Numerical Modelling of Water Flashing at Sub-Atmopsheric Pressure
19 Pages Posted: 29 Jan 2023
Abstract
A CFD numerical study of the flash boiling phenomenon of a water film was conducted using an Euler-Euler method, and compared to the experiments of Saury (2003) on the flashing of a water film. The water film is initially heated at temperatures ranging from 34 to 74°C (1 to 41°C superheat), and the pressure is decreased from 1 bar to 50 mbar during the experiments. We showed that the experiments could not be correctly modeled by a simple liquid/bubble model because of the overestimation of the drag force above the water film (in the gas/droplet region).The GLIM (Generalised Large Interface Model) however, implemented in the neptune_cfd software, is able to differentiate the water film, where liquid/bubble interactions are predominant, with the gas region where the gas/droplet interactions are predominant, and gives nice qualitative results. Finally, we showed that the flashing model for overheated liquid used in neptune_cfd, while developed and validated for high pressure flows, predicted the evolution of the water temperature over time reasonably.
Keywords: Flashing, Computational fluid dynamics, Superheat, Water film
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