How do unloaders function to unload a reciprocating compressor?

Unloaders in a reciprocating compressor play a critical role in regulating the compressor's capacity by controlling the flow of refrigerant into the compressor's cylinders. When the unloaders keep the suction valves open, it allows the suction of refrigerant to continue, but it prevents the compression process from occurring effectively during certain cycles or under specific conditions.

This action effectively reduces or eliminates the load on the compressor, as it can then bypass the compression process when less cooling is required, thus maintaining optimal efficiency and preventing the compressor from becoming overworked.

The other options involve actions that either do not effectively control the compressor's capacity or would negatively impact its operation. For example, closing the discharge valves would hinder the flow of refrigerant out of the system rather than adjusting the compression output. Increasing pressure in the cylinder could lead to further complications and potential damage. Likewise, releasing refrigerant directly into the environment is typically not a desired function and is not how unloaders are designed to operate. Keeping the suction valves open is the method that allows for efficient unloading without causing additional issues in the system.