Investigation of the ejector application in the cryogenic Joule-Thomson refrigeration system

We investigate the application of ejector in the cryogenic refrigeration system. A new refrigeration cycle is proposed using ejector technology to enhance the thermodynamic efficiency of Joule-Thomson (JT) refrigeration system. The ejector combined with the JT refrigeration cycle works with nitrogen and neon mixed refrigerant. The target refrigeration temperature is aimed to near the freezing point of nitrogen (63.15 K). A performance map of ejector-JT cycle is accomplished according to the ejector entrainment ratio and the ejector exit pressure. The effect of the ejector on the refrigeration cycle COP is analyzed by calculating the exergy destruction rate at each component of the refrigeration cycle. The exergy analysis shows that the losses at every component of the refrigeration cycle can be reduced using ejector when the entrainment ratio is properly designed. A lab-scale prototype ejector which has a rectangular cross sectional area is fabricated by stacking thin layers of etching plates. The fabricated lab-scale ejector is tested with JT refrigeration circuit, and the nozzles and the diffuser showed 80% isentropic efficiency.