Experimental investigation and numerical calculation of the cryogenic ejector in a liquid nitrogen system

•Cryogenic ejector experiment system in liquid nitrogen temperature is established.•Primary flow pressure and ejector structure influence on performance are analyzed.•The model of cryogenic ejector is built and is verified by the experimental data.•The errors between experiment and calculation are evaluated. A cryogenic ejector is designed, which can pump liquid from cold plates by high-pressure nitrogen gas. The pressure of primary flow ranges from 300 kPa to 700 kPa and the mass flow rate of jet flow is between 2 g/s and 8 g/s in the experiment. The ejector coefficient and exergy efficiency are calculated for different working conditions. Entrainment ratio reaches up to 1.8 and the maximum exergy efficiency is 0.7. The interdependence of the inlet pressure and flow rate ratio is theoretically evaluated. A model is built to obtain the thermal properties at different parts of the ejector. The errors of pressure, temperature and flow rate between computational results and experimental results are less than 3%, 1% and 15%, respectively. The cryogenic pump box systems are introduced. The exergy analyses are implemented to compare the efficiencies of traditional immersed pumps and the newly proposed cryogenic ejector. When the temperature of primary flow is less than 20 K, the exergy efficiency of the ejector pump is higher than the immersed pump, which is about 0.826. This research effectively settles the problems of the cryogenic liquid extraction and is also significant for the hydrogen energy regasification and utilization.