Estimation of performance of a J-T refrigerators operating with nitrogen-hydrocarbon mixtures and a coiled tubes-in-tube heat exchanger

• Published in: Cryogenics (Guildford) 2018-06, Vol.92, p.27-35
• Main Authors: Satya Meher, R., Venkatarathnam, G.
• Format: Article
• Language: English
• Subjects: Cooling; Design of the heat exchanger; Estimates; Exergy; Experiments; Heat exchanger; Heat exchangers; Heat transfer; Homogeneous model; Hydrocarbons; Mathematical models; Mixed refrigerant cascade (MRC); Nitrogen; Performance prediction; Refrigerators; Temperature profiles; Tube heat exchangers; Tubes; Two phase flow; Uncertainty
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2018.03.007

•Experiments conducted with different nitrogen-hydrocarbon mixtures on a J-T refrigerator.•Temperatures on the shell side wall of the coiled tubes-in-tube heat exchanger measured.•The measured temperatures compared with those predicted using existing correlations.•The results show that the homogenous method is most suitable for predicting the cooling capacity of the refrigerator. The exergy efficiency of Joule-Thomson (J-T) refrigerators operating with mixtures (MRC systems) strongly depends on the choice of refrigerant mixture and the performance of the heat exchanger used. Helically coiled, multiple tubes-in-tube heat exchangers with an effectiveness of over 96% are widely used in these types of systems. All the current studies focus only on the different heat transfer correlations and the uncertainty in predicting performance of the heat exchanger alone. The main focus of this work is to estimate the uncertainty in cooling capacity when the homogenous model is used by comparing the theoretical and experimental studies. The comparisons have been extended to some two-phase models present in the literature as well. Experiments have been carried out on a J-T refrigerator at a fixed heat load of 10 W with different nitrogen-hydrocarbon mixtures in the evaporator temperature range of 100–120 K. Different heat transfer models have been used to predict the temperature profiles as well as the cooling capacity of the refrigerator. The results show that the homogenous two-phase flow model is probably the most suitable model for rating the cooling capacity of a J-T refrigerator operating with nitrogen-hydrocarbon mixtures.