MU-TDOR22
根据所需的清洁度、待去除颗粒的数量和大小以及可接受的维护要求选择过滤器。高效微粒空气（HEPA）机械过滤器（图16）不会释放收集的微粒，因此可用于洁净室和释放有毒微粒的区域。HEPA过滤器显著增加系统压降，在选择风机时必须考虑这一点。图17显示了其他机械过滤器。C2713单元折叠纸气流图16。HEPA过滤器。折叠滤袋过滤器图17。机械过滤器。其他类型的机械过滤器包括过滤器、粘性涂层过滤器和扩散过滤器。过滤可去除比金属过滤器网格中的空间大的颗粒，通常用作静电过滤器的预过滤器。在粘性涂层过滤器中，通过过滤器纤维的颗粒与纤维发生碰撞，并停留在纤维表面。扩散利用气流中存在的湍流将微粒驱动到过滤器表面的纤维上，从而去除细颗粒。静电过滤器（图18）提供较低的压降，但通常需要一个机械预过滤器来收集大颗粒，并需要一个机械后过滤器来收集可能从静电过滤器上吹出的团聚颗粒。静电过滤器使通过电离场的粒子带电，并将带电粒子收集在带有相反电荷的平板上。这些板可以涂上粘合剂。

Filters are selected according to the degree of cleanliness required, the amount and size of particles to be removed, and acceptable maintenance requirements. High-efficiency particulate air (HEPA) mechanical filters (Fig. 16) do not release the collected particles and therefore can be used for clean rooms and areas where toxic particles are released. HEPA filters significantly increase system pressure drop, which must be considered when selecting the fan. Figure 17 shows other mechanical filters. C2713 CELL PLEATED PAPER AIR FLOW Fig. 16. HEPA Filter. PLEATED FILTER BAG FILTER Fig. 17. Mechanical Filters. Other types of mechanical filters include strainers, viscous coated filters, and diffusion filters. Straining removes particles that are larger than the spaces in the mesh of a metal filter and are often used as prefilters for electrostatic filters. In viscous coated filters, the particles passing through the filter fibers collide with the fibers and are held on the fiber surface. Diffusion removes fine particles by using the turbulence present in the air stream to drive particles to the fibers of the filter surface. An electrostatic filter (Fig. 18) provides a low pressure drop but often requires a mechanical prefilter to collect large particles and a mechanical after-filter to collect agglomerated particles that may be blown off the electrostatic filter. An electrostatic filter electrically charges particles passing through an ionizing field and collects the charged particles on plates with an opposite electrical charge. The plates may be coated with an adhesive.