What are non-condensables in a refrigeration system?

Non-condensables refer to gases that do not change state from a gas to a liquid under the operating conditions of a refrigeration system. These gases can accumulate in the condenser, where they interfere with the normal heat exchange process by taking up space and effectively reducing the system's efficiency. When non-condensables are present in a refrigeration system, they can lead to increased pressures and potentially cause operational issues, such as reduced cooling capacity and increased energy consumption.

The other choices do not accurately define non-condensables. Refrigerant gases that help maintain pressure are essential for the system to operate correctly, but they should be condensable substances. The main components of a refrigerant mixture would typically consist of the refrigerants themselves, while chemical additives are not classified as non-condensables. Each of these other options does not represent the unique characteristics and implications of non-condensables in a refrigeration system.