Development and principle of thermostatic control

Development and principle of radiator thermostatic control valve 1. Development of radiator thermostatic control valve:

radiator thermostatic control valve first appeared in Europe in the 1940s. In the early 1980s, China began to develop radiator thermostatic control valve by itself. In the 1990s, Nanjing Julong's products are mainly divided into four categories: high-performance modified nylon, high-performance engineered polypropylene In the middle and late generation of high-performance alloy materials and plastic wood environmental engineering materials in the industry, with the continuous deepening of heat metering policies and technologies and the personalized requirements of the broad masses of the people for room temperature, various domestic and imported radiator thermostatic control valve products came into being and were adopted in many domestic engineering projects

in the room temperature control of radiator heating, the radiator thermostatic control valve can be used for control, and the manual thermostatic valve with good resistance characteristics can also be used for control. The advantage of using radiator thermostatic control valve control is that it can make better use of "free heat" to achieve the purpose of energy saving, while avoiding the cumbersome repeated adjustment by users

II. Working principle and classification of radiator thermostatic control valve

radiator thermostatic control valve is composed of thermostatic controller and valve body. Its function principle is that the user turns the thermostatic controller to the required set temperature. When the indoor temperature exceeds the set temperature, the temperature bag (filled with temperature sensing medium) in the thermostatic controller expands by heating, and the volume increases. Push the valve rod to turn down the valve, reduce the water flow of the radiator, and make the room temperature reach the set temperature. When the indoor temperature is lower than the set temperature, the temperature chamber shrinks and the volume decreases. The return spring in the valve core pushes back the valve rod, making the valve open larger and increasing the water flow of the radiator until the room temperature reaches the set value

1. thermostatic controller

thermostatic controller can be divided into built-in type and remote transmission type according to the location of its temperature packet. Because the temperature bulb feels the temperature of the surrounding air, and the regulating action of the temperature control valve is also caused by the change of the temperature bulb volume, the position of the temperature bulb is very important for the correct use of the temperature control valve. In most cases, when it is necessary to adjust the indoor temperature of the room where this group of radiators is located, the temperature control valve inside the temperature bag should be used. In some specific cases, such as the radiator of this group is blocked by the radiator cover, the temperature control valve is located in the cover, or there are other heat (cold) sources within the close distance of the temperature control valve, such as cooking utensils, strong lighting fixtures, etc., at this time, the temperature bag feels the local high temperature around, not the accurate room temperature, so it is advisable to use a remote thermostatic controller, and place the sensor in a place that can accurately adjust the room temperature and is less disturbed by strong heat sources, In order to achieve the purpose of accurately controlling the room temperature. 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 mainly adjusts the temperature of the living room or master bedroom. The remote temperature control valve can also be used to place the temperature sensor in the living room or master bedroom to collect its temperature for adjustment

thermostatic controllers can be classified according to the different temperature sensing media filled in their temperature packets, which can be roughly divided into the following four categories

(1) steam bulb type

the medium filled in the temperature chamber is a low boiling point liquid. When the external temperature rises, part of the liquid vaporizes into gas, the volume of the temperature chamber increases, pushes the valve stem, turns down the valve opening, and reduces the water inflow into the radiator. When the external temperature decreases, part of the gas liquefies into liquid again, the volume of the temperature chamber decreases, and the valve opening increases, thereby increasing the water inflow into the radiator. The temperature sensing medium in this temperature bag is often in a state of gas-liquid mixture, which has the advantage of rapid action time, but the sealing requirements of the temperature bag are very strict, and it is rarely used in China at present

(2) liquid bulb type

the temperature sensing medium filled in the temperature bag is a special liquid, usually methanol or toluene. This kind of temperature ladle has large volume and short action time. At present, it is widely used in China

(3) solid bulb type

the temperature ladle is filled with solids with high expansion coefficient, mostly paraffin, etc. Due to the small change in the heated (cold) volume of solid relative to gas and liquid, its temperature sensing action is slow, but its volume is relatively small relative to the liquid bulb, which is also partially applied in China

(4) metal sheet

the temperature sensing device of its thermostatic controller is a special alloy metal sheet with memory function, which expands when heated and contracts when cooled, driving the action of the temperature control valve. The temperature sensing device of this product needs to be strictly tested and tested before leaving the factory. At the same time, the life and accuracy of this temperature sensing device will be affected because the metal has the characteristics of fatigue fracture after frequent expansion and bending, and the metal has ductility. Some domestic manufacturers produce this kind of temperature control valve with LED touch screen products, which are rarely seen in foreign products

2. Temperature control valve body

the temperature control valve body is generally made of copper with nickel plating on the surface. According to the angle between its water inlet and outlet and the installation of temperature controller spool, it can be divided into the following types

(1) straight through temperature control valve body: the angle of water inlet and outlet of the temperature control valve is 180 degrees

(2) angle temperature control valve body: the angle of water inlet and outlet of the temperature control valve is 90 degrees

(3) three dimensional temperature control valve body (three-dimensional temperature control valve): the water inlet, water outlet and valve core of the temperature control valve form an included angle of 90 degrees respectively, similar to the X, y and Z coordinates

(4) special combined temperature control valve body: for some new radiators (such as sanitary radiators) and some connection methods (such as single pipe crossover), many manufacturers have also introduced some special combined temperature control valve bodies. I will not list them here

3. Kv value and kVs value of temperature control valve

the water resistance characteristics of foreign control valve products are generally expressed in Kv value. At present, many domestic temperature control valve products also use Kv value to indicate the water resistance characteristics. Kv value is defined as the flow through the regulating valve when the pressure drop before and after the regulating valve is 1bar. KVs value refers to the Kv value at the maximum opening of the throttle valve composed of computer, transmitter, microprocessor, etc. The following formula can be used to convert Kv value into local resistance coefficient commonly used in China