In control systems, the heat dissipated at the end of a loop typically exhibits non-linear behavior relative to the water flow. This non-linearity can be mitigated by using a control valve with inverse characteristics, creating a system (valve + terminal device) that ensures a linear relationship between heat output and valve opening. However, this assumes a constant pressure differential across the valve, which is often not the case in real-world conditions. As water flow fluctuates, so does the pressure differential, leading to deviations in actual performance.
The resulting non-linearity between valve position and heat output depends on both the valve's characteristics and its authority within the system. If the non-linearity is severe, control becomes challenging, especially under medium or light loads, where small changes in flow can cause large variations in heat output. Excessive flow further degrades control, forcing the valve to remain near the closed position, which leads to instability and poor regulation.
At design load, the control valve may only operate close to fully closed, making accurate control difficult. Overflows are a major obstacle to effective control, as they can cause valves to work near their limits, leading to shock and uneven distribution of flow. In such cases, some loops may receive too much flow while others get too little, failing to meet the required performance.
To address these issues, balancing valves are essential for all control loops. They help maintain stable and precise control by ensuring proper flow distribution. Additionally, maintaining the flow rate of the heating or cooling source within manufacturer-specified limits protects equipment and improves system efficiency. However, even if the source flow is correct, improper distribution can still lead to problems—such as reduced supply temperatures in heating zones and increased temperatures in cooling zones.
Installing balancing valves at each unit allows for accurate flow measurement and adjustment, ensuring that both the source and distribution sides are properly coordinated. This not only helps detect and correct issues early but also optimizes the number of units operating at any given time, reducing energy consumption and improving reliability.
Pump head selection should be based on the most demanding loop to ensure adequate flow, but this can result in excessive pressure elsewhere, causing uneven flow distribution. Balancing valves help eliminate residual pressure differences, ensuring consistent flow across all loops. This leads to more uniform room temperatures, better comfort, and lower energy use.
Balancing benefits include reduced temperature variation between rooms, improved comfort, and more efficient control. With balanced flow, centralized controllers can apply consistent strategies across the entire building, and zone controllers or thermostatic valves can function effectively without fluctuations.
In summary, installing balancing valves at critical points in the system is crucial for achieving stable, efficient, and comfortable operation. They provide a reliable way to measure, adjust, and monitor flow, helping to solve many common control challenges.
Accessories of screw and barrel
ZHEJIANG JINJIA PLASTICS MACHINERY CO., LTD , https://www.jinjiascrew.com