Energy and drying time optimization of convective drying: Taguchi and LBM methods

In this study, a novel method for numerical simulation of drying is proposed and the process is optimized by Taguchi method. A 2D numerical solution is performed to analyze coupled heat and mass transfer occurring during drying of a rectangular moist object. The dryer section and the moist object are conjugately simulated where the coupled heat and mass transfer equations are solved together. The lattice Boltzmann method is employed to solve hydrodynamic, heat, and mass transfer equations. This study applied the Taguchi method to determine optimum conditions for drying so as to minimize the drying time and energy consumption. The control factors included temperature, air velocity, and thickness ratio (the moist object thickness to channel width). The following optimal conditions were obtained: temperature (T?=?60?°C), velocity (V?=?0.1 m/s), and thickness ratio (TR =0.1). The results of numerical solution are then compared to the measured data available in the literature, presenting a reasonable agreement.     

THE ANALYTICAL SOLUTION FOR A SEMI-BATCH GAS-LIQUID CONTACTOR MODEL

The time-domain analytical solution for a semi-batch gas-liquid contactor model is presented. The model assumes plug flow for the gas phase and a well mixed liquid for the liquid phase leading to a system of first-order partial differential-integral equations. It is shown that the method of characteristics combined with a transformation and the development of a special Cauchy problem leads to an analytical solution. The solution is useful for the dynamic study as well as for the experimental evaluation of mass transfer coefficients of gas-liquid contactors.     

油井传热瞬态导热函数的高精度近似解

瞬态导热函数是注蒸汽油井热采过程中分析井筒传热的关键函数。目前常用的的瞬态导热函数以及相应的近似解都忽略井筒热容等参数的影响,但在注汽时间较短时井筒热容对传热影响很明显,因此在注蒸汽初期误差较大。新的瞬态导热函数近似解是在考虑了井筒热容的瞬态导热函数的基础上建立的,可以更好地适用于注蒸汽初期。研究结果表明,新的瞬态导热函数近似解形式简单、应用方便,比传统的近似解具有更广的适用性和更高的计算精度,因此有较好的工程实用性。     

一种用于在线测量的电容层析成像图像重建算法

提出了一种新的、快速的电容层析成像算法。在分析极小范数解的基础之上针对ECT逆问题的特点对其进行改进,并利用奇异值分解定理证明这种改进的数值稳定作用,从而从极小范数解的角度解决了ECT逆问题数值解的唯一性和稳定性问题;在此基础上从最优化的角度推导出进一步提高重建图像质量的公式;数值实验表明这种改进是有效的,其图像重建时间近似LBP,然而成像质量比LBP、Tikhonov和Landweber迭代法要好。     

水煤气甲烷化多段绝热反应平衡模型的计算机求解

针对水煤气甲烷化多段绝热反应平衡计算模型,建立了“迭代循环,大小跨步,直接寻优”的数值求解方法,并给出了工业计算实例。     

TPR研究焦炭溶损反应动力学参数求解方法

提出了一种由程序升温热分析（ＴＰＲ）实验结果获得焦炭溶损反应动力学参数的方法。该方法基于数学原理和计算程序，不需将热分析得到的ＴＧ线转化为ＤＴＧ线．在ＰＣ机上可方便快捷地由ＴＧ试验结果获得动力学参数．应用实例证明了该方法的实用价值．     

A Numerical Research on Limits of the Dispersion Model

The axial dispersion in tubular reactors is frequently modeled by the dispersion model, which is an analytical solution under the assumption that the vessel dispersion number is sufficiently small. In this study, limits until which the analytical solution is valid are investigated by comparison with the numerical method. The results show that it is applied only if the vessel dispersion number is small enough and the entrance effect of the tracer is avoided. Therefore, an algorithm based on the numerical solution of the control equation of dispersion is proposed, which allows for higher vessel dispersion numbers.     

Nonlinear stress analysis in adhesively bonded single-lap joint

In this investigation, an analytical elastic–plastic solution was proposed for a single-lap joint. A ductile adhesive joint material was used as the bond material. FM-73 was utilized in the study. The influence of the bending moment was neglected in the solution. The solution was modified for shear stresses. The analytical solution was compared with the FEM solution. An ANSYS 10.0 solution was employed in the numerical solution. Both solutions were compared with each other. These two solutions produced close agreements.     

Comparison of numerical methods for the simulation of dispersed phase systems

This contribution deals with a new numerical method for an accurate and efficient simulation of particulate processes. As an example for dispersed phase systems a detailed model for crystallization processes is considered. After the model derivation, which is based solely on physical principles, different techniques for the numerical simulation of the mathematical model are discussed. State-of-the-art finite volume schemes based on the ‘method of lines’ approach are compared to the recently published ‘Space-time conservation element and solution element method’. The presented simulation results show a strong dependence on the chosen numerical method. Guidelines for a proper selection of numerical methods for the treatment of population balance based models are given.     

Laminar start-up flow in short pipe lengths

A solution method is described for the start-up flow of an incompressible Newtonian fluid in a short pipe. The complete Navier-Stokes equations are solved numerically using a fragmented control volume method. The solution procedure involves a novel approach for accommodating the time-dependent condition for pressure at the pipe inlet. It is shown that the start-up time for short pipes is less than that for long pipes, due to kinetic head development and entrance region effects. Correlations are presented for estimating the start-up time.     

注射成型缺陷的智能诊断

针对注射成型仿真软件提供的大量离散数值数据（如温度场、压力场）难于进行理解和直接用来指导模具设计的现象，提出基于知识（包括CAE仿真数据）的注射成型缺陷智能诊断方法，在阐述注射成型知识组成的基础上，描述了注射成型缺陷诊断原理、实现方法和实施框架，并以气泡缺陷为例，阐述了智能诊断的应用过程。     

超超临界锅炉流动不稳定性的形成机理及研究进展

以煤炭为主要能源的国家火电机组,尤其是煤电机组持续低负荷运行或深度调峰在未来几年将成为常态。在深度调峰过程中,机组负荷多数偏离设计工况,很有可能产生流动不稳定问题。笔者主要研究了现代机组运行的流动不稳定性形成机理及影响因素,分析超超临界机组的流动不稳定性的研究方法。按发生特性归类,流动不稳定性可分为静态不稳定性和动态不稳定性。而在超超临界锅炉系统变负荷运行过程中,主要存在密度波型流动不稳定性、压力降型流动不稳定性和热力型流动不稳定性,几种不稳定现象都影响系统的正常运行。流动不稳定性的主要影响因素包括热负荷分布、管道结构及系统流动参数等。由于分析和计算工具的发展,流动不稳定性的发生条件及其变化规律能较准确预测,大量试验及数值研究表明,热流密度越小,系统压力越大,进口节流系数越大,出口节流系数越小,则系统越趋于稳定。从管道结构上来看,加热长度越短,管道内径越大,则系统越稳定,且具有交叉连接的系统比没有交叉连接的系统和单通道系统更稳定。针对超超临界水流动不稳定性的研究,主要有试验和数值模拟2种方法。试验方法的优势在于可以有针对性地以实际物理系统为研究对象,为相应的数值模拟研究提供有价值的参考。考虑到水在超超临界压力和温度下的流动不稳定试验系统极为复杂,所需费用庞大,数值模拟就成为一种重要的研究手段,其可以借鉴成熟的两相沸腾研究成果,能够方便分析各种参数对流动不稳定性的影响规律。针对超超临界流体系统的流动不稳定性的数值模拟研究,其分析方法通常可分为频域法和时域法。频域分析方法的缺点在于不能很好地解决非线性问题,为有效解决频域分析方法非线性效应消失的问题,可通过Hopf分岔技术来确定极限环的振幅。时域法作为用于分析诸如振荡周期和混沌等非线性效应的最常用方法,结合一系列无量纲数,能在保留动态变化的同时,有效地描述亚临界及超超临界流体的流动不稳定边界。     

均布荷载作用下正交各向异性悬臂梁固端边界条件对位移的影响

本文采用Timoshenko和Goodier处理固端边界条件的两种方法,探讨均布荷载作用下正交各向异性悬臂梁固端边界条件对位移的影响。根据Lekhniskii各向异性弹性理论应力解答,推导在第二种固端边界条件下的位移分量的解析解,并在文献已有部分结果的基础上求出第一种固端边界条件下的x方向位移解析解,然后得出两种固端边界条件下的位移差别。数值算例中将得出的位移解析解与有限元数值解进行比较,两者吻合良好,然后讨论材料各向异性程度、跨高比和材料弹性主轴方向对位移差别的影响。     

聚电解质溶液分子热力学模型

<正>链状聚电解质由于是长链大分子又有很高的电荷密度,其溶液即使在极低的浓度下仍具有很强的负偏差,与Debye-Huckel理论预测的结果相去甚远。工程上使用的Manning模型认为聚离子的电荷密度有一临界值,当超过临界值时,反离子即凝聚在聚离子表面使其实际电荷密度降至临界值。Nagvekar等在该模型的基础上引入NRTL方程,以计及短程相互作用的贡献。Manning等的方法虽然有一定的物理意义,但临界值的确定缺乏可靠的根据。     

新型溶剂法制备再生纤维素纤维研究进展

再生纤维素纤维以可再生、可生物降解的天然纤维素为原料,它的研究和开发对充分利用纤维素资源和促进纤维行业的可持续发展具有重要意义.离子液体和碱溶液溶剂体系对纤维素具有独特的溶解性能,为再生纤维素纤维的制备提供了新方法.这种新型的再生纤维素纤维具有制备过程简单、对环境无污染、纤维力学性能优异或生产成本低等优点,发展前景十分广阔.综述了离子液体法和碱溶液法再生纤维素纤维的最新研究进展,包括溶剂种类及其溶解能力、纤维素原料的性质与选择、纤维的制备方法和力学性能等,同时归纳和对比了各因素对新型再生纤维素纤维力学性能的影响.最后展望了两种新型再生纤维素纤维存在的挑战、未来发展趋势和工业化前景.     

激光光谱法同步测量尿素水溶液液膜厚度与浓度

对尿素水溶液液膜厚度和浓度进行定量分析在工业应用中至关重要,而传统的测量方法只能对液膜厚度和浓度分别进行测量。提出了一种用于尿素水溶液液膜厚度和浓度高精度同步在线测量的新方法。通过灵敏度分析和内部交叉验证,选取了测量精度及灵敏度最高的一对波长组合(7040.75 cm^-1 与 6761.00 cm^-1)。由内部交叉验证可知,该方法测量液膜厚度误差小于1.40%,浓度误差小于5.76%。     

Part I: Dynamic evolution of the particle size distribution in particulate processes undergoing combined particle growth and aggregation

The present study provides a comprehensive investigation on the numerical problems arising in the solution of dynamic population balance equations (PBEs) for particulate processes undergoing simultaneous particle growth and aggregation. The general PBE was numerically solved in both the continuous and its equivalent discrete form using the orthogonal collocation on finite elements (OCFE) and the discretized PBE method (DPBE), respectively. A detailed investigation on the effect of different particle growth rate functions on the calculated PSD was carried out over a wide range of variation of dimensionless aggregation and growth times. The performance (i.e., accuracy and stability) of the employed numerical methods was assessed by a direct comparison of predicted PSDs or/and their respective moments to available analytical solutions. It was found that the OCFE method was in general more accurate than the discretized PBE method but was susceptible to numerical instabilities. On the other hand, for growth dominated systems, the discretized PBE method was very robust but suffered from poor accuracy. For both methods, discretization of the volume domain was found to affect significantly the performance of the numerical solution. The optimal discretization of the volume domain was closely related with the satisfactory resolution of the time-varying PSD. Finally, it was shown that, in specific cases, further improvement of the numerical results could be obtained with the addition of an artificial diffusion term or the use of a moment-weighting method to correct the calculated PSD.     

Nonlinear Analysis of theTorque Transmission Capability of Adhesively Bonded Tubular Lap Joints

Calculated torque transmission capability of adhesively bonded tubular lap joints using linear elastic material properties is usually much less than the experimentally-determined one because the majority of the load transfer of the adhesively bonded joints is accomplished by the nonlinear behavior of rubber-toughened epoxy adhesives.

Although the adhesively bonded tubular double lap joint has better torque transmission capability and reliability than the single lap joint, the nonlinear analytic or numerical analysis for the adhesively bonded tubular double lap joint has not been performed because of numerical complications.

An iterative solution that includes the nonlinear shear behavior of the adhesive was derived using the analytic solution. Since the iterative solution can be obtained very quickly due to the simplicity of the algorithm, it is an attractive method of designing adhesively bonded tubular single and double lap joints.     

用于燃煤烟气除湿消白的湿电平板降膜模拟及试验研究

为了节省电厂空间,提高设备集成应用,提出了一种溶液除湿与湿电相结合的工艺,使用除湿溶液在阳极板布膜,同时实现除尘与除湿功能。通过湿电平板降膜除湿过程的数值模拟与试验,探究了烟气及溶液参数对水热回收性能的影响。结果显示数学模型能够较好地反映该过程,试验工况下湿电平板降膜最高水、热回收率分别可达37.5%和35%,水蒸气所释放的汽化潜热大部分转移到溶液。除湿过程对于湿电除尘效果几乎没有影响,通过焓湿图分析及可视化比较证明,湿电平板降膜除湿可以实现白烟的削弱甚至完全消除。     

On a numerical relaxation method for a chemical reaction-diffusion problem with an instantaneous and irreversible reaction

In this paper we deal with a numerical method for a free boundary value problem in 1D, describing a chemical diffusion problem accompanied by an irreversible and instantaneous reaction which gives rise to a moving internal boundary. Basically, the method consists of four steps: (1) a Landau transformation mapping each of the 2 time varying intervals on a fixed domain, which results in a strongly nonlinear boundary value problem; (2) a central difference method with respect to the space variable, that takes properly into account the various transition conditions; (3) the construction of an ODE containing a relaxation parameter ε to represent the movement of the internal boundary; (4) a time integration of the resulting stiff system of ODEs by suitable computer packages. The numerical method is evaluated by comparison with an analytical solution for a special but nontrivial case, and by a mass-balance argument. The presented method can be extended to the case of several irreversible and instantaneous reactions.