The effect of pore size on filtration performance of coalescing filters was investigated experimentally, using four oleophilic and three oleophobic glass-fiber filter materials. The filters were fabricated into sandwiches composed of a varying number of layers, each of the same filter materials. The results showed that both trend and extent of variation of the excess channel pressure drop with number of layers were dominated by the pore size. As the pore size decreased, the excess channel pressure drop exhibited the increasing, stable, and decreasing trends with increasing number of layers for oleophobic filters, respectively, while it kept growing with number of layers for oleophilic filters. The jump pressure drop controlled by liquid film was inversely proportional to the mean pore size, with an empirical fit equation established to allow quantitative analysis of relationship between film thickness and mean pore size for oleophilic filters. The pore size was a dominant factor in improving steady-state filtration efficiency, as a large-mean-pore-size filter was unable to efficiently separate sub-micrometer-sized droplets even with a high number of layers. Conversely, it was found that re-entrainment of micrometer-sized droplets was prone to occur in small-mean-pore-size oleophobic and large-mean-pore-size oleophilic filters, resulting in the pronounced reduction of steady-state filtration efficiency. Based on quality factors at steady state, a filter with large mean pore size was much superior in separation of micrometer-sized droplets, while a filter with moderate rather than smallest mean pore size, should be applied to separate sub-micrometer-sized droplets.

使用四种亲油性和三种疏油性玻璃纤维滤料，实验研究了孔径对聚结过滤器过滤性能的影响。将过滤器制成由不同数量的层组成的三明治，每种层均使用相同的过滤器材料。结果表明，过孔通道压降随层数的变化趋势和变化程度均受孔径影响。随着孔尺寸的减小，疏油性过滤器的层数增加时，多余的通道压降分别呈现出增加，稳定和下降的趋势，而亲油性过滤器的层数则随着层数的增加而保持增长。受液膜控制的跳跃压降与平均孔径成反比，建立了经验拟合方程，可以对亲油性滤膜的膜厚和平均孔径之间的关系进行定量分析。孔径是提高稳态过滤效率的主要因素，因为大孔径的过滤器即使层数很多也无法有效地分离亚微米大小的液滴。相反，发现在小平均孔径大小的疏油性和大平均孔径大小的亲油性过滤器中容易发生微米级液滴的再夹带，从而导致稳态过滤效率的显着降低。根据稳定状态下的品质因数，平均孔径大的过滤器在分离微米级液滴方面要优越得多，而平均孔径大小却不是最小的过滤器，