Principle of Automotive Air Conditioning Expansion Valve?
2 Answers
Working principle of automotive air conditioning system: The thermal expansion valve is installed at the inlet of the evaporator and is commonly referred to as the expansion valve. The following are the reasons for automotive air conditioning expansion: 1. Expansion valve blockage: Manifested as higher temperature at the cold air outlet inside the vehicle, lower pressure on the high-pressure side, and negative pressure on the low-pressure side. In cases of minor blockage, frost or condensation will appear at the inlet end of the expansion valve; in cases of complete blockage, there will be no temperature difference between the inlet and outlet of the expansion valve. 2. Malfunction: If the expansion valve opening is too small or malfunctions, the symptoms are the same as those of a blockage fault. 3. Excessive opening: If the expansion valve opening is too large, it manifests as higher temperature at the cold air outlet inside the vehicle. The pressure on the low-pressure side is also higher.
The principle of an automotive air conditioning expansion valve, simply put, is a component that controls the pressure change of the refrigerant. In the air conditioning system, the refrigerant exits the condenser as a high-pressure liquid. When it flows to the expansion valve, the valve has a small orifice that allows it to rapidly expand into a low-pressure state. This process causes the refrigerant's temperature to drop sharply, turning it into a gas-liquid mixture, which then enters the evaporator to absorb heat and cool the air. This expansion is based on physical principles, similar to how a spray can cools when released. The expansion valve typically has a sensing bulb or spring mechanism to automatically adjust the flow rate in response to temperature changes. If the expansion valve fails, the air conditioning may provide insufficient or unstable cooling, and it's necessary to check for blockages or wear. During daily driving, keeping the air conditioning system clean can extend the lifespan of the expansion valve. I've seen many cases while repairing cars where expansion valve failure is one of the common issues, so it's recommended to inspect it during regular maintenance.
