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首页> 外文期刊>International Journal of Heat and Mass Transfer >Convective drying of particulate solids - Packed vs. fluid bed operation
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Convective drying of particulate solids - Packed vs. fluid bed operation

机译：颗粒固体的对流干燥-填料与流化床操作

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摘要

The paper addresses results for the case of convective drying of particulate solids in a packed and in a fluid bed, analyzing agreement between the numerical results and the results of corresponding experimental investigation, as well as the differences between packed and fluid bed operation. In the fluid bed simulation model of unsteady simultaneous one-dimensional heat and mass transfer between solids, gas phase and bubble phase during drying process, based on two-phase bubbling model, it is assumed that the gas-solid interface is at thermodynamic equilibrium. The basic idea is to calculate heat and mass transfer between gas and particles (I.e., the drying process) in suspension phase as for a packed bed of particles, where the drying rate (evaporated moisture flux) of the specific product is calculated by applying the concept of a "drying coefficient". Mixing of the particles (I.e., the impact onto the heat and mass transfer coefficients) in the case of fluid bed is taken into account by means of the diffusion term in the differential equations, using an effective particle diffusion coefficient. Model validation was done on the basis of the experimental data obtained with narrow fraction of poppy seeds characterized by mean equivalent particle diameter (d_(s,d)=0.75 mm), re-wetted with required (calculated) amount of water up to the initial moisture content (X_0=0.54) for all experiments. Comparison of the drying kinetics, both experimental and numerical, has shown that higher gas (drying agent) temperatures, as well as velocities (flow-rates), induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity. Bed temperature differences along the bed height are significant inside the packed bed, while in the fluid bed, for the same drying conditions, are almost negligible due to mixing of particles. Residence time is shorter in the case of a fluid bed drying compared to a packed bed drying.
机译：本文讨论了填料和流化床中颗粒固体对流干燥的结果，分析了数值结果与相应实验研究结果之间的一致性，以及填料和流化床操作之间的差异。基于两相鼓泡模型，在干燥过程中，固相，气相和气泡相在固相，气相和气泡相之间同时进行非稳态一维传热传质的流化床模拟模型中，假设气固界面处于热力学平衡状态。基本思想是计算悬浮相中气体和颗粒之间的热和质量传递（即干燥过程），就像颗粒填充床一样，其中特定产品的干燥速率（蒸发湿气通量）通过应用“干燥系数”的概念。在流化床情况下，利用有效的粒子扩散系数，通过微分方程中的扩散项，考虑了粒子的混合（即，对传热和传质系数的影响）。模型验证是基于以狭窄的罂粟种子（平均特征粒径（d_（s，d）= 0.75毫米）为特征）的小份罂粟种子获得的实验数据进行的，再用所需量（计算得出的水）重新润湿直至达到所有实验的初始水分含量（X_0 = 0.54）。实验和数值上的干燥动力学比较表明，较高的气体（干燥剂）温度以及速度（流速）可加快干燥速度。对于较深的床层，此效果更为明显，因为使用相同的干燥剂容量要干燥的湿料量更大。在填充床内部，沿着床高的床温差很大，而在流化床中，对于相同的干燥条件，由于颗粒的混合，几乎可以忽略不计。与填充床干燥相比，流化床干燥的停留时间更短。

著录项

  • 来源
  • 作者

    Milan Stakic; Predrag Stefanovic; Dejan Cvetinovic; Predrag Skobalj;

  • 作者单位

    Laboratory for Thermal Engineering and Energy, University of Belgrade - Institute of Nuclear Sciences Vinca, P.O. Box 522, 11001 Belgrade, Republic of Serbia;

    Laboratory for Thermal Engineering and Energy, University of Belgrade - Institute of Nuclear Sciences "Vinca", Belgrade, Republic of Serbia;

    Laboratory for Thermal Engineering and Energy, University of Belgrade - Institute of Nuclear Sciences "Vinca", Belgrade, Republic of Serbia;

    Laboratory for Thermal Engineering and Energy, University of Belgrade - Institute of Nuclear Sciences "Vinca", Belgrade, Republic of Serbia;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Fine-grained hygroscopic materials; Heat and mass transfer; Drying kinetics; Drying coefficient; Modeling;

    机译：细粒吸湿材料;传热传质;干燥动力学;干燥系数造型;

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