振动流化床中大颗粒与水平管局部传热特性

在二维振动流化床中,以平均粒径1.83 mm的玻璃珠为物料,研究了大颗粒与水平管间局部传热规律;考察了气速、振动频率等因素对局部传热系数的影响,同时与小米和小玻璃珠实验结果进行对比。结果表明:大颗粒与小颗粒局部传热系数有很大差异;对于大颗粒,低速下局部传热系数随振动频率的增大先增加后减小,高速下局部传热系数随着振动频率的增加而降低;一定振动频率下,气速小时局部传热系数在60°左右达到最大,气速逐渐增加后,其最大值向90°转移。通过实验数据得到了计算大颗粒与水平管局部传热系数的关联式,计算值与实验值吻合较好,误差在±20%范围内。结果可为带浸没水平管的振动流化床设计和研究提供参考。

Local heat transfer characteristics of large particles and horizontal tube in vibrated fluidized bed

The local heat transfer pattern between large particles and horizontal tube was investigated by using the glass beads in average diameter 1.83 mm in a two-dimensional vibrated fluidized bed.The effect of the fluidization velocity and the vibration frequency on the local heat transfer coefficient was analyzed.The results acquired by the large particles were contrasted with the millet and the small glass beads.The results show that there is a great difference in the distribution of the local heat transfer coefficient between large and small particles.For large particles,the local heat transfer coefficient increases first and then decreases with the increase of the vibration frequency under the low gas velocity,which decreases with the increase of the vibration frequency under the high gas velocity;under a certain vibration frequency,the local heat transfer coefficient comes to the maximum at 60° under the low gas velocity,which transfers to 90° after the gas velocity increases gradually.An empirical correlation equation for predicting the local heat transfer coefficient of large particles and horizontal tube was established,and the calculated value was in good agreement with the experimental data,with the error in the range of±20%.The results can provide references for future design and research on the vibrated fluidized bed.