共查询到16条相似文献,搜索用时 78 毫秒
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研究了汽液固循环流化床蒸发器的防垢与传热性能。实验表明,在防垢的同时,可有效地强化传热,提高蒸发能力,节约投资。 相似文献
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在二维中试循环流化床中使用组合式固液分布器进行实验,考察下管箱表观液速,主分布器内径、主分布器下插深度,颗粒加入量和粒径对径向管束固含率的影响.结果表明:固含率随主分布器内径、颗粒加入量和下管箱表观液速的增加而增大,随粒径的增大而减小,随主分布器下插深度几乎没有变化;固含率不均匀度随颗粒粒径的增大而增大,随下管箱表观液速、颗粒加入量,主分布器下插深度增加而减小,但达到一定深度后,不均匀度不再随之减小,随主分布器内径几乎没有变化.在综合考虑各影响因素的基础上,提出计算固含率的经验公式,并用实验数据拟合了公式中的参数. 相似文献
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对管内插入Kenics静态混合器的水平液固循环流化床换热器进行实验研究,实验考察了静态混合器扭率、静态混合器安装方式、液体流速、颗粒体积分数对传热性能和流阻性能的影响,并运用综合强化传热性能评价指标(PEC)对其进行分析。实验发现,传热性能和阻力系数均随扭率增加而减小。当雷诺数在10000~45000之间时,扭率为1.5、2、2.5、3.5的Kenics静态混合器的PEC指标均大于1,说明了水平流化床换热器插入Kenics静态混合器能够改善传热。在雷诺数达到25000左右、Kenics静态混合器扭率为2.5、颗粒体积分数为4%时,水平流化床换热器的PEC指标最高达到1.18。当两个扭率均为2.5的Kenics静态混合器安装间距为200mm时,水平流化床换热器的PEC指标最高。 相似文献
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气固循环流化床具有良好的混合、传热、传质、反应特性,同时还具有处理量大、可连续生产等优点,在众多领域均有广泛应用。气固循环流化床是一个由多个单元连接组合形成的循环回路,各单元间相互耦合、相互影响。对整个循环流化床系统进行全回路数值模拟,不仅能够获得更全面和详实的结果,而且在揭示系统流动规律和探究各单元内、单元间、单元与系统间的相互作用上具有独特优势。近十年来,以气固循环流化床全系统为模拟对象的全回路数值模拟研究逐渐兴起。本文对气固循环流化床全回路数值模拟方法的研究进展进行综述,对该方法的应用情况进行详细介绍,并对方法中采用的模型及相应特点进行逐一分析。循环流化床全回路系统同时存在多种流态,有待于建立适用于全回路系统的多流态物理模型(气固曳力模型与固相应力模型)。随着计算能力的提高以及物理建模的不断发展,全回路模拟方法将不断完善并发挥出更大的作用。 相似文献
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Particulate and aggregative fluidizations in a liquid-solid circulating fluidized bed system are characterized by chaotic time series analysis of local voidage and heat transfer fluctuations in terms of the correlation dimension and Kolmogorov entropy. Both correlation dimension and Komogorov entropy of the voidate fluctuation are found to decrease with decreasing bed voidage in both fluidization regimes, suggesting the suppression of chaotic motion of individual particles due to high solid concentration. The correlation dimension of the heat transfer fluctation in the aggregative fluidization regime is higher than that in the particulate fluidization regime. This reflects the complex convective motion of liquid and solid phases induced by the formation of the liquid streaks and aggregates of particles. 相似文献
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设计了实现液固外循环流化床中颗粒正常循环的关键部件——喷嘴,利用CCD图像采集分析系统,获得了其换热管束内固体颗粒的分布情况,考察了液体流量、口径比、喷嘴安装位置、颗粒直径、颗粒初始加入量以及液体黏度对液固外循环流化床换热器管束内含固体积分数的影响。结果表明:口径比及喷嘴安装位置对提高管束内的含固体积分数都存在一个最佳值,颗粒直径、颗粒初始加入量以及液体黏度对管束内含固体积分数也具有较大的影响,同时还通过对实验数据的综合分析,得到了喷嘴在最佳安装位置下液固外循环流化床内含固体积分数的经验关联式。 相似文献
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Shilapuram VidyasagarK. Krishnaiah P.S.T. Sai 《Chemical Engineering and Processing: Process Intensification》2011,50(1):42-52
Experiments were conducted in a liquid-solid circulating fluidized bed to study the effect of liquid viscosity and solids inventory on pressure gradient, critical transitional liquid velocity, onset average solids holdup, axial solids holdup distribution, average solids holdup and solids circulation rate in circulating fluidization regime with riser operated in fixed inventory mode. The results indicate that critical transitional liquid velocity decreases with increase in liquid viscosity. The onset average solids holdup, on the other hand, increases with increase in either auxiliary liquid velocity or solids inventory. The variation of axial solids holdup distribution, average solids holdup and solids circulation rate with liquid viscosity when solid inventory was 0.15 m was dissimilar with either 0.25 m or 0.35 m solid inventory. Correlations were proposed for estimating the average solids holdup and are satisfactorily compared with experimental values. 相似文献
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为了解决水平液固循环流化床中颗粒分布不均匀问题,在内径29 mm、长4 m的水平有机玻璃管流化床内放入Kenics静态混合器,采用CCD图像测量与数据处理系统考察静态混合器的结构、个数、安装位置对液固二相流中颗粒分布的影响;同时,利用U型管压差计考察不同条件下静态混合器的压降。实验结果表明:Kenics静态混合器能明显地改善管内颗粒分布情况;单个扭率Y=3.5的Kenics静态混合器压降最小;2个扭率Y=3.5的Kenics静态混合器间距为40 mm时对颗粒分布影响长度是最长的。 相似文献
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Ying Zheng Jing-Xu Zhu Jianzhang Wen Steve A. Martin Amarjeet S. Bassi Argyrios Margaritis 《加拿大化工杂志》1999,77(2):284-290
Based on experimental results from a 7.6 cm I. D. and 3 m high liquid–solid circulating fluidized bed, the liquid–solid circulating fluidization regime has been separated into two zones: the initial circulating fluidization zone and the fully developed circulating fluidization zone. The distinct hydrodynamic behavior and the influence of particle properties in the two circulating fluidization zones have been studied. The overall flow structure in LSCFB, although still somewhat non–uniform, is much more uniform than that in a gas-solid CFB. Our experimental results also show that the axial flow characteristics and the regime transition can be strongly affected by the particle density. The stable operation range of the circulating fluidization system and the influences of some associated factors, such as the solids inventory and the particle density, were also investigated for the first time. 相似文献