Visualization of cryogenic bubble growth in liquid oxygen during nucleate pool boiling

Unexpected thermal leakage can bring about the generation of successive bubbles in stored cryogenic liquids. The formation of cryogenic bubbles has a direct impact on the duration or even the safety of storage systems. But existing experimental data and correlations can hardly provide accurate prediction for the nucleation and growth of cryogenic bubbles. In this study, a cryogenic testing apparatus was established to investigate the bubble growth of liquid oxygen during nucleate pool boiling under the effects of wall superheat, liquid subcooling, and operation pressure. A periscope-like system was designed for visualization, and a homemade heating base with an etched surface was fabricated for the production of bubbles. It was found that a dramatic transition appears in the waiting and growth periods of oxygen bubbles as the pressure increases from 0.15 MPa to 0.2 MPa, attributed to the competition between the superheat of liquids replenishing the nucleation cavity and the equilibrium superheat within it. Moreover, high-precision dimensionless correlations were developed to predict the growth rate and detachment frequency of cryogenic bubbles. The results provide a more efficient way to predict the growth and detachment parameters of bubbles in cryogenic liquids, benefiting the design of cryogenic liquid storage tanks.