Air con evaporators & expansion valves

The car air conditioning evaporator plays a key role in the heat exchange process that allows the A/C system to operate effectively.

As outdoor air flows through the evaporator fins, it cools down by transferring its heat to the refrigerant. The cooled air is then directed into the cabin at temperatures ranging from 2°C to 10°C.

While air conditioning is typically associated with cooling, one of its crucial functions is to dehumidify the air. Lowering humidity levels is particularly important in cold weather, as passengers can quickly cause condensation to form on the vehicle’s windows.

As the cabin air passes through the A/C system, moisture condenses on the evaporator fins, removing excess humidity from the air. This collected moisture is drained and discharged underneath the vehicle.

The expansion valve receives the refrigerant in a fully filtered, 100% liquid form and reduces its pressure before it enters the evaporator. This pressure reduction cools the refrigerant, which is then sprayed into the evaporator. In car A/C systems, the expansion valve is always connected to the evaporator.

As a precision component, the expansion valve is complex and sensitive to any contaminants or acids circulating within the air conditioning system. If the valve becomes blocked, it can lead to a significant loss of cooling or potentially damage the compressor, as improper flow regulation may allow liquid refrigerant to reach the compressor.