Heat and Mass Transfer in Packed Beds Accompanied by Exothermic/Endothermic Reactions

对沸石13X和硅胶A吸附蒸汽的薄填料床进行了传热传质实验和数值分析。此外，还测量了床层的有效导热系数。吸附速率一般随床层厚度的增加而减小，在吸附速率较高的沸石床层中，吸附速率随粒径的减小而减小。这些减少主要归因于床层内的热传导阻力，或多或少归因于颗粒间隙传质阻力，特别是在吸附期的早期阶段。存在一个最佳床层厚度，在此厚度下，单位传热表面面积的吸附水量最大，因为它既取决于吸附速率，也取决于填充吸附剂的量。在固结层中，吸附期后半段吸附速率提高。吸附速率与吸附剂种类、粒度、床层厚度和床层类型无关，均可用单一的无因次方程表示。考虑蒸汽吸附引起的颗粒热导率上升，Hayashi等人的模型和Bauer-Schlunder模型都能很好地预测吸附剂填充床的有效热导率。通过考虑翅片段内热传导的影响，可以评价固定在翅片侧面上的床的吸附速率。基于考虑床内元素过程的物理模型，对吸附蒸汽的填料床的传热传质进行了数值分析。吸附速率的计算结果与实测结果吻合较好。

Experiments and numerical analyses were made on heat and mass transfer in thin packed beds of zeolite 13X and silica gel A adsorbing steam. In addition, the effective thermal conductivity was measured for the beds.1. The adsorption rate generally decreases as the bed thickness increases, and it reduces with the decrease of grain size in the zeolite bed where the adsorption rate is high. These reductions are attributed mainly to the resistance to heat conduction within the bed and more or less to the resistance to mass transfer in the interstices of grains especially in the early stage of the adsorption period. There is an optimum bed thickness at which the amount of adsorbed water per unit area of heat transfer surface takes a maximum, because it depends on both the adsorption rate and the amount of packed adsorbent. In the consolidated bed, the adsorption rate is enhanced in the latter half of the adsorption period. The adsorption rates can be expressed by a single non-dimensional equation, irrespective of kinds of adsorbent, grain size, bed thickness and types of bed.2. The effective thermal conductivity of the adsorbent packed bed can be predicted well by both the Hayashi et al.'s model and Bauer-Schlunder model, by considering the particle thermal conductivity rise due to the steam adsorption.3. The adsorption rate in the bed fixed on the side surfaces of a fin can be evaluated by considering the effect of heat conduction within the fin segment.4. Numerical analyses were made on heat and mass transfer in packed beds adsorbing steam, based on a physical model taking account of elemental processes which take place in the bed. Calculations of the adsorption rate were in good agreement with measurements.