Performance evaluation of heat exchanger for mixed refrigerant J–T cryocooler

• Experiments are conducted on MR J–T cryocooler to study applicability of the existing correlations.
• We assessed condensation correlations for mixtures of nitrogen–hydrocarbons.
• Cavallini and Zecchin correlation predicts heat transfer coefficients more accurately.
• The present study is first of its kind on the condensation of mixtures at cryogenic conditions.
• The suggested correlations can be used for the design of MR J–T heat exchanger.

In mixed refrigerant Joule–Thomson cryocooler, a multi-component mixture of nitrogen–hydrocarbons undergoes evaporation and condensation process in a helical coiled heat exchanger simultaneously at different pressures. Experimental data and empirical correlations for predicting heat transfer coefficients of evaporating and condensing streams of multi-component mixtures at cryogenic temperatures are unavailable. As a result, design of these heat exchangers is a challenging task.The present work aims to address this challenge. It assesses the existing condensation correlations against the calculated data obtained during experimentation. Experiments are conducted to determine overall heat transfer coefficients along the length of the heat exchanger for various mixtures. The paper studies the applicability of these correlations to the multi-component mixtures at cryogenic temperatures.