What part of a refrigeration system controls the flow of refrigerant from high pressure to low pressure?

The expansion valve is a crucial component in a refrigeration system that specifically regulates the flow of refrigerant from high-pressure areas to low-pressure areas. Its primary function is to reduce the pressure of the refrigerant before it enters the evaporator. When the refrigerant passes through the expansion valve, it experiences a drop in pressure, which allows it to expand and cool down significantly. This process is essential for the refrigeration cycle because it enables the refrigerant to absorb heat from its surroundings within the evaporator, effectively chilling the air or the space that the system is designed to cool.

Unlike the compressor, which compresses refrigerant to increase its pressure, or the condenser, which dissipates heat from the refrigerant and changes it from a gas to a liquid, the expansion valve's key role is to facilitate the transition between high and low pressure. The accumulator is designed to store excess refrigerant and ensure that the system operates smoothly, but it does not play a role in controlling the flow of refrigerant based on pressure. Therefore, the expansion valve is the correct answer because it directly manages the pressure differential that allows the refrigeration cycle to function efficiently.