What are the causes of frost in refrigeration compressors

Related Info

Do you know question and answer with refrigeration compressors？

Don't panic if the refrigeration compressor suddenly stops, remember these methods!

Refrigeration compressor installation conditions and precautions

Screw compressor working principle and structure analysis

Scroll compressor 2020 or will enter the dark moment

What are the causes of frost in refrigeration compressors

The importance of refrigeration compressors in the entire cold storage refrigeration system is self-evident, I believe everyone knows. Next look at the editor to teach you to turn around.
If a large amount of water vapor or refrigerant is sucked into the refrigeration compressor, it may cause frost on the cylinder head of the refrigeration compressor. What's more, it can even cause frost on the crankcase. 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 is wrong, and the fixing is not firm or loose, which will cause the above situation. The main reason is that the temperature sensor may feel the temperature too high in this case, resulting in abnormal automatic opening of the valve core;
The thermal expansion valve mainly reflects the superheat at the outlet of the evaporator. If there is a deviation in the superheat at the outlet of the evaporator, the refrigerant flow rate of the evaporator will be automatically adjusted.
When the value detected by the transmitter deviates from the given value, the physical quantity of the transmitter will change. And it will generate enough energy to directly drive the actuator. Generally, the position change of the actuator is directly linked to the parameter being set.
In the previous content, we repeatedly introduced the incompatibility of the thermal 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 outlet of the evaporator. And usually accompanied by a certain degree of superheat. The temperature-sensing cylinder of the thermal expansion valve is generally close to the outlet pipe of the evaporator, so as to feel the temperature of the outlet of the evaporator.

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 abnormally opened, 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 working. If the superheat at the outlet of the evaporator is too large, the superheating section at the rear of the evaporator will be too long, and the cooling capacity will be significantly reduced; if the superheat at the outlet is too small, it 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 to control the warehouse temperature.
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 and setting 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; 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 the compressor is started, the opening of the suction cut-off valve is too large or opened too early.
4. When there is too much refrigerant in the system, the liquid level in the condenser is higher, the area of condensation heat exchange is reduced, and the condensation pressure is increased. That is, the pressure in front of the expansion valve increases, the amount of refrigerant flowing into the evaporator increases, and the liquid refrigerant cannot fully evaporate in the evaporator, so the compressor sucks in wet steam, the cylinder is cold or even frosted, and may cause "liquid strike" At the same time, the evaporation pressure will be higher.

Related Info

What are the causes of frost in refrigeration compressors

Recent related posts