Supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions

Abstract

This paper introduced supersonic expansion liquefaction technology into the field of hydrogen liquefaction. The mathematical model for supersonic condensation of hydrogen gas in a Laval nozzle model was established. The supersonic expansion and condensation characteristics of hydrogen gas under different temperature conditions were investigated. The simulation results show that the droplet number rises rapidly from 0 at the nozzle throat as the inlet temperature increases, and the maximum droplet number generated is 1.339×1018 kg–1 at inlet temperature of 36.0 K. When hydrogen nucleation occurs, the droplet radius increases significantly and shows a positive correlation with the increase in the inlet temperature, and the maximum droplet radii are 6.667×10–8 m, 1.043×10–7 m, and 1.099×10–7 m when the inlet temperature is 36.0 K, 36.5 K, and 37.0 K, respectively. The maximum nucleation rate decreases with increasing inlet temperature, and the nucleation region of the Laval nozzle becomes wider. The liquefaction efficiency can be effectively improved by lowering the inlet temperature. This is because a lower inlet temperature provides more subcooling, which allows the hydrogen to reach the thermodynamic conditions required for large-scale condensation more quickly.