Talking about the Application of Constant Air Valve in Ventilation and Air Conditioning System

Talking about the Application of Constant Air Valve in Ventilation and Air Conditioning System

The constant air volume valve is a mechanical self-powering device suitable for ventilation and air conditioning systems requiring constant air volume. The air volume control of the fixed air volume valve does not require external power. It relies on the air flow force in the air duct to position the control valve to maintain the air flow at a preset flow rate over the entire pressure difference range.

(I) Application in fresh air system At present, in China, the air conditioning method of fan coil and fresh air system is still relatively common, especially in the hotel room part, most office buildings and office buildings adopt this method. The usual practice is to set up a new wind turbine group on each floor, a new air main pipe in the aisle, and dozens of branch pipes are respectively connected to the rooms from the main pipe. Take the hotel room as an example. The fresh air volume in each room is generally 100 m3/h. How to make the air volume of each branch pipe consistent? Generally speaking, designers often add a wind volume control valve to the fresh air branch pipe, and it is expected that the air volume distribution will be completed by means of later debugging. Since the fresh air system is generally the length of the main pipe, the branch pipe is short, and the adjustment of the air volume control valve is neither intuitive nor the adjustment accuracy is satisfactory. Moreover, the fresh air volume per room is only 100 m3/h, and the air volume is small. It can't be done. The construction unit can only measure the total air supply volume of the fresh air main pipe and ensure that each air supply pipe has a sense of wind. In order to ensure that the fresh air volume delivered by each room can reach the design value, and the construction unit does not need to go to the balance of one room and one room, we only need to add a fixed air volume valve to each fresh air branch pipe, and the above problems can be solved.

People who live and work in high-rise buildings often worry about the lack of new air, and designers often feel aggrieved. Because from the drawing, the value of the new air volume standard is not low, but we often overlook a problem, how to ensure the actual effect from the design point of view, 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 mainly relies on imports, the price is more expensive, the author suggests that it is more suitable for use in four- and five-star hotels and high-end office buildings.
(B) the application of a good air conditioning system in the exhaust system design, its exhaust system must be very reasonable, and this is often not taken seriously. In civil buildings, especially in high-rise buildings, the airtightness of the enclosure is very good, and the positive pressure of the room can be maintained with less air volume. About 85-90% of the fresh air volume must be discharged outside by organized exhaust, so that the air volume of the air supply and exhaust air can be balanced, otherwise no more fresh air volume can be sent into the room.
In civil buildings, the exhaust air is generally discharged outside through auxiliary rooms such as toilets and water heaters. In addition, sometimes an additional exhaust system should be added to ensure the balance of delivery and exhaust. For the bathroom exhaust, it is common practice to have one or two toilet 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 be operated all year round, and the corresponding exhaust system should also be operated all year round. That is to say, the person using the bathroom can not control the opening of the toilet ventilator, and the necessity of setting the ventilator of the bathroom 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 bathroom ventilator with a displacement of 400m3/h is about 40dB, which makes the bathroom lose its quiet.
A large number of toilet ventilators also cause great trouble for maintenance. In order to solve this problem, we can cancel the toilet ventilator, add a fixed air volume valve on each branch pipe of the exhaust shaft, and set up an exhaust fan at the top of the shaft. Such an exhaust system can ensure that the air volume of each layer is approximately equal, and the system control is simple, the operation is reliable, and the bathroom can be quiet.
(III) Application in variable air volume air conditioning system In the variable air volume air conditioning system, the general outer zone adopts the variable air volume mode, and the inner zone adopts the constant air volume mode. In an air supply system with constant air volume and wind pressure, the inner zone is determined. The air volume design is inseparable from the fixed air volume valve.
(IV) Application in purifying air-conditioning system It is essential to maintain the positive pressure value of the clean room in the air-conditioning system. By adding the air volume valve in the exhaust or air supply system, the positive pressure of the clean room can be effectively guaranteed. value. In the clean operating room, the positive pressure of the operating room should be maintained during and after the operation. The fresh air volume required for the positive pressure is the fresh air volume required for the positive pressure, and the fresh air volume required by the personnel. The fresh air volume is only the positive pressure when the operation is not performed. The required fresh air volume, so a double-position constant air volume valve is required on the new air duct.
(V) Application in air duct balance 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 regulating valve or a multi-leaf regulating valve is used to complete the air volume. distribution. In order to ensure that the air volume in important rooms or main branch pipes is not too large or too small, and the blindness of commissioning is reduced, the air volume valve may be appropriately added to replace the three-way regulating valve or the split multi-leaf regulating valve.
(6) Characteristics of the use of constant air volume The fixed air volume valve is an automatic mechanical mechanism. No external power is required. An electric actuator can be added to change the flow setting through the remote control signal. The constant air volume valve can be applied in the air supply and exhaust system. The working temperature is generally 10~50°C, and the pressure difference range is 50~1000Pa, that is, at least 50Pa differential pressure is applied after the valve front valve, otherwise the fixed air volume valve cannot work.
It should be noted that 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 limited by position when it is installed, but the valve shaft should be horizontal. Generally, a linear inlet duct with a distance of 1.5 times the long side of the valve and a linear outlet duct with a distance of 0.5 times are required. The constant air volume valve has high control precision, and the external pointer displays the flow scale. The adjustment accuracy is about ±4%. The current limiting mechanism does not need maintenance. For the system, the fixed air volume valve can be selected in rectangular, circular, thermal and muffling type. 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 is widely used in the delivery and exhaust systems because of its precise adjustment and automatic balance.

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