Studies on coiled wire finned heat exchangers operating with wide boiling mixtures

Heat exchanger effectiveness of more than 90% is required for a J-T refrigerator to function when nitrogen is used as the refrigerant and over 95% when mixtures are used as the refrigerant. Coiled wire finned heat exchangers with effectiveness greater than 97% have been built and tested in our laboratory for use in J-T refrigerators operating with mixtures. Experiments have been conducted on prototype heat exchanger with a nitrogen-hydrocarbon mixture and temperature of the shell measured at some locations. The measured temperatures are compared with some single and two-phase heat transfer coefficient estimation methods available in the literature.