time can suggest the corresponding suitable values to increase the experimental recovery. 相似文献
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Thomas Kleiner Michael Gottanka Alexander Stary Sebastian Rehfeldt Evangelos Bertakis Harald Klein 《化学,工程师,技术》2020,92(8):1065-1073
Stirred tanks are widely used in chemical engineering, which is why there is a large variety of different designs. Numerical fluid dynamics is therefore often used in stirred tank studies that focus on flow behavior. In this work, a generic reaction in a stirred tank is simulated using computational fluid dynamics and the temperature control of the reactor is investigated. Design-critical aspects are derived from the simulation. In addition, the simulation approach is very well suited for a reaction-specific optimization of a stirred tank. 相似文献
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对应用于聚乙烯聚合反应中的三叶后掠-HEDT组合桨的搅拌釜内流场进行了模拟研究,分析组合桨的离底距C 1、桨间距C 2以及转速N的变化对搅拌釜内流场的影响,利用PIV实验对模拟结果进行了验证;将该组合桨与三叶后掠-六直叶圆盘涡轮组合桨进行了模拟对比研究。结果表明:当桨间距与釜内径的比为0.35时,釜内桨叶间的流体流动效果最好,该条件下能够改善搅拌釜上层流体的速度分布;当离底距与釜内径的比值为0.29时,组合桨下方出现了整体的环流,有利于釜底流体的混合;桨叶转速N=90 r/min时釜内流体速度分布均匀,同时上层HEDT桨叶产生的射流方向趋于水平。两种组合桨的对比研究表明:二者流型相近,但前者搅拌功率能够得到明显降低。研究结果可为三叶后掠-HEDT组合桨在聚乙烯聚合反应釜中的工程应用提供参考。 相似文献
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通过CFD(computational fluid dynamics)方法对长期在轨运行的某型液氧贮箱内的压力、温度、气液相界面等参数进行了模拟研究。计算了该型贮箱在轨运行时的平均漏热量为6.84 W·m-2。对贮箱进行了5天的模拟计算,结果表明,贮箱上部的气枕区并不稳定;液相区存在相对高速运动的气团,削弱了液相区的温度分层,使得液相区温度基本均匀。在轨储存过程中,液相温升速率为1.18 K·d-1,压增速率为23.7 kPa·d-1。结合贮箱内气液相运动特点,建立均相模型,该模型与CFD模拟结果吻合较好,可以用来预测长期在轨运行的低温推进剂贮箱内的压力、蒸发量等参数变化。 相似文献
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利用最新流体力学软件ANSYS-CFX12.0对双层六直叶圆盘涡轮搅拌槽内流场进行了数值模拟。采用湍流模型成功的模拟了搅拌槽内的流动,并与对应实验结果进行了对比;考察了同转速,不同搅拌层间距、底搅拌层离底高度下的流场分布,给出了湍流动能分布图,对其搅拌效果的影响进行分析,为该领域研究者提供了借鉴。 相似文献