高效过滤器内气-固两相流动特性的数值研究

Numerical Study of the Gas-Solid Flow Characteristics in a High Efficiency Particulate Air Filter

利用计算流体动力学技术对用于空调净化领域的高效过滤器(High Efficiency Particulate Air Filters,HEPA)内的气-固两相流动特性进行数值研究,该高效过滤器由交错排列纤维组成。模拟时,计算不同运行条件下过滤器的压力损失及不同粒径范围过滤器的捕集效率,并将数值计算值和文献中的经验模型计算值进行了比较。结果表明:和其他经验模型比较,过滤器压力损失的数值预测值和实验关联式吻合较好,误差在2%以内,预测结果也表明,随着迎面风速的增加,过滤器压力损失呈线性增加;在过滤器中不同粒径范围的微细颗粒捕集机理也不同,对于本文所研究的过滤器,粒径小于0.2μm时,主要由布朗扩散起作用,粒径大于0.5μm时,惯性碰撞贡献较大,而粒径位于0.2μm～0.5μm之间时,两种机理作用都较弱,因此过滤器的捕集效率在该范围出现最小值。

The gas-solid two phases flow characteristics in a high efficiency particulate air filter that used in the area of air-conditioning were simulated by computational fluid dynamics technology, and the filter was made of the fibers arranged in a staggered array. The pressure drops and capture efficieneies with different operation conditions and particle sizes were calculated, and the predicted results were compared with the values of the empirical models in the literature. The results indicate： compared with the empirical models, the predicted values of the pressure drops is in excellent agreement with the experimental correlation, and the error is less than 2%. The results also show that the pressure drop increases with the face velocity linearly. On the other hand, the capture mechanism is different for different partiele size. For the filter in this paper, when the particle size is smaller than 0.2μm, Brownian diffusion plays a significant role in the filtration process, and when the particle size is bigger than 0.5μm, inertial impaction is an important capture mechanism which greatly improves the filter efficiency. When the particle size is in the range of 0.2 μm-0.5μm, the Brownian diffusion and inertial impaction can be ignored, and therefore, the capture efficiency has the least value in this range.