Cavitation pressure and bubble nucleation in liquid CO2: Improved classical nucleation theory with effects of line tension

A model for the gas nucleation pressure below the vapour pressure is crucial for predicting cavitation in nozzles and valves and for flashing inception in pipelines. Classical heterogeneous nucleation theory (CNT) predicts nucleation rates for C O 2 that are orders of magnitude too low for temperatures below 260 K. Similar large deviations occur for water for low temperature compared to the critical temperature. Our conjecture is that this problem can be resolved by incorporating line tension (introduced by Gibbs in 1878) at the contact line of the bubble nucleus where the molecules interact simultaneously with the liquid and vapour phases, and the container wall. Line tension lowers the nucleation energy if it is negative (expanding the contact area of the gas bubble), and it was demonstrated that the nucleation pressure can then be modelled successfully for the entire temperature range if the line tension magnitude increases with lower temperature, just as ordinary interfacial tension. Line tension data for the bubble configuration is still lacking for both water and CO 2 , and we encourage further work to obtain such data to test our hypothesis of the importance of line tension in heterogeneous nucleation.