What function does the automatic expansion valve serve in a refrigeration system?

The automatic expansion valve plays a vital role in a refrigeration system by regulating the flow of refrigerant into the evaporator coil. Its primary function is to ensure that the evaporator operates at a consistent pressure, regardless of varying cooling loads. By doing this, the valve reacts to fluctuations in pressure within the evaporator, automatically adjusting the flow of refrigerant to maintain the desired pressure level.

This consistent pressure is essential for optimal heat exchange within the evaporator, allowing the refrigerant to absorb heat effectively from the surroundings before it moves onto the compressor. Without this function, the evaporator could become either underfilled or overfilled with refrigerant, leading to inefficient operation and potential system failure. Therefore, it is crucial for the automatic expansion valve to maintain a steady pressure, enabling the entire refrigeration cycle to function efficiently.

In summary, the correct answer highlights the valve's critical role in maintaining the evaporator's pressure, thereby ensuring effective refrigeration performance.