Thermal expansion valves are divided into internal balance type and external balance type according to different balance methods; external balance type thermal expansion valves are divided into two structural types: F type and H type.
1) Structure and working principle of internally balanced Danfoss DANFOSS expansion valve:
Structural diagram of internally balanced F-type thermal expansion valve. The temperature-sensing bag is filled with refrigerant and placed on the outlet pipe of the evaporator. The temperature-sensing bag and the upper part of the diaphragm are connected by a capillary tube to sense the refrigerant temperature at the evaporator outlet, and the evaporator inlet pressure is felt under the diaphragm. If the load of the air conditioner increases and the hydraulic refrigerant evaporates in the evaporator ahead of time, the temperature of the refrigerant at the outlet of the evaporator will increase, the pressure on the diaphragm will increase, and the valve stem will be pushed to increase the opening of the expansion valve. When the refrigerant flow rate increases, the cooling capacity increases; if the air-conditioning load decreases, the temperature of the refrigerant at the outlet of the evaporator decreases, and the same principle of action makes the valve opening decrease, thereby controlling the refrigerant flow.
2) Structure and working principle of externally balanced Danfoss DANFOSS expansion valve:
The principle of the externally balanced expansion valve is basically the same as that of the internally balanced expansion valve, the difference is that the pressure felt under the diaphragm of the internally balanced expansion valve is the inlet pressure of the evaporator; while that felt under the diaphragm of the externally balanced expansion valve is the evaporator Outlet pressure.
3) H-type expansion valve
The H-type thermal expansion valve has four ports connected to the refrigeration system, two of which are the same as ordinary thermal expansion valves, one connected to the liquid storage drier, one connected to the evaporator inlet; the other two ports, one connected to the evaporator outlet, one Connect the compressor inlet. The temperature sensing bulb is directly in the refrigerant air flow at the outlet of the evaporator. Because the expansion valve cancels the temperature sensing bulb, capillary and external balance connecting pipe in the F-type thermal expansion valve, the adjustment sensitivity is improved, the structure is compact, and the vibration resistance is reliable.
1 From the filter drier 2 to the evaporator 3 From the evaporator 4 to the compressor 5 Measuring hole 6 Ball 7 Spring 8 Movable foot 9 Refrigerant 10 Pressure compensation under the film 11 Metal film 12 Temperature sensing element.