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提出了计算多孔催化剂颗粒有效因子的区域分割法,将整个一维区间划分为几个子区间,然后在每个子区间内用一点配置法求解非线性扩散-反应问题.采用区域分割法,针对三种不同形状的催化剂颗粒,对幂函数型动力学方程和双曲型动力学方程进行了大量的计算.所得的计算结果与正交配置解吻合.区域分割法的优点是使用简便、计算快速.采用区域分割法还可以计算催化剂颗粒死区半径,所得计算结果合理. 相似文献
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目前对篦冷机熟料多孔介质的研究多采用渗流传热理论,通过达西定律与传热方程联立求解,但模型求解过程复杂,不便于工程应用。本文将圆形截面直管换热理论引入到篦冷机熟料多孔介质单元体的研究中,建立了水泥熟料颗粒大孔隙多孔介质单元体直管等效换热模型。通过直管换热理论的方法和思想求解水泥熟料多孔介质的换热过程,以达到降低求解难度的目的。在保证计算精度的前提下,求解出熟料颗粒与流体温度随时间变化的表达式,利用自主设计实验设备进行实验,实验数据与模型计算结果基本吻合,从而验证了直管等效换热模型的可行性。 相似文献
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目前对篦冷机熟料多孔介质的研究多采用渗流传热理论,通过达西定律与传热方程联立求解,但模型求解过程复杂,不便于工程应用。本文将圆形截面直管换热理论引入到篦冷机熟料多孔介质单元体的研究中,建立了水泥熟料颗粒大孔隙多孔介质单元体直管等效换热模型。通过直管换热理论的方法和思想求解水泥熟料多孔介质的换热过程,以达到降低求解难度的目的。在保证计算精度的前提下,求解出熟料颗粒与流体温度随时间变化的表达式,利用自主设计实验设备进行实验,实验数据与模型计算结果基本吻合,从而验证了直管等效换热模型的可行性。 相似文献
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将杂多酸、固体酸、磺酸等负载于各种多孔材料上制成负载型催化剂以替代传统的硫酸催化剂,对多孔材料负载型催化剂催化酯化反应的研究进展情况进行了综述;并对多孔材料的选择和负载型催化剂的发展进行了展望。 相似文献
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本文旨在建立和求解DMFC多孔阳极甲醇氧化宏观动力学理论数模。根据Pt-Ru催化剂上双位机理,得到包含CO和OH覆盖率的甲醇水解本征动力学表达式;通过对该多孔阳极微元体积中的物料和电(荷)量衡算,导出了描述电极中浓度和超电势分布的两个耦联的模型方程。经量纲1化后,获得以量纲1变量和准数表示的普遍化宏观动力学数模。该模型包括催化层厚度l、比表面积a、有效扩散系数De和有效液相电导率κe等工程参数,特别是包括了与动力学参数相关且作为厚度变量函数的CO和OH覆盖率。进而,文中还给出了DMFC多孔阳极效率因子和极化曲线的计算公式。该数模为一非线性二阶微分方程组边值问题,经解耦,可得到两个同解的微分方程。用Newman的BAND(J)程序对方程进行数值求解,并在每一节点计算中嵌入一个计算CO和OH覆盖率的子程序。将模型预测值与甲醇氧化多孔阳极的极化实验数据进行对比发现:当宏观电流密度较低时二者能很好相符;当宏观电流密度较高、CO2形成气泡的影响变大时,实验值有规律地偏低于预测值。详细的宏观动力学分析表明:提高催化剂Pt位甲醇电分解活性以减少功率损失、优化多孔电极微观和宏观结构以削弱两相流影响,应是改善该阳极性能的重要课题。本工作也可为直接乙醇燃料电池(DEFC)、直接硼氢化物燃料电池(DBFC)阳极的理论分析提供参考。 相似文献
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基于两区(two-domain)模型采用基于预处理的时间推进法对铺设有多孔介质层的恒温平板在受限层流冲击射流作用下的流动与换热特性进行了研究,其中多孔区域动量方程采用Brinkman-Forchheimer拓展Darcy模型,能量方程则采用局部热平衡(LTE)模型,并对porous/fluid交界面切应力跳跃条件对多孔介质冲击射流的影响进行了分析。流体的控制方程采用基于密度的有限体积法来求解,并针对于多孔区域低速流动特点采用相对应的预处理矩阵来消除控制方程的刚性。还对Reynolds数、孔隙率、Darcy数、热导率比、多孔介质层厚度等参数的变化对流动结构及换热特性的影响进行了分析。研究结果表明,在目前的计算条件下,在其他参数一定时,Reynolds数、孔隙率对通道内流动结构的影响有限;Darcy数、多孔介质层厚度则对流动结构的影响很大;上述参数对受冲击平板的总体换热性能均有明显的影响。在受冲击平板上铺设适当厚度的高渗透率、高热导率的多孔材料能有效地增强换热性能。 相似文献
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研究了悬浮液中的颗粒在通过逾渗多孔介质时的被吸附特性。采用数值计算的方法;通过求解描述低速流体流动的Stokes方程以及简化的颗粒运动方程;初步得到颗粒在逾渗多孔介质中的运动轨迹;并在此基础上;求得颗粒与多孔介质内表面的碰撞概率;进而研究颗粒的被吸附特性。数值结果表明均匀多孔介质和分形多孔介质对颗粒的吸附存在本质差异。颗粒流出概率(实际中常表示为出口悬浮液中的颗粒浓度)与多孔床深度间的指数关系仅对均匀多孔介质成立;而对分形多孔介质并不成立。 相似文献
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催化剂颗粒的形状优化Ⅰ基本几何形状颗粒 总被引:3,自引:1,他引:2
从反应工程的角度,通过对催化剂颗粒模型的分析和计算,对催化剂外形的优化设计进行了研究,定义了形状优化的指标参数-颗粒的相对活性F,以及异形化形状描述因子-无因次开孔半径X,并提出了颗粒的最佳X的求解方法,在对基本几何形状(无限大平板,无限长圆柱,球形)颗粒的异形化后的颗粒模型进行解析求解的 提出了简化算法,并对颗粒异形化后的X,Thiele模数φ对F的影响进行了探讨。 相似文献
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从流体力学的基本原理出发,本文介绍了一种新颖的流量测量装置——弯管流量计。本章详细推导了弯管传感器的流量计算公式,并讨论了其在实际应用中应注意的几个问题。 相似文献
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A new semi-empirical correlation for third virial coefficients of pure non-polar gases and their mixtures has been developed. It has been formulated as a sum of three contributions: two for pair additivity and non-additivity to the simple fluids and one for size and shape effects of the molecules. These contributions have been correlated with theoretically calculated data for argon, krypton and xenon and with an important set of emperimental data on third virial coefficients for 12 non-polar gases, The final correlation has been applied to 21 pure non-polar gases, 3 quantum fluids and 12 binary mixtures of classical and quantum gases. The results have been compared with other available methods. The overall comparison shows that this new method is equivalent or better than those, and that its major advantage is its predictive capability and its better theoretical representation thai should allow, in principle, its extension to more complex fluids. 相似文献
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The statistical theory of phase transition in fullerides of alkali metals to the superconducting state has been elaborated. The calculation of the free energy of crystals has been performed on the basis of molecular-kinetics and the equilibrium equations have been examined. The critical temperature of superconductivity has been estimated, and its concentration dependence has been ascertained. The calculation results have been compared with experimental data. The numerical estimation for energetic parameters of pairing of Cooper pairs electrons has been performed. 相似文献
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N. A. Khan 《European Journal of Lipid Science and Technology》1973,75(10):599-606
The perennial electron mobility varying in degrees for certain selected substances, has given rise to the interesting features of information only to establish the molecule to molecule concepts of initial oxygenation. The induction period has been found to be distinct from antioxidant has been shown to have its own realm of molecular action with intermolecular electron mobility to other protected molecules and induction period with intramolecular electron mobility of the particular substance concerned under T-t adjustments. The possible seven states of an antioxidant in action over the whole spectrum of autoxidation reactions, have been described to establish its effective molecular functions. The concepts of induction, have been broadened to encompass other aspects, particularly those of biology, the perennial source of transition states and complexes for various life phenomena and processes. 相似文献
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Ramiro Palazn-García Ana María Benavente-Valdepeas 《International journal of molecular sciences》2021,22(9)
Botulism has been known for about three centuries, and since its discovery, botulinum toxin has been considered one of the most powerful toxins. However, throughout the 20th century, several medical applications have been discovered, among which the treatment of spasticity stands out. Botulinum toxin is the only pharmacological treatment recommended for spasticity of strokes and cerebral palsy. Although its use as an adjuvant treatment against spasticity in spinal cord injuries is not even approved, botulinum toxin is being used against such injuries. This article describes the advances that have been made throughout history leading to the therapeutic use of botulinum toxin and, in particular, its application to the treatment of spasticity in spinal cord injury. 相似文献
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