Thermostatic valve?

Searched on Baidu online. Types of thermal expansion valves: Thermal expansion valves are classified into internal balance type and external balance type based on their balancing mechanism ； External balance thermal expansion valves come in two structural types: F-type and H-type. 　　1) Structure and working principle of the internal balance expansion valve: The temperature sensor bulb is filled with refrigerant and placed in the pipeline at the outlet of the evaporator. The temperature sensor bulb is connected to the upper part of the diaphragm via a capillary, allowing it to detect the temperature of the refrigerant at the evaporator outlet; meanwhile, the pressure at the evaporator inlet is sensed by the lower part of the diaphragm. If the air-conditioning load increases, the hydraulic refrigerant evaporates completely in the evaporator ahead of time; as a result, the temperature of the refrigerant at the evaporator outlet rises, the pressure on the diaphragm increases, which pushes the valve stem and increases the opening degree of the expansion valve. This leads to an increased flow of refrigerant into the evaporator, thereby increasing the cooling capacity ； If the air-conditioning load decreases, the refrigerant temperature at the evaporator outlet drops; based on the same principle, this causes the valve opening to decrease, thereby controlling the flow rate of the refrigerant. 2) Structure and working principle of the external balance expansion valve: The external balance expansion valve operates on basically the same principle as a balance expansion valve; the difference is that in the case of the external balance expansion valve, it is the pressure at the inlet of the evaporator that acts on the diaphragm ； The diaphragm of the external balance expansion valve experiences the pressure at the evaporator outlet. 　　3) H-type expansion valve: The H-type thermal expansion valve has four connections to the refrigeration system; two of these connections are the same as those found in conventional thermal expansion valves, one connects to the liquid storage dryer, and the other connects to the inlet of the evaporator ； The other two interfaces are connected to the evaporator outlet and the compressor inlet, respectively. The temperature sensor is located directly in the refrigerant airflow at the evaporator outlet. By eliminating the temperature sensing bulb, capillary tube, and external balance tube found in F-type thermal expansion valves, this expansion valve features improved control sensitivity, a compact design, and reliable vibration resistance. 　　Thermal expansion valves are widely used in central air conditioning chillers. It can both control the supply volume of liquid to the evaporator and throttle the saturated liquid refrigerant. Based on the differences in their structural design, thermal expansion valves are divided into internal balance type and external balance type. Considering that the flow of the refrigerant through the evaporator results in a certain pressure loss, and in order to reduce the superheat at startup and improve the utilization rate of the evaporator’s heat transfer area, when the temperature drop in the evaporator caused by the pressure drop of the refrigerant from the outlet of the self-acting expansion valve to the outlet of the evaporator exceeds 2–3°C, an externally balanced thermal expansion valve should be used.

I only know that there is also an expansion valve in our flat gate valve. It has a double-plate structure. It is used in oil fields.