固定床有效导热系数的研究

Study on Effective Thermal Conductivity of Fixed Bed

采用稳态法和非稳态参数估值法测定了气体静止时固定床有效导热系数(以下简称固定床的有效导热系数),前者采用圆柱体导热模型,求得在某特定温度下固定床有效导热系数;后者根据固定床拟均相非稳态传热模型,获得了适用于宽温度范围的固定床有效导热系数与气体导热系数和固体导热系数之间的关联式。并将填充挤条型氧化铁系催化剂、催化剂载体Al2O3和玻璃珠的固定床的测定结果与前人推荐的固定床有效导热系数的多种计算方法进行比较。结果证明,对于气-固体系计算固定床的有效导热系数较为适宜的经验式为:λb0=λf×10(0.785-0.057lg(λs/λf))×lg(λs/λf)。该经验式在20～500℃对于高、中、低导热系数多种物系的固体颗粒床层均适用。

The static effective thermal conductivity coefficient of fixed bed is measured by method of stable statue and instable statue. The former offers the value of static effective thermal conductivity coefficient at specific temperature on the basis of thermal conductivity model of cylinder. The latter offers the correlation of the static (effective) thermal conductivity coefficient by pseudo-homogeneous instable model. For fixed bed with iron oxide matrix catalyst, glass sphere and catalyst carrier Al_2O_3 respectively, the (static) (effective) thermal conductivity coefficient from experiment were compared with the data calculated by other correlations. It is concluded that the following correlation is an optimum to calculate the static (effective) thermal conductivity coefficient for gas-solid system:λ_b^0=λ_f×10~^((0.785-0.057 lg(λ_s/λ_f))×lg(λ_s/λ_f)) which could be applied to calculate the static (effective) thermal conductivity coefficient for fixed bed with high, middle or low thermal conductivity particles at 20～(500 ℃)