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

The purpose of the expansion valve in a refrigeration system is primarily to reduce the pressure of the refrigerant before it enters the evaporator. This reduction in pressure allows the refrigerant to expand and absorb heat effectively as it enters the evaporator, enabling it to cool the surrounding air or substance effectively. Through this process, the refrigerant turns from a high-pressure liquid to a low-pressure gas, which is crucial for the refrigeration cycle to function efficiently.

This mechanism is essential because when the refrigerant is at low pressure, it can more readily absorb heat, facilitating the cooling process. Thus, the expansion valve plays a critical role in optimizing the refrigeration cycle's overall efficiency and performance. In contrast, other components listed in the choices do not accurately reflect the function of the expansion valve within the system.