Effect of Pleat Spacing and Pleat Depth on HEPA Filter?
Effect of pleat spacing on drag
In the case of a certain size of the HEPA filter, reduce the fold spacing of the filter material, can increase the filter material area of the filter, reduce the filter speed, reduce the resistance of air flow through the filter material. However, with the decrease of pleat spacing, the airflow channel will also become smaller, which will increase the energy loss (resistance) of airflow flow in the airway. Therefore, there is a suitable pleat spacing to minimize the total drag of the filter. For this reason, this paper tests the resistance of three sizes of flat-panel compact HEPA filters with different filter materials and different pleat spacing at 1000 m³.h-1 air volume, and the results are shown in Table 1.
It can be seen from the data in Table 1 that within the scope of this experiment, there are different optimal pleats spacing between two kinds of filter materials and three kinds of common specifications of flat-panel pleated HEPA filters. And the two kinds of filter media have the same law, with the increase of fold depth, the optimal fold spacing also increases correspondingly. The structural parameters with the lowest resistance are shown in Table 2.
The data in Table 2 are different from the structural parameters reported in the literature (Xu Xiaohao, 2005). This also shows that the filter with the same structure form should have different optimal structural parameters by using different filtering materials. Hepa filters with partitions are another common type of filter. Table 3 shows the measured results of filter resistance of two sizes made of filter material B. It can be seen from the data in Table 3 that the diaphragm HEPA filter with a depth of 150 mm has the lowest resistance when the pleat spacing is 4.8 mm(the corrugated height of the separator is 2.4 mm). For a HEPA filter with bulkhead at a depth of 292 mm, the optimal pleat spacing is 5.4 mm(corrugated height of bulkhead is 2.7 mm).
It can be seen that no matter the tightly pleated type or the high efficiency air filter with a separator, when the filter material pleated depth is determined, there is the best filter material pleated spacing. With the increase of filter fold depth, the optimal fold spacing also increases. Different filter media have different optimal structure form.
Effect of crimp depth on drag
In the case of no strict requirements on the depth of the filter size, increasing the depth of the filter material fold can also effectively increase the filter material area, reduce the resistance of air flow through the filter material. The increase of filter material fold depth will also lead to the increase of friction resistance in the airflow channel, therefore, there is also a most reasonable filter material fold depth of the lowest resistance.
FIG. 2 shows the resistance curve of a group of flat-panel pleated HEPA filters. High efficiency air filter(HEPA filter manufacturer) end size is 610mm ×610mm, pleat spacing is 3. 3mm, using imported filter material A, depth is 50 mm, 60 mm, 69 mm, 80 mm and 90 mm, in 850m³.h-1, 1000 m³. It is clear from FIG. 2 that for a fixed pleat spacing, there is an optimal filter material pleat depth that provides the lowest filter resistance.
The resistance curve of a high efficiency air filter with a clapboard made of domestic filter material B. In the depth range of commonly used HEPA filters with partitions (120~320mm), increasing the filter depth can effectively reduce the filter resistance. When the filter depth is small (120 mm), this effect is greater; When the filter depth is larger (292 mm), the drag reduction caused by increasing the depth is not obvious.
It can be seen that for the fixed filter material pleat spacing, there should be the best filter material pleat depth that makes the filter resistance lowest. In order to reduce the filter resistance, can increase the filter material fold depth, but at the same time must consider adjusting the filter material fold spacing.
