What are the reasons for the frosting of Danfoss refrigeration compressors?
The importance of refrigeration compressors in the entire cold storage refrigeration system is self-evident. Danfoss refrigeration compressors are believed to be well known. Next, watch A&S Aerodynamic Co., Ltd teach you how to turn around.
If a large amount of water vapor or refrigerant is drawn into the Danfoss refrigeration compressor, it may cause frost on the cylinder head of the refrigeration compressor. Even worse, it can even cause crankcase frosting. So what is the source of water vapor or refrigerant entering the refrigeration compressor? There are two main points:
1. The opening of the thermal expansion valve is too large, or the installation of the temperature sensor package and the looseness of the fixing are loose. Mainly because the temperature sensor package may feel the temperature too high in this case, which causes the valve core to open automatically;
The thermal expansion valve mainly reflects the superheat at the outlet of the evaporator, and the refrigerant flow rate of the evaporator is automatically adjusted if there is a deviation in the degree of superheat at the outlet of the evaporator.
When the value detected by the transmitter deviates from the given value, the physical quantity of the transmitter changes. It also produces enough energy to directly push the actuator. The position change of the general actuator and the set parameters are directly linked.
In the previous content, we repeatedly introduced the superheat expansion valve according to the balance method, generally divided into two types: internal balance type thermal expansion valve and external balance type thermal expansion valve. The liquid refrigerant absorbs heat in the evaporation of the evaporator and then completely vaporizes when it flows to the evaporator outlet. And usually accompanied by a certain degree of superheat. The temperature sensing cylinder of the thermal expansion valve is generally in close contact with the outlet pipe of the evaporator, so that the temperature of the evaporator outlet is felt.
This pressure difference is balanced by the tension of the ram and the adjustment spring below the diaphragm. If the tension of the adjusting spring is changed, the topping force of the jack can be changed, thereby changing the opening degree 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 automatically changes the needle opening according to the temperature of the evaporator outlet, so that the evaporator outlet superheat is maintained at a certain value.
The opening of the thermal expansion valve is too large, and the temperature sensor package is installed incorrectly or loosely fixed, so that the perceived temperature is too high and the valve core is abnormally opened, so that a large amount of wet steam is sucked into the compressor, causing the cylinder head to frost. The thermal expansion valve is used in conjunction with the adjustment of the superheat of the evaporator. If the evaporator outlet superheat is too large, the superheating section at the rear of the evaporator is too long, and the cooling capacity will be significantly reduced; the outlet superheat is too small, which may cause the compressor to slam or even the cylinder head to frost. It is generally considered that the expansion valve is adjusted to have an operating superheat of 3 ° C to 8 ° C at the outlet of the evaporator.
2. When the liquid supply solenoid valve leaks or stops, the expansion valve is not closed tightly, resulting in a large amount of refrigerant liquid accumulated in the evaporator before starting. The temperature relay is used in conjunction with a solenoid valve to control the temperature of the reservoir.
The temperature relay of the temperature relay is placed in the cold storage. When the cold storage temperature is higher than the upper limit of the set value, the temperature relay contact is turned on, the solenoid valve coil is energized, the valve is opened, the refrigerant enters the evaporator to cool down; when the storage temperature is low At the lower limit of the set 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 temperature of the reservoir can be controlled within the required range.
3. When the Danfoss compressor is started, the suction shut-off valve is too open or too large.
4. When there are too many refrigerants in the system, the liquid level in the condenser is higher, the condensing heat exchange area is reduced, and the condensing pressure is increased, that is, the pressure before the expansion valve is increased, and the amount of refrigerant flowing into the evaporator is increased, liquid cooling The agent does not completely evaporate in the evaporator, so the compressor draws in wet steam, the cylinder hair is cold or even frosted, and may cause "liquid attack", and the evaporation pressure will also be high.