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The characteristics of air volume control valve and its application in ventilation and air conditioning
**Abstract:**
The fixed air volume valve is a mechanical self-powered device designed for ventilation and air conditioning systems that require constant airflow. Unlike traditional flow control valves, it does not need an external power source. Instead, it uses the airflow within the duct to position the valve and maintain a preset flow rate across varying pressure differentials. This makes it ideal for applications where consistent air delivery is critical.
Keywords: Fixed air volume control valve, flow control valve, mechanical self-powered device, constant air volume, ventilation, air conditioning.
**(A) Application in Fresh Air Systems**
In many buildings, especially hotels and office spaces, the fan coil plus fresh air system remains widely used. Typically, a fresh air unit is installed on each floor, with main ducts running through corridors and branch pipes connecting to individual rooms. For example, in hotel rooms, each room usually receives 100 m³/h of fresh air. However, achieving uniform airflow distribution among all branches can be challenging.
Designers often install flow control valves on the branch pipes, relying on post-installation adjustments. But due to short branch lengths and low airflow, these adjustments are often ineffective. As a result, construction teams may only measure the total airflow from the main duct, without ensuring balanced distribution. To address this, fixed air volume valves can be installed on each branch pipe. These valves automatically regulate airflow, ensuring each room receives the design value without requiring manual balancing.
This is particularly important in high-rise buildings, where occupants frequently complain about poor air quality. While design standards may specify sufficient fresh air, actual performance often falls short. Fixed air volume valves offer a practical solution, especially in high-end facilities like five-star hotels or premium offices, where cost is less of a concern.
**(B) Application in Exhaust Systems**
A well-designed HVAC system must also include an efficient exhaust system, which is often overlooked. In high-rise buildings, maintaining positive pressure in rooms requires careful balance between supply and exhaust air. Most of the fresh air must be exhausted to prevent over-pressurization.
Traditionally, bathroom exhaust systems use individual ventilators, which can be noisy and difficult to manage. Installing a central exhaust fan at the top of the shaft, along with fixed air volume valves on each branch, provides a more efficient and quieter solution. This setup ensures even exhaust distribution across all floors and simplifies system control.
**(C) Application in VAV Systems**
In Variable Air Volume (VAV) systems, fixed air volume valves are commonly used in internal zones. These valves help maintain stable airflow despite changes in system pressure, ensuring consistent performance in areas where variable air volume is not required.
**(D) Use in Cleanroom Air Conditioning**
In cleanrooms, maintaining positive pressure is essential. By installing fixed air volume valves in the exhaust or supply systems, the positive pressure can be effectively controlled. For operating rooms, for instance, a dual-volume valve may be necessary to ensure proper airflow during both operation and non-operation periods.
**(E) Duct System Balancing**
During installation, duct resistance may vary, making airflow distribution uneven. While three-way or multi-leaf dampers are traditionally used, fixed air volume valves can be a better alternative in key areas. They reduce the need for extensive balancing and improve overall system performance.
**(F) Features of Fixed Air Volume Valves**
Fixed air volume valves operate mechanically without external power. Some models can be equipped with electric actuators for remote adjustment. They work in both supply and exhaust systems, with typical operating temperatures ranging from 10°C to 50°C and pressure differentials between 50Pa and 1000Pa.
They do not require frequent maintenance and offer high precision, with an accuracy of ±4%. Installation guidelines recommend a straight inlet length of 1.5 times the duct diameter and an outlet length of 0.5 times. These valves come in various shapes, including rectangular and circular, and can be insulated for specific applications.
**(G) Conclusion**
While balancing valves are commonly used in water systems, fixed air volume valves are gaining popularity in air systems due to their ability to provide accurate, automatic flow regulation. Their reliability and ease of use make them an essential component in modern ventilation and air conditioning designs.