Analysis on the blockage phenomenon of automobile air conditioning and refrigeration system

Dirty blockage often occurs in a small area of the circulation area of the refrigeration system, most of which are located on the high-pressure side, such as drying boxes. Once the refrigeration system is dirty and blocked, the refrigerant cannot circulate, so the compressor cannot run continuously. The evaporator is not cold, the condenser is not hot, the compressor shell is not hot, and there is no flow noise in the evaporator.

If clogged, the evaporator will feel cold, but not frost. This is because during throttling and decompression, the refrigerant flows through the micro-clogging dry filter or expansion valve, causing the refrigerant flowing through the blockage to expand, evaporate, and absorb heat. In addition, when blockage occurs, the pressure of the low-pressure part of the refrigeration system is lower than the normal value, and the cooling system with low-pressure protection automatically stops the compressor.

Air conditioner icing is a wet icing phenomenon that typically occurs in structures with expansion throttles, such as thermal expansion valves and throttle tubes. In the initial stage of freezing, the cooling system works normally, the condenser of the car begins to cool, the device works stably, and the sound of the refrigerant activity in the evaporator is clear and stable. As the ice forms, the flow can be heard decreasing and interrupting from time to time. When the blockage stops severely, the refrigerant circulation is interrupted and the condenser cools down gradually. At the same time, extremely low pressure is generated in the low-pressure cooling system, and the electromagnetic clutch is continuously connected and disconnected under the action of the safety pressure switch.

Due to the blockage of the air conditioner, the discharge pressure of the compressor increases, and the sound of the machine increases. No refrigerant flows into the evaporator, the frosting area gradually decreases, the temperature gradually increases, the temperature of the expansion valve also increases, the ice surface begins to dissolve, and the refrigerant begins a new cycle. After a period of time, the phenomenon of freezing will appear again, forming a periodic phenomenon. As we all know, there is an obvious difference between dirty blockage and ice blockage. The refrigeration system cannot work normally after dirty blockage, while the operation and shutdown of the system after ice blockage are intermittent.