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Modélisation des jets diphasiques liquide vapeur et du "Rain-Out"

Abstract : This work aims at modelling flashing liquid jets. It deals particularly with velocity and diameter of droplets formed near the orifice (orifice diameters between a few millimetres and a few decimetres). The model not only calculates changes of temperature, fluid concentration, size and velocity of droplets, but also « rain-out » fraction (liquid which falls down on the ground). This work contributes to developoing tools for estimating safety distances.
An experimental program allowed measuring jet mass flow rate, diameter and velocity of droplets which result from its fragmentation and rain-out fraction. Fluid: superheated water; reservoir temperature: 110 to 160 °C; reservoir pressure: 3 to 10 bar abs; breach geometry: orifices –2 and 5 mm- and pipes – 2 mm diameter, 100 mm length and 5 mm diameter, 250 mm length-.
Measurements allowed validation of the model both for pipe and orifice flow rate and for the aerosol jet. Droplet diameter distribution measurements showed that a few “large droplets” (150 µm < d < 600 µm) exist. They count for more than 80 % of mass even if they are few. These droplets were not mentioned in previous literature. The physical phenomenon which generates them is not known. Nevertheless they seem to us necessary in order to explain the heterogeneous nature of rain-out: observation clearly shows that droplets fall under the aerosol jet.
From a selection of our data and those from CCPS about other fluids (CFC-11, Cyclohexane, Methylamine, Cl2) we built a correlation for the “necessary “ droplet diameter (the one for which the model predicts the correct rain-out). Our model with this correlation allows rain-out fraction prediction within [-10 %, +30 %]. This is a significant improvement of the state of the art.
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https://tel.archives-ouvertes.fr/tel-00012084
Contributor : Andrée-Aimée Toucas <>
Submitted on : Wednesday, April 5, 2006 - 12:35:37 PM
Last modification on : Friday, October 23, 2020 - 4:52:22 PM
Long-term archiving on: : Saturday, April 3, 2010 - 8:57:47 PM

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  • HAL Id : tel-00012084, version 1

Citation

Abdellah Touil. Modélisation des jets diphasiques liquide vapeur et du "Rain-Out". Dynamique des Fluides [physics.flu-dyn]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2005. Français. ⟨tel-00012084⟩

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