What is the primary function of the expansion valve in a refrigeration system?

The primary function of the expansion valve in a refrigeration system is to control the flow of refrigerant to the evaporator. This component plays a crucial role in regulating the amount of refrigerant that enters the evaporator, ensuring that it is metered properly according to the cooling demand of the system. By controlling refrigerant flow, the expansion valve helps maintain the desired temperature and pressure levels in the evaporator, which is essential for the refrigeration cycle to function effectively.

When the refrigerant leaves the expansion valve, it has been reduced in pressure and temperature, allowing it to absorb heat from the environment in the evaporator. This process is vital for the refrigeration cycle, as it sets up the conditions necessary for the refrigerant to evaporate and absorb heat.

The other functions mentioned in the alternate choices do not pertain to the role of the expansion valve. Airflow regulation pertains to fan systems, enhancing system pressure is primarily related to the compressor, and increasing efficiency involves various factors beyond just the expansion valve's control over refrigerant flow. Hence, focusing on the metering role of the expansion valve highlights its essential function in a refrigeration system.