What is the primary function of a surge drum in a flood system?

The primary function of a surge drum in a flood system is to separate vapor from liquid refrigerant. In a typical refrigeration system, particularly those using ammonia, the surge drum serves as a crucial component where the incoming flow from the evaporator can be collected. As the refrigerant enters the surge drum, the differences in density between the vapor and liquid phases allow for the separation of the two.

When refrigerant enters the surge drum, it typically contains both vapor and liquid. Due to the design and functioning of the surge drum, the liquid refrigerant settles at the bottom while the lighter vapor rises to the top, where it can be vented or routed to the compressor. This separation process is critical for ensuring that only liquid refrigerant is sent to the evaporator, thus optimizing the efficiency and performance of the refrigeration cycle.

The other functions mentioned in the options do not accurately describe the primary role of a surge drum. While it is involved in the handling of refrigerant, it does not compress or cool the refrigerant directly, nor is it used as a mechanism to increase pressure in the system. The surge drum specifically focuses on achieving the necessary phase separation to maintain system efficiency.