Evolution of thermodynamic properties of cryogenic liquids in the static storage process

Abstract

During static storage, the complex evolution of the thermodynamic properties of cryogenic liquids poses a challenge to the large-scale development of the energy storage industry chain. A dynamic thermodynamic model for static storage of cryogenic liquid is proposed to explore the evolution of thermodynamic properties, which is influenced by the heat flux and the initial liquid volume fraction. Further, an experimental system for measuring the cold vapor temperature, boil-off rate and pressure is established to verify the accuracy of the dynamic thermodynamic model. Specifically, the cold vapor temperature measurements accurately capture the vertical temperature gradients within the ullage space, with maximum deviations of less than 9% for the average boil-off rate, 5% for the pressure, and 7% for the lossless storage holding time, respectively. Then, the validated model is employed to investigate the evolution of temperature, boil-off rate, liquid thermal expansion and pressure during static storage of cryogenic liquid. It indicates that the cold vapor temperature not only exhibits a more pronounced staged growth compared to the liquid temperature but also determines the evolution of the boil-off rate. The variable evolution of density and liquid volume demonstrates the simultaneous but inverse effects of evaporation and liquid thermal expansion. Importantly, the staged and variable time-varying law of the pressure is comprehensively influenced by cold vapor temperature, boil-off rate, and liquid thermal expansion.