What happens to refrigerant as it moves through the system under proper operating conditions?

The correct choice highlights that refrigerant undergoes phase changes as it circulates through the refrigeration system. In a properly functioning system, refrigerant transitions between liquid and vapor states depending on the specific location within the cycle.

For example, as the refrigerant absorbs heat from the environment in the evaporator, it evaporates, turning from a liquid into a vapor. This phase change is essential for the refrigeration cycle to operate effectively, allowing the system to absorb heat. Conversely, when the refrigerant reaches the condenser, it releases that heat and condenses back into a liquid state.

This continuous process of phase change enables the refrigeration cycle to effectively cool spaces or products by transporting heat away. Other options, while they may contain elements related to refrigerant behavior, do not accurately describe the fundamental mechanics of how refrigerant operates in a refrigeration system. For instance, the refrigerant does not stay at a constant temperature throughout the cycle; it experiences temperature variations as it changes phases. Additionally, it does not remain purely as a liquid or become contaminated in a well-maintained system, allowing the focus to remain on its phase transition characteristics.