Electric Temperature Control Valve

Electric temperature control valve is the main regulating equipment of heating system flow regulation, a heating system without temperature control valve can not be called heat metering charging system. The structure and principle of the temperature control valve are analyzed, and the flow characteristics of the temperature control valve are combined with the flow characteristics of the radiator, and the concept of valve weight is introduced to explain how to ensure the adjustment effectiveness of the radiator system under the combined action of the heat characteristics of the radiator, the flow characteristics of the temperature control valve and the valve weight. The installation scheme of temperature control valve is also introduced. Finally, the energy-saving effect of temperature control valve is described.

The user room temperature control is achieved by radiator thermostatic control valve. The radiator thermostat control valve is composed of a thermostat controller, a flow regulating valve and a pair of connecting parts, of which the core component of the thermostat controller is the sensor unit, that is, the temperature packet. The temperature packet can sense the ambient temperature change and produce volume change, drive the valve spool displacement, and then adjust the radiator water to change the heat dissipation of the radiator. Thermostatic valve set temperature can be manually adjusted, thermostatic valve will automatically control and adjust the radiator water according to the set requirements, to achieve the purpose of controlling the indoor temperature.

Regulating characteristic

The ratio of flow and full open flow under a certain opening G/Gmax is called relative flow, and the ratio of stroke and full stroke under a certain opening l is called relative stroke. The relationship between the relative stroke and the relative flow rate is called the temperature control valve flow characteristic, that is, G/Gmax=f(l). The relationship between them is linear characteristic, fast opening characteristic, equal percentage characteristic, parabola characteristic and so on.

For the radiator, from the perspective of water stability and heat scheduling, the relationship between heat dissipation and flow rate is a cluster of upthrow curve, flow rate G increases, heat dissipation Q gradually tends to saturation. In order to make the system have good regulating characteristics, it is easy to use the equal percentage flow characteristic regulating valve to compensate for the nonlinear influence of the radiator itself (1).

Influence of valve weight on regulating characteristics. Adjustable ratio R is the ratio of the maximum flow rate and the minimum flow rate that the temperature control valve can control:

R=Gmax/Gmin

Gmax is the flow rate when the temperature control valve is fully opened, which can also be regarded as the design flow rate of the radiator; Gmin varies with the valve weight of the temperature control valve. In the radiator system, the temperature control valve and the radiator are in series, so the relationship between the adjustable ratio R and the valve weight is :R=RmaxKV0.5(2)

Taking a certain type of temperature control valve and radiator as an example, the flow capacity of the radiator is 5m3/h, the weight of the temperature control valve is 88%, the actual adjustable ratio is 28, and the corresponding flow can be adjusted in the range of 100%-4%. The actual adjustable range of heat dissipation under different temperature differences between inlet and outlet of the radiator is shown in the following table.

Import and export temperature difference (℃) 25 20 15 10 5

Adjustable range (%) 100 to 11.6 100 to 13.5 100 to 16.1 100 to 20.2 100 to 28

It can be seen that when the temperature difference between the inlet and outlet of the radiator is small, the actual adjustable range of heat dissipation is also small. However, when the temperature difference between the inlet and outlet of the radiator is less than 10 ° C, the minimum adjustable heat dissipation of the temperature control valve is about 20% of the standard heat dissipation, and the effective working range of the temperature control valve is reduced.

In addition, it should be noted that the high resistance of the temperature control valve is determined by the adjustment characteristics of the radiator, and this characteristic of the temperature control valve must be considered when designing, so as to avoid insufficient available pressure.

The basic principle is to control the inlet flow of heat exchangers, air conditioning units or other hot and cold equipment, and a heat (cold) medium to achieve the control of the outlet temperature of the equipment. When the load changes, the flow rate is adjusted by changing the opening degree of the valve to eliminate the impact of load fluctuations and restore the temperature to the set value. Its design principle is as follows:

1. Temperature perception: need to sense the temperature change of the environment or medium. Sensors (such as thermistors, thermocouples, etc.) are often used to obtain accurate temperature signals.

2. Control signal transmission: After obtaining the temperature signal, the signal is transmitted to the control system, usually through a cable or other wireless communication means to transmit the signal to the control device.

3. Control system: After receiving the temperature signal, the control system will process and judge. Depending on the size of the temperature signal and the set temperature range, the control system will decide whether to adjust the valve opening.

4. Electric actuator: Adjust the opening of the valve according to the control signal. The electric actuator usually consists of a power supply, a motor and a transmission device.

5. Valve adjustment: The electric actuator converts the rotating motion of the motor into the opening adjustment of the valve through the transmission device. For example, the flow of fluid can be controlled by rotating the valve disc or by linearly pushing the valve piston.

6. Feedback control: Monitor the actual position of the actuator and the opening of the valve through the feedback device (such as the position sensor), and return the feedback signal to the control system for correction and adjustment.

7. Control strategy: According to different application scenarios and needs, you can use different control strategies, such as proportional control, PID control and so on. By adjusting and optimizing the control parameters, accurate temperature control is realized.