Abstract: In a heat exchanger operating on a liquid-solid circulating fluidized bed, the essential fluidization stability of the liquid-solid two-phase flow and the uniformity of the particle distribution are paramount. These aspects not only represent the descaling capability of the heat exchanger but also have a direct influence on its heat transfer efficiency. Maintaining an equitably spread out particle distribution pattern in the rising tube enhances the interaction of particles with the inner wall, leading to optimum efficiency for both scale prevention and removal. A novel dense-row lower fluidization box structure is incorporated into the conventional experimental setup of the heat exchanger to augment its heat transfer efficiency and explore the intricate dynamics of particle flow in the rising tube. A stable operation of bed fluidization is achieved through experimental research, and subsequent measurements of the rising tube's pressure drop at three distinct flow rates are consistent with the theoretical forecasts. Building upon the stable operation experiments of the newly fashioned dense-discharge liquid-solid circulating fluidized bed heat exchanger, the validity of the computational particle fluid dynamics (CPFD) method in simulating particle distribution is assessed. The deviation between experimental findings and simulation outcomes falls within a reasonable range of 10%, endorsing the reliability of the CPFD simulation approach and its promise of efficiency enhancement in future research. An optimization simulation of the ratio of the straight section's length to the bending radius of the lower elbow tube, a critical factor in flow dynamics, is executed using the CPFD method. The data suggest that a 5:1 ratio for the straight section to the bending radius offers the most uniform particle distribution in the heat exchanger. At this ratio, particle collisions against the rising tube's inner surface are at their highest efficiency, yielding optimal descaling results and leading to peak heat transfer efficiency.

Key words: fluidized bed, fluidization, two-phase flow, CPFD, numerical simulation

摘要： 在液-固循环流化床换热器中，两相流流态化流动的稳定性和均匀性不仅反映了换热器防垢除垢效果，还直接影响换热器的换热效率。为了提高流化床换热器的换热效率，探求床层内颗粒流动规律，在传统液-固循环流化床换热器中应用了新型密排式下流化箱结构并完成了稳定运行实验。基于实验结果，对采用计算颗粒流体力学方法(CPFD)模拟的流场分布结果进行有效性对比，实验结果与模拟结果的误差在10%以内，验证了模拟方法的可靠性。采用CPFD方法对下弯管直管段长度与弯曲半径之比进行了优选，下弯管直管段与弯曲半径之比为5:1时，液-固循环流化床换热器的除垢效果最佳，换热效率最高。

关键词: 流化床, 流态化, 两相流, 计算颗粒流体力学, 数值模拟