Choked liquid flow in nozzles: Crossover from heterogeneous to homogeneous cavitation and insensitivity to depressurization rate

The critical mass flow rate is the maximum that can pass through a constrained geometry such as nozzle. For liquid CO2, it has been shown homogeneous relaxation models systematically underpredict rate. In this work, we demonstrate delay of phase transition necessary to reproduce experiments. To analyze in further detail, two methodologies are presented: (1) delayed model (Delayed HRM), and (2) metastable isentrope (MIM). Delayed HRM readily be incorporated into spatially distributed description fluid flow, e.g. ejectors. MIM assumes isentropic instantaneous equilibrium up limit metastability, yields geometry-independent flux solution set algebraic equations. We compare available experimental data on rates CO2 H2O nozzles, finding they give nearly identical predictions. This suggests mostly determined by achievable degree metastability before onset change, rather insensitive dynamic variables depressurization or towards equilibrium. Using predicted nucleation theory works well at high temperatures, rendering completely predictive. They deviate average 11% from thus outperform large margin, even when latter employs several fitted parameters. Especially good agreement was found with experiments employ lubrication oil, which hypothesized suppress heterogeneous nucleation. superheat lower temperatures must described theory. water find crossover between T≈590 K T≈285 respectively. Moreover, falls single curve temperature–pressure space water, present an empirical correlation curve. By combining expression above methodologies, obtained deviation 3% rates.