What is the role of the expansion valve in a refrigeration system?

The role of the expansion valve in a refrigeration system is to regulate the flow of refrigerant into the evaporator. This is critical because the expansion valve controls the amount of refrigerant that enters the evaporator, ensuring that it is supplied in a proper quantity to facilitate efficient heat absorption. By maintaining the appropriate flow, the expansion valve helps to optimize the cooling process.

As the refrigerant passes through the expansion valve, it experiences a drop in pressure, which allows it to convert from a high-pressure liquid to a lower-pressure mixture of liquid and vapor before entering the evaporator. This pressure reduction is essential for the refrigerant to absorb heat effectively from the environment inside the evaporator, which is the main function of the refrigeration cycle.

In contrast, the other options reference functions that are not accurate representations of the expansion valve's role. For instance, the expansion valve does not increase the pressure of the refrigerant, nor does it directly convert the refrigerant from liquid to gas; that conversion primarily occurs in the evaporator. Additionally, while the refrigeration system does involve the removal of excess heat, this is largely the function of the evaporator, rather than the expansion valve itself.