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Pulsations of the Mass Flow Rate during Pressure Relief

Lucas, D.; Prasser, H.-M.


During two­phase blowdown from pressure vessels considerable pulsations of the discharged mass flow rate were found. Regions of instability were predicted by a linear stability analysis. The oscillations are caused by the following feedback circuit: boil up ­ level movement ­ void fraction of the discharged mixture ­ critical discharge rate ­ velocity of pressure decrease ­ boil up. They were also found at transient simulations. Finally the instabilities were confirmed by experiments. The possibility of the occurence of oscillations increases with the volume of the ventline and the volume void fraction of the discharged mixture. They may influence the pressure relief from pressure vessels as well as from chemical reactors.

Keywords: Two-Phase Flow; Instability; Pressure Relief; Analysis of Stabilty

  • International Journal of Thermal Sciences 42(2003)5-14