What are the types of filters in HVAC system?

Air filters commonly used in ventilation and air conditioning engineering include coarse efficiency filter, medium efficiency filter and high efficiency (or sub-high efficiency) filter. The filter material shall have the functions of fire prevention, moisture prevention and insect prevention.

(1) Coarse effect filter: generally made into blocks and installed on the support. The filter materials are mostly metal mesh, glass fiber, coarse porous polyurethane foam and other materials. The coarse efficiency filter mainly uses the inertial collision of air flow to make the larger particle size (>5 μ m) Of dust particles separated from the air stream.

In order to increase the filtering area (that is, increase the air handling capacity) and reduce the floor area, the "herringbone" structure is often used for the ancestral filter. In order to facilitate the replacement of cleaning filter material, it can be made into drawer type, automatic immersion filter and automatic winding filter.

The metal mesh of the automatic oil immersion filter drives the upper and lower shafts to rotate through the motor. The metal mesh can be turned to the bottom oil tank to clean the filtered dust particles, and then move upward. The oil tank can replace the oil regularly or remove the filtered dust particles.

The coarse efficiency filter can generally be used as the pre-filtration before the high efficiency or medium efficiency filter. Because of its high dust filtering capacity, it is widely used in the primary filtration site.

(2) Medium efficiency filter: It is mainly made of glass fiber or synthetic fiber made of polyester, polypropylene, nylon and other raw materials as filter material. Due to the different thickness and filtration speed of filter material, its dust removal efficiency and range are high, and the particle size of treated dust is greater than 1 μ m. It can be made into drawer type and bag type.

(3) High-efficiency filter: filter materials such as ultra-fine glass fiber are mainly used. The filter material fiber can be made into paper, and the filter paper needs to be folded for many times. The air flow passes through the filter layer at a low speed, and the coarse and medium efficiency filters must be set in front of it for protection when it is used, which can filter less than 1 μ M dust particles are mostly used in clean or sterile air conditioning projects.