PARTICLE-FLUID MASS-TRANSFER IN FIXED AND FLUIDIZED-BEDS
PARTICLE-FLUID MASS-TRANSFER IN FIXED AND FLUIDIZED-BEDS
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DOI：
10.1021/i260062a001
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发表时间：
1977-01-01
期刊：
影响因子：
--
通讯作者：
UPADHYAY, SN
中科院分区：
文献类型：
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作者：
DWIVEDI, PN;UPADHYAY, SN
固定床和流化床中的颗粒-流体传热或传质是设计和开发涉及颗粒和流体系统的各种传热和传质操作和化学反应器所需的基本信息的重要项目。在过去三十年中，对这一问题进行了广泛的研究，关于这一问题的文献数量巨大（Upadhyay和Tripathi，1975年a）。用气体和液体进行了实验测量。测定了从气流中吸收液体蒸气、从多孔颗粒表面蒸发液体和适当固体升华为气流的气相传质速率。在液体的情况下，大多数数据是通过测量合适的固体溶解到液体流中的速率获得的。在少数情况下，数据是通过测量吸附、离子交换或结晶的速率，或通过使用适当的电化学系统测量扩散电流而获得的。在大多数以前的研究中，实验结果表示在无量纲组，然而，在某些情况下，传质系数是直接相关的操作变量，如流速，粒径等。通常的无量纲groupsused是Chilton-科尔本传质系数（Chilton和科尔本，1934年），舍伍德数，施密特数，和粒子雷诺数。在某些情况下，还包括其他无量纲组，例如颗粒与柱直径比或颗粒直径与床高度比、阿基米德数N\T，以改善相关性。此外，研究人员对各种常规无量纲项的定义也不同。传质系数的一般定义是包括施密特群，指数为%;然而，在某些情况下，它被重新定义为指数为0.58。雷诺数和舍伍德数中的特征长度参数通常是颗粒系统的等效颗粒直径或水力直径。有时它会被修改，加入一个被称为形状因子的术语。类似地，使用的质量流率是基于空柱横截面的表观流率G，或通过床的有效质量流率（G/e）。在此基础上，使用了以下三种形式的颗粒雷诺数。
Introduction Particle-fluid heat or mass transfer in fixed and fluidized beds is an important item of the basic information required for the design and development of various heat and mass transfer operations and chemical reactors involving a system of particles and a fluid. It has been widely investigated during the past three decades and the volume of the literature on the subject is enormous(Upadhyay and Tripathi, 1975a). Ex-perimental measurements have been made with gases and liquids. The gas-phase mass transfer rates have been mea-sured for the absorption of liquid vapors from the gaseous streams and evaporation of liquids from the surface of porous particles and sublimation of suitable solids into gaseous streams. In the case of liquids, most of the data have been obtained by measuring the rate of dissolution of suitable solids into a liquid stream. In a few cases the data havebeen ob-tained by measuring the rate of adsorption, ion-exchange, or crystallization or by measuring the diffusion current using a suitable electrochemical system. In most of the previous studies, the experimental results are expressed in terms of the dimensionless groups; however, in some cases the mass transfer coefficient is directly related to operating variables such as flow velocity, particle diameter, etc. The usual dimensionless groupsused are the Chilton-Colburn mass transfer factor (Chilton and Colburn, 1934), Sherwood number, Schmidt number, and a particle Reynolds number. In some cases, other dimensionless groups such as the particle to column diameter ratio or particle diameter to bed height ratio, Archimedes number, N\T, are also included to improve the correlations. Further, the various conventional dimensionless terms are defined differently by research workers. The common definition forthe mass transfer factor is one which includes the Schmidt group with an exponent of%; however, in some cases it has been redefined with 0.58 as the exponent. The characteristic length parameter in the Reynolds and Sherwood numbers is usually the equivalent particle diameter or the hydraulic diameter for a particulate system. Occasionally it has been modified by incorporating a term known as shape factor. Similarly, the mass flow rate used is either the superficial flow rate, G, based on the empty column cross section, or the effective mass flow rate (G/e) through the bed. Based on these, the following three forms of particle Reynolds numbers have been used.