Medium-efficiency combined air filters are mainly used in intermediate filtration of air conditioning and ventilation systems, and in industrial purification in pharmaceuticals, hospitals, electronics, food, etc.

They can also be used as pre-filters for high-efficiency filters to reduce the load on the high-efficiency filters and extend their service life.

Due to their large air-facing surface, they have a large dust capacity and low air velocity, making them considered the current standard for medium-efficiency filter structures.

1. Captures 1-5µm particulate dust and various suspended solids.

2. Employs a heat-fusion process, ensuring structural stability and reducing the risk of leakage.

3. Large air volume.

4. Low resistance.

5. High dust holding capacity.

6. Reusable and reusable after cleaning.

7. Types: Frameless and framed bag type.

8. Filter media: Special non-woven fabric or glass fiber.

9. Efficiency: 60%～95%@1～5µm (colorimetric method).

10. Operating temperature and humidity: 80℃, 80%.

Improvement Methods for Medium-Efficiency Combined Air Filters

1. Selection of Filter Material

Nylon is a composite chemical fiber organic material with low hydrophilicity. Dust quickly detaches upon contact with water and dries rapidly after air drying. It can be rinsed directly with a regular high-pressure water gun without detergent, making it an easy-to-clean material. Its high surface smoothness facilitates dust particle removal, making it an ideal air filtration material.

2. Filter Layer Structure

The outer layer is a stainless steel mesh, providing support for the soft filter material and offering corrosion resistance. The inner layer is an improved mesh structure for a four-layer nylon air filter with a filtration accuracy ≤5μm and a filtration efficiency >40%, meeting the requirements of GB/T14295-93 and European Standard G3. The filter layers feature a bent design to increase the filtration area.

3. Filter Structure Design

The filter is designed as a plate structure, with two installation dimensions: 595×595×30 and 595×255×30, to accommodate adjustments for different air conditioning unit cross-sectional areas. Its structure includes: a 1.5mm thick stainless steel U-shaped frame for corrosion resistance; 30mm thick plates; and corrugated filter material to increase the filtration area, with each filter having an effective filtration area of 0.36m². The initial resistance is approximately 40Pa. The original medium-efficiency filter was removed, and the existing filter mounting frame was utilized. The frame dimensions are designed as 600×600 and 600×300, facilitating the installation of the 595×595×30 and 595×255×30 plate filters respectively. Installation is done by assembly, allowing for easy disassembly. Figure 3 shows the improved and modified air filtration flow section in the air conditioning unit's storage compartment. The air conditioning unit's flow surface is 2.1m × 1.8m, accommodating 12 plate filters (9 large and 3 small).

The medium-efficiency filter in the air conditioning system for the leaf storage compartment has been changed from a bag filter to a plate filter, and from composite fiber to nylon. This significantly improves its characteristics of easy cleaning, easy replacement, long service life, and high efficiency, overcoming the shortcomings of bag filters made of coarse fibers and non-woven fabrics, such as difficulty in cleaning, installation difficulties, high air resistance, high pressure loss, low filtration efficiency, and negative impact on fan energy conservation. While meeting the cleanliness requirements for secondary air filtration, it also reduces the fan pressure differential and fan operating load, saving energy consumption.