title: Flashing liquid jets and two-phase droplet dispersion I. Experiments for derivation of droplet atomisation correlations.
abstract: The large-scale release of a liquid contained at upstream conditions above its local atmospheric boiling point is a scenario often given consideration in process industry risk analysis. Current-hazard quantification software often employs simplistic equilibrium two-phase approaches. Scaled water experiments have been carried out measuring droplet velocity and droplet size distributions for a range of exit orifice aspect ratios (L/d) and conditions representing low to high superheat. 2D Phase-Doppler Anemometry has been utilised to characterise droplet kinematics and spray quality. Droplet size correlations have been developed for non-flashing, the transition between non-flashing and flashing, and fully flashing jets. Using high-speed shadowography, transition between regimes is defined in terms of criteria identified in the external flow structure. An overview companion paper provides a wider overview of the problem and reports implementation of these correlations into consequence models and subsequent validation. The fluid utilised throughout is water, hence droplet correlations are developed in non-dimensional form to allow extrapolation to other fluids through similarity scaling, although verification of model performance for other fluids is required in future studies. Data is reduced via non-dimensionalisation in terms of the Weber number and Jakob number, essentially representing the fluid mechanics and thermodynamics of the system, respectively. A droplet-size distribution correlation has also been developed, conveniently presented as a volume undersize distribution based on the Rosin-Rammler distribution. Separate correlations are provided for sub-cooled mechanical break-up and fully flashing jets. This form of correlation facilitates rapid estimates of likely mass rainout quantities, as well as full distribution information for more rigorous two-phase thermodynamic modelling in the future.
authors.affiliation: Cardiff University, Cardiff, UK. ClearyV@Cardiff.ac.uk
authors.forename: Vincent
authors.initials: V
authors.lastname: Cleary
authors.forename: Phil
authors.initials: P
authors.lastname: Bowen
authors.forename: Henk
authors.initials: H
authors.lastname: Witlox
mesh_terms: D000335:Aerosol Propellants / Q000737:chemistry*; D000393:Air Pollutants / Q000737:chemistry*; D000397:Air Pollution / Q000517:prevention & control*; D002617:Chemical Industry; D015386:Hazardous Substances; D008962:Models, Theoretical; D018570:Risk Assessment; D013696:Temperature; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: D000335:Aerosol Propellants; D000393:Air Pollutants; D015386:Hazardous Substances; D014867:Water