Treatment of frost in crankcase when compressor head frost is serious

Treatment of frost in crankcase when compressor head frost is serious The frost on the cylinder head is caused by a large amount of wet steam or refrigerant sucked into the compressor. The main reasons for this situation are: 　　 1. The opening of the thermal expansion valve is adjusted too large, the temperature sensor is installed incorrectly or the fixing is loose, so that the temperature is too high and the valve core is opened abnormally. The thermal expansion valve is a direct-acting proportional regulator that uses the superheat at the outlet of the evaporator as a feedback signal and compares it with a given superheat value to generate a deviation signal to regulate the flow of refrigerant into the evaporator. Letter, regulator and actuator in one. 　　When the parameter measured by the sender deviates from the given value, the physical quantity of the sender changes and generates enough energy to directly drive the actuator. The position change of the actuator is proportional to the adjusted parameter. The thermal expansion valve can be divided into two types: internal balance type thermal expansion valve and external balance type thermal expansion valve according to different balance methods. 　　Liquid refrigerant evaporates and absorbs heat in the evaporator. When it flows to the outlet of the evaporator, it has completely vaporized and has a certain degree of superheat. The temperature-sensing cylinder of the thermal expansion valve is close to the outlet pipe of the evaporator, and the temperature of the outlet of the evaporator is felt. If the liquid filled in the warm pack is the same as the refrigerant, the pressure of the liquid above the diaphragm of the thermal expansion valve is greater than the pressure of the liquid below the diaphragm, and the higher the temperature of the evaporator outlet, that is, the greater the superheat, the higher the temperature above the diaphragm The greater the liquid pressure. 　　 This pressure difference is balanced by the tension of the adjusting spring under the diaphragm through the ejector rod. If the tension of the adjusting spring is changed, the jacking force of the jack can be changed, thereby changing the opening of the needle valve. Obviously, the degree of superheat of the evaporator will also cause changes in the opening of the needle valve. When the adjustment spring is adjusted to a certain position, the expansion valve will automatically change the opening of the needle valve according to the temperature of the evaporator outlet to keep the evaporator outlet superheat at a certain value. 　　The opening of the thermal expansion valve is adjusted too large, the temperature sensor is installed incorrectly or the fixing is loose, so that the temperature is too high and the valve core is opened abnormally, causing a large amount of wet steam to be sucked into the compressor and causing frost on the cylinder head. The thermal expansion valve is used in conjunction with the adjustment of the superheat when the evaporator is in operation. 　　The evaporator outlet superheat is too large, then the evaporator rear superheat section is too long, the cooling capacity will be significantly reduced; the outlet superheat is too small, and may cause compressor liquid blow or even frost on the cylinder head. It is generally believed that the expansion valve should be adjusted to the working superheat of the evaporator outlet at 3℃～8℃. 　　 2. The liquid supply solenoid valve leaks or the expansion valve is not closed tightly during shutdown, resulting in a large amount of refrigerant liquid already accumulated in the evaporator before starting. The temperature relay is used in conjunction with the solenoid valve for control. The temperature sensing package of the temperature relay is placed in the cold storage. When the temperature of the cold storage is higher than the upper limit of the starting set value, the temperature relay contact is closed, the solenoid valve coil is energized, the valve is opened, and the refrigerant enters the evaporator to cool down; when the temperature of the storage is low At the lower limit of its setting value, the temperature relay contact is opened, the solenoid valve coil current is cut off, the solenoid valve is closed, and the refrigerant stops entering the evaporator, so that the storage temperature can be controlled within the required range. 3. When there is too much refrigerant in the system, the liquid level in the condenser is higher, the condensation heat exchange area is reduced, and the condensation pressure increases, that is, the pressure in front of the expansion valve increases, the amount of refrigerant flowing into the evaporator increases, and liquid refrigeration The agent cannot be completely evaporated in the evaporator, so the compressor sucks in wet steam, the cylinder is cold or even frosted, and may cause "liquid strike", and the evaporation pressure will be high.