Abstract:

The horizontal heat exchange tube bundle is an important factor affecting the flow uniformity of solid particles in the heat exchanger. The discrete element method was used to construct the flow calculation model of the built-in horizontal tube bundle solid particle heat exchanger. Effects of tube bundle arrangements and horizontal tube distance on the flow of solid particles in the heat exchanger were studied. The results showed that the uniformity of particle flow through the staggered tube bundle was better than that of the in-line tube bundle. The particle flow non-uniformity number of the staggered tube bundle was 0.00721, which was 42.3% lower than that of the in-line tube bundle. The standard deviation of particle residence time of the staggered tube bundle was 0.029, which was 39.1% less than that of the in-line tube bundle. With the decrease of the horizontal heat exchange tubes distance, the degree of deformation of the particle layer and the fluctuation of residence time would increase if the particles passed through the staggered tube bundles. And at the same time, the uniformity of particle flow deteriorated significantly. The particle flow non-uniformity number increased from 0.00721 to 0.00996, an increase of 38.1%. The increase from 0.029 to 0.039 was the standard deviation of particle residence time, which increased by 33.8%. The difference in particle velocity in the shear zones was enlarged, and the average particle velocity gradient increased from 5.97×10^-4s^-1 to 7.85×10^-4s^-1, an increase of 31.4%.

Key words: granular flow, particulate processes, moving bed, heat exchanger, tube bundle arrangements, horizontal tube distance

摘要：

换热器内设的水平换热管束是影响换热器内固体颗粒流动均匀性的重要因素，基于离散单元法构建了内置横管式固体颗粒换热器的流动计算模型，研究了管束排列方式和水平管间距对换热器内固体颗粒流动的影响。结果表明，颗粒流过错排管束的均匀性优于顺排管束，颗粒层的形变和停留时间波动性均较小，颗粒流动不均匀度为0.00721，比顺排管束的减少了42.3%，错排管束的颗粒停留时间标准偏差为0.029，比顺排管束的减少了39.1%。当颗粒流过错排管束时，随着水平管间距的减小，颗粒层的形变和停留时间波动性均增大，颗粒流动均匀性显著恶化，颗粒流动不均匀度由0.00721增大到0.00996，增大38.1%，颗粒停留时间标准偏差由0.029增大到0.039，增大33.8%，剪切区内颗粒速度差异增大，颗粒平均速度梯度由5.97×10^-4s^-1增大到7.85×10^-4s^-1，增大了31.4%。

关键词: 颗粒流, 颗粒过程, 移动床, 换热器, 管束排列方式, 水平管间距