The constant air volume valve is a mechanical self-powered device, which is suitable for ventilation and air conditioning systems that require constant air volume. The air volume control of the fixed air volume valve does not require external power. It relies on the air force in the air pipe to locate the position of the control valve, thereby maintaining the air flow at a preset flow rate within the entire pressure difference range.

Application in fresh air system At present, in China, the air-conditioning method of fan coil unit and fresh air system is still common, especially in hotel guest rooms. Most office buildings and office buildings adopt this method. The usual practice is to set up fresh air units on each floor, lay fresh air mains in the walkways, and connect dozens of branch pipes to each room from the main pipe. Take a hotel room as an example. The fresh air volume in each room is generally 100m3/h. How to achieve the same air volume in each branch? Generally speaking, designers often add an air volume regulating valve to the fresh air branch pipe, hoping to complete the air volume distribution through later debugging methods. Since the fresh air system generally has long main pipes and short branch pipes, the adjustment of the air volume control valve is neither intuitive nor the adjustment accuracy is ideal. Moreover, the fresh air volume per room is only 100m3/h, and the air volume is very small. Can't be done. The construction unit can only measure the total air supply volume of the fresh air main pipe to ensure that the air supply branch pipes have a sense of wind. In order to ensure that the fresh air volume sent to each room can reach the design value, and there is no need for the construction unit to go to a room-by-room balance, we only need to install a constant air volume valve on each fresh air branch pipe, and the above problems will be solved.

People who live and work in high-rise buildings often worry about the lack of fresh air, but designers often feel wronged. Because from the drawing, the value of the fresh air volume standard is not low, but we often overlook a problem, how to ensure the actual effect from a design perspective, and the application of the fixed air volume valve in the fresh air system is a powerful measure.

Because the current fixed air volume valve is mainly imported and the price is more expensive, the author suggests that it is more suitable for use in four- or five-star hotels and high-end office buildings.

Application in the exhaust system A good air conditioning system design, its exhaust system must be very reasonable, and this is often not paid attention to. In civil buildings, especially in high-rise buildings, the airtightness of the envelope structure is very good, and the positive pressure value of the room can be maintained with less air volume. About 85-90% of the fresh air volume must be exhausted outside through organized exhaust air, so as to ensure the balance of air supply and exhaust air volume, otherwise no amount of fresh air volume can be sent into the room. In civil buildings, exhaust air is generally discharged outside through auxiliary rooms such as toilets and boiling water rooms. In addition, sometimes a set of exhaust system should be added to ensure the balance of air supply and exhaust. For bathroom exhaust, the usual practice is to install one or two bathroom ventilators in each bathroom, interlocking with the exhaust fan on the exhaust shaft. We know that the fresh air system in high-rise buildings should operate all year round, and the corresponding exhaust system should also operate all year round. In other words, the person who uses the bathroom cannot control the opening of the bathroom ventilator, and the necessity of installing a bathroom ventilator is gone. Moreover, the operation of an exhaust system such as a large fan with dozens of small fans is difficult to match and uneconomical. The noise of the toilet ventilator with an exhaust air volume of 400m3/h is about 40dB, which makes the toilet lose its quietness. A large number of toilet ventilators also bring great trouble to maintenance. To solve this problem, we can cancel the toilet ventilator, add a constant air volume valve on each branch of the exhaust shaft, and install an exhaust fan on the top of the shaft. Such an exhaust system can ensure that the exhaust volume of each floor is approximately equal, and the system is simple to control, reliable in operation, and the bathroom can be very quiet.

Application in Variable Air Volume Air Conditioning System In a variable air volume air conditioning system, generally the outer area adopts the variable air volume method, and the inner area adopts the constant air volume method. In an air supply system with constantly changing air volume and air pressure, the constant air volume design of the inner area is Inseparable from the constant air volume valve.

Application in clean air-conditioning system It is very important to maintain the positive pressure value of the clean room in the clean air-conditioning system. Adding a set air volume valve in the exhaust or air supply and exhaust system can effectively ensure the positive pressure value of the clean room.

Clean operating room The positive pressure of the operating room must be maintained when the operation is in progress or not. The fresh air volume during the operation is the fresh air volume required to ensure the positive pressure plus the fresh air volume required by the personnel. The fresh air volume when the operation is not in progress is only to ensure the positive pressure The required fresh air volume, so a two-position constant air volume valve is required on the fresh air pipe.

The application of the balance of air pipes and piping in the whole air system, due to the influence of building conditions, the resistance between the branches is definitely not balanced. Generally, a three-way control valve or a split multi-leaf control valve is used to complete the air volume distribution. In order to ensure that the air volume on important rooms or main branch pipes is not too large or too small, and to reduce the blindness of debugging, the air volume valve can be appropriately set to replace the three-way regulating valve or the split multi-leaf regulating valve.

The characteristics of the use of constant air volume The fixed air volume valve is an automatic mechanical mechanism, without external power, and an electric actuator can be added to change the flow setting through a remote control signal. The constant air volume valve can be used in the air supply and exhaust system. The working temperature is generally 10-50℃, and the pressure difference range is 50-1000Pa. That is, at least 50Pa pressure difference should be applied before the valve and after the valve, otherwise the constant air volume valve will not work. This point should be paid attention to, because the wind pressure value of the fresh air unit of the fresh air system is generally not large. The fixed air volume valve is not restricted by the position when installing, but the valve disc shaft should be level. Generally, it is required to have a straight inlet duct 1.5 times the long side of the valve and a straight outlet duct 0.5 times the distance away. The constant air volume valve has high control accuracy. There is an external pointer to display the flow scale. The adjustment accuracy is about ±4%. The flow-limiting mechanism does not require maintenance. To match the system, the constant air volume valve can be rectangular, circular, heat-preserving, and silencing.

Concluding remarks Just as the balance valve is more and more adopted by the majority of designers in the air conditioning water system, the constant air volume valve will also be widely used in the air supply and exhaust system due to its accurately adjustable and automatic balance characteristics.