1. Structure and working principle of radiator temperature control valve
Temperature control in the user's room is achieved by the radiator thermostatic control valve. The radiator thermostatic control valve is composed of a thermostat controller, a flow regulating valve and a pair of connecting members, wherein the core component of the thermostat controller is a sensor unit, that is, a warm pack. The temperature pack can sense the change of the ambient temperature and produce a volume change, which drives the valve spool to generate displacement, and then adjusts the amount of water in the radiator to change the heat dissipation of the radiator. The temperature setting of the thermostatic valve can be artificially adjusted, and the thermostatic valve will automatically control and adjust the water volume of the radiator according to the setting requirements, so as to achieve the purpose of controlling the indoor temperature.
2. The regulation characteristics of the radiator are determined by the thermal characteristics of the radiator, the flow characteristics of the temperature control valve and the valve authority.
The ratio of the flow rate of the temperature control valve to the full open flow rate at a certain opening degree is called the relative flow rate; the ratio of the stroke of the temperature control valve at a certain opening degree to the full stroke is called the relative stroke. The relationship between relative stroke and relative flow is called the flow characteristic of the thermostatic valve, ie: G/Gmax = f(l). The relationship between them is characterized by linear characteristics, fast opening characteristics, equal percentage characteristics, parabolic characteristics and so on.
For the radiator, from the perspective of water conservancy stability and heat regulation, the relationship between heat dissipation and flow is expressed as a cluster of curves. As the flow G increases, the heat dissipation Q gradually becomes saturated. In order to make the system have good regulation characteristics, it is easy to adopt a regulating valve with equal percentage flow characteristics to compensate for the nonlinear influence of the radiator itself (1).
The effect of valve authority on the regulation characteristics. The adjustable ratio R is the ratio of the maximum flow to the minimum flow that the thermostatic valve can control:
R=Gmax/Gmin
Gmax is the flow rate when the temperature control valve is fully open, and can also be regarded as the design flow rate of the radiator; Gmin varies with the weight of the temperature control valve. In the radiator system, since the temperature control valve is connected in series with the radiator, the relationship between the adjustable ratio R and the valve weight is: R = Rmax (2)
Taking a model of temperature control valve and radiator as an example, the flow capacity of the radiator is 5m3/h, the valve weight of the temperature control valve is 88%, the actual adjustable ratio is 28, and the corresponding flow rate can be adjusted by 100%- 4%. The actual adjustable range of heat dissipation of the radiator under different inlet and outlet temperature differences is shown in the table.
Import and export temperature difference (°C) 25 20 15 10 5
Adjustable range (%) 100~11.6 100~13.5 100~16.1 100~20.2 100~28
It can be seen that when the temperature difference between the inlet and outlet of the radiator is small, the actual adjustable range of the amount 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 is worth noting that the high resistance of the temperature control valve is determined by the adjustment characteristics of the radiator. The design of the temperature control valve must be considered in order to avoid the situation of insufficient capital pressure.
3. Temperature control valve installation position
3.1 Radiator thermostatic valves are generally installed on the inlet pipe of each radiator or the main inlet inlet pipe of the household heating system. Especially for the built-in sensor, vertical installation is not recommended, because the thermal effect of the valve body and surface pipe may cause the wrong operation of the thermostat controller. It should be ensured that the sensor of the thermostatic valve can sense the temperature of the circulating air in the city and must not be used by the curtain box. Covered by a heating cover.
3.2 In order to reduce investment, it is proposed to install only one temperature control valve on the indoor system (one heating system).
Normally, a thermostatic valve should be installed on each set of radiators (ie each room). In order to reduce investment, it is proposed to install only one temperature control valve on the indoor system (one heating system). The following is the first analysis of the thermal characteristics of the single-tube system, that is, the flow and room temperature changes, and pointed out the installation method of the temperature control valve.
3.2.1 Single-tube indoor system only installs a temperature control valve in the end room. The five-story upper-single-tube single-flow downstream system (also applicable to the indoor single-tube downstream system) is calculated using the thermal network simulation analysis software. The results are shown in Table 1. Table 1 shows the case where the water supply temperature is constant. This situation is more representative than the actual working condition in which a large heating system has uneven flow distribution. Under the design external temperature, if the actual flow rate is less than the design flow rate (relative flow rate is less than 1), the upper layer heat and the lower layer cold phenomenon occur. Where the actual flow rate is greater than the design flow rate (relative flow rate is greater than 1.0), the upper layer cold and lower layer heat occur. Situation.
Table 1: Flow rate and room temperature change when the water supply temperature is constant in the upper split single-tube downstream system
Room temperature (°C)
Relative flow rate (%) 5 layers 4 layers 3 layers 2 layers 1 layer
1.80 18.5 18.7 18.9 19.3 19.6
1.00 18.6 18.3 18.2 17.7 17.5
0.48 17.8 16.8 15.8 14.8 13.5
0.24 17.3 15.3 12.3 9.9 8.6
Note: water supply temperature 81 ° C
The above-mentioned change law between room temperature and flow rate is universal. When the outdoor temperature is not equal to the design outside temperature. This change law still exists. The only difference is that when the external temperature is designed, that is, when the temperature is the coldest, the vertical deviation of the system is the most serious, that is, the room temperature deviation between the highest layer and the lowest layer is the largest; as the temperature is warm, the vertical imbalance It has also gradually slowed down. The reason for this vertical imbalance phenomenon in a single pipe system is mainly caused by the inconsistency between the flow rate change and the surface temperature of the radiator. In general, the amount of heat dissipated by the heat sink depends primarily on the average surface temperature of the heat sink. In the design state, the heat transfer area of ​​the radiator is selected according to the average temperature of the design surface of each layer of the radiator under the design conditions. However, in actual operation, due to the uneven distribution of flow, the ratio of the average temperature of the surface of the radiators of each layer will be different from the design conditions. When the actual flow rate of the riser is less than the design flow rate (ie, the relative flow rate is less than 1.0), the temperature difference between the supply and return water of the riser is greater than the temperature difference during the design. At this time, the average surface temperature of the upper radiator is higher than the average surface temperature of the lower radiator. It is more conducive to heat dissipation, so there is an upper heat and cold phenomenon; when the relative flow rate is greater than 1.0, the opposite is true.
The vertical imbalance of the single-tube system is characterized by the higher the flow rate and the higher the room temperature at the end room; the smaller the flow rate, the lower the room temperature at the end room. According to this thermal characteristic, for a single-tube system, one temperature control valve per household should follow the following principles. Ann:
(1) For a single-tube downstream system, a temperature-controlled valve shall be installed on the radiator at the end of the indoor system;
(2) For a single-tube indoor system with a spanning pipe, a temperature-controlled valve shall be installed on the inlet water supply pipe or return pipe of the indoor system. The remote temperature sensor of the temperature control valve shall be placed at the end of the indoor system. in;
(3) For the upper split single-pipe downstream system of the old building, one temperature control valve of each riser should be installed on the radiator of the lowest floor room. At this time, the heat supply should be measured by the heat distributor. It should be pointed out that the use of such a temperature control valve has the advantages of improving the regulation performance of the heating system and reducing the initial investment of the project; the disadvantage is that the room temperature of each room is the same standard and cannot be adjusted as desired. .
3.2.2 Double-tube indoor system A temperature-controlled valve is installed at the indoor entrance. The vertical misalignment of the double pipe system is caused by changes in the system flow caused by changes in the natural circulation action head. The ideal solution for this type of system is to have a thermostatic valve on each radiator. Some real estate developers are reluctant to increase investment and cancel all temperature control valves, although there will be no serious imbalances in the indoor system, but it will inevitably lead to vertical imbalance between the layers in the building. This is also proven in engineering practice. In order to reduce the cost and not affect the adjustment function of the heating system, in the double-tube indoor system, a temperature control valve is installed at the indoor entrance, and the remote temperature sensor can be placed in any room. This solution, although the room temperature adjustment of each room lacks flexibility, it improves the unevenness of heat and cold between the layers in the building, which is in line with the current domestic economic situation.
4, the energy saving effect of the radiator thermostatic valve in the heating system
The radiator thermostatic valve is correctly installed in the heating system, and the user can adjust and set the temperature according to the requirements of room temperature. This ensures that the room temperature of a room is constant, avoiding the imbalance of the riser water volume and the uneven room temperature of the upper and lower layers of the single pipe system. At the same time, through the effects of constant temperature control, free heat, economic operation, etc., it can not only improve the comfort of the indoor thermal environment, but also achieve energy saving.
Constant temperature control - Dynamically adjust the output as the climate changes, control the room temperature constant, and save energy. At the same time, eliminating temperature levels and vertical offsets can also be beneficial loops to reduce energy waste while at the same time making unfavorable loops meet flow and temperature requirements.
Free heat—the heat of sunlight, human activity, cooking, electrical appliances, etc. is called heating free heat. This part of the heat is not fully considered in the design operation due to uncertainty, and is only considered as a safety factor. After the room temperature control, this part of the energy can replace part of the heat dissipation. At the same time, the room temperature difference of different orientations can be eliminated, which improves the comfort of the city's thermal environment and saves energy.
Economic operation - office buildings, public buildings do not need full load heating at night and rest days. Residential users also try to avoid unheated heat to save energy and heat. Different temperature control modes can be implemented in different rooms: when the staff is concentrated in the living room, the bedroom temperature can be lowered, the living room temperature can be increased; during the rest period, the bedroom temperature can be increased, the living room temperature Can reduce settings and more. These measures can be achieved through the radiator thermostat valve, which has achieved energy saving purposes.
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