The voidage function and effective drag force for fluidized beds
The voidage function and effective drag force for fluidized beds
复制标题
流化床的空隙率和有效阻力
DOI：
10.1016/s0009-2509(03)00054-x
复制
发表时间：
2003
影响因子：
4.7
通讯作者：
P. Wright
中科院分区：
文献类型：
--
作者：
Yassir T. Makkawi;P. Wright
本文对常规床层内的有效阻力进行了实验研究。将B组和B/D组不同粒度分布的两个床层在直径13.8 cm的塔中在空气中进行流态化。利用双平面电容层析成像技术，通过测量脉冲气体试验中颗粒的速度和浓度，计算了颗粒所受的阻力。本文研究了用“修正函数”(1−εS)n来可靠估算有效阻力的有效性。参数n主要依赖于相对粒子雷诺数(Rep∗)，以及有效静力和水动力的空间变化。文中还指出，有效阻力系数与颗粒雷诺数(Rep)之间的简单关系式可以用来估算实际流态化过程中的有效阻力。分析表明，计算得到的阻力与颗粒重量相当，可以更好地了解颗粒动力学以及多尺寸颗粒床层混合物的空间分凝程度。本文给出的类比可以推广到床层有效阻力系数随颗粒物理性质变化的广义关联式。
Here, an experimental investigation on the effective drag force in a conventional fluidized bed is presented. Two beds of different particle size distribution belonging to group B and group B/D powders were fluidized in air in a 13.8 cm diameter column. The drag force on a particle has been calculated based on the measurement of particle velocity and concentration during pulse gas tests, using twin-plane electrical capacitance tomography. The validity of the voidage function “correction function”, (1−εs)n, for the reliable estimation of the effective drag force has been investigated. The parameter n shows substantial dependence on the relative particle Reynolds number (Rep∗) , and the spatial variation of the effective static and hydrodynamic forces. It is also illustrated that, a simple correlation for the effective drag coefficient as function of the particle Reynolds number (Rep), expressed implicitly in terms of the interstitial gas velocity, can serve in estimating the effective drag force in a real fluidization process. Analysis shows that, the calculated drag force is comparable to the particle weight, which enables a better understanding of the particle dynamics, and the degree of spatial segregation in a multi-sized particle bed mixture. The analogy presented in this paper could be extended to obtain a generalized correlation for the effective drag coefficient in a fluidized bed in terms of Repand the particle physical properties.