What is the primary function of the purge unit in a centrifugal chiller?

The primary function of the purge unit in a centrifugal chiller is to remove non-condensibles from the condenser. In a chilled water system, non-condensibles, such as air or other gases, can accumulate in the condenser. These substances can hinder the system's efficiency by taking up space that would otherwise be occupied by refrigerant, thus reducing the overall heat exchange performance of the chiller.

By extracting these non-condensibles, the purge unit helps maintain optimal system pressure and enhances the heat transfer process, which in turn supports the chiller's efficiency and performance. Efficient removal of these gases ensures that the refrigerant can condense properly, leading to better cooling and system operation.

Other options involve functions that are either not primary focuses of a purge unit or are managed by different components within the cooling system. For example, increasing pressure in the system or adding refrigerant is managed by other components in the chiller system, while enhancing cooling efficiency is a result of improved performance but not a function specific to the purge unit itself.