What is the working principle and function of the expansion valve?

[VanLucia]

The working principle and function of the expansion valve are introduced as follows: 1. The working principle of the air conditioning expansion valve is: The thermal expansion valve controls the flow of refrigerant entering the evaporator by regulating the superheat of the gaseous refrigerant at the evaporator outlet. According to different balancing methods, expansion valves are divided into externally balanced and internally balanced types. In dedicated air conditioning systems, due to the branching of the evaporator and the use of showerhead distributors, the pressure drop is relatively large, resulting in different temperatures at the evaporator inlet and outlet. 2. As a throttling device in the refrigeration system, the expansion valve is one of the four essential basic system components required for the refrigeration cycle. Its main functions include: Throttling and pressure reduction, which primarily involves reducing the pressure of the high-pressure liquid refrigerant after condensation in the condenser, then regulating the flow of refrigerant through the evaporator and controlling the superheat at the evaporator outlet. The magnitude of this superheat is equal to the system's return gas temperature minus the evaporation temperature.

[StAngelina]

The expansion valve is a real workhorse in the car's AC system – I like to think of it as a flow regulator. When high-pressure liquid refrigerant rushes in, its tiny orifice reduces pressure, causing the refrigerant to instantly expand into a low-pressure state that absorbs heat. After cooling the air, it's blown into the cabin. Its key role is precisely controlling flow rate to match compressor operation, preventing evaporator icing or refrigerant backflow that could damage the system. If your AC fluctuates between hot and cold on the highway, a clogged expansion valve might be the culprit. Regular valve cleaning or refrigerant purity checks can help. These components wear over time – they're durable but need maintenance. Think of it as the AC system's heart valve – reliability depends on minimal malfunctions.

[OAyla]

I've been driving for over a decade, and the principle of the expansion valve is quite simple. It allows the refrigerant to transition from high pressure to low pressure, absorbing heat and cooling down during expansion, functioning like a small valve to regulate flow and ensure the evaporator works properly. Its role is to balance system pressure, preventing the compressor from being overloaded and causing high fuel consumption. If your car's AC is unstable and doesn't cool well on hot days, a clogged expansion valve is a common issue. I've experienced this once during a repair—after replacing it, the cool air came rushing back. It also helps save energy, reduces waste, and impacts overall driving comfort. During maintenance, use a diagnostic tool to check the valve's opening degree—prevention is always better than repair. Try to avoid driving on dusty roads to keep the valve clean and more durable.

[Phoebe]

In the car air conditioning system, the expansion valve plays a crucial role. It reduces the pressure of high-pressure liquid refrigerant through a narrow passage, causing it to expand into a low-pressure state and rapidly absorb heat to cool the air. Its function is to precisely regulate refrigerant flow, preventing the system from becoming too cold or too hot. As a car owner, I've noticed that if the air conditioning airflow is uneven, there's a high probability the valve is faulty. During regular maintenance, it's important to inspect the valve body and clean any dirt to prevent clogging. Simply put, it acts like a flow controller—poor maintenance can easily lead to air conditioning failure, and replacing it can be troublesome. Proper vehicle care saves both money and hassle.