Calculation Method of Static Pressure Box for Fan Coil Unit of Central Air Conditioning

Static pressure box is one of the necessary equipment for large space central air conditioning fan coil unit system. It is a traditional ventilation facility. It is often used in constant humidity, constant temperature and clean space air distribution system. Under normal circumstances, only high-power air conditioners above 5HP will use static pressure box. Because low-power air conditioners are basically zero static pressure, static pressure box is not needed.

The static pressure box of the central air conditioner is also called a pressure stabilizing chamber, and is mainly used for connecting a box body with a relatively large space of air supply openings. After the central air conditioner supplies air to the space, the flow rate will be reduced to a speed close to zero, where the dynamic pressure is replaced by static pressure, and the static pressure of each air supply opening is ensured to be similar, thus realizing the effect of uniformly supplying air to each air supply opening.

The static pressure box of central air conditioner is a necessary accessory for the air supply system of air conditioner to reduce dynamic pressure, increase static pressure, stabilize airflow and reduce airflow vibration.

The main function of the central air conditioning static pressure box is to provide uniform pressure for each branch pipeline. However, due to the different central air conditioning projects, the volume of the static pressure box is not fixed, which requires the static pressure box calculation according to different central air conditioning working conditions. The calculation method of the central air conditioning static pressure box:

1, Height * depth = static pressure box cross-sectional area, static pressure box cross-sectional area *2.5m/s= fan coil air volume, as for how to match the height and depth, according to the requirements of their configuration;
2. When designing the static pressure box of the central air conditioner, if it is designed according to the specified wind speed, the box will be very large, which will cause a lot of inconvenience. Therefore, the long side of the general static pressure box will be designed according to the 400mm width of the outlet duct and the 400mm height of the outlet duct.
3. The thickness of the static pressure box of the central air conditioner is preferably greater than 600mm, and the wind speed of the cross section should not be less than 2 m/s. Attention should also be paid to the air flow buffer zone at the inlet and outlet of the static pressure box.
4. Generally, the experience in designing the silencing static pressure box of central air conditioner is 5-10db/m, and the impedance compound type is 10-15dB/m;
5. With machine grade beads L/3m/s, the area of one side of the static pressure box of the central air conditioner can be calculated, so that the width can be calculated according to the height of our room.  If the width is known, the area of the static pressure box can also be calculated by using the width * length.

The calculation method of static pressure box of central air conditioner is illustrated with examples:
If the room is 4m high, the height of the unit is 2m, because a soft joint of about 0.5m will be used at the junction of the static pressure box of the central air conditioner, so this will be subtracted, and a height of 0.5m will be set aside above, so the static pressure box height can only be 1m, and this height, width and other values can be determined.
The calculation method of the static pressure box of the central air conditioner is not difficult. As long as you remember the formula inside and have a fixed reserved size, you can easily calculate the size of the static pressure box of the central air conditioner.