Which of the following is NOT an important physical property of a refrigerant?

The important physical properties of a refrigerant include its miscibility, odour, and toxicity, each playing a vital role in ensuring safe and effective operation in refrigeration systems.

Miscibility refers to the ability of a refrigerant to mix with lubricating oils, which is crucial for maintaining proper lubrication in the compressor and ensuring efficient operation.

Odour is also relevant because it can serve as a safety feature; if a refrigerant has a distinct smell, it can help detect leaks.

Toxicity is an essential consideration, as it pertains to the safety of individuals who may come into contact with or be exposed to the refrigerant. Knowing a refrigerant's toxicity helps ensure that appropriate safety measures are taken to protect users and maintenance personnel.

Specific volume, while a relevant thermodynamic property that relates to the refrigerant's density and performance, is not typically categorized as a critical physical property when evaluating the safety and usability of refrigerants in practical applications. Therefore, it is understood to be the least important in the context of this question.