Relationship between the cooldown characteristics of J–T refrigerators and mixture composition

The performance of Joule–Thomson (J–T) refrigerators is strongly influenced by the composition of the refrigerant mixture used. The mixture composition changes if leaks occur, or when a silica-gel drier is used in the system. In this experimental study, we show how the composition changes can be estimated from the cooldown characteristics of J–T refrigerators without using a gas chromatograph. A novel way of representing the cooldown characteristics of J–T refrigerators is presented. The variation of compressor power during the cooldown is also discussed. The results presented here are useful for developers as well as field service engineers in selectively modifying the composition without discarding the entire mixture.