What is the best example of a non-condensable substance in a refrigeration system?

• A. Freon
• B. Ammonia
• C. Air
• D. Carbon Dioxide

Answer: (C)

In refrigeration systems, non-condensable substances are gases that do not change state through the pressure and temperature ranges typically found within the system. They can accumulate in the system and lead to inefficiencies or prevent the proper functioning of the refrigerant cycle.

Air is the best example of a non-condensable substance because it remains gaseous at the system's operating temperatures and pressures. Unlike the refrigerants like Freon or Ammonia, which are intended to condense and evaporate in the system's cycle, air does not condense under these conditions and will remain in its gaseous form. The presence of non-condensable gases like air within a refrigeration system can reduce efficiency, increase pressure, and negatively impact the overall performance of the system.

Freon, Ammonia, and Carbon Dioxide are all refrigerants designed to undergo phase changes from liquid to gas and vice versa, making them suitable for the refrigeration cycle, but not classified as non-condensables in the context of decreasing system efficiency.