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Analysis on the selection of flow control valve design
Heating systems that implement heat metering and charging mechanisms can significantly improve energy efficiency and reduce overall consumption. Currently, the energy efficiency of our heating systems is only around 30%. Most attention is given to the boiler and network heat loss, while the heat loss at the user end is often overlooked. This user-side heat loss, primarily due to uneven heating, accounts for approximately 30% to 40% of total losses—this is a substantial figure. The introduction of a heat metering system aims to tap into this hidden potential for energy savings.
The system achieves energy savings through three main approaches: first, by installing flow control valves to balance the flow and address uneven heating; second, by using temperature control valves to regulate heat based on solar energy, appliances, and lighting; and third, by raising residents’ awareness of energy conservation, such as reducing unnecessary window openings. Out of these three methods, two rely on the use of flow control valves, which highlights their crucial role in the overall system.
Therefore, the correct selection and design of flow control valves are essential. A thermostatic valve, for instance, is a key component used to regulate indoor temperatures. It consists of a thermostat, a flow control valve, and connectors. The thermostat, acting as a sensor, detects ambient temperature changes and adjusts the valve to regulate heat output. These valves can be manually adjusted and automatically respond to maintain desired room temperatures.
There are two types of thermostatic valves: two-way and three-way. Three-way valves are typically used in single-pipe systems with bypasses and offer greater flow control but are more expensive. Two-way valves are suitable for both single- and double-pipe systems, with different resistance characteristics depending on the setup.
When designing a temperature control valve, it's important to select the right KV value based on the system’s flow requirements and pressure conditions. Proper sizing ensures optimal performance and prevents issues like noise or inefficient operation. In some cases, smaller calibers are preferred to enhance regulation accuracy.
Electric control valves are used in automated systems and require external power. They are ideal for unattended thermal stations and work in conjunction with computer monitoring systems. Unlike thermostatic valves, they do not rely on temperature sensing alone but adjust flow based on pre-set parameters.
Balance valves, whether manual or self-balancing, play an essential role in maintaining system stability. They help prevent excessive flow in certain areas, ensuring that thermostatic and electric valves operate efficiently under controlled pressure conditions.
Self-balancing valves automatically maintain flow balance without external power, making them ideal for dynamic systems. However, they have specific minimum pressure requirements, and improper installation can lead to inefficiencies.
Differential pressure regulating valves function similarly to self-balancing valves but focus on maintaining a constant pressure difference across the system. They help stabilize flow and reduce the need for frequent adjustments of temperature control valves.
In variable flow operations, the choice of flow control valves—whether manual, self-balancing, or differential pressure—can greatly affect system performance. Manual valves provide good balance but require frequent adjustments, while others offer more automation and better long-term stability.
Overall, the integration of proper flow control devices is essential for achieving efficient and sustainable heating systems. By addressing both system-wide and user-specific heat losses, these technologies contribute to a more energy-efficient and comfortable living environment.
References:
Tu Guang-bai, Yuan Zhe-ning, Huang Baomin et al. *Heating Metering Technology*. Beijing: China Building Industry Press, 2003.
Cui Xiaoqian, "On the Application of the Balance Valve." *Proceedings of the 12th Academic Symposium on Thermal Power Construction*, Zhengzhou, Beijing, China Construction Industry Press, 1986.
Chen Qiang, male, born February 1976, engineer, address: Graduate School of Logistics Engineering, People's Liberation Army, Postal Code: 400016, Tel: (023), Mobile: , E-mail: cq1997.