The core problem of compressor oper
What are the reasons for the frost of the refrigeration compressor
The importance of the refrigeration compressor in the entire cold storage refrigeration system is self-evident, I believe everyone knows it. Next, let's watch Xiaobian teach you to turn things 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 may even cause frost in 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 sensing bulb is incorrect, and the fixing is not firm or loose. The main reason is that the temperature sensing bulb may feel the temperature is too high in this case, which will cause the valve core to automatically open abnormally;
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, it will automatically adjust the refrigerant flow of the evaporator.
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 push the actuator action. Generally, the position change of the actuator is directly linked to the set parameters.
In the previous content, we have repeatedly introduced to you the incompatibility of superheated expansion valves based on the balance method, which are generally divided into two types: internally balanced thermal expansion valves and externally balanced thermal expansion valves. The liquid refrigerant absorbs heat in the evaporation of the evaporator, and then it is completely vaporized when it flows to the outlet of the evaporator. And it is usually accompanied by a certain degree of overheating. The temperature sensing tube of the thermal expansion valve is generally close to the outlet pipe of the evaporator, so as to feel the temperature of the evaporator outlet.
This pressure difference is balanced by the tension of the ejector rod and the adjusting spring under the diaphragm. If you change the tension of the adjusting spring, you can change the top force of the ejector rod, thereby changing the opening of the needle valve. Obviously, the degree of superheat of the evaporator will also cause the change of the needle valve opening. When the adjusting 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 sensing bulb is installed incorrectly or the fixing is loose, so that the felt temperature is too high and the valve core opens abnormally, causing a large amount of wet steam to be sucked into the compressor, causing frost on the cylinder head. The thermal expansion valve is used to adjust the superheat degree when the evaporator is working. If the superheat at the outlet of the evaporator is too high, the overheating section at the rear of the evaporator is too long, and the cooling capacity will be significantly reduced; if the superheat at the outlet is too small, it may cause the compressor to strike or even frost the cylinder head. It is generally believed that the expansion valve should be adjusted to the evaporator outlet with a superheat of 3℃～8℃.
2. The liquid supply solenoid valve is leaking or the expansion valve is not closed tightly when the machine is stopped, causing a large amount of refrigerant liquid to accumulate in the evaporator before starting. The temperature relay is used in conjunction with the solenoid valve to control the storage temperature.
The temperature sensor 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 set value, the contact of the temperature relay is turned on, the solenoid valve coil is energized, the valve opens, and the refrigerant enters the evaporator to cool down; At the lower limit of its setting value, the temperature relay contact opens, cuts off the solenoid valve coil current, the solenoid valve closes, and the refrigerant stops entering the evaporator, so that the storage temperature can be controlled within the required range.
3. When starting the compressor, the suction stop valve is opened too large or opened too early.
4. When there is too much refrigerant in the system, the liquid level in the condenser is higher, and the condensation heat exchange area is reduced, which increases the condensation pressure, that is, the pressure before the expansion valve increases, and the amount of refrigerant flowing into the evaporator increases. The agent cannot evaporate completely in the evaporator, so the compressor sucks in wet steam, and the cylinder hair is cold or even frosted, which may cause "liquid hammer", and the evaporation pressure will be high.
