Which of the following is NOT considered a secondary coolant?

The correct choice of ammonia as not being a secondary coolant is based on its classification in refrigeration systems. Ammonia is primarily used as a primary refrigerant. It absorbs heat from the environment and changes states, being effective at low temperatures and having good thermodynamic properties.

In contrast, secondary coolants, such as glycol, sodium chloride, and calcium chloride, are used to facilitate the transfer of coolness from the primary refrigerants to the areas or objects that need to be cooled. Secondary coolants often have lower freezing points and are mixed with water to allow for heat transfer in systems like ice rinks.

Glycol is commonly mixed with water to lower the freezing point for applications in ice rinks. Sodium chloride, or salt, is utilized due to its efficacy in lowering the freezing point of water, which helps maintain a consistent cooling effect. Calcium chloride also operates on the same principle, being a strong brine used for similar cooling applications.

Thus, the identification of ammonia as a primary refrigerant distinguishes it from the other options, which are categorized as secondary coolants. This understanding of coolant classifications is crucial for the efficient operation and management of ice facilities.