Performance of J–T refrigerators operating with mixtures and coiled wire-finned heat exchangers

Abstract

Joule–Thomson refrigerators operating with mixtures require heat exchangers with an effectiveness of over 96% for the system to function. The hot (high pressure) stream enters the heat exchanger in a superheated condition and leaves in a subcooled state. The cold (low pressure) stream, on the other hand, enters the heat exchanger in a two-phase state and leaves in a superheated state. The streams undergo a temperature change of over 200 K in the heat exchanger. The above requirements mandate the use of innovative heat transfer surfaces in the heat exchanger. Coiled wire-finned heat exchangers have been employed successfully in this work. In this paper, we present the performance of the J–T refrigerator with two different wire-finned heat exchangers (wire-fin pitches of 8 mm and 12.7 mm) measured in our test stand. About 20 K lower temperature could be obtained when the wire-fin pitch was changed from 12.7 to 8 mm. The exergy efficiency of the refrigerator also improved.