Final answer:
A refrigerant oil that is hygroscopic is one that readily absorbs moisture. It is good at dissolving other substances and has a low surface tension, making it a good lubricant.
Step-by-step explanation:
A refrigerant oil that is hygroscopic is one that readily absorbs moisture. This means that it has a strong affinity for water and can attract and hold onto water molecules from the surrounding environment. Hygroscopic refrigerant oils are commonly used in air conditioning and refrigeration systems to help remove moisture from the system, preventing issues such as corrosion and ice formation.
Hygroscopic oils are not necessarily crude or unrefined, and they do not necessarily covalently bond to water molecules. However, their ability to absorb moisture makes them good at dissolving other substances, including water-soluble contaminants. This property helps to keep the refrigerant and the system clean and functioning properly.
Additionally, hygroscopic oils tend to have a low surface tension, which means that they spread out over a larger area compared to oils with higher surface tension. This property can enhance the lubricating abilities of the oil, making it a good lubricant for various components in the refrigeration system.