Structure of a High Efficiency Glass Fiber Filter Medium

ABSTRACT

The analysis of the real internal structure of a high efficiency glass fiber filter medium was carried out to provide detailed structure data, e.g., for more realistic calculations of the filter performance. The procedure of the structure analysis is described in detail and the most important results are presented and discussed. The fiber diameter distribution was found to be constant throughout the HEPA medium studied. The fibers tended to be oriented perpendicular to the direction of air flow, but there was no preferred direction of orientation within the plane of the filter medium. The interfiber distance distributions in parallel as well as in perpendicular orientation to air flow direction were found to be of the expected exponential shape for distances > 1 μm. On the other hand, the frequencies of the distances < 1 μm increase and the exponential shape of the curves is no longer observed.