Which type of valve maintains a constant pressure in refrigeration applications?

The expansion valve is crucial in refrigeration systems as it regulates the flow of refrigerant into the evaporator while maintaining a constant pressure. This type of valve works by allowing the high-pressure liquid refrigerant to expand and convert into a low-pressure gas.

In refrigeration applications, the pressure needs to remain stable for efficient heat absorption in the evaporator. The expansion valve adjusts the amount of refrigerant that enters based on the pressure and temperature of the refrigerant in the system. By doing this, it ensures optimal performance of the refrigeration cycle, preventing fluctuations that can lead to inefficiencies or potential damage to the system.

A float valve, on the other hand, is generally used to maintain a level of liquid in a tank or to control liquid flow by using a float mechanism. A pressure relief valve is designed to release excess pressure in a system to prevent damage, rather than maintaining a constant pressure. A vane valve is typically associated with controlling fluid flow in larger applications, such as in compressor systems, and does not specifically focus on pressure maintenance in refrigeration.

Therefore, the expansion valve is the appropriate choice for maintaining constant pressure in refrigeration applications.