Thermostatic control valves can be classified according to the different temperature-sensitive media filled in their temperature packs, and can be roughly divided into the following four categories:
1) The medium filled in the steam warm bag type warm bag is a low-boiling point liquid. When the external temperature rises, part of the liquid vaporizes into gas. The volume of the warm bag increases to push the valve stem, and the valve opening is closed to reduce the inflow of water into the radiator. When the external temperature decreases, part of the gas is liquefied into liquid again. The volume of the warm bag decreases and the opening of the valve increases, thereby increasing the inflow of water into the radiator. The temperature-sensitive medium in this temperature bag is often in a mixed state of gas and liquid. Its advantage is that the action time is rapid, but the sealing requirements for the temperature bag are very strict, and it is rarely used in China at present.
2) The temperature-sensitive medium filled in the liquid warm bag type warm bag is a special liquid, generally methanol or toluene. This kind of warm bag is large in volume and short in action time, and is currently widely used in China.
3) The solid warm bag type warm bag is filled with solids with high expansion coefficients, and the balance valves are mostly made of paraffin. Since the volume change of solids is smaller than that of gases and liquids when heated (cold), its temperature sensing action is slower, but its volume is smaller than that of liquids, and it is also used in some countries.
4) Metal sheet The temperature sensing device of the thermostat controller is a special alloy metal sheet with memory function. Due to thermal expansion and contraction, this metal sheet drives the temperature control valve to operate. This kind of product requires strict experiments and testing of its temperature sensing device before leaving the factory. At the same time, due to the characteristics of metal such as fatigue fracture after frequent expansion and bending, and the metal is malleable, it will be affected by this kind of temperature sensing device life and accuracy. Some domestic manufacturers produce such thermostats valve products, but their foreign products are rarely seen.
