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Radiator thermostatic control valve principle and application
Abstract: This paper introduces the history, principle and classification of radiator thermostatic control valve. Combined with the engineering examples, it expounds how to use the radiator thermostatic control valve correctly in the different radiator arrangement in the heating system in the new situation. In the early 1940s, China began to develop its own radiator thermostatic control valve, into the mid-90s, the late, with the heat exchanger thermostat control valve household metering bypass radiator thermostatic control valve in the 1940s first appeared in Europe, With the continuous deepening of heat metering policy and technology and the masses of people on the personalized requirements of the room temperature, a variety of domestic and imported radiator thermostatic valve products came into being, and in many domestic projects have been adopted. In the radiator heating room temperature control radiator thermostat control valve can be used to control, but also can be used to control the resistance of the manual temperature control valve better. Advantages of using radiator thermostatic control valve control is to make better use of "free heat" to achieve the purpose of saving energy, and meanwhile avoiding the cumbersome repeated adjustment of the user. First, the radiator thermostatic control valve working principle and classification Radiator thermostatic control valve consists of two parts of the thermostat controller and the valve body. Its principle of action for users to spin-thermostat controller to the desired set temperature, when the indoor temperature exceeds the set temperature, the temperature controller within the temperature package (filled with warm medium) by thermal expansion, increase the volume to promote the valve stem, The valve is closed, reducing the radiator inlet flow, so that the room temperature to set the temperature. When the indoor temperature is lower than the set temperature, the temperature of the package shrinkage, the volume decreases, the valve spring return to the valve spring, the valve open large, increasing the radiator inlet flow until the room temperature reaches the set value . 1. Thermostatic controller thermostat according to its location in the temperature package can be divided into temperature package Built-in and Far EasTone. As the temperature of the package feel the ambient air temperature, while the thermostatic valve adjustment action is also due to changes in the temperature package generated, so the location of the temperature package for the correct use of temperature control valve is very important. In most cases, you need to adjust the indoor temperature of the room where the set of radiators, the thermostat should be built-in temperature control valve. In some specific cases, if the radiator of this group is covered by the radiator cover, the temperature control valve is located in the hood or there are other hot (cold) sources within the close range of the temperature control valve, such as stoves and strong lighting fixtures, etc. Temperature package is felt around the local high temperature is not accurate room temperature should be used remote-type thermostat controller, the sensor can accurately regulate the room temperature by the heat source less interference in order to achieve accurate control of the room temperature purpose. In some special systems, such as the horizontal single-pipe downstream system, the radiator temperature control valve can only be installed in the first group of radiators, and the user adjusts the temperature in the living room or the master bedroom, and may also use the remote-type temperature Control valve, the temperature sensor placed in the living room or master bedroom to collect its temperature adjustment. The thermostat controller can be classified according to the different temperature mediums which are felt by its temperature package, which can be roughly divided into the following four categories. (1) steam temperature package type. The medium filled in the temperature package is a kind of low-boiling liquid. When the external temperature rises, some of the liquid is vaporized into gas, and the volume of the temperature package increases to push the valve stem to close the small-valve opening and reduce the inlet flow into the radiator When the outside temperature decreases, some of the gas is liquefied again into liquid, and the volume of the warm bag decreases. The valve opening increases to increase the water inflow of the radiator. This warm package temperature sensing medium is often in a gas-liquid mixed state, the advantage of the role of time is rapid, but very strict requirements of warm package seal, the current application in the country rarely. (2) liquid temperature package type. Temperature package filled with warm medium for a special liquid, usually methanol or toluene. Such a warm package larger, shorter duration, is currently widely used in China. (3) solid temperature package. Filling within the temperature package is a high coefficient of expansion of the solid, mostly paraffin and so on. As the solid relative to the gas and liquid heating (cold) small changes in volume, so the temperature sensing action slower, but the volume is relatively small liquid temperature package, there are some applications in the country. (4) metal slice. The thermostat controller temperature sensing device is a special kind of alloyed metal sheet with memory function. The sheet metal is expanded by the heat and contracted by the cold to drive the thermostatic valve to move. Such products require rigorous testing and testing of their temperature sensing devices before they leave the factory. At the same time, due to metal fatigue-cracking and other characteristics change after frequent stretching and bending, and the metal is ductile, Device life and accuracy impact. Some domestic manufacturers to produce such temperature control valve products, its foreign products rarely seen. 2. Thermostatic valve Body temperature control valve body is generally copper, nickel appearance, according to its inlet and outlet temperature and installation of the spool angle can be divided into the following categories. (1) through-type temperature control valve body: temperature control valve inlet and outlet angle of 180 degrees. (Figure 1) (2) angle temperature control valve body: temperature control valve inlet and outlet angle of 90 degrees. (Figure 2) (3) three-dimensional temperature control valve body (three-dimensional temperature control valve): temperature control valve into the water, water and the valve core into 90-degree angle, similar to X, Y, Z coordinates. (Figure 3) (4) Special combination of temperature control valve body: for some new radiators (such as bathroom radiators, etc.) and some connection methods (such as single-tube span), many manufacturers also introduced some special combination Thermostatic valve body. Do not list it here. 3. Temperature control valve Kv value and KVV value Foreign regulating valve product water resistance characteristics generally expressed as Kv value, many domestic temperature control valve products also use the Kv value marked water resistance characteristics. The Kv value is defined as the flow rate through the regulator when the pressure drop across the front valve of the regulator valve is 1 bar. Kvs value represents the Kv value of the maximum opening of the control valve. The following formula can be used to convert Kv values ​​to local resistance coefficients commonly used in China. Second, the radiator thermostatic valve in a variety of radiator system, the proper use of 1. In most of the old radiator heating systems in our country, the vertical single pipe or double pipe system is adopted. (1) In the vertical single-pipe downstream system, the radiator of the radiator can not be installed because the water of the front radiator flows through the next radiator and each radiator is located on a different floor. Consider converting such a system to a vertical single-tube spanning system so that you can install a thermostatic valve in front of each radiator or adjust a manual valve with better performance. (Fig. 4) (2) In the vertical two-pipe downstream system, due to the vertical offset problem, the radiator thermostat valve with preset function can be installed during the system transformation. The so-called preset function that the thermostatic valve body has a predetermined initial resistance of the device, the device can be set by the initial resistance of the temperature control valve, set the initial resistance between different floors can be resolved to some extent Vertical imbalance problem. However, this method in the actual use of the need to do the following work. Designers should do a more detailed hydraulic calculation. During installation, the contractor should carefully compare the flow resistance diagrams of the water resistance provided by the supplier to the accurate preset position of the thermostatic valve. After the operation of water supply, individual adjustments may be made according to the specific circumstances. Due to the dual-pipe system with high resistance temperature control valve (to be described in detail later), while the preset adjustment further reduces the valve opening, so there is a high demand for heating water quality, otherwise easily lead to obstruction. (Figure 5) 2. In recent years, with the continuous development of household heat metering technology, indoor heating in the vast number of civil and industrial buildings set up a ring system has also been widely used, but also the most widely used indoor design Heating arrangement. Radiator heating horizontal layout is divided into: horizontal single-pipe downstream (standard is not allowed, not recommended), horizontal single-tube leapfrog, on the sub-two-tube type, the next sub-two-tube, Type and other categories. (1) Horizontal Single-pipe Downstream: The horizontal single-pipe downflow system has the similarities with the vertical single-pipe downstream system described above. After the heating hot water flows through the former group of radiators and then flows into the next group of radiators , So it is not advisable to install a temperature control valve or a manual adjustment valve on each radiator. This system installs the temperature control valve, may consider in the first group radiator front of water installs the far-reaching temperature control valve, the thermostatic valve remote sensor in the main room which needs the temperature control, like master bedroom, living room. The drawback of this arrangement is that the action of the temperature control valve will lead to the change of the heating hot water flow in the whole room, and the signal collected by the temperature control valve is only the signal of one of the rooms, and the temperature of the other rooms fluctuates accordingly, And can not be effectively fine-tuned. This approach can also be considered in the first set of radiator front-end installation of high quality, opening and flow of a linear relationship between the manual control valve, the valve can be coarse adjustment of the system. This radiator arrangement is "standard" is not allowed, we do not recommend this method. (Figure 6) (2) horizontal single-tube leaping: horizontal single-tube leapfrog is more used in recent years, an indoor arrangement, the advantage of each group can be individually for accurate temperature control of the radiator, to adapt to the user Room personalized requirements, but also in line with "household metering, sub-room temperature," the policy requirements. At the same time as part of the hot water (without radiator heat transfer) into the next set of radiators to improve the next set of radiator water temperature to ensure the heating quality. Relative to other households set ring indoor horizontal layout, single-tube leap is a relatively simple, wide range of adaptations to the layout. In specific applications, there are many different forms of application depending on the variety of thermostatic valve products used (manual regulators). (2.1) two-way temperature control valve plus cross-tube form: (Figure 7) This way the structure is relatively simple, low cost. However, there are some problems in practical application. Many projects, due to indiscriminate use of high-resistance two-way thermostatic valve, causing the radiator into the hot water is too small. Some projects in some wrong use, in order to meet the needs of the radiator water had to install a regulating valve across the pipe to increase part of the resistance across the pipe. Even with a low resistance two-way thermostatic valve also have to calculate the radiator inlet flow coefficient. The radiator inlet flow coefficient is the ratio of the resistance of the radiator passage and the passage of the pipe. Single tube in the level of cross-tube system, generally more than 30%, to ensure that the radiator inlet flow. However, this calculation is more complicated. (2.2) Bypass thermostatic valve form Now some manufacturers have introduced a special by-pass thermostatic valve that accommodates radiator access (including temperature control Valve) combined with the bypass branch as a whole, and the bypass branch becomes a bypass valve with adjustable resistance. Its advantage is to simplify the calculation and installation, due to the adjustable bypass ratio, to adapt to a wide range of systems can be individually adjusted according to the specific circumstances. Such bypass temperature control valve can also calculate the radiator inlet flow coefficient. Currently in some projects have also been gradually adopted. (Fig. 8) (2.3) Other Special Types of Thermostatic Valves There are many new types of radiators currently on the market. To cope with these new radiators, various special types of thermostatic valve products have emerged. (3) horizontal double tube form. Dual-level indoors also through the radiator in each group to install water temperature control valve, sub-room temperature control. Adopting this kind of arrangement, the heating quality is good, multiple sets of radiators can be connected in series, and different radiators have little influence on the system through the thermostatic valve regulation. However, whether the upper or lower level double pipe arrangement is adopted, the indoor pipe More complex layout, the overall decoration of the room, aesthetics have a certain impact. (Figure 9) This arrangement is the same as the vertical two-tube system, the greater the end resistance, the less impact of system fluctuations, it should be selected high-resistance radiator thermostatic valve. (4) Radiation double tube. This arrangement is also known as the "Octopus" layout, also belong to the indoor horizontal double-tube category. Install one point / sump at the entrance of each household. Each loop of the sump / sump is connected with a set of radiators. Its advantages are flexible layout, conducive to the sub-room temperature control, but the pipeline layout is more complex, higher cost than the previous several indoor layout. In this system should also refer to the dual-pipe system using high temperature resistance temperature control valve, if the use of reliable manual valve can be installed in each group radiator inlet, can also be installed in each sub / collector On the centralized control. In August 2003, the Ministry of Construction issued the Guiding Opinion on Pilot Work on Reform of Urban Heating System. In the future, new public buildings and residential buildings in cities and towns, where central heating facilities are used, must be designed and installed A household heating system with household metering and room temperature control and the implementation of a new method of metering according to calorie consumption. Entering the 21st century, the masses of the people are constantly increasing their demands for energy conservation and thermal comfort, and the policies of household metering and room temperature control have also been gaining in popularity. Radiator temperature control valve will also get a broader application prospects. However, the temperature control valve can not be simply installed, for different systems using what form of temperature control valve or other manual control valve, you need to go through detailed calculations and based on a deep understanding of the product, At the same time in the installation and post-commissioning should also communicate with the design and manufacturers, according to the specific circumstances of the appropriate adjustments in order to achieve full and reasonable use of the purpose. References: 1. Zhang Xihu Deng Yanchun "some common problems in heating design" 2. Xu Wei Zou Yu editor of "heating system temperature control and heat metering technology" China Planning Press 2000 edition