In a DX system, what does the expansion valve control?

In a direct expansion (DX) refrigeration system, the expansion valve plays a critical role in regulating the flow of liquid refrigerant into the evaporator. Its primary function is to reduce the pressure of the refrigerant, which causes it to expand and cool as it enters the evaporator. This cooling effect is essential for the refrigeration cycle, as it allows the refrigerant to absorb heat from the environment or the medium being cooled.

By controlling the flow of liquid refrigerant into the evaporator, the expansion valve ensures that the correct amount of refrigerant is present to effectively absorb heat. If too much refrigerant enters, it can flood the evaporator, reducing efficiency, while too little can lead to insufficient cooling. Therefore, the expansion valve is crucial for maintaining optimal operating conditions in the DX system.

The other options refer to different components or functions in the cooling cycle. For instance, while the compressor is responsible for moving the refrigerant and creating pressure, it's not directly controlled by the expansion valve. Similarly, controlling the pressure and temperature of the refrigerant across other components, such as the condenser, falls outside the specific role of the expansion valve.